I have recently purchased an amplifier for my repeater. This was actually my first amplifier purchase ever and should probably have asked more questions prior to buying it. The repeater is a Motorola XPR8400 UHF R1 running in dynamic mixed mode. The amp I purchased is TPL Communications PA6-1BE-RXRFPSM UHF 100W. I've heard that some amps have issues with digital signals and some don't depending on the amp class. I tried to do research on this but there is little to no information online. Was able to confirm though through an acquaintance who never heard of that is maintaining a repeater system running a 250W TPL amplifier in DMR without any issues. What is the theory behind digital signals vs analog and repeater operations? Will this specific amplifier transmitting DMR work or will I run into problems? Lastly, if this amplifier is not suited for DMR which make and models are?

  • $\begingroup$ This is a good question, I'm looking forward to some answers. Two things come to mind immediately: the "digital" modulation probably has an amplitude component to it, which may require a more linear amplifier than just phase modulation. And digital transmissions likely involve transmitting in timeslots, hundreds of times per second, and possibly also receiving between the transmitting slots, like a cellphone does. None of these will work well with a simple hard limiting "FM" amplifier. $\endgroup$
    – tomnexus
    May 19 at 23:59
  • $\begingroup$ ChatGPT gave me the best answer. Very detailed but it was unable to tell me anything about my specific amp. It’s a very common commercial amp and I’m hoping that someone familiar with it could provide some critical information on the specific amp. $\endgroup$
    – Mike
    May 20 at 17:08
  • $\begingroup$ Hah, yes, maybe it has swallowed a summary of the issues. But it also hallucinates and fabricates things. What is the amplifier, perhaps someone here will look it up. $\endgroup$
    – tomnexus
    May 21 at 1:39
  • $\begingroup$ The difference in the amplifiers depends on what modulation you are using. Some amplifiers take shortcuts that make them less linear. You would need a more linear amplifier for AM or FM vs. SSB and even less for CW. FM and AM need a fairly linear amplifier, so likely a digital signal would not have a problem with the same amp. If you've already hooked it up and you're not getting distortion that breaks things, likely it is fine. Duty cycle is a bigger concern -- especially for a repeater that might have 100% duty cycle. $\endgroup$
    – user10489
    May 21 at 12:19


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