80 meter under-eave loop

[K3WEC]

I am contemplating putting up an 80 meter-ish loop under the eaves today.  I will be using 17 gauge aluminum electric fence wire because that's what I have.  I will also be using plastic electric fence standoff insulators which are about 1" in height.    This will be fed with 450 ohm window line to my manual tuner w/integrated balun so I can play around with it as a multi-band. 

I've read numerous links and articles.   I understand the limitations and compromises.   It will be a very low antenna, NVIS.   I'm totally fine with that on the lower bands.   I have no idea how the RF will play with the house wiring and devices nor how the house wiring will play with noise until I try. 

I'd like to know if anyone is actually using this type of setup at present and how it's working.   

[K3WEC]

Another question.... will there be any effect to the antenna if I wrap the wire around each insulator standoff for the purpose of pulling it taught between each standoff?   In essence I'd have a one-turn coil at each insulator.

[KB3ONA]

I used to have a loop running all the way around my house under the eaves and it was a full wave on 40m. I also had an SGC auto tuner in one corner. It worked but not too well. I live in the Phoenix area and had a very difficult time reaching people on the MARS nets within 200 miles. I believe there were a lot of loses due to it's close proximity to the house/stucco walls. It did work on all bands though and I managed to make a few contacts. After a while I got frustrated with it and installed a folded dipole along the side of my house (1/4 wave on 80m) at 5' off the ground, and I got much better signal reports and didn't have much a problem getting out 750 miles or so. I even made one CW contact in Alaska with it. The NVIS Dipole is a much better choice. I still have it up in that configuration and use it regularly.

Gene (KB3ONA)

[WB6BYU]

Another question.... will there be any effect to the antenna if I wrap the wire around each insulator standoff for the purpose of pulling it taught between each standoff?   In essence I'd have a one-turn coil at each insulator.

It will shift the resonant frequency slightly, but it also makes a difference if the wire shorts across the
loop (since you are using bare wire.)  As the aluminum oxidizes any unintentional contact may become
intermittent.

I regularly tie knots in my antenna wires - I use stranded, insulated wire and treat them like ropes.
It shifts frequency somewhat, but the antennas still work once I tune them up.


While I don't actually have one up at present (having moved to a house in the country with
plenty of space for antennas) I have used them in the past and installed them for others.  I suspect
your loop will be a fair bit shorter than a full wavelength on 80m (unless you have a very large house),
and therefore not as efficient as a half wave dipole, but still capable of making contacts.  Some loops
have seemed to have higher losses than others, and I don't have a good explanation other than
perhaps due to the building materials involved.

[K3WEC]

Thanks guys, I did try it and sadly it is not functional.  I can not get it to tune on transmit w/my manual tuner. SWR seems be at infinity.  Not sure what's up.   As far as receive goes, noise level is essentially nothing, which is great....except signal strength is many S units below the old staple-to-the fence 80 meter dipole I was using.   Oh well.

[WB6BYU]

What is the total wire length?

Did you check the DC continuity of the loop by measuring the resistance across the ends of
the feedline in the shack?  It is quite easy to get a poor contact to the aluminum wire since
aluminum oxide is a good insulator.  Usually if an antenna is that bad then the problem
is more often a poor connection.  But you could also have a very high impedance if the
lengths of the feedline and the wire happen to work out wrong.

[K3WEC]

What is the total wire length?

Did you check the DC continuity of the loop by measuring the resistance across the ends of
the feedline in the shack?  It is quite easy to get a poor contact to the aluminum wire since
aluminum oxide is a good insulator.  Usually if an antenna is that bad then the problem
is more often a poor connection.  But you could also have a very high impedance if the
lengths of the feedline and the wire happen to work out wrong.

The total length is +/- 260 ft.  I have not checked the feedline DC continuity - thanks for the suggestion. Honestly I was a little tired after seeing that it didn't work well and tabled the troubleshooting.   I will also check the connections.   Since I was joining window line (copper clad) with aluminum, I used wire nuts as a temporary junction.    That idea could have been junk.    Thanks for the suggestions...I will report back soon.

[WB6BYU]

Wire nuts should work if you scrape the aluminum oxide off the wire and put some OxGard or
NoAlOx on the joint to inhibit further oxidization. 

