[Amps] High frequency heater supplies

[Steve Thompson]

W7RY wrote:
> We have been finding issues using switching power supplies on commercial
> 2-way radio base stations and repeaters. 
> The spurs are spread up and down the band at the intervals of the
> switching frequency. This causes lots of interference. Although the
> spurs are low, (40-50dB down), they are still a problem when you are
> trying to receive close to an affected transmitter.
I'd echo Jim (K9YC)'s comments about mechanisms. In Europe, all spurious 
has to be -36dBm; 80dB down at 25W and 86dB at 100W. That demands a 
particular mindset, and often requires linear rather than switching 
supplies. For dc supplies in an amplifier I think that correct grounding 
and filtering can provide the necessary suppression, but I was 
interested to know if anyone had experience with heaters. It looks like 
I'll have to do the experiment....

Steve