[10gigs] Power loss thru T/R relay

[Dr. Gerald N. Johnson]

I wrecked my TR relay several years ago from putting out full power RF 
before the relay switched. I use an FT857D for my IF and it has a CW 
friendly option to automatically transmit CW while in USB mode simply by 
closing the key. Trouble was that it put out RF at full power before the 
relay switched and the tiny microwave contacts didn't survive the 3 watt 
power switching. Most microwave relays will carry a lot more RF than 
they will switch. I have disabled that automatic CW option (which makes 
the IF work like an FT-817) and so require squeezing the PTT button on 
the microphone before transmitting CW and that has made the present 
relay survive for several years. My transverter is a DEMI and it has 
complex circuity to run the relay coil even to run a 24 volt coil from a 
12 volt supply that surely doesn't speed up the relay.

73, Jerry, K0CQ

On 2/13/2020 8:06 PM, Jon Platt via 10gigs wrote:
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>
> Yup, I do use sequencing. Its the DB6NT SEQ4. I'll be looking at that
> systems operation too, but it is sequenced.
>
> 73, Jon
>
>
> -----Original Message-----
> From: WA2VOI, Donn <wa2voi at mninter.net>
> To: Jon Platt <w0zq at aol.com>; Tactical mail/notification list for
> coordinating and discussing 10GHz operating topics. <10gigs at www.chris.org>
> Sent: Thu, Feb 13, 2020 3:57 pm
> Subject: Re: [10gigs] Power loss thru T/R relay
>
> Quick question, Jon: Do you have any kind of sequencer in the system ?
> Its possible the
> loss is due to (at least) partial "hot switching" whicl can (will) pit
> the surfaces of the
> TX-side contact. Is it possible to get inside the relay to look ?
>
> In any case, good luck.
>
> 73 Donn
> WA2VOI/0
>
> ----- Original Message -----
> From: "Jon Platt via 10gigs" <10gigs at www.chris.org
> <mailto:10gigs at www.chris.org>>
> To: <10gigs at www.chris.org <mailto:10gigs at www.chris.org>>
> Sent: Thursday, February 13, 2020 9:49 PM
> Subject: [10gigs] Power loss thru T/R relay
>
>
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>
> Most of you are familiar with my portable 10 GHz system .... a DB6NT
> transverter with a
> DK2FD 6.2 watt amp on a 65cm dish. Looking back through my documents I
> see the 6.2 watt
> amplifier was purchased in early 2004, and although I can't find my
> original DB6NT
> information, I think that it was purchased a full year prior to that,
> 2003 or 2002.  In
> any case, since 2004, my system has been unchanged, aka 16 years or so.Â
> Â Over those 16
> years I estimate maybe 7,000 to 10,000 Q's, most during the 10 GHz
> contest but also
> including RS Q's, June & September VHF, Aug UHF, and SBMS. Â
> During last falls 10 GHz contest some commented that my signal wasn't as
> strong as usual
> compared to other stations .... not terrible but perhaps noticeably
> down. I finally got
> to looking into things and discovered that there is about a 4 dB loss
> going through the
> transmit side of the original SMA T/R relay so my 6 watts was maybe
> around 2 watts.Â
> Again, not terrible but noticeable.  Receive seems OK, its the
> transmit side.  So
> tomorrow I will replace that SMA T/R relay and see where we stand. Â
> I suppose it pays to actually check things out every once in a while,
> not every 16 years.
> 73, JonW0ZQ
>
>
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