Motorola Power Programming

[WQYC236]

I have a Motorola CDM 1550 LS+ that puts out 42 watts on high and 23 watts on low. I noticed in the programming software that the high/low power level is adjustable up to 48 watts on high power. Is there a reason that people (or Motorola) sets the power level at less than the maximum? Is it better on the radio to leave it set to 42 watts or crank it up?

 

That being said 23 watts does most of what I want talking on the repeater. Once in a while if I'm trying to push a signal from the wrong side of a mountain or bad area I do need to go to 42 watts but that's the exception. What do you guys think?

[SteveC7010]

I have a Motorola CDM 1550 LS+ that puts out 42 watts on high and 23 watts on low. I noticed in the programming software that the high/low power level is adjustable up to 48 watts on high power. Is there a reason that people (or Motorola) sets the power level at less than the maximum? Is it better on the radio to leave it set to 42 watts or crank it up?

 

That being said 23 watts does most of what I want talking on the repeater. Once in a while if I'm trying to push a signal from the wrong side of a mountain or bad area I do need to go to 42 watts but that's the exception. What do you guys think?

 

I run CDM's exclusively. My POV has a 50 watt VHF CDM1250. I leave Tx Power set to 45 watts for high power, and 20 watts for low power.

 

If you enable one of the programmable buttons as High/Low Power, you can use the high power when needed and run low power the rest of the time.

[WQYC236]

I run CDM's exclusively. My POV has a 50 watt VHF CDM1250. I leave Tx Power set to 45 watts for high power, and 20 watts for low power.

 

If you enable one of the programmable buttons as High/Low Power, you can use the high power when needed and run low power the rest of the time.

 

Thanks! I do have a High/Low button set. Was just wondering if it would be harder on the radio at 48 watts?

[SteveC7010]

Thanks! I do have a High/Low button set. Was just wondering if it would be harder on the radio at 48 watts?

 

I think that Motorola designed the radio to run at max or nearly max power. Now if you spend a lot of time rag chewing, it might be best to drop the power a bit. The hotter you run the PA and finals, the more chance of premature failure of a component. For a UHF mobile, in the CPS programming I'd set high power at 40 watts, and low power as low as possible, probably about 20 watts.

 

I have a 25 watt CDM1250 for UHF. It will go to 30 watts, but I keep it at 25 for high power and 5 watts for low power. It gets out fine on a quarter wave antenna on the roof of the truck.

[WQYC236]

I think that Motorola designed the radio to run at max or nearly max power. Now if you spend a lot of time rag chewing, it might be best to drop the power a bit. The hotter you run the PA and finals, the more chance of premature failure of a component. For a UHF mobile, in the CPS programming I'd set high power at 40 watts, and low power as low as possible, probably about 20 watts.

 

I have a 25 watt CDM1250 for UHF. It will go to 30 watts, but I keep it at 25 for high power and 5 watts for low power. It gets out fine on a quarter wave antenna on the roof of the truck.

 

Thanks, that helps. Love those Motorola's!

[quarterwave]

Most modern ones will back the power off on their own based on heat. I also set my 40 watt radios at about 35, and on my older M1225's I run 35 in hi, and 6-7 in low. With a 1/4 wave, 6-7 works great 80% of the time. 

[SteveC7010]

Most modern ones will back the power off on their own based on heat. I also set my 40 watt radios at about 35, and on my older M1225's I run 35 in hi, and 6-7 in low. With a 1/4 wave, 6-7 works great 80% of the time. 

 

Good points! I set my CDM1250 for all GMRS channels to default to 5 watts. If I need to, I can switch to high power, but that's not often.

 

I realize that the update 95A isn't effective for a while longer, but I have the radio on the bench right now so I've changed all the GMRS channels to match the new specs. There's not a lot of traffic up here anyway so I won't be interfering with anyone.

[rfmedic]

99% of commercial mobile radios were designed around end users who made short transmissions in bursts - dispatchers, drivers, etc... They were never intended for the 50-75% duty cycle that the hobbyist/gmrs world utilizes them for without additional cooling. Hence why they run extremely hot if you are BSing for 20minutes or longer. The UHF CDM is intended to be run at 40watts in high power. Additional cooling such as a small fan on the heat sink would be a good idea depending on your talking habits. The reason the software allows you to program up to "48watts" is to adjust to 40watts without having to do an alignment/power calibration on the unit in the field. Depending on soft-pot settings sometimes "42" gives you 40 or "46" gives you 40 etc... 

