> This is prevented by the requirement that PTT be "looped through" the
> KAT500. When the KAT500 is tuning (or switching), PTT to the amp is
> interrupted.
This only moves the hot switching from the KAT500 to the amplifier.
Whilst the KPA500 can handle hot switching due to its PIN diode T/R
system (we won't talk about the clicks that result) other amplifiers -
particularly those with vacuum relays on the output - will certainly
suffer a catastrophic failure (damaged relays and/or "flashover" due
to the transient no load condition) if asked to hot switch on a
regular basis.
73,
... Joe, W4TV
On 10/10/2012 11:33 AM, Jim Brown wrote:
> On 10/10/2012 7:59 AM, Joe Subich, W4TV wrote:
>> Most relays have significantly higher "carry" ratings than "switch"
>> ratings and will not survive repeated switching at full power.
>> While the KAT500 may be fast enough to switch during the "ramp up"
>> time at the start of a transmission, that is still pushing the
>> envelope - particularly if one is using it with a "legal limit
>> amplifier".
>
> This is prevented by the requirement that PTT be "looped through" the
> KAT500. When the KAT500 is tuning (or switching), PTT to the amp is
> interrupted. The only condition under which this does not work well is
> with an amp like the Titan, whose 30 year old logic won't allow
> interrupting PTT to stop TX because that would hot-switch the T/R relay.
> When using that amp, I transmit a dit or two (or tap the mic) to let the
> KAT detect frequency so that it can switch bands before I transmit "for
> real."
>
> 73, Jim K9YC
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