[Elecraft] K2 8R/keyline-RF Timing Questions

[w2bvh]

Steve,

Well here are the measurements you were asking for (curiosity got the 
best of me and I decided to throw a test set up together and see what I 
see before going on vacation).

These measurements were done with the new K2 firmware just recently 
installed: v2.04P/1.09.

1. In CW mode, 8R Hold= normal with t-r delay set to 0.02 sec
    a) 8R goes low and rf starts rising 17ms +/- 1ms later
    b) RF starts declining and 8R rises 5ms later. Please note this is a 
normal 90%-10% fall time measurement. RF is at 100% output 5ms before 
the       rising edge of 8R and declines exponentially from that point 
in time. At the rising edge of 8R the rf is essentially 0.

2. In CW mode, 8R Hold= normal with t-r delay set to 1.0 sec
    a) measurements exactly as above. So I assume that  in this set-up  
t-r delay means speaker un-mute delay.

3. In CW mode, 8RHold=hold with t-r delay set to 0.10 sec
    a) 8R goes low and rf starts rising 18ms later. Same as above
    b) RF starts declining and 8R rises 0.10 sec later
    c) I tried with t-r delay 0f 0.05sec and for that value RF starts 
declining and 8R rises 0.05 sec later.

4. In SSB mode with a constant audio tone injected int to the mic 
connector and with PTT keyed using a hand key connected to the key jack 
on the back apron, I get the following result:
    a) 8R goes low and rf starts rising 18ms later
    b) RF starts declining and 8R rises 10 ms later
    c) these measurements are independent of the the value of t-r value 
and 8R Hold value.

Conclusion is 8R Hold=hold causes 8R to rise t-r delay seconds after rf 
starts to decline in CW mode. Otherwise the 8R line's timing is fixed 
and as described above.

Hope this helps in your transverter design or sequencer design (if any). 
My guess is that you'll be ok with the G5Y's and no sequencer. BTW, in 
my hb 2 meter transverter, I use the extra pole on a relay to short the 
input of the receive front end to ground when in transmit. This  
renders  relay isolation  much less important. I also key the bias on 
the power gain stage to off with an extra relay while in receive (you'd 
think grounding the the input of the transmit string during receive 
would be enough, but there's enough rf floating around in there that it 
isn't... at least in my case.... ymmv).

As for the power level handled by the relays in my hb transverter, its 
about 30 watts. I'm dry switching them which should help a lot. I'll 
learn by experience, but so far they're surviving.

One other thing I ought to try is to see if  8R Hold = hold/normal value 
is stored per band. It would be nice to have quick qsk on HF (I've been 
using 20 ms since I built the K2 in 2000) and a much longer delay (say 
100 - 200 ms) in vhf/uhf to save the transverter relays.

GL & 73,

Lenny W2BVH

ps- if you get a chance, keep me posted on how things work out for you.
   


Steve Kavanagh wrote:
> Lenny:
>
>   
>> It would be interesting to see the
>> differences in timing (if 
>> any) for the normal mode and what the 8R Hold mode
>> timing is. BTW  I put 
>> a question on the Elecraft list a few weeks ago
>> about 8R Hold; what it 
>> does any why it should be used in favor of 8R normal
>> but there were no replies.
>>     
>
> The 8R Hold mode holds the 8R line in transmit until
> the T-R delay (or VOX delay, I think, but I won't be
> using VOX with transverters so I haven't checked)
> times out.  This reduces relay chatter in transverters
> and amps and is there specifically for this purpose, I
> believe.  I don't think it does anything noticeable
> within the K2 itself.  I also don't know if there is
> any offset in time between the dropout of the 8R line
> in VOX mode and any RF output resulting from audio
> levels too low to hold the VOX in.
>
>   
>> Agreed. I would be a worth while measurement. I'll
>> try and do that one 
>> too. For that I'd need to rig up a connection to a
>> new mic plug 
>> connected to a tone generator to watch the rf go
>> away while keying. 
>>     
>
> Perhaps for VOX mode testing.  In PTT mode you really
> need to compare the timing of the PTT line and the RF
> output. I would imagine just saying "ahhhhhh" (might
> be too low pitched though to count as a steady state
> signal for this sort of test) or whistling into the
> mic would be sufficient.
>
>   
>> I used G5V relays. They are pretty fast and I was
>> able to get a sleeve 
>> of them pretty inexpensively on ebay.  I have a hb 2
>> meter transverter 
>> that works fb with them and the  K2 (with the old
>> s/w).
>>     
>
> Yes, I see they are FAST !  How much RF power did you
> put through them on 2m ?  I imagine the SWR would be
> pretty acceptable for my 6m application (though maybe
> not the isolation ?).  The G5Y and G6Y are actually
> intended for UHF operation and have pretty good
> isolation between transmit and receive pins, but they
> are a bit slower.
>
>   
>> Anyway. Best of luck getting on VHF+.  
>>     
>
> I've been on (all bands up to 24 GHz) for years...just
> trying to upgrade the IF rig and get slightly out of
> the QRP category on some bands as well.
>
>   
>> When I have more timing numbers 
>> I'll be sure to send them to you. 
>>     
>
> I'd appreciate that.  I'd do it myself if I had a
> suitable oscilloscope.  It might be worthwhile putting
> a little article on Elecraft website.  The transverter
> stuff there is getting dated (pre K60XV) and doesn't
> deal with all the fine details.
>
> Have a good trip !
>
> 73,
> Steve VE3SMA
>
>
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