Re: Unexpected measurements

Jerry Gaffke
 

Could be a transmit low pass filter thing, all that stuff around relays KT1,KT2,KT3.
5mhz shares a LPF with 3.5mhz, so if the knee on that filter is a bit low it will attenuate 5mhz.
Likewise 18mhz shares a filter with 14mhz.
Maybe those inductors have too many turns, or wrong caps installed?

However, 10mhz shares a filter with 7mhz, and since it's the low freq that's attenuated 
this suggests something different s going on, but could still be in the LPF somehow.

I'd probably hack the firmware so the 30mhz LPF is always selected, it should then have little effect
on the lower frequencies.  Expect a nasty square wave at your dummy load (lots of harmonics)
but the anomalous readings on 5mhz, 7mhz and 18mhz will disappear if it's LPF trouble.

Jerry


On Thu, Jan 17, 2019 at 11:24 AM, Peter Russell wrote:
5Mhz and 21Mhz are a bit of a puzzle, but I'll delve a bit further and see what the drive levels are like.(Could this be a filter thing? I'm not sure what the bandpass filters are tuned to.)

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