[Amps] Drake L4 Slow Relay

[Tony Brock-Fisher]

Quite often the cause of the 'missing first dit' is that the exciter is making RF before the amp has switched over to transmit. The exciter sees a high SWR, and on rigs such as the 765, folds back the output. The SWR and the foldback circuit has to stabilize before full output is regained. There are two approaches to remedy this: speeding up the amplifier relay and speeding up the switchover signal to the relay. 

On Icom rigs, there is usually a solid sate version of the PTT signal available on an output connector known as 'SEND' which is actually faster/earlier than the closure of the internal PTT output relay. Use a solid state buffer between the 'SEND' line and the amp keying circuit to speed up the transition.

 Alternatively you can try to speedup the amp relay actuation with a circuit that overdrives the relay briefly on closure, such as this one:

http://www.yccc.org/Articles/AL1200relay.html

(note that this applies to the AL-1200 which is a 12V relay; I don't know what voltage the L4 uses, but if it's 110V like Heath, you better not use this idea!)

-Tony, K1KP