Motorola GR300 UHF Repeater and Power Amp

[WQOC472]

Hello,

I recently bought a Motorola GR300 UHF Repeater. I found this Amp (see pictures) the guy selling it said it would work perfectly with a GR300,

Here is what the seller told me:

"This is a 100Watt PA 450-470MHz you need a power supply to run this 13.8VDC that's all 2watt in 100watt out put. you can turn down your GR300 to 2watts feed to the amp will boost to 100watts."

My Question is will this work for my GR300??

Thanks!

 

[WQOC472]

Also forgot to mention, i am running this GR300 on GMRS. The antenna is up about 50ft on a tower.

 

[techsender]

If you are using the internal duplexer on the repeater then this amp probably exceeds the power ratings on the duplexer. You would also need a continuous duty power supply for the amp.

Best bet is run the GR300 as designed and get as much antenna height as possible. On UHF height above average terrain is the best way to increase range. Use a high quality heliax and good jumpers.

 

[WQOC472]

Can the GR300 be programmed to 2 watts? also, i have an extra antenna, can i set the second antenna up to receive and use the existing antenna to transmit and bypass the duplexer?

 

[cmdrwill]

Can the GR300 be programmed to 2 watts? also, i have an extra antenna, can i set the second antenna up to receive and use the existing antenna to transmit and bypass the duplexer?

NO, unless you have the LPI version GM300, and the 25 watt and 45 watt GM300's go spurious and over heat at anything less that 15 watts on the 25 watt radio and 25 watts on the 45 watt radio.

BTW GMRS IS limited to 50 watts output power..........

Yes you can use two antennas with 20 feet vertical separation, RX antenna at the top.

 

[davidgcet]

we used to run GM300's at 4W feeding 350W PAs for paging and they were spurious as hell. we ended up bypassing the first stage of our amps so we could pump 15W in and get 350 out.

BTW, at UHF you are going to need a power supply capable of at least 40A for that PA, maybe even more.

 

[gewecke]

Also forgot to mention, i am running this GR300 on GMRS. The antenna is up about 50ft on a tower.

I sent you a pm about your amp.

73,
n9zas

 

[fineshot1]

What has been said above is true. Your not going to get the GR300 power out low
enough to use for this amp.

It is a really nice quality commercial amp. Powerwave bought out the old Milcom
amp manufacture and this looks like the same design as the old Milcom amps.

I have a couple similar to this but not in uhf and they work well and barring a lightning
or power hit will last a long time.

 

[ramal121]

Heed the warnings above. If you turn down a M44 or M34 radio to 4 watts, if it will do it, it will certainly twist off and be a royal pain. As cmdwill stated, if you have a LPI version GM300 (what is that, a M14?) that will be OK. That radio is rare but comes as 2 watt and can cranked up to 4 watt. What I would do is look for an amp with 15 watts in and whatever out (keeping the 50 watt limit in mind), let your mobiles run cool and let the amp take the brunt of the heat (if you have M34s, if you have M44s run them full by themselves and tell everyone its an intermittent duty repeater). Any class C Motorola PA should not be lowered any more than 20% of its rated power.