XTL5000 low power setting

[K6GBW]

So a friend of mine told me that running an XTL with the low power set at less than 15 watts is "bad" for the radio. The CPS will let me take low power down to 4 watts. So is there anything at all to what he's saying or is this nonsense?

Thanks,

Brian

 

[prcguy]

The only thing bad might be some transmitters can get noisy with an increase in spurious emissions or the power can be unstable when turned down too far. It’s a common problem with class C amplifiers.

 

[K6GBW]

Okay, I had heard about the spurious emissions but no other issues. I've been running this XTL5000 R1 UHF model at 8 watts on low power for about a year now and it's seemed fine. I just didn't want to damage it.

Thanks for letting me know.

 

[vagrant]

My XTL5K R1 UHF is typically set to 10W and I have used it like that for 5 years. Once in a while I will bump it to 40W. I have not checked for spurious emissions and I have never experienced an issue with it.

Your question has me wondering why Motorola would allow CPS to turn down the power to an unstable/improper setting if the radio truly did not properly handle it. I am an amateur and there are professionals here that may chime in.

 

[prcguy]

Okay, I had heard about the spurious emissions but no other issues. I've been running this XTL5000 R1 UHF model at 8 watts on low power for about a year now and it's seemed fine. I just didn't want to damage it.

Thanks for letting me know.

I just checked the code plugs on my fleet of UHF XTL1500s and XTL2500s and low power is set to 5W and that’s what I use most of the time. Software will prevent you from selecting any less than 4W on these 45W UHF radios. The 1500 and 2500 use the same RF deck as your 5000.

 

[K6GBW]

Vagrant, I had the same thought. I think I’ll just turn it down to about 8 watts and see if it has any issues. If not, that’s how I’ll run it.

Thanks guys!

 

[KevinC]

Pretty sure any “real” radio won’t have issues setting the TX power as low as the programming SW lets you. Now if you go into tuner (or other brands equivalent) and start jacking with stuff no telling what will happen.

 

[nokones]

If the CPS will allow you to adjust the power as such, Motorola would not let you have that capability if it causes the radio to operate outside the emissions guidelines. That would affect the FCC Type Acceptance of the radio.

 

[Project25_MASTR]

The issue of running low power output on Motorola radios is a legacy mindset. With the older generation of radios (i.e. stuff designed back in the 1990's or earlier) the RF power amplifiers weren't as stable and had much narrower bias ranges before you would reach saturation points. More modern stuff (such as the TRBO line and XTLs) have more modern amplifiers with a wider bias range that allow a lot more flexibility.