RSGB Tonight@8 – An entry-level talk on End Fed Half Wave antennas by Colin Summers, MM0OPX

The presentation

Aimed at newcomers to amateur radio, this presentation will be an entry-level talk which will touch on antennas generally but will focus on the End Fed Half Wave Antenna (EFHW) – transformers, construction and performance.

About Colin

“I first became interested in radio around 12 years old when my cousin showed me an FM CB radio where we would use these to talk to each other. We would regularly stay at our grandparents at the weekend where we would listen to shortwave radio and local FM non commercial stations. I started building CB antennas like dipoles and even once built a 3 element wire Yagi on fencing slats for the summer Sporadic E! I had a break from radio from the age of 17 to 29. I then discovered the 3-tier licence system which allowed HF access from the get-go. I soon enrolled in a weekend Foundation course which ran in May 2011 and by the end of November the same year I had my Full licence. Particular thanks go to John, GM1BSG & Stirling Amateur Radio Society in which I gained so much initial experience in contesting and field setups.

Radio took a back seat again when my daughter arrived in 2015 but I got interested again in 2019. From 2019 till now my passion is designing and building efficient HF field portable antennas deployable by one person. This was driven by the fact I have a small garden and cannot have antennas set up all the time. In the autumn of 2012, I was lucky enough to operate as VE4/MM0OPX deep in the Boreal Forest of Northern Manitoba on at lake on the Nelson River. My aim was to work back into Europe on SSB which I did several times and have a QSL card to prove it!”

[Applause] [Applause] [Applause] a [Applause] [Applause] [Applause] oh [Applause] [Applause] [Applause] [Applause] W [Applause] [Applause] [Applause] A Hello and welcome to tonight at8 as you may know the rsgb recently ran a special poll to run find out what new and returning lenses would most like to see a webinar about and antennas was one of the most popular requests so tonight we’re very pleased to welcome Colin

Summers mm0 opx who’s going to tell us about the end fed halfwave an antenna which is relatively easy to make yet can be very versatile and and effective welcome to tonight to date Colin can you give us a quick preview of what you’ll be showing us this

Evening hi David hi everyone yeah so tonight as you say I’m going to be giving an overview on the nfed halfwave antenna so for HF so generally speaking 40 m up uh I’m going to talk about um the basic components and I’m also going to talk about the the Transformer in a

Little bit of detail sounds wonderful thank you Colin well before your presentation a reminder that if you’re watching this on Monday the 6 of November then this is live and you can ask questions and make comments on either YouTube chat or batc messaging at any time during the presentation or

Straight afterwards please include your first name and call sign if you have one within every message I note that you can make this video stream fill your screen on most devices usually by double clicking on the picture or pressing the full screen button so now back to Colin

To learn all about the end fed halfwave antenna thank you David so we’ll start with our uh our contents page so I’m going to talk a little brief little bit about me uh my history uh in in amateur radio and personal life um and then I’m going to give a basic

Overview of the multiband H HF uh infed halfwave antenna and generally I’m going to be speaking about um bands 40 m through 10 m although I do mentioned 8 m a couple of times um I’m going to talk about the infed halfwave um component descriptions and selections so give you

A little idea um you may not know but I’m really into building so I would encourage anyone to do that so going to give some hints and tips there um and then I’m going to dive uh quite a little bit into testing Ned halfwave Transformer efficiency and this was the

Primary reason um why I actually got into Ned half waves and then once we’ve done that uh from that testing I’m going to talk about some alternative of nfed halfwave course and after that if you’ve got any questions for me hopefully I’ll be able to answer

Them okay so uh I am 41 years old um I live in a small town in West loan just outside Livingston so it’s Junction 3 of the M8 um in my day job I’m a lead manufacturing engineer um I’ve worked here all my working life 25 years and we

Make man we make hydraulic drives um quite interes in white fairy job um and obviously manufacturing I get to uh I I I get to see all all types of manufacturer and it also helps me within within the hobby um I was first licensed

In 2011 as mm6 NLC um all of a sudden I discovered the um three tier system because I’d been away from radio for a little while um but I got the bug van so I quickly progressed got my um intermediate and by the November I have

Had my uh fuel license and call of mm0 opx I do have lots of other Hobbies um which include fishing playing the guitar but amateur radio for the last four or five years uh has been my main hobby it’s I think it’s that good that um there’s there’s so much to amateur radio

Um that we’re always learning something new and I have no RF or Electronics knowledge so basically what I’m going to show you tonight so if I’ve been able to do this um you know any of you can do that too okay so the end fed halfway so just

A very brief overview um so it’s not a new antenna and from the the little bit of research that I’ve done it was actually first patented in 1909 B hands burgo uh in Germany and that was known as the nfed Zep um and Zep was short for

Zeppelin so um if you know your history you know what happened to the Hindenburg uh but you know the antenna is usually multi- banded although monoand versions do exist I actually have one some here um in the garage here but we’re going to talk about monoband

Tonight um on The Mod on these monoband versions we use a toroidal Transformer uh and that lets us use multiple bands with one single wire um no radial are required for this antenna which is a big benefit over say a ground mounted vertical um and typically uh no tuner or

Matching is required for the harmonically uh related bands so before we get into the the Ned halfwave I just want to actually just basically look at a dipole so when we talk about a halfwave um an Ned halfwave and a dipole fundamentally are not that different all that we’re

Doing is we’re feeding so we’re putting our coax to a different bit of the wire but the the radiation of the pattern so where your signals are going to go is going to be effectively the same if you want to look at it in simple terms but

This is a halfwave dipole and on any antenna we have voltage and we have current as you can see here with the dotted line and this solid line here so this is obviously just representative of a a half wavelength and uh if you know any maths at all you know that’s

Basically like half of the S Wave okay so taking that a little bit further um these very basic drawings here sketches so looking at the top here if we have a dipole so hopefully most of us know what a dipole is that that we learn this when we do our foundation

License so uh we take a half length piece of wire for a given frequency we feed it in the middle so we put one half of the wire to the center of the coax the other half to the shield and we have a dipole and it’s a very

Good antenna typically it has a a an impedance of round about 70 ohms but for us using 50 oh ohm coax that’s close enough that we we can usually get a match um taking that the next step down we’ve got in the middle here we’ve got

