[AMPS] Re: QRO QSK

[Rich Measures]

>
>If you want to handle the worst case of an infinite VSWR at 1500 watts, then
>your PIN diode switch  needs to handle 15.5 amps peak of RF at the lowest
>frequency in use. Similarly, it needs to be able to stand at least 1550
>volts reverse on the 'off' side of the switch. 

€ I have never seen a PIN diode with that much piv. 

>For 'typical' HF diodes with
>recovery times of 10 microseconds, this probably means about 4 amps forward
>current [I don't have the equations with me here at work].
>
>The drivers for this are not a negligible design problem...........neither
>are getting the PINs.
>
€  and then there is the matter of dealing with lightning discharges in 
the neighborhood.  I had a 5000v doorknob capacitor short from a 
lightning discharge that was over 1000m from my 160m antenna.  
>........
>Trouble is, having had full QSK, I don't like it anyway......
>
€  Full QSK on CW can be irritating if the RF gain control is not backed 
off to attenuate extraneous noise, or if the person on the other end is 
making tearfully-boring 5 - 10 min.  "lock to talk" monologues instead of 
conversational replies.  
However, like it or not, QSK switching speed in the amplifier is needed 
with modern radios, even if the radio is being operated on push-to-talk 
SSB -- because modern radios begin producing RF in as little as 5mS after 
the PTT switch is pressed.  If the amplifier's relay contacts are not 
fully closed when RF arrives, the contacts can not survive.  .  
>
-  cheers, Peter
>
>
>
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Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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