Topband: Loud clicks

[Paul Christensen]

> "Here is what we discovered after replacing the amp TR relay. The amp TR 
> relay operates at 20ms, the Yeasu FT1000d operates at 12ms and the K3 
> default is 8ms. The K3 was reprogrammed to 16ms and the problem went away, 
> However the FT 1000d xmt delay cannot be changed. I found a simple circuit 
> to speed up the TR relay on the amp (see www.k6xx.com ) fast relay for 
> details. This circuit brings the amp operating speed to approx 10ms 
> without damaging the relay. If you have a K3 just go into the xmt setup 
> menu and change the xmt delay to 16ms. This should prevent any damage to 
> your amp relay and or tubes. "

Larry,

Be careful when adjusting the RF delay on rigs like the K3.  You may find 
that when delaying the RF envelope in the menu that additional key 
compensation is required to bring back proper keyed element spacing in CW. 
For ops who are primarily SSB or digital mode users, this does not present a 
problem.  However, the Icom 7700 and 7800 apply RF at 9 ms and unlike 
Elecraft, Icom provides no menu to alter it.

The new SPE 1K-FA solid-state amp suffers from the same related problem.  It 
uses general-purpose frame relays in the T/R circuit.  The designers did 
take advantage of the fact that the relay's release time is substantially 
faster than the pull-in time and thus activate the output relay on Rx rather 
than Tx.  Even so, to compensate for this "best effort," SPE applies MOSFET 
bias at ~ 15 ms.  So, if you're using a fast transceiver like the Icom 7700 
or 7800 series, the result is hot-switching.  The Icom is already generating 
RF at 9 ms but bias isn't applied to the SPE amp until 15 ms.  The 
hot-switching occurs not at the T/R relays, but rather it occurs with the 
instant activation of bias at 15 ms.  Monitoring a CW waveform on a scope 
shows the clear effect of a sharp leading edge truncation that appears 
identical to a hot-switched relay.  Also, the Elecraft K3 allows the user to 
invoke "handshaking" between the rig and amp through the accessory 
connector.  Still, I found CW timing errors that I could not live with.

My long-term plan for the SPE amp is to replace the output relay with a 
Gigavac GH-1 and input relay with an Aromat/Matsushita RSD-12V.  The latter 
of which is now an obsolete part, but still available through AG6K, and some 
"bottom feeders" on the internet.  However, my short-term fix works so well 
that I may leave it as it is.  I modified an Ameritron QSK-5 and designed a 
small PCB in the SPE amp using optical-isolation devices for the digital 
signaling lines:

http://72.52.250.47/images/QSK-5-Interface.pdf

What I give up with this temporary fix is the ability to use the amp's 
internal antenna switch.  Actually, I could modify that too, but my goal was 
to modify only to the extent that I could quickly reverse the mod, leaving 
no trace left behind in the event I want to later sell the amp.  To that 
end, I've accomplished the goal.

Now, the SPE amp switches incredibly fast with the SPE amp and operates more 
smoothly than anything I've used in the past.  W8JI deserves credit for his 
excellent design of the QSK-5.  OTOH, the QSK-5 as supplied by Ameritron 
requires a bit of help to bring up to reliable standards.  For example, if 
the KEY2 RCA panel jack becomes loose, the QSK-5 will hot-switch.  I detest 
when manufacturers depend on the metal cabinet framework for RF and 
DC-switching return paths.  I had to bond all panel RCA jacks and bring them 
back to circuit ground with a separate buss bar conductor.  Likewise, the RF 
input jacks rely upon the chassis for a return path and I added toothed 
solder lugs to the SO-239s and brought the returns back to the common RF 
ground point.  Finally, the line cord was replaced with an IEC type since I 
hate to find the end of a power cord when I need to perform some form of 
maintenance on a piece of equipment.

Paul, W9AC