An off center fed dipole this is another favorite of mine so if we take that feed point and we just put it off so off off center as it says so if we put that 1/3 of the way up we have an impedance roughly 2 200 ohms and we can basically

Feed that with a 4 to1 ball and that’s actually going to give us a multi-band antenna uh I’ve used this and typically say you make it for 40 m you would get 40 20 10 something you may get 15 but 15 could be a bit funny then taking that H further again

Uh if we feed this same piece of wire but we feed it at either end we’ve then got our our end fed now the impedance here will vary I it will be round about 2 and 1/2 3,000 ohms um and then this is where you see people using a 49 to1 56

To1 64 to1 Transformer because we can’t just hook up our coax so we need to transform that and petence down to something that our uh radio uh will be happy with so I think the main convenience for the infed halfwave is the fact is that’s a multiband antenna makes it very very convenient

And uh humans in general will always take the easy convenient option and I think this is why the M Fed so popular so um as I said we’re going to be talking about generally speaking because my experience with infed half waves has been U from 40 m through 10 but um yeah

We’ll say we’ll touch on 80 so for 66t of wire or 21 M approximately um we can have an antenna that will cover 40 20 15 and 10 um if we double that length of wire um we then would get 80 H sorry yeah 80 30 20 17 15 12 and 10 because

These are all harmonically uh related bands so you may think that great I only need one wire so that’s going to cover all the bands and some people do that but there is some some disadvantages some disadvantages to that we’ll cover we’ll cover that in a little

Bit so the basic uh Ned halfwave antenna setup so this is about as simple as it gets to try and uh explain it so this blue big blue box in the middle is our Transformer so that’s our 49 to1 uh our 64 to1 um so coming from that we would

Have our antenna wire here on the right so this would be a half wavelength for the lowest frequency that we we would intend to uh use so for example we would use you know that 21 M or 66t of wire which gives us that half wve now uh I’m going to contradict

Myself a little bit here but I’ve put them in for because this is very good housekeeping here um normally a um and for halfway will have a connection for a counter Poise um and I’ll put my hand up and and be honest that um I never

Actually used this I used it in some testing but generally if I’m operating portable I found that I don’t need to so your counter Poise it it can help with basically think about it almost like radials um but using this small counter Poise wire instead now this only needs

To be 5% of a wavelength at your lowest operating frequency so that’s 2 m on 4 M so it doesn’t need to be very long and this helps to stop something called common mode um or flowing down the shield of the coax and going back to

Your uh Shack in your radio and and giving some issues so from the Transformer we can see that there’s another short piece of coax um and you you need to put the basically you need to put the choke which I’m going to talk about next you need to put

That a little bit further away from the Transformer um I actually read this Steve Ellington’s done a lot of work on Ned halfwave and I’ve actually done these experiments uh myself so you basic again you put a 5% uh or 05 length of U coax so that would be two

Two M uh on 40 m a little bit of coax before you get to your choke so I I’ll tell you just a quick little story about this usually I don’t use a choke so I connected my uh coax up to my Transformer um I trimmed the antenna the

Wire for lowest s SWR and all was great and I decided to actually add a choke right at the Transformer and it actually changed where my SWR dip was um so I knew that the choke was affecting it I then put in this little jumper of coax

And then the wire uh the SWR went back to where it was originally so uh just a little tip cuz I see some people saying put your choke right to the Transformer but don’t put it a little bit further away that’s just a just a an idea

Doesn’t need to be exactly 5% of a wavelength but if it’s round about that it’ll be okay and then from your choke we want a length of coax back to your radio and that that can be any length but of course you want to keep that as

As short as possible just to minimize losses so while we’re talking about chokes um it’s not certainly not my specialized subject here um but um these are basically the the two um I would say the two gurus when it comes to common mode chokes so G3 txq and gm3 skk and

The chokes I use are actually the gm3 SE PK chokes they use these little funny shaped cores I don’t know what you would call that almost Loval um and basically these three chokes here cover basically low bands mid bands and the higher bands so 160 through 10 m uh they’re very easy

To build um so you know I would certainly recommend that but I’m not an expert on chokes but there there’s many many designs out there and Steve uh he actually had he’s done a multitude of experimentation uh and if you if you look it up you you’ll find this little

Table um and there’s many different ways you could actually make a choke so looking at typical SWR curves of the infed halfwave um this is typically what you may see but it it probably won’t always be um um just basically depending on maybe your ground conditions maybe anything that could be

Interacting with the antenna but it does give a representation of how you can actually get a nice match a nice s SWR right across the HF Spectrum which again which is very nice especially if your radio uh it doesn’t have a a tuner or an ATU um one of the complaints I hear

Regularly uh about the Ned halfwave is its performance on the higher bands um and I know quite a few people that’s done AB comparisons so they have two antennas set up for 10 m for example one of them being an Ned halfwave and another one being in for example uh a T2

LT um flow Port antenna or some sort of vertical and they say that the the Ned halfwave is is well down multiple s points down than the Ned halfwave and that’s just what I’m going to explain here so top left here you can imagine that if you have a a half length piece

Of wire and you have it say half a wavelength from the ground you get these two lobes so it’s almost By Di directional if you then feed that same piece of wire with a signal for 20 M you can see then we get these four loes um

And again three three half waves or one and a half wavelengths for 15 M you can see that we get even more loes but not only do we get these lobes we get these massive nulls so if you’re getting signals coming in here they’re going to be massively down um then then say

Perhaps you know what it would be on 40 and again by the time you get to 10 m you get even more of these Peaks and NS so it could be even worse and certainly that’s why I believe that um performance can suffer so it’s not always the case

That more uh wire in the in the air is is always better I think there is a sweet spot when it comes to it so configuration of your uh infed halfwave this is just three examples but the good thing about the infed half is it’s quite a tolerant antenna so uh you

Could basically string it up on your chimney run it about your garden um as long as you’ve not got too many bends in it um I know the general saying is don’t make any Bend um more than 90° but you can go a bit more than that so again the

In inverted V which is typically we would run a normal dipole when we have our COA R up the middle but we’d have our of our Transformers at one end um there the inverted V is very good so for us here in the UK If you have a an infed

Halfway inverted V you will have a very strong signal around the UK uh and locally around Europe excellent for that um running it as an inverted l so running straight up then straight across um that’s a gives you a little bit lower uh angle of radiation um so it’s a

