UHF Antenna suggestions

NodrogCop · Post by **NodrogCop** » Fri Aug 01, 2003 5:35 pm

Need a suggestion for a mobile antenna:

I'm currently using a 780XLT for monitoring solely UHF channels. However, I'm ~20 miles away from the repeaters. I'm currently using a cometelco dual band that's not quite getting it done. I'd like to switch to a UHF antenna.

Any suggestions? 1/4 wave? 5/8 wave?

Thanks in advance.

Gordon

fire-medic8104 · Post by **fire-medic8104** » Fri Aug 01, 2003 10:09 pm

You would probably do fine with a 1/4 wave, but to be safe something with a gain would probably work better.

I use a maxrad 5db gain antenna on the roof of my work van and I can hear our repeater which is at 150' greater than 70 miles away with no problem.

70351 · Post by **70351** » Fri Aug 01, 2003 10:38 pm

I think that if the current dual band antenna isn't "getting it done" as you put it, then a UHF gain antenna would be in order. Might as well use something like a 5 db gain or similar (the higher the better).

Quarter wave's are nice but if your 20 or so miles from the repeater and your current antenna isn't performing the way you'd like, then a gain antenna is what you should use.

Randy

nmfire10 · Post by **nmfire10** » Sat Aug 02, 2003 4:55 am

If everything is in one general direction, you may try a directional antenna as well.

NodrogCop · Post by **NodrogCop** » Tue Aug 05, 2003 6:00 pm

Thanks for the advice guys.

I'm looking to order a 5db gain UHF mobile antenna in black. Does anyone have a good source that might also be quick? I'd like to have it for the weekend, if possible.

I have a query in with Multec Communications, but as some of you know, they aren't always the fastest.

I'd prefer Comtelco or Antenex as a brand, but am flexible.

Matt - great suggestion which I hadn't thought about. Unfortunately, it won't apply here.

Thanks for any help.

Gordon

USPSS · Post by **USPSS** » Wed Aug 06, 2003 6:16 am

The difference between 5/8 over 5/8 and a 1/4 wave antenna is about 10% in transmission range and about 5% in recieve range. What you might look at is how long your feed line is?? What type of cable if it is longer than 15 ft.? what type of connector is used and is it correctly installed? Is the antenna mount correctly grounded? Also remember the front end of a scanner can easily be desensed by some local transmissions not in the same band.

Is the antenna positioned on the trunk lid or the roof? The roof would more than make up for the 3db loss the trunk provides.

Are you using a small diameter NMO center pin or a large one, Large will degrade perfromance about 3% over the small one on UHF frequencies.

Will or I can provide you with whatever you would like for Comtelco or Antennex antenna's but check all this out before you spend any extra money.

NodrogCop · Post by **NodrogCop** » Wed Aug 06, 2003 5:26 pm

Stan -

The feed line is about 12 ft using microloss from Comtelco. It's using a BNC soldered connector that is installed correctly - I hope so, it was ordered from the company that way. The antenna mount is grounded correctly - I checked when I first intstalled it.

The antenna is mounted on the roof of a Silverado, and is a small pin dual bander.

What has me confused is that I'm borrowing a Maxrad dualbander from a friend that is significantly taller but with 3db gain, and getting much better reception. Is it simply the gain, or a combination of the greater height?

I've already tried an Antenex phantom that I had and it was only marginally better than the Comtelco dual bander.

DOH!! I forgot to mention a very key point -- the topograpy around here is tough - lots of small hills and valleys...our county system has problems here that no one else has. How much factor would that play?

Thanks for the input -- that has been quite an edcuational experience so far.

Gordon

USPSS · Post by **USPSS** » Thu Aug 07, 2003 7:12 am

First problrm is the small dual bander, they are not very good at chapturing signal's, actually Maxrad makes a decent Scanner antenna that looks like the small dual bander and works well, the larger Maxrad dual bander is not a bod antenna but it is tall. Try a 1/4 antenna and you might find it works great.

NodrogCop · Post by **NodrogCop** » Wed Aug 20, 2003 4:51 pm

Just a big, public thank you to Stan --

I found a 1/4 wave and it turned out to be just what I needed. I don't have to worry about the height either - garages aren't a nightmare in my Silverado! I'm going to get crackin' on some antenna knowledge...

Thanks again!

Gordon

nmfire10 · Post by **nmfire10** » Sun Aug 24, 2003 7:15 am

You know, this just occured to me. I suggested the directional antenna. Wow, a yagi and rotator motor on the roof of a car would look kind of strange, wouldn't it

I have a Comtelco dual band antenna on my truck used only for UHF (19" Whip making it 1/4 wave VHF & 3/4 wave UHF). It is ok. I want to try it with a regular 1/4 wave UHF and see what the difference is. In fact, I think I will order one now!