Radio Question

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.

Also do a search on "broomstick antennas". Could ask over in rec.radio.shortwave too...

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

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

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.

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.

Maybe a flagpole on the roof with an American flag. Who could object?. Of course the halyards are your antenna....

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

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

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

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

Pete sez: "I've seen something like that in far west Texas, near London. There

More'n likely.

Bob Swinney

Could have been an "electric fence" also.

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.

My dad set one of those up at Guadalcanal.

-- Ed Huntress

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

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

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

If the mast is wood, you could wind a helix around it. If it has guy wires, you could insulate at the top and bottom and make a sloping V with multiple feeds to change direction.

Sure.... assume an infinite trailer roof. :)

Gunner may want to look at a grounded horizontal loop running around the perimeter of the trailer roof, far enough from the edge that the antenna isn't visible from the ground. Bring the end down the side of the trailer a couple of inches and put the tuning capacitor inside.

Look at the HF antenna on the Chinook as an example.

Third picture down:

You don't want to get too wrapped around the antenna. Down at those frequencies it takes a real big directional antenna- like a Beverage or a Rhombic- to make a big difference. (The one at work that was used to talk around the world is about the size of perhaps six football fields) Otherwise you are sucking in as much noise as signal.

Make sure you use Monster cable for good reception.

Kevin Gallimore