Little bit better for DX and this dotted line is that’s typically how I run it when I’m out portable because it’s very difficult to keep that flat top um and another uh very popular way that I like to do it is basically just run um as a vertical I actually raise

The uh feed point off the ground a little bit a couple of meters I put it on my 12 M spiderbeam pole um and I like running sort of 20 M up on the antenna um and it works very very well excuse me I’ll just get a drink of water

So I briefly said I was just going to touch on 80 M and it’s not something I’ve got a lot of experience with but um credit to g0 K for his nice uh drawing here so you could have a basically 66t ined halfwave and on the end of that you

Can add a little coil so 110 micro Henry coil and beyond that you could add say two 2 and 1/2 M of uh wire so this will then work on um 8040 uh 84025 and 10 so it just gives you 80 M now it will be a compromise giving you

80 M but any antenna is better than no antenna as as the old saying goes and because it’s electric electrically the right length for 80 M but um physically it’s shorter you will get a narrower bandwidth um I have made a couple of these coils on on the right hand side

Here this is one that I made last year and you can see that I’ve almost got it to 110 micro henries with my little LCR meter here I used a little online calculator and this was actually a dole to make so what the coil does is

So for frequencies um 40 m up it basically acts as a choke so it stops any signal going past it but on 80 M it allows the signal to basically go past it and actually then sees the coil and then it it allows you to get a match on

M so if that’s something that you’re interested in now there’s a lot of a lot of people like to build their own antennas but um then a lot of people just like to buy and that’s perfectly understandable I I I bought antennas myself for for a long

Time and when it comes to the N fed halfwave you basically got two options you can either um buy buy your just your Transformer and put your own wire in it so you’re doing a little bit of yourself um or you could just by actually the whole thing um so the

Transformer yeah and and the wire um but even though you buy it with a wire it’s highly likely that you may need to do some adjustment uh on the wire uh and that just to your local environment um the ground can have a massive effect on your infed halfwave and and that’s why

We want to try and keep it up as high as we we practically can cuz that will minimize losses so as I said um why not make your own nfed halfwave Transformer um and it’s a really good project for the new radio amateur um they can look complicated but they’re not

Really now um as I said we see people talking about a 49 to1 or a 64 to1 and a question I see quite a lot is well how how do you actually work out that that’s a 49 to1 or a 64 to1 so I’ll I’ll

Explain it in my speak um um and how I look at it um and hopefully that’s understandable to you so on the left hand side here we have a a typical 4921 Transformer so we have two primary windings which is these uh coiled wires together here and then we have uh 14

Secondary windings now that’s the single wir here but it’s actually also here as well so the primary and the secondary are actually intertwined so so every time time the wire goes through the middle of the fair8 core be counting that as one turn so I’ll just count this one up so

There’s one turn two turn so that’s our primary and then if we count 1 2 3 4 5 6 7 through the middle 8 9 10 11 12 13 I’ve missed one out here somewhere but there is 14 there trust me so there’s 14 secondary so if we take four 14 and we

Divide that by 2 that gives us 7 and if we take 7 and square it so 7 * 7 that gives us 49 and that’s our 49 to1 and then on the right hand side here we’ an example of a 6 to4 64 to1 so we have

Three primary and we have 24 secondary so if we take 24 and we divide that by three which is 8 8 * 8 is 64 it’s a 64 to 1 so um you could could have say um uh four four primary uh four primary turnings and you could have 28 secondary

So 28 divid 4 is 7 7 * 7 49 to1 so there’s different ways you could wind a 49 to1 or a 64 to in different combinations of wire so if we look at the uh if you look at Ned halfway Transformer in a little bit more detail I just want to run

Through the components here um so we’ve got a a diagram and the real thing here so we have enamel copper wire or Magnet Wire more commonly known as here that we use to basically wrap around our Transformer or Transformers if they’re stacked uh we have a ferite core um

Typically we use uh 43 material but there is various different types of uh cores and materials out there we’ve got primary windings which are highlighted here in green you can see that they go no further they just go between the Earth or the the shield and um the uh Center

Conductor got the second the re windings are red um and then we’ve got a capacitor here now the capacitors I find I think it’s actually some of the most interesting part of the nid halfwave um and in quite simple speak the capacitor simply improves your SWR

On bands above 20 M so it lowers the s are and it also so then it gives you a wider bandwidth so you’re able to say get most of 10 m and so in simple terms that’s what it does is it also plays an important job in actually making the

Transformer more efficient so without it you’ve got a bit more of a lossy transformer where we’ get the the um Transformer heating up a bit um and from there we have an RF connector back to the radio that could be AO 239 it could be a BNC Etc

Etc and you’ll notice that we’ve effectively got a short u so a short at direct current um so if basically if you put a multimeter across it you would see a short at DC but because radio frequency RF is AC the the antenna it doesn’t see

That so I’m going to talk about some of the the basic components for the infed halfwave um so these are ones that I’ve actually used personally and you may see some pliers here some names but you know you could pick your own but and these are just examples that I found so you

Don’t need to go too big with your wire um so typically when I’m making sort of my 100 wat infed halfwave I’m using wire that’s round about 1 mm in diameter I think I’ve got 1.12 here I’ve also used 1.16 you can go bigger but it’s just

Sort s or sorer on your hands to actually wind um and you can go with a much smaller wire I use a 63 mm wire and this is lovely for like say small trp cores but you could go bigger or go SW depending on your application and

There’s some sort of uh things are recommended now um looking at um the cores the fite cores and these are by and far the most popular cores that we use uh in the Ned halfwave excuse me uh on the left hand side here we have a um an ft

14043 so the 140 stands for 1.4 of an inch and the 43 stands for the M the material you need to look at the data sheet to see what the composition is and I’ve got the sizes here as well as the the part numbers so uh as I believe it’s

Only a company called fair that actually make these cores and sometime there’s they’re branded as amadon I think it’s amadon yes but they’re all made by Fair right on the right hand side here we have a the Ft 24043 which is typically for running higher power um and that’s 2.4 in so generally

Speaking this is what we see and what people use now I spoke earlier about the capacitor and this is the one that I actually seen recommended and I would recommend it to you to use and I use this on all my infit half waves that I build whether they’re qrp or they’re

Running um a couple hundred Watts um this TDK capacitor is the one that I would recommend um there’s two of them actually one has got short legs one’s got longer legs it doesn’t matter which one which one you get because you’ve got to trim uh the legs

