CDM1550 - adjusting TX low power level

[g8tzl2004]

I have a 40W CDM1550.

In CPS you can adjust the low and high TX power levels to any value between 20-48W BUT not less than 20W.

I want to set the low power level to 5W.

I presume you do this using the Tuner software. Do you just adjust one value ie. the "20W level", so that its actually 5W?

Will you then be able to use CPS to adjust the TX power from 5W to 48W ...although I guess the CPS still displays 20-48W values?

Maybe instead of just one value you might have to adjust several values for different test frequencies...but do you still need to adjust the "20W level" so that its actually 5W? Or can you actually select a "real" 5W figure for the low power level?

[N4KVE]

You can't go to 5 watts with that radio. Below 20 watts the radio will be very innefficient. Just like I wanted to run my 100 watt MCS2000 at 20 watts. I was told 50 watts is the lowest my radio will go & still have a clean signal. GARY N4KVE

[RadioSouth]

Like Gary said. To do 5 watts you need the low power version, you should have no problem swapping. Funny things happen when you run these under spec power, you need to stay withing range.

[g8tzl2004]

Thats a pity!!! Its good to have 48W but I don't need to run 20W for local contacts!!!

My 10m 29MHz Maxtrac was originally running 90W but I lowered this down to 50W with no problems. At the time there were conflicting views about lowering the power...some had had stability issues others did not. Maybe its band dependant? OK on VHF but not on UHF? My CDM is UHF.

I guess Motorola would advertise them as 1-48W radios if it was OK..but you would think that it would make sense to design them for 1-48W operation not just 20-48W!!!

The CDM1550 is a good radio but it does not have the same flexibility as my MCS2000...no front panel SQ adjust, no front panel PL select , no easy zone up/down which retains channel position within zone thereby enabling repeater listen on input feature etc

[Will]

Below a certain power level the transistors are operating way out of their rated curve. This puts the transistor in class A dissipating/ drawing lots of current which overheats the transistor. The transmitter can go spurious.

Be glad the radio goes down to 20 watts. The older Maxtrac/Radius do not go that low.

[CircleBat]

you can make the high powered radios go down to about 6 - 7 watts by playing with the tuner software.. you hafta play with the settings by adjusting one point at a time

Circlebat

[g8tzl2004]

But is the CDM stable at 6-7 watts? See other feedback re. the PA overheating at lower power levels and going spurious!!

[CircleBat]

Had a few cdm1250 and 750 where I had to pin it down to 6 - 8 watts and was very stable... been running for the last 4 years with no problem... your gonna hafta have a lot of patience to do this as it can be tricky and save a copy of your codeplug before you start this..

Circlebat

[g8tzl2004]

I presume you have to adjust the TX low power softpots down to 6-8 watts for around 7 test frequencies across the band?

Or is there more to it - adjusting temp compensation stuff etc?

[escomm]

Other than the spurious emissions you'll be creating.........