Message-ID: <004d01c81721$de7ddfd0$06cdfc3e@g3kev>
From: "hamilton mal" <g3kev.ham@virgin.net>
To: "rsgb" <rsgb_lf_group@blacksheep.org>
Date: Thu, 25 Oct 2007 16:12:07 -0000
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Subject: LF: 500 tx
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Hi all
I built a class E type TX in a couple of days, my own design layout etc and
kept it simple, but I am experienced having built equipment over the years
from the valve era, then transistors and today mostly IC technology. The
problem for most would be getting the components and this is where Radcom
falls down, not a single advert even for a resistor. The trouble with the
big suppliers like Farnell is the cost ie minimum order of =A320 each time a
component is required.
My EASY START tx should be easy to get going for most and I would submit the
cct but I do not want to get bogged down with preparation details and find
it would not be published in Radcom.
My cct consists of an IC706 transmitting a couple of watts on 5 mhz / sq
wave conv / divide by 10 / amplified by a 4426 / FET pa / matching coil/C
cct for class E then an old TV line out transformer matching the pa to 50
ohms / 5 pole LPF / SWR meter and away the rf goes via 50ohm coax some 50
metres to the base of the antenna matching network / 1/4 wave inv L at about
33 metres vertical and the rest horizontal.
This is my approach and gives VFO control and good freq stability.
Most of the components were from the junk box hence an economical build. To
date it has proved totally reliable and no smoke. Using this approach would
be an EASYSTART for those contemplating 500.
The PA coil is about 50 years old,  ex TU5 tuning unit ceramic former with a
tinned copper winding, just right for the job. The condensers are also ex
equipment, high voltage.
Is Radcom interested???
73 de Mal/G3KEV