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70cm preamp / preselector?



Hello to the list,

I have a couple of items that may be of use to someone. I'm offering these
here first, with the hopes that they
can help someone work the birds or for some other ham use.

I have two quantity, and the items are marked 'Preamp 420 - 450 MHz'.  These
look to be mast-mounted units.
There are two Type N female connectors, one for ANTENNA and one for RX.

Each unit has a pair of tuneable filters on the input, and a trimmer cap in
the amplifier circuit. These units are
powered via the coax from the shack, just like a downconverter.

I do not have any test equipment for 70cm, so therefore I have no specs
whatsoever for these units. I will include the
schematic that I received with the units, although it does not appear to be
the original.

I built a simple enclosure for one of the units from 3" ABS pipe and a pipe
cap. The unit alone measures
approx 5 3/4" long, 3" in diameter. The enclosure is approx 8 3/4" long.

I also want to pass along what I've found by experimenting. I did not receive
any specs with these units,
not even the operating voltage. I've started by applying 9 - 12v and found the
units did not amplify signals. At 18v,
the units had enough gain to overcome the filter loss. I have not attempted
voltage over 18v.

Perhaps someone on the list will recognize these units, and can provide more
information?

>From what I found by experimenting, I believe that these units should more
appropriately be called '70cm Preselectors'.
To begin with, I'm not sure how many preamps include filters. The filters are
effective, but again I don't have any specs..
These units may be of use to someone who has the problem of strong adjacent
signals.

Here are links to some pictures I've taken. Caution dial-up users, pictures
are large - about 400k each.
http://web.totalusa.net/yokshs/preamp.jpg
http://web.totalusa.net/yokshs/preamp2.jpg
http://web.totalusa.net/yokshs/preamp3.jpg
http://web.totalusa.net/yokshs/preamp4.jpg


Price?  Please email me direct at k0kn at qsl dot net with an offer. The first
offer gets their choice of with / without
the custom (hi hi) enclosure.

73,

Kyle Yoksh
K0KN
Olathe, Kansas
Amsat# 35249
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