Mobile scanning

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lu81fitter

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Mar 26, 2014
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252
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Marshall County, Illinois
OK. I am new to Radio reference. I love monitoring my scanners and have 4 of them. I have read many comments/posts here about having 1 scanner with two antennas. Everyone seems to disagree on if this is a good thing (unless I just don't understand).
What I would like to do is hook 2 antennas, one for 150-158 MHZ and one for 450-470 MHz, to one scanner in my truck.
Are there a multitude of problems with matching the antennas and coax? Will a bandpass filter work?
I am not an antenna guru, but i thought this would work if there aren't matching problems.
Without going in to a scientific explanation, am I able to do this or not? I'm still confused. I WILL NOT be transmitting on theses antennas. RECEIVE ONLY!
There is a lot of talent here. Hoping to find an answer.
Thanks for your input.
 

lu81fitter

Member
Joined
Mar 26, 2014
Messages
252
Location
Marshall County, Illinois
The VHF hi signals are closest to me and I can receive them well. The UHF (453-460) range departments are 30-40 miles and come in weak. I tried a Tram/Browning BR-180 antenna with marginal results. Was hoping to try a 6" whip and an 18" whip together. A tee connector does not work. I thought a filter would work if I put it on, but there may be problems with matching.
Good grief!
 

zz0468

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Feb 6, 2007
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You're in luck.

You want VHF highband and UHF? The luck is in the fact that the two bands are harmonically related. What this means is, if you put in an 18 inch quarter wave whip for VHF, it will work well as a 3/4 wave antenna for UHF. You don't need to do anything else to get satisfactory results. It works well enough that, with careful cutting, you can transmit on both bands as well.

You COULD use two separate antennas, each run through a band pass filter and tee'd together at the radio, but the coax lengths between the two filters is critical, and without a network analyzer, a Smith Chart, and the knowledge how to use them, your results will be random and probably unsatisfactory.

Another possibility is a commercial diplexer (NOT a duplexer). They are available for both amateur and commercial use. Available at your local amateur radio stores.

I'd just use an 18" whip and save a ton of grief and some money. But keep in mind, 30-40 mile weak UHF signals won't magically get stronger with just about any working UHF antenna. One a vehicle, at best you'll get a few db gain, enough to change a 0.5 microvolt signal to a 0.7 microvolt signal. That's barely noticeable.
 
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