[NLRS] question of transverters vs radios

[Gerald]

On Mon, 2006-01-09 at 15:48 -0600, Mike wrote:
> 
> 
>    Hi  all,  I'm  looking  for  some discussion about the merits of using
>    radios I already have vs going with an sdr1000 and transverters.
>    Here's  my  situation.   I  have a 706mkIIG with no special filters or
>    features, a FT736R with just 144 and 440 and no special features and a
>    1.2GHz  transverter  by  MM.   Basically  I  have 6, 2,  and .7 meters
>    covered with ssb and 23 cm if I ever get it hooked up.  I was thinking
>    of buying a 222 MHz module for my 736r at a cost of $375 from ebay.  A
>    similar  transverter  from  DEM  would  be ~$400 but require alot more
>    effort to interface it.
>    I  also  have  it in my mind that sometime soon I'd like to try an SDR
>    1000  out  but that would require several transverters and cost just a
>    bit.
>    The easy thing to do is just get the 222 module plunk it in and presto
>    I have another band, albeit with no antenna up at the moment.
>    The  best  long term solution from a specs perspective seems to be the
>    sdr1000   route   since   it  is  technically  very  capable  and  the
>    transverters   generally   have   a   better  nf  and  perhaps  better
>    sensitivity.   The  biggest  problem here is that I'd probably only be
>    able to afford to buy the sdr 1000 and one band for the moment.
>    What thoughts might ya'al have out there?
>    Thanks much
>    Mike
>    KBØozn
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> NLRS at mailman.qth.net
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If I don't get too involved in other things, I should have a paper for
the CSVHF conference on improving the 2m and 6m performance of the
FT-736 that also works on the 220 module. Fundamentally the front end
gain is low caused by improper termination of the balanced mixer. Adding
a MMIC between the mixer and the crystal filter helped the front end
gain, the intermod, and made my 220 module sound like a really live
receiver, unlike the 2m module where it takes running the audio gain
control all the way up (and the getting ears blasted when a S3 signal
shows up) for weak signals. I have an FT-726 which I prefer for hearing
on 2m and 432 to the 736. But these days the 736 with 220 module is the
only way to get on 222 without a transverter. I'm only 20 miles from
channel 13 and it still takes a double cavity filter to keep from
hearing TV buzz all across the band.

Today I have a couple FT-857D and they beat the 726 and 736 for
reception on VHF and aren't bad on VHF either. Their noise blanker works
(which isn't the reputation of the 706) and they are versatile though
compact. They have provisions for displaying the transverted frequency
for a couple extra bands and in transverter mode they run 4 watts out
despite the menu setting which can be handy. They have a bandswitch
output (if not over run by CAT) that could be used to run relays to
select the antennas, amplifiers and transverters. There is a pin on the
power connector that will cut power back to 20 watts if grounded
(battery saver).

I'd like to find a 1240 module for the 736 but they are getting scarce
and there is some demand to drive the prices up.

Another thing I like about the 857 that bugs me in the 726 and 736 is
that the 857 doesn't shift the actual receiver frequency when shifting
modes from USB to CW which makes cross mode and mode changes easier when
working weak VHF and up signals.

W1GHZ has a transverter board made specifically for the 817 to get it on
222 which should work with the 857 nicely too, though its low power
barefoot.

-- 
73, Jerry, K0CQ
Dr. Gerald N. Johnson, electrical engineer
All content copyright, Dr. Gerald N. Johnson