Greetings to all,
After a few days playing with the stand alone QSK-5, I think I have
it working just about as good as it will ever work. I had to fix two cold
solder joints, tighten RCA Phono connectors, and move a wire wound resistor
to avoid a HV (480 V) short. A little quality control would really help.
Now the unit works, but with one glaring exception.
The stand alone unit uses two relays to bypass itself when turned
off, or when it has not been keyed for a few seconds. This feature allows
signals to reach your receiver with the
QSK-5 turned off. These relays have to actuate before actual RF is applied
to the PIN diode board. There is a delay circuit on the power supply board
that holds these relays in (once activated) for about six seconds, on this
unit. So, if you just start sending a string of CW these relays must
completely actuate before RF can be applied to the PIN diodes. One of these
relays is a fairly fast reed relay. The other is a very slow open frame T/R
relay -- the same relay used in several commercial amps.
So, what is the problem? The QSK line of most transceivers have
between 15 and 50 MS delay from the time the QSK line is activated before RF
(CW) is transmitted. Unfortunately, the close time of the open frame T/R
relay used in the QSK-5 is noticeable longer than 50 MS. Therefore, the
first dit of a CW string will be lost, or truncated. Is something is being
hot switched here?. If you do not believe me, take a listen to your CW,
not with your receiver monitor, but off the air with another receiver. Look
at it with a scope. With my scope hookup, I see a solid horizontal bar
representing the drive power followed shortly by the full trapezoid
developing. Of course, you do not see this for the rest of your CW
transmission because the relays are completely activated -- Just on the
first dit. When you test this for yourself, remember to let the 3 to 6
second time delay, built into the QSK-5, elapse. The relays must open
before you can test their close time.
I can menu select the QSK delay time on my transceiver. With the
delay set to 15 MS, I see this problem 9 out of ten times. At 20 MS, about
the same. At 25 Ms, 4 to 5 out of ten. At 30 MS delay, 2 to 3 times out of
10. With 50 MS delay the problem still occurs, but it might go 10 to 15
times before it happens.
So what is the answer? FASTER RELAYS? That is if you just have
to use the relays. I thought that the main reason for going to diode
switching was speed. It does not make sense to me to design a beautiful,
fast switching PIN diode board and then slow it down with ancient, slow,
mechanical relays that detracts from its performance. It seams to me that
some solid state switching, or vacuum relays are in order here. But, look
what that will do to the cost of the unit.
It should be mentioned that when using the internal QSK-5PC, this
situation never occurs because there are no relays involved. However, there
are other issues. With the internal board, the amp must be turned on or no
signal will pass through the QSK board to the receiver. Perhaps, that is
why the relays were added to the stand alone unit?
We pay a price for anything that is worthwhile. I think that both
QSK-5 units are quite worthwhile. I prefer the internal unit to the stand
alone unit. If you do not have a problem with having to turn your amp on
while just receiving, that is the way to go. That is the price I pay for
Diode switching QSK. OF course, relay QSK avoids all of this.
73 de Lon, K5JV
1110 Golden Bear Ln.
Kingwood, TX 77339
281-358-4207
281-358-4234 FAX
281-795-1335 CELL
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