This is just to say, hey, don’t be alarmed by the size and weight when you get your hands on this “bigger” ferrite core, hi.
Speaking of coupler weight, the wind load and mast stability are also not to be forgotten …
BTW, The built-up impedance couplers with the “smaller” ferrite core (1:49, 1:64 standard, 1:81) have not only proven themselves for me for several years, but also for my SOTA colleagues HB9BIN, HB9CBR and HB9IIO.
I’m only suggesting the 10g one in your picture - I’m sure Andy will manage that 
The weight is no problem but that postage from Mouser is! Well unless I can get the order up to when free delivery kicks in. 
Fraser, thanks for pointing out this video. Well done and good efficiency comparison. Even if the difference is maybe only 20%, I prefer to radiate the difference in power instead of heating the core. I think this is one of the few videos that doesn’t repeat the old myths but measures and shows data.
Unfortunately, after I commented his interesting video, my comment got censored. Google’s AI seem to punish longer comments, even if the sentiment is positive. Fortunately, we don’t have such “clever” AI on this forum 
BTW: I had to redo the two wires of my 7-band EFHW, because after about 250 activations, the Sotabeams wire broke intermittently. No visual indication where it was broken, but according to the SWR values, it must have happened somewhere around 10m length. It’s amazing how relatively well even a completely detuned antenna with only 1 W power (because of the final protection) still works. And since I don’t have stronger wire that light and well visible (e.g. NOT black), I used the same new yellow wire again. Let’s hope for the best.
73 Stephan
I have made about 10 antennas using the Fairrite 2643625002 toroid, all with great success. Mostly used with KX2 / 3 and G90.
Malen
VE6VID
I strongly recommand the DX Wire UL. No issuse in hunderts of activations.
Best greetings Stephan
Chris
I did not have the same experience of DxWire UL. The Black insulation does not like low temperatures and cracked badly. After about 6 Sota activations in the winter time the antenna wire was junk and ready for the bin!
Since then I just use surplus PTFE wire from ebay, much tougher at any temperature.
Its possible I just had a bad batch of wire. I have other types of DxWire wire and been good, including my home 160m T which uses a DXwire stainless steel cored heavy duty Litz wire.
73 Gavin
GM0GAV
Had made the same experience some years ago. Now DX Wire has improved the UL. I have mine 2 or more years and it looks like new.
73 Chris
I’m using simple plastic isolated braid 0.25 mm the whole year for the last 6 years. The only problem was a break at a crimped terminal, failure from crimping.
73, Ludy
Thanks Chris,
Yes, I thought about that as well, but when I got a 22m long piece of DX Wire UL about two years ago, there was a written note included that the wire should not be kinked or it will break. Apart of that, I really like to see the wire (and other stuff) outdoors, but black does not show much contrast.
@GM0GAV PTFE as insulation sounds good to me, most likely better than PVC. Do you know of any concrete product on eBay or elsewhere?
73 Stephan
There was stand in the flea market at Friedrichshafen selling 25m lengths of PTFE covered wire for €4.
This supplier is in China so should be no problem shipping to Switzerland.
https://www.ebay.co.uk/itm/274005190163
This one is in England but says posts to Europe
Thanks a lot to both of you for the information!
@OE5JFE probably good quality and therefore pretty expensive for 20m of 0.75mm2, but it would be too heavy anyway. The diameter of the Sotabeams wire is just right, but I wouldn’t mind if it would be slightly thicker.
@MM0FMF I will investigate about these products, but if one has long term experience with a product, that would help a lot. When I was in Friedrichshafen, my wire was still OK. But anyway, the new wire that I mounted a week ago should be fine for the next two years. The junctions, especially the soldered ones are still more brittle…
73 Stephan
I use it for transformer / balun windings. It is probably to heavy and expensive for antenna wire. But it came to my mind.
That would be it for me difinitively! My SOTA antennas are made of yellow insulated 0.14mm² (AWG 26) stranded wire.
It’s light, small - and yellow is visible in undergrowth and scrub.
I do that too.
By the way, PTFE cables of usable length can be found in old electric cookers with ovens. It’s worth taking the side cutters to the recycling centre.
73 Armin
Stephan,
as Andy suggests this one at £25 delivered for 100m is a good deal. Although I have not used this one, it will be perfect IMO.
https://www.ebay.co.uk/itm/134125411437?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=_RdlLXL_QH-&sssrc=2047675&ssuid=UdwHQ_lXS--&widget_ver=artemis&media=COPY
I have mainly used this one, really excellent quality - very tough and does not kink.
https://www.ebay.co.uk/itm/393268010319?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=43PxUDIuTFe&sssrc=2047675&ssuid=UdwHQ_lXS--&widget_ver=artemis&media=COPY
Its more expensive, but if you contact the seller they will cut to length you need and give you a good deal. I imagine postage to Continental Europe would be reasonable, it was always just sent to me by regular post in a padded envelope.
I have just inspected my 9m antenna made of this wire, used for almost all my activations 2017 to 2021. It looks like new, being PTFE it feels very slippy. See picture.
73 Gavin
GM0GAV
Gavin, thanks a lot for your feedback!
I put some of my observations together, in the hope it may be useful for somebody else.
Yes, this is definitely a good deal, probably because of stock clearings. A local Swiss distributor asks for more than ten times this price! Its from Habia, a German cable producer.
I checked their spec. sheet (https://www.habia.com/globalassets/documents---downloads/single-wires/single-wires---ptfe---ee.pdf) and my conclusions are:
Yes, this one looks also interesting. It’s not silver plated and has only 7 strands, but it seems also of high quality. The producer is Nexans from France.
I found a spec. sheet at: https://www.farnell.com/datasheets/319605.pdf.
On page 90 you’ll find the different versions.
Yours is the KZ 05 - 06 (22AWG). It’s also a bit on the heavy side (6.2g/m, nearly double than the one from Sotabeams), also due to its thick insulation.
Both the AWG24 ones, the KZ 05 - 05 and the KZ 04 - 05 (thinner insulation) would also be high quality and light alternatives.
Just to be clear: basically any wire will do the job, but I like to look for the optimal solution, that I really don’t need, since I still have enough wire from Sotabeams that does its job perfectly (until it breaks). Of course, I would test one or the other wire for robustness in the field, its expansion over time and find out its velocity factor by experiment, which is fun.
73 Stephan
I weighed the wire I bought in the rally on the kitchen scales and it is approx 6g/m It does feel heavier than non-PTFE cables. I think a big contributor to the weight is that PTFE has a density of 2.2g/cm3 versus 1.1g/cm3 for PVC.
I was sufficiently interested in this article by KW4TI that I built one. I have little motivation to build any other combinations of EFHW transformers to compare it to.
Yes, the density of PTFE compared with PVC is definitely on the heavier side, but depending on the designed withstanding voltage, the insulation might be thicker as well (e.g. the KZ 05 - 05 vs. the KZ 04 - 05: 600V vs 250V)
If I interpret the information correctly, the voltage breakdown for PVC is about 20kV/mm and for PTFE between 20-80kV/mm, so in general PTFE should not need such a thick insulation like PVC to withstand the same voltage breakdown.
I’m less concerned of the additional weight of the wire to carry, but the sagging and the wind resistance of the thicker wire diameter. Usually I carry 2 different EFHW antenna wires that sum up to about 33m of total wire length. So the weight of Gavin’s wire, compared to the one of Sotabeams would only increase the weight by about 110g.
73 Stephan
