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Hang-up on Relay Using QSK

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KY7M

Hang-up on Relay Using QSK

Towards the end of CQWW CW, I was having issues with the K3 not getting back
to receive when I stopped transmitting. This was an intermittent problem -
if I keyed the radio again with a dit or two, I could get back to full
receive. I could still hear signals, but greatly attenuated when the relay
would hang up. I was using QSK with the K3 and my Alpha 87A. I am not
seeing any fault indication on the 87A and I am trying to figure out if the
problem is in the K3. I also have a KPA500 but have not used it in a
contest lately to know if the problem would repeat with another amplifier or
barefoot. It seems to happen only after heavy use. I think I experienced
it a week earlier in the WAE RTTY contest as well, but did not do as much
operating as in CQWW.

73,

Lee, KY7M

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Vic Rosenthal

Re: Hang-up on Relay Using QSK

Lee,

The Alpha 87A uses PIN diodes for t/r switching, so unless someone
modified it, it's not the amp t/r relay, which is the usual culprit for
this problem.

It could also be a poor connection somewhere in the antenna circuit.
Sometimes a coax plug or socket is oxidized (or whatever) and it has
high resistance for small voltages such as received signals; a shot of
RF cleans it up.

I had a problem like this which drove me nuts for months. It turned out
to be a corroded solder joint in a balun (at the antenna feedpoint, of
course).

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 1 Dec 2015 19:06, KY7M wrote:

> Towards the end of CQWW CW, I was having issues with the K3 not getting back
> to receive when I stopped transmitting. This was an intermittent problem -
> if I keyed the radio again with a dit or two, I could get back to full
> receive. I could still hear signals, but greatly attenuated when the relay
> would hang up. I was using QSK with the K3 and my Alpha 87A. I am not
> seeing any fault indication on the 87A and I am trying to figure out if the
> problem is in the K3. I also have a KPA500 but have not used it in a
> contest lately to know if the problem would repeat with another amplifier or
> barefoot. It seems to happen only after heavy use. I think I experienced
> it a week earlier in the WAE RTTY contest as well, but did not do as much
> operating as in CQWW.
>
>
>
> 73,
>
>
>
> Lee, KY7M

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Guy Olinger K2AV

Re: Hang-up on Relay Using QSK

In reply to this post by KY7M

Hi, Lee,

K3 does not have a T/R relay in the RX path. It uses PIN diodes, which are
just peachy fine at 100 watt power levels. Amplifiers are another separate
problem. QSK is a strain on any amplifier running 1500 watts. This is
because affordable PIN diodes for the usual circumstances sort of disappear
beyond 500 watts or so. Ask anyone that has owned an Alpha 89, which came
out with PIN diodes for T/R switching. They never did that again. The pin
diodes will hold as long as you NEVER, EVER do anything like transmit into
an open or very high SWR.

One of the most common QSK caused problems in amplifiers is insufficient
delay setting in the transceiver (ANY brand or model) to allow amplifier's
t/r relays to close AND settle before RF is applied to the amplifier. This
is sometimes called "hot-switching".

The outcome of hot-switching is burned contacts at minimum producing the
problem you describe and others. At worst if allowed to continue, this can
produce burned a burned bandswitch with irreparable damage, ruined
transmitting capacitors, arc paths in various places, or damaged internal
coax runs. For certain kinds of transmitting tubes, the tubes can be
damaged by non-engineered states present during an arc-fault.

Many amplifiers will NOT t/r switch and settle in the K3's 8 ms minimum
delay, and some require MORE delay than advertised.

There are aftermarket t/r boards which drive vacuum relays such as Jennings
RJ-1A to quicker closures by a very short burst of higher than normal
actuation voltage. These produce measured switch delays in the 2-5 ms
range. But hard QSK use does wear down the vacuum relay after a while and
they need to be routinely replaced to avoid issues.

BEFORE you tear apart your K3 or send it back to Big E, PROVE beyond a
shadow of a doubt that it is NOT the t/r relay circuitry in your 87A. The
FIRST reason to do this is to make sure that the inevitable amplifier
damage caused by a bad relay in the 87 is headed off. If the relay is not
contacting properly at times, TAKE THE AMP OUT OF SERVICE and get the relay
fixed, or a quicker circuit installed. You could easily save your self a
$1000 repair bill on the 87.

The 87 will switch to transmit by grounding the relay jack. The next time
that the receive goes weak, unplug the cable from the 87's relay jack. Then
see if you can make the RX come back by repeatedly grounding the 87's relay
jack while the K3 sits unkeyed in RX mode.

If you can make the RX come back up that way, the problem is in the 87A,
and it's time to take it out of service.

