>
>> In the 2 meter amplifier after a 3 minute CW transmission at about 20
>>wpm
>>into a dummy load, the average anode exhaust temperature went from 205
>>degrees F
>>to just under 100 degrees F when using the EBS.
>
>This is the aim.
>
>EBS seems to have a poor reputation because of either:
>
>1. Being the only means of keying the amplifier, which is guaranteed to
>cause hot-switching. Competent EBS works along with the hard-wired PTT
>line - it cannot replace it.
>
>2. Being RF-actuated at too high a level (ON4UN suggests around 0.5W in
>a kW amplifier, related to the dynamic range of he speech processing for
>SSB).
>
>3. Being too slow to turn on.
>
>Any or all of the above can cause a poor signal, and then of course
>there's:
>
>4. Being unreliable and easily damaged.
>
>... but it doesn't have to be that way.
>
>Like many other features in amplifiers, EBS can be very useful if it's
>competently done - or a disaster if not.
>
? Good points, Ian. The solution is to allow the transceiver to control
the EBS with its +DC-V on Tx signal. This gives the RF relay contacts in
the amplifier at least a 5mS headstart so they can be closed Before RF
arrives. When the EBS is controlled by RF arriving from the transceiver,
this is not the case. In other words, when the transceiver DC-controls
the T/R switching in the amplifier, all will be well -- provided that the
amplifier T/R switches faster than the transceiver.
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