>See notes interjected below {{ ----}}...
>
>-----Original Message-----
>From: Rich Measures [SMTP:measures@vc.net]
>Sent: Monday, July 05, 1999 9:42 AM
>To: Richard W. Ehrhorn; 'n4kw@citrus.infi.net'
>Cc: amps@contesting.com
>Subject: RE: [AMPS]n4kw@citrus.infi.net RJ-iA relay contact-life on CW?
>
? ? Warning: This document has erronius attribution marks.
>
>Dick EHrhorn wrote:
>...snip...
>>'The '78 vacuum T/R relay coil is similarly driven via an RC from an
>>~30-35v source, and showed ~2 ms both ways.
>>
>? Do you mean 2mS for initial make and 2mS of bounce?
>
>{{ ~2ms initial make, shorter bounce @ this voltage...}}
>.... snip....
>
>>until xcvr rf output has disappeared,
>
>? How could such a thing happen if the transceiver keys the relays in
>the amplifier?
>
>{{ With separate exciters often used in the past - and some presumable
>occasionally even now in use - there's not necessarily a predictable timing
>relationship between xctr control relay opening and trailing end of rf,
>since the exciter has no internal T/R relay to interrupt output. In prin
>cipal and perhaps in reality, even with some xcvrs not designed for QSK
>(e.g., S-line) and using relatively slow (10-20 ms?) conventional T/R
>relays, there's no absolute assurance that in every case with every model
>the trailing edge of a "dah" (or switching transient) might not last past
>the initial opening time of the fast T/R relays in the amp. When
>manufacturing amps for use with other equipment over which one has NO
>control, better safe than sorry - especially when effective protection is
>inexpensive.
>
>? A friend of mine owns a 91B. I hear the roughness on channel as the
>RF actuated bias circuit rapidly switches during voice modulation. I can
>hear the adjacent channel spitting. Would it not be better to keep the
>bias in sync with the RF relays? For those who do not use Lock-to Talk,
>I can see no reason to have the RF relays closed and the bias in
>non-linear mode. . . Do you use high speed VOX, or do you prefer
>Lock-to-Talk?
>
> {{ Tetrodes generally need to idle at considerably higher Ip than gg
>triodes to achieve very good linearity.
? agreed
>In lock-to-talk this results in
>unnecessarily high plate dissipation, power supply drain, and total heat
>generation during pauses.
? Why cater to lock-to-talk miscreants? Lock-to-talk is unnecessary.
With SSB VOX, amp tubes cut off in a fraction of a second during pauses
and between words. .
> ALPHA 91B and 99 electronic bias control systems
>allow the tubes to idle "ON" at ~70-100 mA Ip whenever in lock-to-talk with
>no drive; with drive >50 mW or so Ipo is increased to ~400 mA. As I think
>Tom described a week or two ago, the transition from ~70 mA Ip to ~400 mA
>when drive is ~30 dB below peak does not generate noticeable spit or
>splatter.
? I can hear it in the 91B.
>If that does occur, odds are the "no- drive Ip idle" level isn't
>adjusted correctly. }}
>
? Apply linear bias whenever there's current in the RF relay coils and
there can never be an instance where non-linear bias is applied during
TX. Sometimes mo' simler is mo' betta.
>........
>
- cheers, Dick.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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