More Notes On The NVIS HF Antenna
Just saw the new NVIS Ant article – looks interesting – I’ll have to try that (smirk!).
Some notes on it –
Any horizontal ant within ~1 wavelength of ground will have strong interaction with the ground. One effect is the ground ‘loads’ the wire, so that the resonant length is shorter than if it was up in the air. The one I had in WY was resonant at 3923 KHz (the nightly WY net), and about 7% or so shorter than the math gives you. Depends A LOTon how moist the ground is. Also, keep the ends in the air, not on the gournd.
Mine in WY had the wire cut for resonance at 3.5 MHz, and I wrapped the ends back onto the main wire for higher in the band (like 3.923 MHz). This makes it even shorter for resonance, and doesn’t seem to hurt the radiated signal much at all.
I was originally prompted to try this by the attached article I found several years ago. [SEE LINK BELOW] is my idea of heaven. The pictures are worth studying.
In the 1st pic is a VERY low 40m loop, called Loop on Ground (see https://kk5jy.net/LoG/ ). Strongly depends on ground moisture content (dry is better – remember how dry WY was?). To the far left is a pole that is one end of a low wire ant. Note your Cobra Head (!) in the loop right in front of the tent. The other coax towards you goes out to an ant in 3rd pic.
2nd pic is the beloved Falcon-II 150. (God Bless Harris). Note the BNC adapter (doubt that is standard issue – but shoud be), and the ground wire from the GND post to a rod in the ground. And of course the field log and dogbone!
3rd pic shows a good lookin guy (man, I need to lose some weight) with probably 80m/40m low crossed dipoles on a tent pole mast. GREAT antenna – the mast is NOT ruck-portable – but a 15-20′ tree will work fine.
4th pic shows what I took to be a low dipole (maybe 50′ or so long?) with a reflector on the ground. In the air is another dipole, barely visible – center looks to be in the tree by the Luxurious Accomodations.
These are ALL ruckable wire NVIS antennas, made by hand – NOT Mil issue. God Bless these guys, and Bless them again for sharing.
Bless you sir, and Take Care – keep doin’ what you’re doin’ – we need it.
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Can’t download the PDF. Says not authorized
Ken
We are working on fixing this. Should be fixed early this coming week.
5
Links working now, thanks