Radio Question

Covert feedline (small magnet wire suitably camoflaged) from a window down to the clothesline. Nothing says the line could not be some stranded number 14 THHN wire, eh? Tie the ends off through doubled-over six-pack plastic ties as an insulator. I would make the wire white BTW.
Hang a few towels, etc on it for further blending in.
A longwire like this works great - I've been using one like this inside my attic (slate roof over cedar shakes) and with a 20 foot random wire I can run my National SW-3 just fine. There's plenty of signal.
I've been meaning to build a trap dipole for the backyard.
Jim
Reply to
jim rozen
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Stealth antennae are very site and situation specific. Think camou: use your ingenuity to devise a conductor of some extent that looks like something the rules don't forbid or is invisible because it looks like something familiar. Flagpoles, cutesie picket fences, clotheslines, a rabbit hutch made of chickenwire, decorative low-voltage lighting as is often used on RV's, etc etc.
Electrically short antennae have very very low radiation resistance, so a tuned matching network can make a big difference. I disagree with the poster that said they are only suitable for transmitting, though I will agree that once you reach atmospheric noise threshold then further gain t without directionality is of little benefit.
The matchbox would need to be tuned along with the rcvr. Tune for max noise from the radio at the freq of interest. A simple JFET preamp may help, or not, depending on the sensitivity of the radio. If the radio has a 3-gang tuning cap then it already has a tuned RF stage. If it doesn't, then a preamp will help.
Reply to
Don Foreman
Jim, Likely what you saw up the canyon was what telephone guys call "parallel". Parallel was just that; two conductors laying side by side, about 22 gauge or so (I'm sure a Telco guy can correct us here). The conductors were very hard drawn copper, or an alloy, to give strength against wind and ice loading. If one didn't know better, it looked like a single wire.
Single wire, ground for the other side, telephone circuits are not possible today because of all the AC currents they would share the ground with. Maybe one would work only over a very short distance, say one span or less. Dunno. I talked on one of the "ancients" about 40 years ago, in rural Kansas, and it was so noisy as to be almost unusable.
Bob Swinney
Reply to
Robert Swinney
Make an insulated base for the yagi pole and put insulators in the guy wires. Now you've got a 12' whip antena. Should work pretty good.
Ted
Reply to
Ted Edwards
Hmm. I like that. Could even be loaded at the bottom. The trailer roof now makes a lovely ground plane. Am I allowed to say 'ground plane' now?
Jim
Reply to
jim rozen
How about a "telephone wire" or "intercom wire" from your RV to another one? You can decouple the RF with capacitors so that the wire can also be used as an antenna as well as its official purpose.
Reply to
Rex Tincher
LOL...Yeah Gunner, I know you google, etc... Which leads me to believe that you posted this as a spark (some on topic for a change), there are a half a dozen site with plans for simple magnetic (Ferrit bar and magnitic wire, you know the crap they call an antenna inside an el-cheapo transister radio) which is most likely what you'll end upmaking in the long run with your requirements for 'low profile' Hell Gunner, just whip up one of those damn magnetic antenns, make sure you've got plenty of lead wire, and simply set the damn thing in which ever window works best for the station you are tuning to. You can't get no lower profile then that and expect to actually pick up anything., Heck, with a say 24 inch piece of ferrit, wrap it with around 30 feet or so of magnetic wire. You can even add a tuning cap if you want to get fancy, but as a general coverage antenna you don't need all that for just receiving, YMMV. You can mount this type of antenna in the window(s) either flat or top side.
If you need to be lower profile then the above, might I suggest a coat hanger.
n.
Reply to
North
Maybe a flagpole on the roof with an American flag. Who could object?. Of course the halyards are your antenna....
Reply to
Roger_Nickel
Others have answered the antenna part. As for the connection, you want good-quality coaxial cable, with the shield terminated well at the receiver and at the place in the RV's wall where it passes through. This effectively places the entire receiver "outside" the RV, as a shield wall completely surrounds the receiver (you hope) and is then carried out through the shield of the cable. This is how it is done on aircraft, which are also pretty horrible EMC environments inside the fuselage. You may have to put a line filter on the power plug to the receiver to keep computer hash from sneaking in on the power cord.
Jon
Reply to
Jon Elson
I've seen something like that in far west Texas, near London. There were glass insulators spiked in the top of fence posts.
Pete Keillor
Reply to
Peter T. Keillor III
What I saw in west Texas may have been out of service, glass insulators with what appeared to be a single wire. On the other hand, there was nothing near that road but more road, brush, and miles and miles of not much else. There were no power lines in sight along the road, IIRC.
Pete Keillor
Reply to
Peter T. Keillor III
AM broadcast band signals are vertically polarized when they're propagating in ground-wave mode: in other words, over distances up to 150 miles or so. Once it bounces off the ionosphere, as in late-night skip, the polarization is random. It doesn't matter which way your antenna is polarized then.
Short wave is almost all ionospheric-skip, so it never matters which way your antenna is polarized.
That's the rule-of-thumb, but it only applies to line-of-sight (VHF) or other space-wave transmission (some ducting, satellite, etc.). There's no way to predict polarization in sky-wave, which is ionospheric skip. And true ground wave is always vertical, as one end of the wave is "sunk" into the ground.
This stuff is covered well in all editions of the ARRL Antenna Book.
-- Ed Huntress
Reply to
Ed Huntress
Pete sez: "I've seen something like that in far west Texas, near London. There
More'n likely.
Bob Swinney
Reply to
Robert Swinney
Gunner, can you get away with a CB antenna? You really don't need a lot of antenna for SW reception, a moderate sized mirror mount whip should work pretty well & I'm sure you wouldn't be the only one in the park sporting one.
Howard.
Reply to
Howard Eisenhauer
Sure this all sounds right in theory. But if there are other metal items nearby they're going to scramble the polarization, so he really doesn't have to work too hard to get a vertical antenna.
Other mobile homes count pretty well as devices to convert from vertical to horizontal.
Jim
Reply to
jim rozen
Well in about 1977 there was a ground return, single wire, telephone line in Nevada. I don't know when, or if, it was replaced with paired wiring.
Bill K7NOM
Reply to
Bill Janssen
That's true, but it doesn't address the same issue. The point was that there's no inherent signal strength advantage in having a vertical or a horizontal antenna (in terms of polarization) for HF, short-wave reception, nor for BCB at night.
There are noise issues, and some others. But polarization with a sky wave (a wave skipped in the ionosphere) is not one of them.
BTW, I found my old antenna handbook, and a bit about why longer antennas typically pick up more signal than resonant antennas.
-- Ed Huntress
Reply to
Ed Huntress

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