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[VHFcontesting] Nice VHF amps available reasonably priced.

To: NEWSVHF@mailman.qth.net, "vhfcontesting@contesting.com" <VHFcontesting@contesting.com>, VHF@w6yx.stanford.edu
Subject: [VHFcontesting] Nice VHF amps available reasonably priced.
From: Terry Price <terry@directivesystems.com>
Date: Tue, 19 Jan 2021 15:40:36 -0500
List-post: <mailto:vhfcontesting@contesting.com>
Folks, thought I would pass this along. I've bought several of their HF-6m
amps, 2m amps and 70cm amp (these are just the pallets, I add my own
support electronics and relays). They work VERY well and the workmanship on
the boards is first class.

The HF/VHF units use a pair of MRF300's which are a cheap plastic tab
device that is about $40 each from Digikey. They require 50V at 10-15A and
12v for bias. I've found a device, a TL783 which is a 3 terminal regulator
that unlike 78XX series which will only take up to 36v on the input,
TL783's will take 50V and give up to 700ma output current, more than enough
to run relays and provide 12v bias. These devices only need two resistors
to set the voltage. I build mine with a pot in place of one resistor so I
can adjust the voltage to suit whatever relays I'm using.

If you are looking for medium power, 500w class, for these bands, check
them out. I have no affiliation with them, just a happy customer. Shipping
can take months with the current COVID situation but I've gotten some
within weeks.


Terry Price - W8ZN
Directive Systems and Engineering
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