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

[Duane Grotophorst]

What I'm currently doing here with all of my DEM
transverters is to use an ~20dB (may actually be
closer to 23-25 dB) attenuator on the IF Radio's TX
port. For the RX side I use a sepparate RX input to
the IF radio. I then run the IF radios at ~20W of TX
power. With 100W max capable IF radios the worst case
overdrive would only be about 6-7dB, the signal may
sound like garbage but transverter should survive. For
the 4 Ten Tec Pegasi I use for 6 and 2M the N4PY
control software easily configurable to limit max TX
power to the 20W, for the 580 Delta and Corsair II's
still in the mix for now I depend on the dial markings
for the TX and ALC controls, - which I then keep my
paws off of. Not the best way, but acceptable as long
as there is that 20+ dB attenuator in the middle.

It is pretty much just a matter of time (even with an
ALC based approach) before you will slam the
transverter with full TX power from the IF radio. So I
wanted a method to 'hard limit' the max power level
that transverter could ever see. The relatively high
power TX IF drive/attenuator approach seemed to be the
easiest and best way to go to achieve that. The
biggest downside to this approach is that the 10M IF
leakage signal is quite strong and can be quite loud
on the other radios.

Also by using the ~20 db attenuators for all of the IF
radios they are all interchangeable with any of the
transverters. I built the attenuators from Vectronics
300W dry dummy loads, drilled a hole for a BNC
connector direcly below the SO239. I then soldered in
some 1/2W resistors (values from ARRL handbook + some
experiemnetal fudging) to make 'Pi' type of
attenuator. I didn't even concern myself with the
exact amount of attentuation, I was only concerned
about being relatively close, and making all of them
about the same.

Duane
N9DG
EN53bj

--- Brent Casavant <b.j.casavant@ieee.org> wrote:
> On Thu, 5 Jun 2003, Dr. Gerald N. Johnson,
> electrical engineer wrote:
> 
> > Why not derive some of the ALC from the output
> voltage (RF) of the
> > transverter? Put in fixed ALC to keep down spikes,
> then do the fine
> > control with ALC derived from the transverter.
> Then you have control for
> > when you get excited trying to work a new grid
> keeping you from
> > splattering all over...
> 
> I thought the same thing.  In fact when I ordered
> the TIB I thought
> that's essentially what it did.  Little did I know
> that it's not
> much more than a voltage divider that you set at a
> fixed value
> to drive the ALC.
> 
> Ideally I'd like to run everything just the way you
> mentioned.
> Unfortunately a severe lack of test equipment stands
> between me
> and that objective.
> 
> Anyway, I gave in and ordered the 10W drive option
> from DEM a few
> minutes ago.  I guess my problems will go away
> Monday night.
> 
> Brent
> 
> -- 
> Brent Casavant            http://www.angeltread.org/
> 44.9067N 93.0558N 907F    -.- -.. ..... . -- -...


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