Anyway uh just a word of warning that um you see a lot of No Name capacitors on eBay um and and places like that Market online marketplaces so I would always go for a branded type capacitor um and I should have mentioned earlier but the spec of this is 100 P

Farad so that’s what I found it works for me typically you’ll see people using um so uh 100 or they may use 2 220 p farad uh capacitors um uh in series I think that yeah and that basically then that gives you0 so around about 100 P

Fared but that that can vary depending on the application so wire for your Ned halfwave um there’s lots of choices I’m going to give you three here uh I’m a big fan of this so beams wire um it’s very lightweight I use it for a number of antennas um it’s

Cross-sectional it’s. 22 mm it can be a little bit fiddly to work with um just you’ve got to be careful that when you’re stripping it um it it’s good for over just over 100 wats I think soab be rate it to 150 wats want to1 SWR so it’s

Really nice and lightweight so it’s ideal for your H for the S people people that want to do a little bit of walking hike and whatever but um it’s not great uh under tension so uh for a for a home installation if you want to put a little

Bit of tension it’s probably not the choice to go for the middle ground um and I typically go with this wire uh quite a lot uh this is TR rated cable um and it’s very common to buy from uh electrical wholesalers suppliers you can find it

Online and You’ have no doubt you’d even uh find it locally so this is good up to around about a kilowatt um and so this is 75 mm wire um and I buy it at 100 m spools it’s about uh I think it’s I think off the

Top of my head it’s about5 for for 100 m so it’s really quite good value again you can’t put massive stretch on it but you can put a little bit into it um if you really want want to go heavy duty um there is there is a number

Of kind of military style Kevlar core wires um and this is one that I’ve actually used myself personally and I purchased some antennas a long time ago so it’s a it’s like a looks like this wire actually looks like Shield of like the shielding of a coax looks like a tin

Copper but I think it’s maybe even silver coated and it has a a Kevlar uh Center going through the middle of it is extremely strong so maybe if you want to up like a a flat top or something something with a lot of tension this

Would be the word to go from and but by the time you get it it’s about a pound meter now the reason why I actually got into Ned half waves is I came across a video on YouTube um there a channel called evil layer electronics and they were showing a

Couple of couple of Transformers uh they were saying that there were a lot better and a lot less lossy uh than some of the some of the ones that we were currently using so that’s that’s what got me into it um so that’s what I’m going to talk

About next and this is actually just a selection of some of the cores that I’ve actually checked here um if I could have kept them all wound I would have done so but I basically run out of cores um and I couldn’t keep buying more couldn’t

Afford to keep buying it more right so you may be wondering why we would actually want to check uh the loss in a Transformer so again one of the things you hear people talking about is their Transformer actually heating up and their s SWR going High um and that’s

Because they’re getting some losses in the Transformer and eventually the the faery cores actually heat up uh they lose their properties and then the the Transformer stops working so in front of you here is a method I think it’s basically known as the backto back method and it’s a way of

Checking uh Transformer efficiency uh the good good thing about this method is um it doesn’t matter the type of Transformer it could be a 4:1 a 9:1 uh 49 to1 it doesn’t matter um you basically use I’m using I I use my Nano VNA and it’s a very cheap one uh I

Purchased it back in 2018 or 2019 2.8 in screen and and it’s done me Great Guns so you don’t have to spend a lot of money here so the block diag on on the left here you’ve got your your VNA so basically you take um signal out one and

Then you put it through a Transformer so this would be the high yeah the high side of the Transformer and then you feed it into the high side of another Transformer and these have to be identical um this is probably the downside uh of of this form of testing

Is that you need two identical Transformers so you so you the two Heights High sides together you then take out the low side and you put it back into the the VNA so you could maybe just about see this yellow curve on on the VNA here and

You’ll actually get a negative value on your uh VNA or vector Network analyzer and this is basically telling you the losses now because you’re checking across two Transformers you then need to half your losses so you need to bear that in mind uh there is another method um to to do

This I actually seen a video for that um just a couple of weeks ago there I can’t remember the the uh the call sign who of the of the radio amateur but um people have done some tests and it actually the comparison actually ties in with the

Backto back test so it doesn’t really matter which one that you do as long as you’ve got a valid method right so the fair right FT1 40 43 which we looked at earlier again um looking at losses of that so on the left hand side here this

Was what I actually uh checked very very this is the first comparison the first check that I did and this is probably the most common infed Transformer um winding style and after checking with the nanov VNA you could see that are efficiencies here on the face of it they look

Terrible but they’re not that bad um so you can see that across HF that we basically we’re just less than 70% but it’s pretty even the reason why I have not applicable on 80 M on some of these is quite simply I didn’t check 80 M um I

Should have checked that but at that at the time I wasn’t interested in 80 but I really should have checked I then tried some uh other windings so I looked at um the descriptions are here so instead of the windings spaced out I had them close together you

Can see that improved things I then tried a different type of 49 to1 so a 20 three primary uh 21 secondary that improved things on the lower bands but you can see it starts to fall off a cliff uh on 10 m and I then tried actually struggled to fit all this

Wire on but uh four turn primary 28 turn secondary um you can actually see what it’s done so for 80 M and 40 m and even 20 M it would actually make a very good infed halfwave Transformer but look what happens by the time you get to 10 m

You’re losing you know you put 100 wats uh your coax you’re only getting um 80 coming out at the other end of the Transformer so um we can do better I think looking at the 24043 I didn’t do a lot of testing on this um but looking on

The left hand side here again this is your typical infed halfwave and it’s actually not too shabby at all so for people that are running your kind of 100 Watts SSB or CW it’s not too bad at all you can see that I’ve got the key here

The key here um but it’s just what you want to to make that so again we’re we’re we’re over 75% 2015 we’re up to 82 10 m you know we’re 78 so it’s not actually that bad um a lot of people like to run more power obviously than 100 wats um and

That can be a little bit of an issue on the Ned halfway I’m not going to cover that tonight uh but if you basically take three of your two40 43 cores and you stack them um you can basically have greater power handling so like you could see here so from 160

Through 20 it’s actually a very efficient uh Transformer you won’t actually get much better than these figures 90% is roughly where it can top out or where I’ve seen efficiency topping out but if you look on again on 10 MERS you can see that the the performance again starts to fall off a

