On the fringe

[woodb]

Hey all,

I live in St. Louis (mo) county and am trying to pick up the city system (800mhz mot now, moving to a new p25 system). I am on the very fringe of being able to pick it up now, as I can drive up an down my street and pick up random snippets of the system here and there.

I recently installed a scantenna2 (in my garage.. sigh), as most of my scanning is in the basement where my office is. Last night I was picking up their system fairly well, but today I can't (crc errors in the win500 console dump). I am assuming it is the moisture in the air today?

Either way, I need a little boost to get reception I think. As I can't mount the antenna anywhere other than where it is now, I have a few questions:

1) would switching out the rg6 that came with the scantenna with lmr400 (or something like it) make a dramatic difference? I can't make the run shorter, as the supplied length "just makes it" from the garage to my office down here.

2) should I look at an antenna more suited for 800mhz? a yagi perhaps (mounted in the garage as well)?

3) amplifiers? would they help?

Any recommendations to push me over this hurdle (while working within the constraints of my antenna location) would be helpful.

Thanks!

 

[Don_Burke]

The first thing I would try is hooking the scanner up to the antenna with the shortest cable possible as a test. That would tell you if replacing the feedline has any promise.

 

[woodb]

excellent suggestion!

tried with a 3ft coax cable and it picked the system.. so would 40ft of lmr400 be comparable to 3ft of just cheap tv interconnect in terms of loss?

thanks so much..

 

[kc9neq]

woodb:it is my understanding that the p25 part of the st. louis, mo system is having problems.
i read in a post somewhere that the city will switch back and forth from p25 to mot when the system is having trouble.
test your radio and antenna by programming your radio to the illinois state police starcom 21 system.
its p25 and you will be able to receive it in st. louis county with no problems.

 

[majoco]

If you can pick it up with the scanner close to the antenna, then it's clear that your losses are in the cable. You have also got two mismatches using 75ohm TV coax in a 50ohm system, although there is not a lot in it. Probably IMHO your best option is an amplifier mounted at the antenna and fed with power from the scanner end. I use a GME Kingray TV VHF/UHF antenna amplifier with the gain turn right down to overcome cable losses and it works well. The only problem is a pager transmitter about 500yards away that splatters around the marine VHF band a bit.