Yesterday I had my first connection with Lars, SA4BLM on 80m in cw. I’m still surprised how far you can go on 80m with 10W around noon, over 1000km.
Certainly this is only possible if your chaser have a very quiet reception area. Lars also has a Beverage antenna, another advantage.
I use a normal 20m long EFHW with a 1:49 transformer and the 9m long coaxial cable as a counterweight. The atu in the KX2 easily adjusts the gross mismatch at 3.5Mhz.
With this solution I have been able to work regularly german stations, such as Fred from Dresden, DL8DXL, Michael, DJ9BX, Michael from Bodensee, DJ5AV and the reliable chaser Fred, DL1FU.
Hi Christoph,
Indeed 80m can be magic. Let me tell you about my best magic 80m experience.
From ON to W5 on 80m in cw with 500 milli W. Antenna 20 m long endfed antenna, 3m above ground, endfed was 0,3mm/0.3mm copper wire (Kupferlackdraht). QSO was greyline dx. QSO was NOT a SOTA QSO I answered a cq from the W5 station.
73
Patrick
Hi Chris,
I found you on 40m when you made your very last QSOs, but you were up and down in the QSB, sometimes dissappearing and barely copiable at some other moments. I waited for a good moment but I suddenlt saw your 80m spot
I went there, just in case, but I didn’t hear other thing than noise.
Lars beverage is a great help for a clean RX on that band.
My antenna was an inverted vee home made bazooka dipole with the appex about 14m up and the ends about 5 meters a.g.l.
I hope for better luck next time.
73,
Patrick, what a big fun. Your aerial wire was very thin. But it works, I know.
My wire for Sota activation is a DX-Wire UL with a nylon core and only 5 of 0.1mm Cu . A 20m line has a resistance of 1.1 Ohm. But the Cu is wrapped around the core, thats the trick.
Yes, 20m finally played the ball for us.
I feel fully recovered for the first time today after my 3rd chemo last week and I’m thinking about a possible SOTA before the forecasted rain arrives. But it’s very windy and I’m hesitating…
Perhaps a bit later, at around Noon and the begining of the afternoon.
Looking for more S2S with you and many others.
73,
My immediate gut reaction is there’s not enough copper! I use either 26 x 0.1 or 13 x 0.1 wire. Obviously it works but it does appear to have significantly less surface area than the wire I use and it feels counter-intuitive. I wonder what the resistance is like when driven with 10 or 14MHz not DC?
This is very interesting, especially when taking into account that your EFHW antenna was in reality lambda 1/4 long and therefore employing a low impedance.
Did you bridge/bypass your 1:49 broadband transformer?
Anyways, this also shows that in general the conditions are more important than the efficiency of the antenna, at least on one side of the QSO-partners.
Indeed. Years of engineering has taught me that when something seems wrong it needs further investigation. Normally these investigations show some kind of user errors or assumptions were not true. Or that the theory is wrong.
I see Stephan saying it’s 6 x 0.25 not 6 x 0.1 which will make a difference.
I am a long way from being convinced that this calculation is even approximately valid when the strands are in close proximity and indeed touching each other. The current won’t flow independently in each strand. I would have thought that the perimeter of the bundle as a whole would be what mattered.
I’m using the Sotabeams lightweight wire with 7x0.2mm tinned copper.
The very simplified circumference would be:
0.2mm * 3.14 = 0.628mm * 7 cores = 4.4mm
20m wire has a resistance of 1.76 Ohm, a bit more than the DX-Wire UL, which corresponds pretty well with the increased diameter compared to the Sotabeams wire.
The strands of the DX-Wire UL are wound around fibers of Aramid (to improve tensile strength), which also helps to increase the surface on RF.
Both wires are tinned and that’s where most of the RF flows, which is about 6 times less conductive than copper, but does not oxidize that easily as copper.
To me, a further improvement to increase the circumference for RF would be to insulate each stranded fiber with some sort of coating. Probably not easy to solder nicely. I checked the expensive antenna wires products from DX-Wire, but they don’t seem to sell this kind of wire. Probably hard to find such wire that should be also light and easy to wind.