Cliff not terrible but starts to certainly fall off um and this may or may not add to the the poor performance thing on 10 m but I think that’s probably be more to do with uh uh the radiation pattern so can we do any better and I think that we

Can so the video or the the YouTube channel that I mentioned earlier so Evol Electronics uh actually had these two cores um and I actually purchased these cores before I did any testing so for the small core on the left here the 2643 625 002 so and then on the right the 26

43251 02 now the this Chunk on the right here there’s only a couple of grams difference in weight from a 24043 but so it’s it’s actually much the same mass but if you look at these you can see that they’re much chunkier so they’re taller um so basically the ratio

Of the height to width is is a little bit different from the 14043 and the 24043 and I think this is why they’re actually somewhat better this is the uh little qrp core here uh the 5002 core um and initially I thought I’d actually want to watch because the

First time I actually checked this we were up over 90% efficiency and I actually SE evil L he had actually done this so I thought well I don’t need to reinvent the wheel I I’ll just go with that I checked it and we had these really good low

Losses but unfortunately when I actually tried to set it up as an antenna uh I could not get a low s SWR on 40 m um it wouldn’t go when I set up the antenna either inverted V or inent inverted L My Chosen preference the SWR wouldn’t go

Below say it was like 2.3 2.4 to one which was really frustrating and I won’t go into detail but I tried a number of things I had a lot of people help tried to help me do this do that nothing really worked so I started playing about

With um some other windings which you could see here this winding here is really quite interesting I actually stacked two of these little cores together um and you can see that it made it very efficient on 80 M and 40 m but again on the higher frequencies it fell for Cliff on the

Right hand side here this 64 to1 winging this is actually the winging that I actually used for my my finished Ned halfwave um and again it wasn’t because it was the most efficient it was that compromise that I could actually get a low SWR um with the with the Transformer

So I wish I could have went with this one but unfortunately had to take that little bit of a hit but we’re still good we’re still you know pretty consistent you know and I’m using it 40 m up so I’m still over 82% for for all the bands so

I’m quite happy with that and it turned out a great little uh Transformer this is probably the core that most people will be interested in so this is the one2 core more comparable with the 24043 and you can actually get basically the highest efficiency that I’ve actually seen from a from from a

Transformer I won’t go through uh all of these but um you can see all the different configurations that I’ve done um um I even did a a seven term second yeah one term primary and a seven term secondary and you can see how bad it was but um again I had

The same problem that I had with the um little qrp core is that when I actually went with this winding here um I I couldn’t get a low SWR on 40 m um and I’m not quite sure why a 49 to1 wouldn’t work um but what I ended up doing was some

Suggested they say put an extra turn on your secondary and that’s what it did so two turns primary 15 turns secondary which then turned it into 56 and a bit something to1 so I just call it the 56 to1 and what that did was it really didn’t change the efficiency over the 49

To one really maybe even improved some of it um but what I actually did was it actually brought down the S SWR so it’s actually below 2 to1 as an inverted l in 40 m and it’s below 1.5 to1 uh as an inverted V so more than good enough and basically

This is this is probably my favorite Ned halfwave So and I’ve seen a lot of people actually doing this as well seen a lot of videos a lot on social media a lot of people seem to be going for this now and they seem to be sticking with the the 56 to1

Transformer so we have our uh efficient cores or sorry more efficient cores I guess uh I guess some people may may not think it’s maybe not worth a while but I C certainly think it’s worthwhile getting as much as we can uh uh from these Fair cores

Transformers so the qrp core I then turned it into this little Ned halfwave and I’ve got the $1 note for comparison um and it’s a really cute little thing I managed to find a little Hammond 1551 enclosure which was almost perfect for it um you can see these marks inside the

Case I had to take my drel and actually basically remove some of the material from here um and also from the matching lid so I could get the the lid to fit flush but this only weighs about 50 g 55 G um and it’s not expensive to build um

It’s maybe 122 something like that for the parts alone the problem that you’ll actually have as Postage and Packaging for the parts so this is obviously I use this 6 3 mm wire the core the same TDK capacitor uh the enclosure that I mentioned um I use M4 stainless steel

Hardware um I typically use 304 grade stainless steel um and I find that more than good enough for me you can go with 316 which is marine grade but unless you’re by the C I wouldn’t bother it’s not worth the extra price and I go with

A an anel BNC and I can actually buy most of this stuff from it’s usually Digi key I buy from and I can buy the BNC I can buy the enclosure I can buy the capacitor I can buy the little faite core and all from uh a Digi key I think

You got to spend about £35 plus that but say you’re a few few friends or a club you could actually do this as a club buy which would make it quite an an inexpensive build um looking at the bigger infed halfwave now I was going to go into this

Presentation how to wind the the Transformers and stuff but there’s there’s a lot of people out there that could explain this better than me so I thought it was better just showing you the components that have actually been using um to build these Transformers so I’ve used the 1.12 uh

Millim ano copper wire the one2 core and same TDK capacitor an RP 1044 enclosure I’ve used bigger stainless steel Hardware M6 typically I use M6 for anything other than the Cure P small stuff this yellow board in here this was a little project in itself I’d never designed anything in uh printed circuit

Board material so I had some people help me so it’s just a plain board but I had it I had it made by a Chinese PCB company these blank boards I had the holes put in them as part of that uh manufacturer and I was able to just

Basically cable tie the core to this you don’t need that that’s entirely optional um but it was just a nice little side project for me and this has an so239 on it and I I I favor the on eBay mme he has some good um good value and good quality RF

Connectors now something I’ve not covered is power handling and this is quite uh this could be quite a what would would we call evocative or not not evocative is not the word uh contentious subject here um with power handling and what different Ned halfwave Transformers can actually handle now i’ I’ve actually

Done some tests and I’ve actually done some you know sort of I would call F duty cycle tests so predominantly ft8 so these three on the left here the 14043 oh little typo here I mistake this should be a 24043 and the one2 core so I actually

Run these on fd8 and Rand them continually on ft8 until the the SWR just started to rise so that was when the core reached reached saturation point or something called cury Point Curry Point um when it lost its properties so what I found was the 1443

Around about 30 Watts if you’re on 30 watts and an ft8 for long enough so you’re what is it 16 seconds on 16 seconds off whatever it may be you you’ll start to uh any more than that and you’ll start to have the S SWR rise on the

