[Elecraft] PR-6 issue when QRO

[Joe Subich, W4TV]

> The TR relay has been replaced by a TR switch that Dick, K5AND
> designed that uses Schrack relays that are spec'd to switch in 8
> msec.

Is the K5AND TR Switch design documented anywhere?

Does it use a single relay or multiple relays?  Is there any chance that 
the input replay is dropping out while the SB-200 is still making
RF?

Do you have any separate receive antennas connected to the "bypass"
ports on the PR6?  Do the receive antennas have a "front end saver"
inline?

Short of a problem elsewhere, I do not see how 6 meter RF from the
amplifier can get back through the K3 T/R switch, HPA and LPA to
even get to the PR6.

73,

    ... Joe, W4TV


On 4/29/2012 11:56 AM, Gregg Marco W6IZT wrote:
> Joe:
>
> It is a 6m only amp. Yes, the K3 is set to bypass the PR6 when on HF. The TR
> relay has been replaced by a TR switch that Dick, K5AND designed that uses
> Schrack relays that are spec'd to switch in 8 msec.
>
> 73
> Gregg
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Joe Subich, W4TV
> Sent: Sunday, April 29, 2012 11:34 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] PR-6 issue when QRO
>
>
> Greg,
>
> Is that SB-200 a "modified for 6 meters only" amplifier, one that has six
> meters added to the HF bands or is the problem happening when operating on
> HF bands?
>
> Is the K3/PR6 configured to bypass and turn the PR6 off when operating on
> HF?
>
> 73,
>
>      ... Joe, W4TV
>
>
> On 4/29/2012 11:10 AM, Gregg Marco W6IZT wrote:
>> 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.
>>>
>>
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