[Elecraft] K3 with a Kenwood TL-922A

[Vic K2VCO]

The big relay in the TL-922 is too slow, with or without a diode.

On 9/3/2011 12:38 PM, Fred Townsend wrote:
> Please see comments below.
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Vic K2VCO
> Sent: Saturday, September 03, 2011 11:51 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 with a Kenwood TL-922A
>
> Actually, I believe that the K3's amp keying output could handle the +120v
> key line of the
> 922 with no trouble. My TL922 came with a diode across the t/r relay, by the
> way.
>
> BUT -- there is a much bigger problem with the TL-922. That is that the
> relay is very, very slow. You would probably have to increase the TX Delay
> of the K3 to prevent hot-switching, and increasing it beyond 12-15 ms messes
> up your keying. Buffers and soft-keys CANNOT fix this problem.
>
> Vic: Do you realize that placing a diode across the T/R relay slows it down?
> If you are going to quickly swing the relay you are better off to shunt the
> key line with a transient absorbing device like a transorb.  As the name
> infers that's a zener that especially designed to absorb transients. That
> will speed the decay of the relay field rather than delaying it. The type
> transorb used must be selected to have a sustaining voltage greater than
> normal key line voltage. You want the transorb to only conduct during the
> transient period.
>
> 73
> de Fred, AE6QL
>

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