Re: Default K3 transmit delay may be too short for slow QRO amplifiers

Posted by Dimitry Borzenko on Jun 09, 2018; 7:39pm
URL: http://elecraft.85.s1.nabble.com/Default-K3-transmit-delay-may-be-too-short-for-slow-QRO-amplifiers-tp7641790p7641848.html

Hi Bob.
Transceiver can not supply multi sequenced events, but can prevent to
burn LNA if have long TX DLY time and input of sequencer connected to
PTT of K3.
You can say,  who connect sequencer to the transceiver, sequencer must
engage TRX and not contrariwise.
Two ways is right, but every way have weakness.
In first way when sequencer gives PTT command to TRX - pushing on
"Send", "XMIT" or PTT on  microphone or keyer will destroy LNA etc. if
do not use TX Inhibit.
In second way when we have enough delay between PTT signal and RF output
- we need to set delay time little bit more then all commutations needs,
for example I know my mast LNA needs 30ms, PA 40ms plus additional 10ms,
so for safety use 80mS is enough(if U use delay time between LNA off and
PA ON).
I have use sequencer in the PA( sequence ~60mS) and generate -9V for
TS-2000, for K3S I need different voltage for TX Inhibit, all this
signals needs only because I do not have option to set TX DLY more than
20mS!

Regards.


------ Original Message ------
From: "Bob McGraw K4TAX" <[hidden email]>
To: [hidden email]
Sent: 09.06.2018 2:46:26
Subject: Re: [Elecraft] Default K3 transmit delay may be too short for
slow QRO amplifiers

>From experience, in an operation as you describe, a sequencer is almost
>mandatory to assure each item switches as it should and that proper
>feedback on that item to the sequencer to allow it to proceed to the
>next interval and switching.  I don't feel one can relay just on the
>radio to perform this function.  My sequenced EME station put the
>transceiver in the transmit mode as the last item in the timing of
>events.    I don't understand how one can expect a transceiver to
>supply multi sequenced events.
>
>I've fried enough mast mounted preamps, coax relays and caused amp
>flash overs enough times before a proper timed sequencer was employed.  
>  Legal limit power on 70 cm can really do nasty things.
>
>73
>
>Bob, K4TAX
>
>
>On 6/8/2018 12:56 PM, Dimitry Borzenko wrote:
>>Hi group.
>>Please understand, this nice transceiver is used not only for HF. but
>>also for VHF,UHF and uppp.
>>So, more TX DLY is needed!
>>LNAs, polarization switches, PA and transverters in the transmission
>>line.
>>Sequencer is nice device but if U press XMIT button - BIG BAGA BUM :(
>>I hope Elecraft engineers will add additional  TX DLY.
>>
>>Tnx a lot.
>>
>
>
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