 

-RfMedic

[WQYC236]

Thanks for all the good information everyone! One question in my mind is...are there radios for GMRS that are built for the 50%-75% duty cycle end user?

[WQYC236]

99% of commercial mobile radios were designed around end users who made short transmissions in bursts - dispatchers, drivers, etc... They were never intended for the 50-75% duty cycle that the hobbyist/gmrs world utilizes them for without additional cooling. Hence why they run extremely hot if you are BSing for 20minutes or longer. The UHF CDM is intended to be run at 40watts in high power. Additional cooling such as a small fan on the heat sink would be a good idea depending on your talking habits. The reason the software allows you to program up to "48watts" is to adjust to 40watts without having to do an alignment/power calibration on the unit in the field. Depending on soft-pot settings sometimes "42" gives you 40 or "46" gives you 40 etc... 

 

-RfMedic

 

Something else you may be able to answer for me. I have a brand new 850 CCA battery in my 2005 Ford Explorer. My CDM 1550 is wired directly to the battery using the heavy gauge wiring harness that comes from Motorola with the radio, no modifications. I just tested my alternator/charging system, so I know it's working perfectly. My problem is I can't talk very long on low power (23 watts) with the engine off without the radio beeping at me. When I start the motor it goes away. I can't talk at all on high power (42 or 43 watts) without the engine running. Any suggestions or is this normal? I have another brand mobile rated at 50/40 watts, VHF/UHF that talks for at least a half hour without any noticeable problems, it's just the Motorola. 

[Logan5]

CCA batteries are meant for short burst of amps for "cold Cranking Amps"  you should have a Deep Cycle battery with a proper battery isolator and a separate "Low voltage disconnect" and fuses for your radio and Aux equipment.

[WQYC236]

CCA batteries are meant for short burst of amps for "cold Cranking Amps"  you should have a Deep Cycle battery with a proper battery isolator and a separate "Low voltage disconnect" and fuses for your radio and Aux equipment.

 

It's the highest capacity battery that will fit in the vehicle, are you saying I need some special type of battery beyond a high capacity car battery? Everything is fused.

[Logan5]

If you are having issues starting the ICE after heavy radio use, you should consider a secondary battery for radio and other AUX devices. this set up would include a deep cycle battery, a battery isolation circuit, a low voltage disconnect and an additional fused distribution panel. CCA batteries are not good for continuous use when ICE is not running. CCA batteries are made to crank for a few seconds and maybe glow plugs and then the Primary ICE charging system kicks in and supplies all the voltage. Using a CCA batteries for long periods damages the battery and will require frequent replacements.

[Logan5]

After market Manufactures offer secondary battery platforms for some automobile makes. Like the crown vic. but you can also find user modifications on Youtube. it is easier in full size trucks. more space and some diesel battery mods fit the gas models and makes for a clean install.

[WQYC236]

After market Manufactures offer secondary battery platforms for some automobile makes. Like the crown vic. but you can also find user modifications on Youtube. it is easier in full size trucks. more space and some diesel battery mods fit the gas models and makes for a clean install.

 

What's confusing is I used to be able to talk for at least 30 minutes with out any problems and that was with an older, lower capacity battery. The issue seemed to show up after the two Motorola's were programmed this last time. We added some frequencies, checked the power output to a dummy load, and also checked the frequency alignment. Everything looked good. I'm wondering if the CDM 1550 LS+ series has an internal adjustable set point for the low voltage alarm? Maybe that inadvertently got changed to a higher voltage number. Does that sound reasonable?

 

I have also been considering what you are suggesting with a duel battery set up, more so for emergencies than just my convenience. 

[rfmedic]

What's confusing is I used to be able to talk for at least 30 minutes with out any problems and that was with an older, lower capacity battery. The issue seemed to show up after the two Motorola's were programmed this last time. We added some frequencies, checked the power output to a dummy load, and also checked the frequency alignment. Everything looked good. I'm wondering if the CDM 1550 LS+ series has an internal adjustable set point for the low voltage alarm? Maybe that inadvertently got changed to a higher voltage number. Does that sound reasonable?

 

I have also been considering what you are suggesting with a duel battery set up, more so for emergencies than just my convenience. 

 

I would try switching out for another CDM1550. I would also watch my battery voltage. SOME of the CDMs have had that problem where once voltage hits 11.5VDC the VCOs start to unlock and you get the beeping. Try another CDM, check voltages, reseat power connections on battery, verify inline fuse. My initial thoughts.

 

-RF Medic