R-32,
A 160M NVIS antenna probably should be up around 40' - 60' for better results, ie, more ground loss if you get to close to the ground. (15'-25' for 75m, 7'-15' for 40m, since
the actually ground can vary by soil type, water table, etc.. its not really critical.)
To low heats the worms up and wastes the RF, the antenna will tend to use less
wire due to ground capacitance and also will be more widebanded,
ie, you find yourself trimming off 3' (160m-75m) at a whack when tuning and end up
scratching your head about how your calculations
for the wire length could be off that far.
Since I don't have any biological antenna supports (aka, trees) handy I just strapped some unused fence rails (18' lodgepoles) to the fence posts out in the back pasture.
Then since we have lots of baling twine around I used those for the insulators. Basically laid the wire out, looped the twine over the wire, tied to the top of the rails/supports before
strapping to existing fence posts. Leave the twine kinda long and you can just spin them to tighten up the wire. I ended up using 7 supports. Had some RG-8 handy that the dog had chewed an end off of so just stripped it back a bit more, then wire nut attached each side of electric fence wire to shield
and center wire. Used the twine in about a 12" loop to strain relief the wire/coax
connection. The baling twine is free so that is what I used for insulators. I run that coax to
the radio room and into an antenna tuner so that I can use it multiband without damaging
the transmitter. Not the most optimized set up but it sends a decent signal out.
Gooches law: 'RF gotta go somewhere'.
hereOh, might want to put a neon bulb across it and a good 10K - 100k resistor to ground to
drain the static charge. Heard something arcing last winter inside the antenna tuner.
Let me tell ya.. When you disconnect the coax to see whats arcing it will give you a hell
of a jolt off of snow static and wind charge!
heMy inverted V/ fan dipole for 75m/160m is a little higher and seems to be heard a little
bit better. Center of that is at 35' with the ends at 12' off the ground.
By the way a fan dipole is a great way to go multiband without a tuner.
Just attach multi dipoles to the same feed point. Offset them a little bit (5'-20') when
you string the ends out so that they don't interact as much when you trim to frequency of
interest. Oh, and a 160m dipole works great at 17m.
For receive only a beverage antenna is the cats meow. With the correct tuning circuitry
you can even make them directional with steerable nulls. Takes alot of wire, mounted out
of the path of critters like deer (8' high should do it) So if you have an existing straight
run of fencing you can run it along the top of the fence. I am (back burner project) going to cut some pvc pipes about 5' long and slip over the top of an existing barb wire fence
with a run of electric fence wire on top of that. Our house is sorta in a corner of a 25 acre fenced in property so should be able to run 1000' n/s and e/w. Going to make sure those
buggers have a -really- good static drain and disconnect outside of the house.
A beverage antenna works on the principal of being multi wavelengths long, since the
speed of rf is slower thru metal then free space (velocity factor) you end up with an averaging effect so that fading of signal is not as noticeable. I used to be into VLF, LF and MW DXing and have a little bit of esoteric knowledge for lowband receiving, emphasis on the little bit, some of those MWdxers are -really- into listening to some 25W station in the middle of Mongolia, sometimes you get about 45 seconds when the conditions are justttt right to hear and ID the dx station.
By the way if anyone over on that side of the ridge wants to experiment with the lowfer
band I would love to take part.
Lowfer band is an unlicensed band at 160kHz-190khz, multi mode (usually build your own)
1 Watt transmitter with 50' max wire. Sounds hard but +1000 miles is possible.
R-32, just hook that fence up to your radio and see what you get.. I put two strands on our fence so I can disconnect one and use it if I want.
A SGC237 autocoupler would probably do the trick for multiband use.
That tuner worked quite well in Uganda with full wave loops for missionary NVIS comms
when I install some hf systems for WOMF. They were resonant antennas and did not
need a tuner but I wanted them to have the option of going clandestine and using the whole hf band if needed as some of their folks were in Sudan had need to be sneaky at
times. Pretty much install and forget as they take care of mismatches automatically.
height=8
Quoted: Start talking about your set up above.... I have 5 acres, and LOTS of this electric fence wire. I also have it set up all along all of the fences on my property, I was thinking about trying to use it for something. The stuff that is up right now is no longer hooked up to the hotbox, but it is still hanging about 4' off the deck.
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