Antenna Length ?

[AWH100]

Hello everyone. I'm using a Uniden 396XT portable with a telescoping antenna like the one shown from Scanner Master: All-Band Telescoping Whip Replacement Antenna (BNC).

I am trying to find the best length for this antenna for the frequency of 154.4450 to 155.9700 to listen to a particular town.

Anyone know what the best length might be to pickup this frequency ? Does anyone have a chart showing antenna length for particular frequencies ?

Also if there is a particular antenna that really works well in this range, I would probable buy it. Any ideas ?

Thank you for your help.

 

[popnokick]

18 inches for a 1/4 wave at 155 mHz is what you'll find on any of the many easily-located calculators found in a Google or other search. Some of them will give to you with a long decimal inch figure... but all you need is the 18 inches. But I doubt it's going to help much. To really begin to get some serious distance in your handheld scanner you have to get an antenna that is NOT a telescopic whip directly attached to the scanner. I'm talking about an external antenna in /near a 2nd floor window... or better, in an attic or crawlspace. It doesn't have to be something you go out and buy. You can make one of these for very low cost and very little effort. (Scroll down the page to the wire version which will run less than $10... even if you buy the parts new.) Use cable TV coax (RG-59 or RG-6) and be sure to get an adapter for the connector on the 396. ALSO- If you have an old TV antenna on the roof or in the attic, turn it so it is vertical and hook it up. You'll be surprised how well that works. But to make a simple antenna, look at this:
Homebrewed Off-Center Fed Dipole - The RadioReference Wiki

 

[cpetraglia]

I would use 16 inches or just a bit more if it extends that far. That will be about 1/4 wavelength for your desired frequency. Just search for antenna design charts. There are many out there.

 

[Voyager]

No, 18" is correct. Use that or as close as you can get to that.

 

[AWH100]

antenna length

Thanks for the help. I need to clarify a bit better. I bring my 396XT to work with me and use ear-buds to listen. I work in a cubical so I can't go crazy with an antenna. Wish I could. The town that I want to listen to is the town that I work in, so am not looking for long distance coverage. I can pick them up, but depending where the cars are in town, I can loose the transmissions from the cars or their mobiles.

 

[marksmith]

Extending to 18 inches will help but I would suggest just moving the radio around in different places will probably do some good as well now that we know your situation. Its amazing how just moving it away from a computer or other electronic devices can help.

BCD536HP/HP2/996XT/PSR800/396XT/996T

 

[popnokick]

If your desk is near a window, that is likely to help. If not.... well, you're probably hosed. Between computer interference and typical office building construction that deadens most RF from getting into the center of the floor (including cellular).... the outlook for you being able to hear mobile units is not good. Even if you find a "hot spot".... that mobile is going to move (unless everything is via a repeater, which your description implies it's not).

 

[KC3ECJ]

Amateur Vertical Antenna Calculator

 

[AWH100]

Was hoping for a miracle guys, but not surprised. Hate it when work gets in the way. I need to ask to be put by a window, but don't think they will accommodate me. Great vertical antenna calculator. This is what I was looking for, thank you.

 

[Ed_Seedhouse]

These calculated lengths are for resonant antennas. With modern sensitive receivers resonance is not so important, so I'd just get out as much length as you reasonably can. There is really no need to exactly tune your antenna for resonance for receive. For transmitting it's important, but not so much for receive.

 

[KMG54]

If you have an old TV antenna on the roof or in the attic, turn it so it is vertical and hook it up. You'll be surprised how well that works.
Don't tell pcrguy that, he says they are not tuned to the right frequencies. My wineguard 1100 is the best scanner antenna I own, and I have a lot.