In the RSS there is a coarse power adjustment and a fine tuning adjustment. The R1225 that was purchased 2nd hand is listed as a M04GRC90C2AA but was putting out a solid 40W into a dummy load when tested. The model number should be a 1-10W radio - found in the tuning the coarse power soft pot was turned up to the maximum. I've currently turned it back down to 10W - which should let it do a 100% duty cycle.
What's the difference between the 10W & 40W PA's?
Is there an electronic difference? is the heatsink different?
R1225 Power Output
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jorenwendschuh
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motorola_otaku
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Re: R1225 Power Output
A true 2-10W R1225 will have a small Maxtrac-style heatsink on the PA. The 40W PA has a much larger heatsink with 5'' fins. It sounds like someone bought a 10W unit and stuck a 40W PA on it - nothing wrong with that, but the model number will still show it being a 10W radio.
Neither one is rated for continuous duty, and you shouldn't try to run them that hard without de-tuning the power to 40% of maximum and beefing up the forced-air cooling. Ideally you should turn it way down (1/2 to 2 watts) and drive a real continuous duty PA with it. I've done it with a true factory 10W R1225 and a 75W MSF5000 PA and it worked fine.
Neither one is rated for continuous duty, and you shouldn't try to run them that hard without de-tuning the power to 40% of maximum and beefing up the forced-air cooling. Ideally you should turn it way down (1/2 to 2 watts) and drive a real continuous duty PA with it. I've done it with a true factory 10W R1225 and a 75W MSF5000 PA and it worked fine.
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jorenwendschuh
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Re: R1225 Power Output
Yes, it does not have the Maxtrac style heatsink on the back end - sounds like it's a 40W PA. Whats the reason the course adjustment needed to be topped out to drive the PA to 40W? Is a 'true' M44 radio able to push more than 40W if the course adjustment is moved upwards, or is this the reality with the 'true' radios as well?
I keep seeing documentation saying that the PA's are rated for continuous duty if turned down to 25W for the 40W radios and any 10W
Ex:
http://www.condord.com/lmr/motorola/MOT ... nglish.pdf
http://www.indcom.net/admin/mydoc3/GR12 ... 0Sheet.pdf
What's the reason the 'spec' sheets from Moto say that they can run at 100% but they can't?
I'm looking into a 'real' PA for it as the time & cash allow. Whats the difference for an amp running wide vs narrowband?
I keep seeing documentation saying that the PA's are rated for continuous duty if turned down to 25W for the 40W radios and any 10W
Ex:
http://www.condord.com/lmr/motorola/MOT ... nglish.pdf
http://www.indcom.net/admin/mydoc3/GR12 ... 0Sheet.pdf
What's the reason the 'spec' sheets from Moto say that they can run at 100% but they can't?
I'm looking into a 'real' PA for it as the time & cash allow. Whats the difference for an amp running wide vs narrowband?
Re: R1225 Power Output
The 2 - 10 watt UHF R1225 PA is rated continuous duty, and they can run up to 14 or 15 watts intermittent duty.
The 44, UHF high 25-45 watt PA is ONLY intermittent duty due to the heat buildup even with the longer heatsink. Which is what you seem to have on your R1225.
The later R1225 44 radios have the longer fins on the heatsink. AND NO you can not run them at anything lower than 25 watts due to the very low efficiency at 25 watts. They will burn up.. I actual operation 33 watts seems to be the lowest power that does not have excessive dissipation, heat build up.
If all you need is 10 watts, then switch out the PA circuit board with the 2 to 10 watt LPI board in your big heatsink and run 10 watts all day.
Even so, all the R1225, GR300, GR500, repeaters in operation around here have fans with thermostats on the PA. The temperature controlled fan with the thermistor on the heatsink is on most of the later repeaters. Even Quantars have thermistor controlled fans.
The 44, UHF high 25-45 watt PA is ONLY intermittent duty due to the heat buildup even with the longer heatsink. Which is what you seem to have on your R1225.
The later R1225 44 radios have the longer fins on the heatsink. AND NO you can not run them at anything lower than 25 watts due to the very low efficiency at 25 watts. They will burn up.. I actual operation 33 watts seems to be the lowest power that does not have excessive dissipation, heat build up.
If all you need is 10 watts, then switch out the PA circuit board with the 2 to 10 watt LPI board in your big heatsink and run 10 watts all day.
Even so, all the R1225, GR300, GR500, repeaters in operation around here have fans with thermostats on the PA. The temperature controlled fan with the thermistor on the heatsink is on most of the later repeaters. Even Quantars have thermistor controlled fans.