From: gary@ke4zv.uucp (Gary Coffman)
Subject: Re: Hamtronics receive/transmit converters?
Reply-To: gary@ke4zv.UUCP (Gary Coffman)
Organization: Destructive Testing Systems
Date: Thu, 28 Jan 1993 04:19:14 GMT

In article <1993Jan26.202519.27840@nntpd2.cxo.dec.com> little@nuts2u.enet.dec.com (nuts2u::little) writes:
>Has anyone tried the Hamtronics 2 meter receive converter or 70 cm
>transmit converter?  I'm also trying to find an inexpensive 70 cm
>linear amp to build to go with the transmit converter.  There was a
>70 cm transverter and amp design in QST in late 1991, any
>experiences with those?

I had lots of trouble with the Hamtronics 70 cm receive converter.
The LO was very dirty and required considerable tweaking with a
spectrum analyser to be both clean and start reliably. Other people
have told me that they weren't pleased with it's performance either,
but hadn't the equipment to determine exactly what was the problem.
The crystal furnished with the kit was of low activity and the circuit
is intolerant of that. Your experience may be different depending on
the quality of parts you receive. The converter is IMHO a generally
weak design, subject to strong signal overload and requiring a hot
crystal. Their XV4 transmit converter seems to be better. I don't
have one, but several people I know have built them and they seem
to perform acceptably. Their helical filter GASFET preamps are quite 
good, we use one on our repeater. So it's a mixed bag.

I haven't built the transverter in QST though a friend has. He hasn't
reported any problems with it. I did build the author's 902 MHz 
transverter and it worked first time. I expect the 432 MHz design 
is sound as well.
    
>My goal is to build an OSCAR station for my parents with the least
>amount of cash outlay.  I can loan (give?) them my old Kenwood R-599
>receiver and an HR-2510 10 meter transceiver, so I figured
>inexpensive receive/transmit converters would be the way to go.  Any
>other suggestions that would let me get them up on AO-10/AO-13 for
>under $300?

Aside from a transmit converter to 435 MHz, and a receive converter
from 145.8 MHz, you'll probably need an antenna mounted GASFET preamp
and a 100 watt amp. Of course you need steerable gain antennas for
2 m and 70 cm. The benchmark is the KLM 22C and 44CX  with a Mirage
D1010N. That will allow comfortable SSB contacts even when squint
angles are poor. Under better conditions, 10 watts is enough power,
especially if you're satisfied with CW contacts.

You'll want to build your own antennas to stay within budget, wooden
2x2 booms and aluminum clothesline wire elements will work, or a helix
will be fine on 435 MHz. A Mirage would blow the whole budget by itself. 
A modest tube amp, say from an old commercial radio, GE or Motorola, that 
was re-biased to AB1 could get you the necessary power cheaply. You can 
build excellent GASFET preamps yourself and save $60 right there. Feedline
is important, and expensive. 9913 is the minimum cable for the uplink
feed at $0.62 a foot. RG-58 will do following the preamp if the run isn't 
too long. CATV hardline is an alternative for the transmit line. The loss 
is low and the cable is often free as a roll end from the local cable company. 
There have been several articles in the ham press about fashioning your own 
connectors from ordinary plumbing supplies. Don't sweat the VSWR mismatch.
You can retune the antenna driven element matching network a bit and it
will work fine.

Getting a functional SSB station for under $300 is going to be quite a
challenge. If you go with Campbell's transverter, you're looking at
nearly $200 for the kit. A 2 m receive converter is going to set you
back another $70 or so, and a preamp is $79 if purchased, and close
to $20 if you build it yourself. You probably need $60 of cable, and
even the homemade antennas are going to run $15-$20 a piece unless you
can scrounge the materials for free. Then you have to fabricate an Az-El
mount for the antennas. Some pipe fittings and a Radio Shack tripod will
do, but that's at least another $30. Then there's still the matter of
a power amplifier. Even the surplus tube conversion is likely to cost
$50. A budget of $500-600 is more realistic unless your scrounging 
skills are very well honed.

Gary
-- 
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
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