[Elecraft] Low output power on 24 and 28MHz resolved and Xverter Integration example

[Mike Lewis]

In case anyone else sees this -

I was inserting the PLL/BFO/VFO mods and then did a full tuneup.

1.  I had to add caps to BFO caps C173 and C174 to pull the frequency down 
to 4912.56.   Was at 4913.7 before adding caps.   Made C173 a 220pf cap and 
add another 220pf across C174 as I recall - in any case the suggested values 
were not enough for my case.

2.  The power output tuning on 10M and 12M was very very touchy to adjust.  
Further, I could get 14W on 28.1, but go up to 28.3 and it was only 6W and 
28.5 was practically nothing.   I expected the bandpass filter cap changes 
to narrow the bandwidth, but not this much.  What was more interesting was 
24MHz would only get 6W out, again very touchy.     I chalked this up to 
normal issues and put it in service while I would search the archives later.

3.  While in service, I use the DEM transverter interface unit at J13 to 
drive my transverters.   I noticed my drive level had decreased 
significantly (28.1 and 28.2 IF).  Part of the problem was the sharp 
bandpass attenuating at 28.2 (used for 2M voice and chat) versus 28.1 (used 
for 1296 xverter and 2M JT44 EME).  Even at 28.1 it was worse than before.

4.  After researching the archives, I looked at T4, T2, and other common 
suggestions, but no change.

5.  On a hunch, I decided to try adjusting the 15M slugs while keying up on 
10M.  This had a drastic effect on 10M/12M power output.   This should not 
be.

6.  Found that relay K5 was permanently in the active postition, leaving the 
15M bandpass filter in parallel with all other bands.  Continuity tests in 
circuit verified this.  (Pin 3 and Pin 8 should be grounded when not 
selected).  Except for the lower 24MHz output (6W) and narrow 10M bandpass, 
you would not have ever noticed this.   IO controller voltage was confirmed, 
and upon extraction of the relay, I could use a battery and operate the 
relay, hear it, but the contacts did not move.  Before extraction, I tried 
removing the control board and powering up, which should reset the latching 
relays, but no change.

7.  While I am waiting for a replacement relay, I put some temporary solder 
bidges across the K5 pins to bypass teh bandpass filter.   Now the K2 tuned 
up perfectly.

8.  Putting the K2 back in the transverter setup, I was getting 25W out on 
both 222 and 144 xverters.  They were previously only set to 7 watts, and 
the failure condition were down to 1 watt out.   That tells me this rig 
(bought it used) was probably always like this, but changing the 10M cap 
values probably made it more noticable.   I had never used 24MHz on this rig 
yet.

9.  The best part about all of this was it mostly solved a low output issue 
I had with my new 222MHz transverter.  Apparently the original drive level 
was enough to easily drive the 2M xverter, but my 222 needed a bit more and 
I was marginally driving it.   Now I can lower the 222 xverter bias to 27mV 
setting (TP3/4) adn get full output power.  I then reduce my output with R22 
to about 10W to drive an external amplifier.

10.  Ready for some serious operating now.  Every relevant mod now 
completed.    For the curious, I am using a RigBlaster for the computer 
interface and doing meteor scatter, JT44, and JT44 EME on the K2 driving 
external 120 to 300 watt amps on 2M and 22MHz.   I built custom cables from 
RG316 and crimp SMA and BNC connectors, with a SMA Tee attached to a BNC to 
SMA adapter for my 28MHZ IF daisy chain (running split IF and split RX/TX on 
144 side also).  The 144 is set to 7 watts for my external amplifier but is 
routed through a pair of SMA latching relays (SP4T) to feed the 903, 1296, 
and "next" transverter.   These require much lower drive level so I use a 
latching SMA transfer relay in the 28MHz IF line to cut in a 20dB 
attenuator.  This lowers my 144 output to around 100mW.  This is all 
controlled by a single 3P4T rotary switch that switches PTT (taken from the 
2M xverter back panel), the SMA relay, and attenuator transfer switch.  A 
DC-DC converter modile rated for 28VDC at 2A output is used to drive my 
28VDC relays.  I used latching relays for signal routing to lower the 28VDC 
power requirements.   These are available cheap on eBay from aircraft 
teardowns I have noticed.  The PTT goes out to the external amps.

11.  One tricky feature you DEM TIK2 users might note.   The Elecraft 
transverters are automatically selected and 12VDC is available at JP9 pin 1 
when a particularxvcerter is enabled.   I use this power to operate the TIK 
unit when a transverter is selected by bythe rotary switch described 
earlier.  Routing the TIK enable out the KIO2 DB9 connector to the 
transverters using pin 4.  It is an ALC line, but I have no need for this 
signal so I hijacked it at the KIO2 rear panel oard where the internal cable 
connects to run to the control  board.  Pulled the ALC line and inserted the 
TIK enable (relay power really).

The transverters only use 3 wires and ground, so they have an extra unused 
wire.  I hooked this up to pin 4 on each daisy chain KIO2 cable.  Inside 
each transverter, I use a shoring plug (the type with exposed metal tab from 
my computer junk box) and soldered a wire to it and pin 4 of the DB9 via a 
0.170A resettable fuse (very inexpensive) and a series diode.  I also use a 
current limiting resistor (I allowed for 80ma for the TIK relay) though the 
resettable fuse is likely enough.     I burned up the wire inside the K2 
from the TIK2 once on an earlier similar scheme to externally switch this 
from a front panel switch, it was not pretty.  I now use current limiters on 
all these type interconnects :-) no more cutting corners.  There was power 
available at the DB9 and during connection you WILL touch one to the case.

One other change I made for the TIK2 was to run the TIK2's buffered 8R 
signal in place of the KIO2 unbuffered 8R in case I need to extract this for 
PTT duty later.    As in the ALC highjacking, I intercepted 8R at the rear 
panel KIO2 board at position 9.  The ALC can be found next to it at position 
7 on J2.  I also shorted resistor R1 on the KIO2 board though I may regret 
this move later (see other war story above).

System now works really slick.  Next upgrade will be to figure out how to 
use the KRC2 decoder to automatically select all my transverter lineups so I 
only have to hit the band up and band down buttons - no other switches 
requires to remember (I am a VHF contest rover - simplicity is the rule).   
To allow this however, The operation of the K2's transverter selction logic 
must be changed in formware so that I can:
a.  get direct readout on more than 2 transverter bands
b. separate the TRN menu assignment from the transverter address - reason is 
most of the microwave transverters all use the same 2M transverter as their 
IF, so I need to be able to specifiy the same transverters, but assign 
different frequency offsets for direct readout.
c.  ensure the KRC2 can assign any output port to any transverter band (not 
transverter address) selected by the front panel (not limited to XV1 trhough 
3 for example).

Hope this helps someone or give you some more ideas.   I have pictures of 
the finished self-contained HF through 1296 box.  It is highly portable and 
self contained in an oak boax with aluminum shelving, speaker, 1296 power 
amp, bulkhead antenna jacks - easy setup!

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