[Elecraft] PR-6 issue when QRO

[Gregg Marco W6IZT]

Don:

I have replaced the open frame relay with Schrack relays

73
Gregg

-----Original Message-----
From: Don Wilhelm [mailto:w3fpr at embarqmail.com] 
Sent: Sunday, April 29, 2012 10:12 AM
To: Gregg Marco W6IZT
Cc: 'elecraft'
Subject: Re: [Elecraft] PR-6 issue when QRO

Gregg,

Unless you have changed the open frame relay in the SB-220, it will take at
least 15 ms to switch and be clear of the contact bounce.  I would suggest
you change the stock relay for something faster.

73,
Don W3FPR

On 4/29/2012 8:55 AM, Gregg Marco W6IZT wrote:
> I use my K3 on 6 meters with a concerted SB-220. When using the PR6 
> connected to the KXV3 as intended and using the amp, the GaAs FET is 
> destroyed immediately. My work around was to employ an external TR 
> relay on the K3 to switch TX RX, connecting the PR6 to the RX side of 
> the relay and to the RX input of the KXV3.Using this arrangement has 
> worked fine for the past few years.
>
> With E skip season approaching I thought that I would try to resolve 
> this problem and get rid of the extra RF plumbing.
>
> My initial thought was the TR relay in the amp might be too slow and 
> RF was being reflected back into the K3 during the transition from TX 
> to RX. After looking at the K3 block diagram I doubt that this is the 
> case as the PR-6 should be switched out of the circuit well before any 
> RF is present at the output.
>
> For reference the TR relays in the amp are spec'ed at 8 msec to switch 
> and the K3 is set at 8 msec TX delay, which I believe is the default.
>