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[AMPS]n4kw@citrus.infi.net RJ-iA relay contact-life on CW?

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Subject: [AMPS]n4kw@citrus.infi.net RJ-iA relay contact-life on CW?
From: measures@vc.net (Rich Measures)
Date: Mon, 5 Jul 1999 20:46:15 -0700


>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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