[Elecraft] PR-6 issue when QRO

[Gregg Marco W6IZT]

It has me stumped too Joe.

The TR switch uses two SPDT Tyco/Schrack relays. Dick layed out the PC
board. He has used it in several amps that he has built. Is it possible that
one of the relays is dropping out early? Maybe.

Nothing else is connected to the PR6. I thought about the RX antennas, but
they were not connected to the PR6. My RX antennas are disconnected from the
K3 and grounded during TX using the key out as the control line.

-----Original Message-----
From: Joe Subich, W4TV [mailto:lists at subich.com] 
Sent: Sunday, April 29, 2012 4:06 PM
To: Gregg Marco W6IZT; Elecraft Reflector
Subject: Re: [Elecraft] PR-6 issue when QRO


> The TR relay has been replaced by a TR switch that Dick, K5AND 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 The TR relay has been replaced by a TR switch that Dick, K5AND 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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