Amplifier Placement

emtprt · Post by **emtprt** » Sat Aug 21, 2004 7:40 am

I recently purcahsed a UHF amp for my gr1225 repeater. I realize that I will need a new duplexer once I start using the amp.

Do I connect the amp between the radio and duplexer or between the duplexer and antenna?

When I tested the amp at 50 watts I placed it between the antenna and duplexer and my reception decreased. When I transmitted with a portable no voice could be heard from distant locations.

Thanks for your Help

Mark

N4DES · Post by **N4DES** » Sat Aug 21, 2004 8:08 am

The amp goes between the transmit radio and the duplexer.

Nand · Post by **Nand** » Sat Aug 21, 2004 11:43 am

As Mark says, the amp goes between the TX power out and the duplexer. But if all you want is to increase the output to 100 watts as you suggested in an earlier post, then you may as well forget it. Doubling the power is only 3 dB better and not worth it even if you were not to run in all kinds of additional trouble.
Better invest in a premium feed line and antenna if you haven’t done this yet. This will pay off on both the TX and RX side.

Nand.

bernie · Post by **bernie** » Tue Nov 16, 2004 10:45 am

My two bits worth:

Nand has it exactly right.

Dan562 · Post by **Dan562** » Sat Nov 20, 2004 7:21 am

Nand is exactly right with his comments about increasing RF Power. Increasing your RF output 3 dB will only increase the Tx Range 25% or 1 to 2 miles which is zip as far as additional coverage. There are 3 things to increase system coverage: A good commerical antenna, RFS/Cellwave, Sinclair or Andrews (formerly DB Products) +6 to 9 dB Omni Gain, Heliax Cable feedline FSJ4-50B SuperFlex 2.32 dB Insertion Loss / 100' @ 450 MHz or LDF4-50A 1.51 dB Insertion Loss / 100' @ 450 Mhz and the proper connectors.

One thing no one has touched upon is the antenna height. A UHF repeater station is only as good as the antenna height so mounting the antenna on a low building 2 to 4 floors high will produce RF coverage proportional to 30-50 feet Height Above Average Terrain (HAAT) unless the location is on a mountain top but I don't think this is your case. If you went from 50' to 100', you would notice a +6 dB increase in coverage, add a +6 to 9 dB Gain Antenna and the Low Loss Heliax Feedline will make all the difference in the system coverage. Add a mountion top site and you'll think you've died and gone to heaven.

Dan

Big Towers · Post by **Big Towers** » Thu Nov 25, 2004 6:44 pm

Add a mountion top site and you'll think you've died and gone to heaven.

Is there any other kind??

thebigphish · Post by **thebigphish** » Thu Nov 25, 2004 8:00 pm

i'm happy with the 20 footer on top of a 2 story..

chartofmaryland · Post by **chartofmaryland** » Fri Nov 26, 2004 4:26 pm

Best of all, Antenna and Hardline do not require relicensing for more ERP.

If you own the location of the Installation, make sure the total height is under 200 feet or FAA and blinking light time.

Get the best you can afford.

CHART

RKG · Post by **RKG** » Fri Nov 26, 2004 6:50 pm

Be careful. I don't know what service this transmitter is licensed in, but if it is public safety or industrial business, the license DOES have an ERP limit.

Amplifier Placement

Amplifier Placement

RF Signal Increase