Repeater receiver preamps

[W3NPA]

I have a repeater made from 2 old Motorola MCS-2000 radios. Coverage is good on transmit, but the receiver radio seems to have only mediocre sensitivity.  I was wondering if an external FET preamp could be installed between the receiver radio and the duplexer, to make the repeater "hear" better. I know us hams use preamps for weak signal work on 2m, seems it could be done on FM on GMRS....

[Sshannon]

18 minutes ago, W4udx said:

I have a repeater made from 2 old Motorola MCS-2000 radios. Coverage is good on transmit, but the receiver radio seems to have only mediocre sensitivity.  I was wondering if an external FET preamp could be installed between the receiver radio and the duplexer, to make the repeater "hear" better. I know us hams use preamps for weak signal work on 2m, seems it could be done on FM on GMRS....

First try swapping the two radios to see if the receiver in one is better than the other. 

[W3NPA]

Well I would but the ham I bought them from programmed one to be a receiver and the other to be a transmitter only. I do not have the cables,  software and experience to reprogram them, so that option is out.

[Radioguy7268]

Was the repeater receiver ever working better than it is right now? Or, has it always been a little deaf since you've had it?

Adding a pre-amp won't fix a failed radio, but it might help to overcome some loss in the receive system. Generally, an MC2000 has a really hot front end (receiver) that wouldn't need a pre-amp. If you're not receiving well, then I'd look 10 other places first before I'd settle on adding a pre-amp as the solution.

Do you have a way to measure sensitivity? What's the amount of signal needed to break squelch? Is it the same before the duplexer as it is after? How much de-sense can you measure? What type of duplexer cables are you using?

 

[W3NPA]

It's always been only mediocre.  Could be because my antenna is only mounted at the 40ft level. It hears way better than my HT, but that's not saying much. I have no test equipment.  I'm guessing the radio is fine and my antenna is too low.

[Sshannon]

23 hours ago, W4udx said:

It's always been only mediocre.  Could be because my antenna is only mounted at the 40ft level. It hears way better than my HT, but that's not saying much. I have no test equipment.  I'm guessing the radio is fine and my antenna is too low.

So you probably have about 50 feet of cable running to your antenna, maybe a little more. What kind of cable are you using?

What kind of kind of duplexer are you using?

What are you using for an antenna?

What seems disappointing about your reception.  Is it range or clarity or what?

[gortex2]

I guess whats your expectation ? Many folks come on here and get all excited to put a repeater on the air and find out it covers 5 miles from home then get disappointed. Most large coverage repeaters are on high buildings, mountains and tower sites. If you have a 40' antenna at home don't expect miracles. The questions asked above will help diagnose an issue if there is one. 

What do you feel it should do ? 

[W3NPA]

Lately it's been working really well. Antenna height above terrain is not optimal,  so my expectations were probably a  bit too much. Thanks for the replies.  Mark WRKM-215 / W4UDX