24043 I found that figure to be about 70 Watts again if you’re run an SSP you run 100 wats no problem on it but it will depend you know it’ll depend on the number of factors compression so on and so on the length of your over L of your

Transmission now the one2 core um this will handle 100 wats ft8 for hours and hours on end um I know that ft8 is not a is meant to be a it’s a low signal mode it’s not a low power mode um but I actually had the opportunity to to run

100 wats ft8 during uh it was a contest so for 4 hours continuously I run ft8 100 wats and I actually didn’t use my radio for this I should point out I use my radio to drive my amplifier it’s not good running your radio radio that kind of power on on

Field duty cycle for long periods of time but this this this this core handled the 100 WS no problem and on the 502 uh qrp core I haven’t done any FDA on it but I have done a lot of CW and it will hand handle 10 wats of CW no

Problem at all so you know it’s going to handle that you know maybe 20 WS of SSB uh quite happily just a couple of pictures here I don’t actually have that many pictures of actually setups um so the left hand picture and the middle picture here I

Went on holiday last year I went up to the north of Scotland so this is uh uh near Dorn and this was actually the very first outing with this little qrp Transformer and my first Contact was actually into Brazil now probably more to do with the salt water than anything

But it was actually a thrill to actually work Brazil right off the bat with this Transformer and then I worked another another station in Brazil right at the back of it on 20 M so I actually had it set up as an avadel so I had some these

Are actually sand sand Stakes so I had my 10 m spider beam pull and this it was a kind of inverted L on the right hand side here again it’s hard to see but this has got the 100 W INF fed halfwave this is on a 12 M

Spiderbeam pole and you can see there’s a bit of a kink in it here and that’s basically runs down here uh and I’m running it as an inverted l now um you can use a number of supports to get your infed halfwave up if you’re

At home as I say you could put it on the end of your house whatever um but I am a big fan of spiderbeam uh Mass poles um I I held off for a long time before I actually purchased these um but now that I’ve actually got one and I’ve actually

Got the 12 and a 10 m I found that they’re they’re excellent poles they’re very heavy duty um and if you happen to break a section you can actually replace one of these so um certainly worth the money if you’re able to save up for one of these I would certainly recommend the

Spiderbeam polls for for for any um actually any sort of amateo application for that matter so there we go so I hope you’ve en enjoyed that um I’ve probably not covered everything I wanted to cover um and if you’ve got any questions I’ll do my best to answer them back to you

David thank you very much Colin yes we’ certainly got a few comments and questions for you so that’s no danger and do take the opportunity to have a a quick drink as well uh lovely presentation complex subject but we’re as you know we’re aiming this for beginners so there may be terms if

You’re watching this that you don’t understand or anything and that’s what this is all about so please don’t be afraid to ask that or any other questions or comments if you haven’t already asked them please ask them now and don’t forget your name and a call

Sign if you have one as well on each message and I’ll try and read as many of those as I can to Colin um Colin I mean the infed halfwave as you say it’s sometimes as mixed reviews I use one personally and I think it’s really good all round antenna and and

Ideal for people who maybe as as well we’ve got who are in areas where um a mast and and formal antennas just wouldn’t really work is this a sort of your go-to antenna now yes certainly it’s certainly on my list for working portable um so when I

Was first I was first licensed I still stayed at home um home with my and Dad and they had a quite a big Garden so um I was able to put up quite a lot of different antennas but where I live now you know it’s your typical Suburban

Garden so it’s very difficult to to put up you know big antennas beams or anything so I I do enjoy putting up the Ned halfwave um I quite running it because of where we are in the solar cycle um I like running it and because I

Have a young daughter as well I can’t have permanent setups all the time um so basically I quite often I’ll go and set up my spider beam pole in the garden I’ll set up maybe 5 minutes um I’ll put the Ned halfwave up it and then I’ll

Operate for a couple of hours um and then 5 minutes to take it down again so it’s quite a versatile antenna um but you can just use it for you know any band you want so you don’t need to put up this you know even like the full 66

Ft or or uh even double that for 80 M the big long length of wire if you just want to run say 10 m for example great time to be running 10 m you could just do that with a with a halfway for 10 m

Which is which is not a not a big piece of wire yeah indeed and uh dare I say if you choose the color of the wire carefully as well it can be even more disguised in AB background can’t it um let’s let’s read some of the questions

And comments to you firstly um the first one’s from Paul Green is there any advice on how you tie off the antenna wire at the end uh in other words do you expose the inner wire when trying tying to a dog bone which is one of the insulator types is any hints appr

Appreciated he says you you can try I I tend not to worry too much about that um ideally if you can yes but normally I just tie off a not I don’t actually I was looking to see what I have one handy here but normally um I was looking for my so beams

Wire but yeah so there’s some of this wire here but normally I just tie off and a not I don’t worry about it too much um typically I’m working portable so it’s never out in the elements for for that long um something that’s quite good is something called uh liquid

Electrical tape um and you could take a little dab of the stuff and just put it on here and it’ll basically suck in and basically seal up uh the wire um or you could use a little bit of adhesive or glue Lin heat shrink a little bit of

That over the end um so it doesn’t feel and just basically squeeze it and you can seal your wire off like that so there there’s a couple of ways you can do it but I don’t worry too much about about it if I’m perfectly honest so not

Really critical you can just tie not at the of the day all right y I think one of the by the way one of the wonderful things about this is we’re all used to seeing quite amazing Rigs and things that we don’t probably stand much of a chance of building but antennas of

Course is one of those things that most of us can build as you’re showing us tonight um and you know I’m always telling people that you know you you tend to think about the radio and the mic and and things because that’s the bits you see in the shack but actually

The bit that’s up in the air is probably the most important part of your radio station do you agree oh absolutely um you know yeah I I fully agree and I I I don’t I don’t have a lot of I haven’t personally invested in a lot of big

Radios not that there’s anything wrong with that but I think it’s always better I mean I look about my garage here and so for sort of the last five years I would say I’ve went to say that as far as as I’ve obsessed in building antennas and it’s just a thoroughly enjoyable

Subject and as I say I’m not someone that comes from an electronic or a radio or an RF background so it’s really something that that anyone can do yeah um I touched on it there yeah where we are in the solar cycle you don’t need to put up anything too extravagant to to

