A shortwave receiver vehicle antenna

[TObject]

I am looking for recommendations for a vehicle mounted antenna to receive broadcast and amateur radio signals in the frequency range 100 kHz ? 30 MHz. I know; anything is going to be a compromise. I want something relatively sturdy, innocent looking, and not very high.

Mostly I am interested in the wavelengths from 24 through 52 meters (6 ? 12 MHz), for news stations. This is going to be a receiving-only antenna.

50 Ohm unbalanced feeder.

[Jeff McRae]

Something usable while mobile, or when in camp?

For RX only, capture area is your friend - so the longer the better. A simple Francis Amazer CB whip would be my choice. Is it all vertically polarized?

[Jerry Bransford]

For listening the the HF shortwave bands, there's no particular length needed other than the longer the better. You'll find that most shortwave station antennas are horizontally polarized but a vertical antenna will work pretty well anyway... or at least well enough.

[Stu Olson]

Having ran HF mobile out of my TJ for a few years, I'll toss in my 2 cents.

I used a 108" CB whip attached to an automatic HF tuner.

Without the antenna tuner "tuned", you would swear the band was dead, especially down around 40 meters (7 Mhz) and up to through 20 meters (14 Mhz). Hit the TX button on the transmitter....about 2 seconds for the tuner to adjust itself, and the receiver s-meter and speaker pretty much popped to life (assuming the band was in fact active). The bandwidth of the antenna on 40 meters was about 10 Khz....after that, the tuner would re-adjust itself.

That all being said....the TJ is a very noisy platform to run HF receive on. With the ignition off, things were great. Turn on the engine, I would normally see the s-meter jump to a solid S-9. It made weak signal reception all but impossible. I recently pulled my HF/VHF multi-mode transceiver out of the TJ and replaced it with a $5 GE CB radio (which works very well).

[Jerry Bransford]

Try listening to that same 40m band with the tuner out of the circuit some time Stu. If my MFJ tuner is in my multi-band ham dipole antenna circuit, I notice the same thing but if it's not in the circuit, my ham receiver receives pretty well across the HF band. Like a mistuned antenna tuner makes an antenna perform worse than if it had no tuner at all, for receiving anyway. Of course the same can't be said for transmitting.

[Daless2]

If you are going to put this on your truck I have an idea for you.

If you are going to use this for Receive only, then as was mentioned before, Length is your friend.

I think Stu mentioned an 11-meter CB antenna he was using with a tuner. That would work, but as Jerry mentioned, with a tuner you have to tune it right.

A tuner will ?null? out much of the other received signal on off bands. MFJ makes a very inexpensive (Under $50) manual tuner that lets you switch it in and out of the antenna circuit. Jerry?s point is a good one. If on receive only, if not tuned right you will null out what you want to hear.

Tune to the frequency you want, then switch the antenna tuner in and tune it for a better signal and to null out interference.



OK, here?s what I did.

For years I had a HF rig in my Power Stroke. I carried a portable antenna to use at a camp, but never used it to transmit while driving. I did however enjoy listening in as I drove down the road, just didn't want to hump an antena around to do it.

I built a very simple (did I mention simple) receive only antenna using Aluminum tape, taped to the outside camper top on top. It was a simple Dipole.

The aluminum tape formed a pattern that looked like this ?[]?, running around the edges of the top of the camper top.Front, sides and back.

It was terminated with one side connected to the center of the coax, the other side to the shield directly.

It worked great! And was out of the way and for the most part no one even knew it was there.

The aluminum tape lasted for years on the top of that camper top. The connections to the tape must be mechanically sound. I did this buy literally screwing the coax to the tape with a through bolt. One for each side.(Through the fiberglass top.)

I used a homemade antenna tuner much like what you could buy from MFJ. One that could be switched in and out at will.

Might want to try it, see if you like the reception you get. I sure did.

If you try it, do it first without drilling the holes in the top. Then if you don?t like it no harm.

Hope this helps you out my friend.

Frank
KB4SJD

[Stu Olson]

Originally posted by Jerry Bransford
Try listening to that same 40m band with the tuner out of the circuit some time Stu. If my MFJ tuner is in my multi-band ham dipole antenna circuit, I notice the same thing but if it's not in the circuit, my ham receiver receives pretty well across the HF band. Like a mistuned antenna tuner makes an antenna perform worse than if it had no tuner at all, for receiving anyway. Of course the same can't be said for transmitting.

That makes sense, Jerry. As I said, I recently pulled the radio out of the TJ and the 1/4 CB whipe antenna was never reinstalled after the corner guards were put on a couple of years ago.....so I'll take your word for it.

[TObject]

Thank you for the recommendations everybody.

I have a little black box shortwave radio that I can control from a computer, so I am thinking about mounting it on a vehicle; maybe even devising some kind of mobile computer/navigation/communication system.