I never had a house large enough that i could fit a full wave 80m loop around under the
eaves.  Instead it got run out to the trees in the back yard, along the fence, etc.

[K3WEC]

It's really not a large house, at least by today's standards.  It's a single level that has a lot of projections including covered open porch, rooms that jut out from the main structure as well as a rather large chimney that juts out.   I attached to the very outside of the eave (under), which is probably 3 ft from the structure.    I gained probably 15-20 feet just going around the chimney itself.   Obviously that part isn't under an eave.

[K3WEC]

Wire nuts should work if you scrape the aluminum oxide off the wire and put some OxGard or
NoAlOx on the joint to inhibit further oxidization. 

Is there any "homebrew" paste I can make from common household/garage chemicals?

[WB6BYU]

Grease may work.  I've seem some folks add graphite to it, but I don't know if that really helps - the
point is to keep the moisture away.

Copper and aluminum are a particularly bad combination from a corrosion point of view.  Perhaps
a better approach would be to use use a stainless steel bolt with some washers and a nut:  put
the copper and aluminum wires around the bolt with at least one stainless washer between them
so they don't touch each other.  A star lock washer on each end will help make and maintain
contact by breaking through any outer oxidization.  Then you can dip it in wax or coat it with
RTV sealant if needed.

[K3WEC]

I tried this by scraping the aluminum with a knife to get the oxidation off and coating it in Vaseline.  Guess what?  It works MUCH better!   The receive is pretty decent.   Unfortunately when I first tried tuning it on transmit a couple days ago, my tuner (MFJ) arced and it continues to do so.   It may be toast.   At low power levels (25 watts or so), I can now tune it down to a very reasonable SWR (maybe 1.5 or so) on 75m.    If I try increasing the power the tuner arcs and the SWR of course goes of scale.    I hope I can fix the tuner now!

[N3LCW]

... my tuner (MFJ) arced and it continues to do so.   It may be toast.   At low power levels (25 watts or so), I can now tune it down to a very reasonable SWR (maybe 1.5 or so) on 75m.    If I try increasing the power the tuner arcs and the SWR of course goes of scale.    I hope I can fix the tuner now!

The tuner is most likely fine, it just might not be able to handle the complex reactances at higher power levels.  Try adding an external capacitor or inductor in series with the feedline, or even better yet, at the loop.  Of course this will be frequency dependent as I am sure the tuner will handle some frequencies better at higher power.

[WB6BYU]

The impedance on 80m should be pretty tame, actually, as long as both wires are making
good contact.  It will depend somewhat on the length of the feedline, and if the loop
is detuned by proximity to metal (such as aluminum rain gutters.)

Open up the top of the tuner and see.  Might just be a loose connection.  I've seen the
coil unsolder and/or melt the supports in such tuners when operated well below rated
output power if presented with a radical load (as might be the case when tuning up the
feedline without an antenna connected), but that usually requires operating it for a while
to get it good and warm.

One trick I used on my MFJ tuner was to run the jumper wire from one side of the balun
to the ANT 2 port (using a banana plug to connect to the SO-239 jack) instead of to
the single wire output post.  That allowed me to use the ANT 2 THRU position to check
the SWR straight out of the balun without the tuner in line.  That actually worked pretty
well when the feedline to my loop was just the last few feet of wire on each end, but
at least it will give you an idea of what the tuner is trying to match.

[WO4V]

Years ago, I lived in an apartment complex in a city about 200 miles from home while on a job that required my presence during the week. After exhausting several HF antenna options for 80 meters, I finally noticed that a rain gutter running around the complex was split right above my kitchen window of my apartment. One night I tapped each side of the gutter with sheet metal screws and ran some nearly invisible magnet wire out the window to each side of the split gutter. Voila'! I had a near 80 meter dipole that would load fine with my manual tuner. I could run about 800 watts to this makeshift antenna with no problems (I thought) until one night in the middle of a QSO with my Elmer back home I got a knock on the door. Seems that a neighbor was looking for a "CBer" blanking out his TV and phone around the neighborhood somewhere, and since he had noticed my pickup truck with an antenna attached, he thought I might have some idea who it could be. Well, I hastily told him I didn't know any around the area (which was true!). After this incident, I gave up trying to work low bands from an apartment and subsequently rented a house out in the country more conducive to ham activities. Point is, the antenna worked fine, just don't try this from an apartment!

73, Dave