Really Work the world good good advice uh Paul Temple has asked a question any tips for keeping the SWR dip midband across 40 m to 10 m when I cut for phone segment on 40 m i get dips on higher bands moving progressively away from mid even with a capacitor he

Says yes that that that this can this can be an issue um I wasn’t going to I don’t have a massive experience this but I have I have experienced it’s all about looking for a happy medium um so depending what type of radio that you’re

Using and typically if I see an S SWR of 2:1 or below I I tend not to worry an S SWR of 2:1 is 11% loss so I I really don’t worry I used to be uh pedantic about it and try to get it as low as possible but

Unfortunately you can’t do too much what some people H do do is so say you have your Transformer say 2 or 3 MERS from the Transformer up some people actually put a brake in there and actually put they can put a a capacitor in there or

They can put an inductor there so a little Co coil of wire a few turns of wire so you could try that I’m not I can’t remember off the top of my head which way it needs to go so say 2 m up from each Transformer if you wind say

Three or four turns um a little coil what that will do is that that’ll actually shift that um s SWR dip and it shouldn’t really affect the higher bands so that’s one way that you could actually look at perhaps moving that um but again it just depends all cores and

All in half waves can be different just just depending um but there’s things you can do out I’m not an expert on that but certainly a capacitor or a or a a little coil or an inductor just close to the the Transformer can sometimes work just to shift that yeah just experiment then

With that thanks over on batc now Peter G8 ckb first he made a comment um and I’m just going to try and address that he said I’d take you to task over the chokes that you credit to gm3 he repeated introduced himself introduced them to radcom readers but they come

From an article published by Chuck w 1his well this isn’t really a criticism of you and obviously Ian isn’t here to defend himself either so I just thought I’d better mention it though because uh Peter has brought it up and I mean one of the difficulties I guess with all

This sort of thing is who invented thing who’s what first but but anyway acknowledging what you say Peter and I’m sure that um if you were to contact umg M3 then he’ll address it but anyway he comes back on something else as well he asks why you do you use a 3 kilovolt

Capacitor because he says 500 volts is more than enough in a 500 sorry a 50 ohm system absolutely um just because that’s what was easiest to get a hold of and I haven’t done a lot of experimenting myself I’m honest you with with capacitors so I’ve seen seen other

People testing these tdks um they’re very very cheap they’re easy to get a hold of so just quite as simple as that but he’s absolutely right um 3kv is is actually Overkill 500 volts would be more than enough and uh if you can get a a decent um brand

Capacitor 500 volts that would be more than ample sure although I guess it’s good to have a bit of headr room of these things and um as you say they are some capacitors which aren’t labeled um I tend to use branded ones as well and I think the last time I bought something

Like this for an nfed halfway that the club did earlier this year was about 40p something like that so it’s not a huge cost really these these cores I want to talk to you about because um I must admit I’ve tended to stick to the fair right ones the ones you’ve mentioned the

240 and 43 um that g0k a ya Who You also mentioned earlier he’s a member of our club and Steve um tends to use that there really is a mixture and one other one tip if I like to might you don’t mind me sharing with everybody watching

As well is that when you get a collection of these things it’s very important to label them when you get them because otherwise you won’t know what they all do and they all look the same unless you’ve got some very specialized test gear I guess you’d

Never know how to identify them do you agree with that absolutely and I actually have some um they’re not mine I to send them back but I had them sent labeled to me so I have some ft24 43s um and they’ve actually labeled 43 but I also have ft24

52s and these are absolutely identical um so if they weren’t labeled up you’re absolutely right um yeah so I’m lucky that I don’t have like the the the the the cores I recommend these are the only ones I have so I won’t mix them up but

Certainly the 140 and the 240 size it’s very easy to do that yeah just a little tip anyway Ian Monroe comes and asks a question now winding M impedance matching Transformer which you covered earlier on in the talk as the wire is wound from the bottom of the diagram

Turns progress clockwise around the core after the wires cross over wire crosses over why are turns added anticlockwise it it it can actually a lot of people do this basically to suit where you actually want to have your antenna Point connection you could just wind The Wire around the core if you

Want to um I’ve done on the experiments I’ve done they call that the crossover so it doesn’t really matter as long as it goes through it but um as I say I’ve done both you can do it either way but depending on your um on your on your Transformer and what

You end up with you can see that I’ve got my antenna connection here so I don’t actually have a crossover here you can see that I’ve just started winding and it just goes all the one way but say I had the antenna connection on the on

The top here if I put in the crossover I could then bring it up here um and with this core it wouldn’t actually make any difference to the efficiency of the core um if I did the crossover or not so a lot of it can be down to personal

Preference yes and um in fact g0 fvt came back um to Ian as well and just said that he he reckons that uh to continue this the same way but the crossover is there to reduce the effects of end capacitance which must make a difference as well

Yep yep um as I say this this is this is where it almost uh gets me a little bit stuck because I have an Electronics background here um but that’s that’s that’s that’s certainly how I understand it there and I think that’s also part of

The the uh what the capacitor does and I think it it kind of counteracts some of the the leakage inductance there that that can be with and with the Transformer now earlier on you mentioned the use of a a nanovna to do the testing and I’m sure many of the beginners

Watching this in particular may not have heard of one or if they have they wouldn’t know how to use one or whatever I thought I’d just look it up because I know that on tonight to 8 a couple of years ago we actually did a a talk about

The Nano VNA it’s a very useful bit of test equipment but it can be a bit daunting it’s only about 50 or so roughly isn’t it but it can be a bit daunting to you so if I may I’m just going to mention that um if you want to

Look back at the tonight date webinars page of the rsgb we’ll give you the link at the end um and have a look at the 12th of April 2021 then we covered a talk by Alan Wy um all about how to use the nanovna because is a really useful

Bit of equipment not just to test the SRS but other Effectiveness as well of Transformers isn’t it it can do far more than probably what I’m actually going to do with it but I I’ve been amazed what I could do with the the Nano VNA but what I think it

Does have a a very sharp learning curve with it but because there’s so many of them out there there’s there there’s videos Galore on YouTube and that I’m I’m I’m very much a visual learner so once you get the basics with the the the Nano VNA and the critical thing what I

Found is uh I think you you need to do is you need to ensure that it’s calibrated correctly and it’s calibrated correctly at the point of use so if you have a little bit of coax on there you need to make sure that it’s calibrated at that point with the open short and

