antenna combining

Post by **wavetar** » Mon Feb 05, 2007 11:02 am

Anyone out there seen a solution to allow multiple 800MHz trunked radios to use a single antenna?

A company called Telular built a unit called a "quadlink" years ago which allowed 4 cellular phones to share a single antenna. I believe it was rated for 15-watts on each input. Something similar for trunked radios is what I'm looking for.

I actually have a couple of quadlinks laying around & might get into testing with them, but just wondering if anyone here knew of a current product for trunking radios.

Todd

Post by **xmo** » Mon Feb 05, 2007 11:18 am

Tx-Rx makes frequency agile control station combiners.

http://www.txrx.com/product/product_vie ... EFB65C5033

Post by **wavetar** » Mon Feb 05, 2007 12:07 pm

xmo wrote:Tx-Rx makes frequency agile control station combiners.

http://www.txrx.com/product/product_vie ... EFB65C5033

Interesting...could've used one of those last year when installing 12 back-up base stations at a comms center...would've saved a lot of cable running! It's a little larger than I was looking for, as this application is in a vehicle, but thanks for the link!

Bruce1807 · Post by **Bruce1807** » Mon Feb 05, 2007 12:26 pm

Insertion loss is a little high but as im in the process of designing a new EOC I just got to order 2 x 8 channel units and see how they work.
I will post when I get a quote

tvsjr · Post by **tvsjr** » Mon Feb 05, 2007 1:47 pm

I'd love to know a ballpark price on such units... I know what regular TX combiners cost... I can't imagine these being cheap.

Bruce1807 · Post by **Bruce1807** » Mon Feb 05, 2007 4:48 pm

i sent in a request for quote this afternoon.
I bet there expensive as we use all tx/rx 800Mhz combining and TTA's for our 4.1 system. We even use their antennas
They make good stuff though and the antennas are brilliant and survived 200 mph gusts durinfg a major hurricanne

MSS-Dave · Post by **MSS-Dave** » Mon Feb 05, 2007 5:17 pm

http://dbspectra.com/WebSite/Product_In ... 7&sIdCat=2

Here's another vendor. Don't know if this would fit your bill better..

Dave

RKG · Post by **RKG** » Tue Feb 06, 2007 6:45 am

If you look at the cut sheet for this item, you will see that the insertion loss is huge (8 to 15 dB, depending on band and number of ports).

Post by **xmo** » Tue Feb 06, 2007 7:24 am

The frequency agile magic comes at a price!

That insertion loss could be a concern in some applications, but in many cases it is an advantage. Most trunked systems are designed with recevier amplifier / multicoupler front ends that use excess gain to optimize receiver sensitivity for enhanced talk in range. The downside is that every dB of surplus gain ahead of the base station receivers reduces system IM rejection by two dB!

As a result, strong signals from control stations and close in mobiles easily generate harmful IM. For many years Motorola has advised the need to be sure the control stations are attenuated to lessen this issue. The control station power has typically been reduced through the use of varilators.

These control station combiners will simultaneously provide high isolation between stations, provide attenualtion to reduce the risk of system IM, and make for a simple antenna installation.