Re: Elecraft Digest, past chirp report

[Elecraft mailing list]

On 20/01/17 18:01, [hidden email] wrote:

> From: Wayne Burdick <[hidden email]>
> To: Guy Olinger K2AV <[hidden email]>
> Cc: Doug Smith <[hidden email]>, Elecraft Reflector
> <[hidden email]>
> Subject: Re: [Elecraft] K3: past chirp report
> Message-ID: <[hidden email]>
> Content-Type: text/plain; charset=windows-1252
>
> This is not a factor in synthesizer switching. Both the old and new synths incorporate their own voltage regulators, preserve identical signal integrity down to a power supply voltage of around 9 VDC. That's about as low as the radio can go in any case.
>
> Wayne
> N6KR

Does the radio still chirp when run on a large linear PSU, or from a
very well charged battery.  (In a vehicle with the engine running for
example.)

Unless specifically designed for such use, Switching PSU's are generally
quite poor in regards to dynamic regulation (such as would be needed for
QRO CW or SSB.)

However, from what Wayne describes above, even if the incoming DC dips a
little, I get the impression the DC rail for the synthesizer itself is
likely to stay clean.   But, while the SMPS is recovering from a sudden
large load being applied, it could introduce a burst of noise on the PS
lines, that might couple into other things causing trouble.

Similar things also happen when the load (RF) is suddenly turned off,
then though, you get a voltage spike, and maybe some "cycle skipping" in
the PSU as it tries to prevent such...

What make/model of PSU?   I've yet to find one for the "Amateur" market
that is anyway near half as good as the mega bucks SMPS cinder block
sized things we use in the commercial multi kW QRO amps we handle at
work.  And even they have a few issues when the amp is carrying high
levels of pulsed RF.

And the types designed for telecom or "server" use, are often very much
poorer in regards to dynamic regulation, especially if the RX current
draw is a under 10 to 15% of their rated max load, as they would have
been designed for a high power delivery, that does not vary much.

73.

Dave G0WBX.

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