[Elecraft] K2 / XV50 interfacing to power amplifier?

[w2bvh]

Thanks for your reply and explanation of your "footswitch mod" circuit 
Don. It makes perfect sense now that you've elaborated on the 
functionality. And I can see how putting a properly wired sequencer 
between a foot switch and the "footswitch mod's" PTT input would protect 
my amp.

I simply misunderstood the function of your mod.  I thought the 
"footswitch mod" activates  the K2 and/or XV50 keyline without producing 
rf. Based on that (wrong) assumption,  I expected the XV50 "Key Out" 
port to enable my amplifier after I pressed the foot switch.

I'll build up a sequencer and wire it in.

Tnx & 73,
Lenny W2BVH

On 1/13/2012 7:43 PM, Don Wilhelm wrote:
> Lenny,
>
> The W3FPR "footswitch" mod should work with the XV50 just like it does 
> with the base K2.
> The K2 cannot be keyed until the "PTT" line to the W3FPR circuit is 
> closed.
> The XV50 will be keyed as normal by the K2 firmware through the cable 
> between the K2 and the XV50.  You should have NO connection to the 
> XV50 Keyin line.
>
> Maybe your calling my circuit the "footswitch" mod is your problem - 
> it is really PTT for CW, and will do the job if it is connected 
> correctly into the system.  You need to have a sequencer. The 
> footswitch (or whatever other switch you choose) starts the sequencer 
> chain - the first output from the sequencer isolates any preamps, the 
> second output activates the amplifier, and the third output goes to my 
> circuit to make its "PTT IN" input active.
> That last action will then allow a dot or dash key closure into the K2 
> - the K2 in turn will activate the XV50.
>
> If your problem is on SSB rather than CW, and you use the PTT line in 
> the mmic jack,  you may need to make one additional change to the K2 - 
> open the PTT line before it gets to the SSB board.  You can normally 
> just not put the PTT jumper on the mic configuration header, and then 
> run a wire between the mic jack PTT pin to the DOT input of my W3FPR 
> CW PTT circuit.
>
> 73,
> Don W3FPR
>
> On 1/13/2012 6:50 PM, w2bvh wrote:
>> HI!
>>
>> If you have a K2 / XV50 combo and have interfaced it to a power
>> amplifier I'd like to hear from you on how you did it and what pitfalls
>> you might have encountered.
>>
>> I've got a 6 Meter KW amp that I'd like to hook up to the K2 /XV50 and
>> I'm concerned about possibly hot switching the RF on the output side of
>> the amp with its 25 mS rf relay. The amp is switched active by grounding
>> its keyline input.
>>
>> According to Elecraft, RF is only delayed by 3 mS from when the rig is
>> keyed and as stated above, my amplifier output relay takes 25 mS to 
>> switch.
>>
>> I tried adding the W3FPR footswitch mod to the K2 hoping it would do the
>> trick.  It works  just fine when the K2 is set for any of the HF bands,
>> but it doesn't seem to have any effect when using 6 Meters. Its possible
>> that I implemented it wrong, but I don't think so because it does work
>> OK without the XV50.
>>
>> Ideally I'd like to have a set-up where the K2, XV50 and amplifier could
>> be thought of as just a single high power transceiver whose band switch
>> has been set to 6 Meters.
>>
>> Any experience you've had doing a setup with the K2, XV50 and a power
>> amp would be very much appreciated.
>>
>> 73
>> Lenny W2BVH
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