This also is just another example of our strange predilection to always
blame the K3 first, which after noting what actually was found, is most
often just dead wrong.

73, and Good Luck
Guy K2AV

On Tuesday, December 1, 2015, KY7M <[hidden email]> wrote:

> Towards the end of CQWW CW, I was having issues with the K3 not getting
> back
> to receive when I stopped transmitting. This was an intermittent problem -
> if I keyed the radio again with a dit or two, I could get back to full
> receive. I could still hear signals, but greatly attenuated when the relay
> would hang up. I was using QSK with the K3 and my Alpha 87A. I am not
> seeing any fault indication on the 87A and I am trying to figure out if the
> problem is in the K3. I also have a KPA500 but have not used it in a
> contest lately to know if the problem would repeat with another amplifier
> or
> barefoot. It seems to happen only after heavy use. I think I experienced
> it a week earlier in the WAE RTTY contest as well, but did not do as much
> operating as in CQWW.
>
>
>
> 73,
>
>
>
> Lee, KY7M
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Guy Olinger K2AV

Re: Hang-up on Relay Using QSK

In reply to this post by Vic Rosenthal

A LOT of the 86's, 87A's and 89's have had the pin diodes removed
because of the usual problems with pin diodes and replaced with a
relay board. This has been done just because the owner is tired of the
expense of the TX pin diodes, or living in circumstances that
frequently present pin diode blow up events.

Some folks I know had that mod done right away after they bought one
used. Real QSK afficionados sometimes just deal with the diodes, which
would put the problem somewhere other than the K3 and the amp, as in
Vic's post. 86's, 87A's and 89's are legend for pin diode problems
which is why so many have been converted to relays and need to be
checked on intermittent RX problems just like any relay t/r amplifier.

Such comments as this one in an eHam evaluation on an Alpha 86 are common:

"I use the Alpha 86 for CW, RTTY contests and DXing. Since I had RF
Concepts put in the vacuum relays, the reliability has been
excellent."

I know replacing the pin diodes is what I would do immediately on
purchase of one of those. These days such things as W7RY's QSK boards
for various amps make that relatively easy and result in an an
outstanding amp for QSK. At some point I will have an SB-220, an
AL1200, a homebrew 3-1000Z, and an HL-1K all modified with a W7RY
board.

73, Guy.

On Tue, Dec 1, 2015 at 12:45 PM, Vic Rosenthal 4X6GP/K2VCO
<[hidden email]> wrote:

> Lee,
>
> The Alpha 87A uses PIN diodes for t/r switching, so unless someone modified
> it, it's not the amp t/r relay, which is the usual culprit for this problem.
>
> It could also be a poor connection somewhere in the antenna circuit.
> Sometimes a coax plug or socket is oxidized (or whatever) and it has high
> resistance for small voltages such as received signals; a shot of RF cleans
> it up.
>
> I had a problem like this which drove me nuts for months. It turned out to
> be a corroded solder joint in a balun (at the antenna feedpoint, of course).
>
> 73,
> Vic, 4X6GP/K2VCO
> Rehovot, Israel
> http://www.qsl.net/k2vco/
>
>
> On 1 Dec 2015 19:06, KY7M wrote:
>>
>> Towards the end of CQWW CW, I was having issues with the K3 not getting
>> back
>> to receive when I stopped transmitting. This was an intermittent problem
>> -
>> if I keyed the radio again with a dit or two, I could get back to full
>> receive. I could still hear signals, but greatly attenuated when the
>> relay
>> would hang up. I was using QSK with the K3 and my Alpha 87A. I am not
>> seeing any fault indication on the 87A and I am trying to figure out if
>> the
>> problem is in the K3. I also have a KPA500 but have not used it in a
>> contest lately to know if the problem would repeat with another amplifier
>> or
>> barefoot. It seems to happen only after heavy use. I think I experienced
>> it a week earlier in the WAE RTTY contest as well, but did not do as much
>> operating as in CQWW.
>>
>>
>>
>> 73,
>>
>>
>>
>> Lee, KY7M
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

alorona

Re: Hang-up on Relay Using QSK

In reply to this post by Guy Olinger K2AV

>This also is just another example of our strange predilection to always
>blame the K3 first, which after noting what actually was found, is most
>often just dead wrong.

>Guy K2AV

Yes. The problem almost always is not with the K3. I'd say 80% of the time it's the logging or computer program connected to/controlling the K3.

Another 5% of the time it's external connections -- grounds, coax connectors, relays, baluns, etc.

Another 5% of the time it's operator error.

Another 5% is "It's supposed to work that way."

And the remaining 5% is other factors, including the K3 itself.

Al W6LX
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