Load and but it could it could do so much to nanovna um mine as I say mine was quite an early one but I was able to update the firmware in it which brought it up to date um even with that tiny 2.8 in screen you know I could hook it up to

The computer um but yeah I can’t say anymore and that it’s a fabulous little bit of Kit and it’s certainly well worth buying even if you don’t use it or don’t use it a lot um there will come there will come a point where you say oh I

Could actually check that or or I wonder if I can do that and then you’ve got the you’ve got it there to do it yeah absolutely thank you um I’ve got a a message now a question which I think you partly covered I’m just trying to find

It now was a I’m afraid I don’t have a call sign and the name on the YouTube account is squeaky toy killer and me anyway the question was is stranded copper wire better or or one solid core better I know you were quoting stranded 702 once earlier what do you think is

Best for antenna wise like this um I I think it it’s got to suit your uh suit your application um personally I like to use a stranded just because it’s more flexible and but RF actually tra RF I mean that’s I suppose that’s one of the funny things for RF

And I didn’t I only learned this not too long ago the RF only froze on the outside of the wire and not through it and but it comes down to personal preference I do have um what they call hard drawn I’m looking about hard drawn copper wire which is basically this

Magnet Wire and it was like pre-stretched wire and I used that for a number of years and that was an excellent antenna wire so it really suits the application but for me I’m working portable even at home here effectively I’m working portable so I’m putting antennas up putting them down

And when you have a solid wire um it’s not conducive to bending so uh if it’s for a for a for a permanent installation it’s good um but if you need that flexibility in The Wire it’s it’s as I say it’s not so good Str it a bit better

Okay um useful tip here from Paul Temple who says that farite which is the manufacturer of the toroids um they have a video on a identifying toids so that that might be very helpful if you’ve got a a box of these I mean I often see them

At rallies don’t you you often see radio rallies with boxes toids and no identification on them but be be aware think and I and I think that’s something that you’ve got to be aware of even when you’re buying them I think you know sometimes it’s difficult to know what

You’re actually buying because really if we were buying a 240 43 is it 43 is it 31 material is it 52 you know we’ve just got to trust them um but um it’s another good thing if if if you can afford it and you could maybe even get from some

Of the some of the companies you know basically you know what you’re getting and maybe you could Club togethers I see I typically buy from Digi key so I basically save my pennies for a few months and I I basically get the order over £ 35 Plus the vat which is near and

Up near 50 and I I put in an order that way least and I kind of a bit more sure of I’m knowing what I’m getting yeah as you say club together with some of your friends Neighbors at the club um Tim G5 TM asks would the 100 watt Transformer

On FTA cope with the currently legal limit of 400 wats SSB uh I don’t think so no um I I I um when I did that test I actually went out and actually was was checking the Transformer and it did get quite warm so in short I I can’t give a concrete

Answer to Tim but um no I don’t think so I think we would need to go with something else and that is the the uh the problem with Ned half leaves is for running Q running running high high power um there there isn’t a a core like

This one2 core which is great and nice and efficient right across HF there doesn’t seem to be a core existing for the same for running higher power um obviously us as radio amateurs are relying on uh commercially for these cores being available um but yeah maybe someday we’ll discover one or they’ll

Dis discover a combination of cores um if you just want it for like a spot frequency and I think that would be easy enough to do but um certainly not you won’t find one that’s efficient all the way across HF or 90% efficient all the way across HF um but U perhaps someday

We’ll discover something yeah um uh gz F says that PTFE insulated wire is good for RF work because it has the conductors silver plated generally um yep and uh ad G6 ad asks a question do you prefer the end fed half wve over the adjuster wave Colin that’s

A new one on me ad just you know what that is yeah that was an antenna that I came up with a long long time ago that um it basically just a variable length uh quarter wave that was on a on fishing reels that I can adjust in and out and I

Actually can do that with here I’ll just actually just I’ll grab it oh I love the name by the way adjust a wave Pat almost I think no no as I say it’s for anyone anyone so what you’re actually look at here is the 100 W INF halfwave

And you can see there’s a fly fishing reel here with wire on it and basically there’s a reel here on the other side so basically I run it up to a pulley and back down again so I can basically just adjust this for Whatever frequency I

Want to operate on I love it I love it so is fishing another hobby of yours by yes yes I did yeah fun funn enough that was how I was able to to basically Source those but answer to add’s question so um in simple terms yes

Because I think that a half wve beats a quarter wave and it has the benefit of not needing radials but it’s horses for course isn’t it depends what sort of convenience that you want but if you said give me an adjusted wave on 20 M or give me an N half wave

On 20 M I would take the NIT halfwave right and there we are and that’s a probably a good point to end I think we’ve covered most of the questions from people lots of lovely compliments for you you’ll be able to look at them yourself Colin as well on YouTube

Afterwards and on BC I’ll just pick a couple out Steve M1 St says a great summary Colin uh nfed halfwave is my favorite for portable quick and easy to set up in a park and Summit and Graham G8 NWC says great presentation on a popular antenna for many used for many

Portable operations and can definitely recommend Collins little qrp version and a great project for a club construction project absolutely Colin thank you very much indeed for tonight’s talk I’m sure you’ve inspired many people to give it a go antennas is definitely something that you can make yourself and this is not

Something that’s going to cost a fortune either um and something maybe ideal to make on these cold winter evenings thank you very much indeed for definitely thanks thank you thank you there we are and that does end this webinar and thanks once again to Colin Summers mm0 opx and thanks also to the

Team who helped put the series together behind the scenes the rsgb annual construction competition is now underway and incidentally includes a category for beginners the competition is judged online so you don’t need to send your projects away and you have until the 1st of March 2024 to enter for full details

Visit rsgb g/c construction dcomp or see the latest radcom for more information and next month’s tonight date webinar we’ll be focusing on radio construction and the construction competition so I hope you’ll be able to join us for that and if you’d like to see details of our future webinars or watch recordings of

Previous programs in the series please visit rsgb dogwear where you can also send us comments and feedback and if you subscribe to the rsgb YouTube channel you’ll be notified of all upcoming tonight to dat webinars as well as other new videos and presentations from the society on a wide range of amateur radio

Topics until next time this is David g70 RP signing off and clear [Applause] bye-bye [Applause] Oh [Applause] [Applause] [Applause] [Applause]