[Elecraft] Al-572 and KXPA100

[Vic Rosenthal K2VCO]

This isn't a problem with the KX3's SWR detection circuitry. If it is 
detecting a high SWR, it's because the KX3 is producing RF output before 
the t/r relay has closed and the relay is hot-switching. The SWR 
detection is doing its job and protecting the KX3 and the amplifier!

The solution is either to speed up the amplifier's relay or add some 
more delay before the start of RF generation after the assertion of PTT 
by the KX3, as you say.

On 3/18/2014 8:14 AM, bruce whitney wrote:
> Regarding keying another amplifier from the KX3/KXPA100: There is a
> problem currently being addressed beyond the (electrical specs of
> current and voltage) capacity of the PTT line to key another
> amplifier. Currently the KXPA100 cannot be used to key an amplifier
> with slow frame relay TR switching. The SWR detection cicuitry in the
> KXPA is too fast to allow the external amp (non-QSK) to go to
> transmit without tripping out on "ANT FAULT". If you want to drive an
> amplifier with non-QSK relaying you will have to use manual PTT to
> key the amplifier to transmsit before giving it any RF power. I
> understand our Heros at Elecraft are working on incorporating a menu
> adjustable timing delay to allow VOX keyng without the ANT FAULT
> problem. Bruce W8RA


-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/