[R-390] Two questions

Fri, 29 Mar 2002 07:24:45 -0800

The 4700 (.0047) cap is usually installed in parallel with an electrolytic
to improve (or provide) capacitive reactance at higher frequencies.  Do you
think it might have been added in your keyer to reduce RFI in the circuit?
It may also help keep circuit noise at bay at higher keying speeds.

73 de Bill, AB6MT
[email protected]

----- Original Message -----
From: "Scott, Barry (Clyde B)" <[email protected]>
To: "R390 (E-mail)" <[email protected]>
Sent: Friday, March 29, 2002 7:12 AM
Subject: [R-390] Two questions

> 1.  Did all 390 models include the squelch.  It was an option on the 390A.
>
> 2.  I was looking at a schematic (a keyer) a couple of days ago and
noticed there were two caps in parallel -- a 22mfd and a 4700pfd.  These
feed a solid-state VR.  Why would it be necessary to have this arrangement?
When caps are in parallel, doesn't the circuit see this as simply the sum of
both capacitances -- in this case 22.0047mfd.  It would seem the 4700pfd is
insignificant with respect to the 22mfd cap and I can't see the need for it.
Any thoughts as to why this was done?
>
> 3.  Hammarlund.
>
> Thanks,
>
> Barry(III) - N4BUQ
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