Antenna Question...

[convE36]

I am about to run down to the local Radio Shack and purchase this...

http://www.radioshack.com/product/index ... age=family

I plan on putting it on my roof so I can monitor the Fire and Ambulance better than I can now. (Since this antenna's peak performance is in the 152-470MHz range)

My question is;

Since I pick up the 800MHz trunking freqs (for Riverside Sheriff) very, very clear, (using the stock rubber duck) this new radio shack antenna should still recieve those 800MHz freqs well right?

Any advice on this antenna?

How long of cable can I run without losing range?

(Using a Uniden BC246T)

Please respond ASAP, I am leaving soon to go buy it.

[convE36]

I purchased that antenna and it works AMAZING!!!

100% better reception on all bands. I even pick up CHP all the way from San Bernardino to El Centro. I was never able to monitor them before. The 800MHz trunking freqs are still crystal clear.

Awesome antenna for your money!

[318]

If you get the 800MHz frequencies that good, then that antenna will not reduce your signal. You can probably receive the 800MHz stuff with a paper-clip placed in the antenna jack, or maybe even with no antenna at-all. (Try it...)

If your in an area where the 800Mhz frequencies your wish to monitor are comming in strong, then that antenna will be just fine, Your doing the right thing in trying to improve your VHF sensitivity. Since CalFire uses so much simplex and repeaters on distant hill-tops in Riverside County, a good VHF antenna is the way to go.

As far as feed-line goes... the shorter the better. Each foot adds just a little signal loss. Also the more connectors/adaptors you use also contribute a-lot to signal loss. The best thing to do would be to run just the amount you need to get from the antenna to the scanner, then cut off the rest and crimp on a new BNC connector.

Lengths of 50-feet or less are common and should be good. If your running over 50-feet you may start to notice some signal drop-off, depending on the band.

~318

[convE36]

Can someone explain to me about "grounding" my outdoor antenna?

Do I need to "ground" it for scanning or is that only for transmitting?

[convE36]

Besides the grounding question above;

What would be better? (As in minimum loss and better reception);

Using one 50-foot coax RG-58 cable (total of 50-feet)

or

Using two 20-foot coax RG-58 cables with a female-to-female adapter to connect the two cables (total of 40-feet)

Thanks for the help!

[318]

Grounding helps eliminate noise and will provide you with a better signal overall.

Did you read my post above about the coax? One 50-foot run would be better then two 20-foot runs connected together. Each connector is about a 3db (or more) loss. You would have less loss with the 50-foot run, even-though you would have 10-feet to spare. Can't you crimp on a connector? Why not take that 50-foot run and trim 10-feet off and crimp on a connector. To be honest, you will not notice a difference with or without the extra 10-feet...

Keep in mind that there is better, lower loss cable you can buy too like RG-8, RG-8x and the LMR series like LMR400. That stuff is better suited for higher frequencies (like 800Mhz and Microwave) and longer runs, but if your like me nad everything has to be perfect, it may be worth looking into for you.

~318

[zz0468]

Grounding helps eliminate noise and will provide you with a better signal overall.

No it won't. The antenna he bought has a built in counterpoise (ground plane) so grounding it will have no effect on signal levels. The grounding requirements are for safety only. The only time a ground will impact received signal levels is if the ground connection itself is used as a counterpoise to the antenna, like a vertical broadcast antenna, or a random wire short wave antenna. As to the noise reduction, maybe, but probably not. I've seen antenna grounds induce more noise than cure it. Unless you go all out to bond everything properly (expensive!), you more than likely have created a ground loop. Mankind has yet to device a better noise maker than a ground loop.

Each connector is about a 3db (or more) loss.

Not true, either. Even a PL259, one of the worst connectors out there, has less than a db of loss at 800 MHz if it's put on correctly. BNC connectors are about 0.1 DB below 1 GHz.

You would have less loss with the 50-foot run, even-though you would have 10-feet to spare. Can't you crimp on a connector? Why not take that 50-foot run and trim 10-feet off and crimp on a connector. To be honest, you will not notice a difference with or without the extra 10-feet...

At 800 MHz, that 10 feet of RG58 probably has more loss than the connectors to splice two 20 foot pieces. But either way is less than desirable.

Keep in mind that there is better, lower loss cable you can buy too like RG-8, RG-8x and the LMR series like LMR400. That stuff is better suited for higher frequencies (like 800Mhz and Microwave) and longer runs, but if your like me nad everything has to be perfect, it may be worth looking into for you.

You're suggestion of LMR400 is a good one, although I wouldn't use it on microwave frequencies. As a microwave engineer with 30+ years experience, I know there are FAR better choices!

I apologize for poking so many holes in your post, but I hate to see so many false myths be propagated.

[ddoug4uonly]

Can someone explain to me about "grounding" my outdoor antenna?

Do I need to "ground" it for scanning or is that only for transmitting?

If you live in an area with a lot of lightning storms, then you would want to ground your antenna.

[convE36]

I went with a 50-foot RG-58 coax cable and now my antenna is on top of my roof with about a 12-foot mast. Much more high up and has line of sight to many areas.

I might just be crazy, but it seems like I was picking up more signals when I had the 20-foot cable and the antenna was lower.

I ran the new cable through my attic, it runs next to my satellite coax cables a little. Would that effect anything?

Advice?????

[zz0468]

You WERE getting more signal when the antenna was lower. You added about 4.3 DB more loss by extending the cable, probably more loss than you gained by raising the antenna. Advice? Use better cable. RG58 is no good for VHF and above for lengths longer than a few feet. Use RG8 at the barest minimum, LMR400 is good. 50' of LMR400 has less loss than 20 feet of RG8 at 800 MHz.

Running coax next to other cables is fine. That's what it's for.