[NLRS] Setup of DEM TIB/222-28 + IC-706MkIIg

[Brent Casavant]

Hello all,

Just yesterday I took posession of my new DEM TIB and 222-28 transverter.
Right now I'm in the process of trying to adjust both of them for
operation with an Icom 706-MkIIg.  The RX adjustment on the 222-28 was
straightforward, though apparently the potentiometer they used in my
transverter operates backwards from the way the instructions detail
(i.e. clockwise increases RX gain instead of decreases it).

So I moved on to adjusting the TX section.

So far I don't know that I'm having much luck.  My HF wattmeter isn't
capable of operation below 2 watts, and I'm supposed to be adjusting
the voltage sent from the TIB on the ALC line for 200mW or less.  The
706 takes an ALC input in the range of 0 to -4V.

For my first attempt I started with the ALC set to -4.5 volts.  I keyed
up, and the VHF wattmeter on the output of the 222-28 and read about 15
watts for CW, FM, and SSB.  That didn't seem quite right (particularly
for SSB), as I'd expect the power output to be zero.  The 222-28 manual
said that at full output power I should expect to see about 6W of draw
on the power supply, but even counting the 706's power in the mix, I'm
seeing about 5W.  Neither the VHF wattmeter nor the power supply
current reading fluctuate at all on SSB.

Thinking that perhaps the TXIF gain on the 222-28 wasn't set at DEM
(which seems to be confirmed by the potentiometer being set all the
way to an extreme), I tried varying it.  No difference no matter how
I turn the potentiometer.

OK, this makes sense so far as the ALC at -4.5 volts should mean that
the 706 isn't putting out any RF (seemingly confirmed by the 706's
own power meter, but then again I'm guessing it may not deflect at
all at 200mW).  So I adjusted up to -4.0 volts, then -3.99 volts,
then -3.90 volts, -3.8, -3.7, -3.5.  All across this range I see
zero power output on the 706's bar graph, and only a constant 15W
on the 222-28's output.

As a last resort (and not expecting this to work in the first place)
I put my multimeter in AC volts mode and connected it across the
RF output of the 706.  Zilch, zero, nada.

Given the symptoms, I suspect that the 706's RF output is still fully
supressed at -3.5V but I don't dare go above -3.5 right now because
I fear blowing out the transmit end of the 222-28.

Does anyone on this list have advice on where I should go from here?
I'm particularly interested in hearing from anyone who has used a
combination of a 706MkIIg, DEM TIB, and DEM 222-28, but even if you
haven't used that combination I'm happy to listen.

If anyone thinks that a phone conversation would be sufficient to guide
me through the process and you have the time to spare tonight (Wednesday),
please call me at 651-493-6693.  Or if anyone is in the east metro
(near South Saint Paul) and is willing to try a contact on FM (I only
have a ground plane right now) please let me know.  I'll be monitoring
223.500 unless I'm tinkering or checking email.

Thanks in advance,
Brent, KD5EMB

-- 
Brent Casavant            http://www.angeltread.org/
44.9067N 93.0558N 907F    -.- -.. ..... . -- -...