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[AMPS] Bird Wattmeters

To: <amps@contesting.com>
Subject: [AMPS] Bird Wattmeters
From: Peter_Chadwick@mitel.com (Peter Chadwick)
Date: Tue, 17 Oct 2000 09:27:15 +0100
For anyone interested, thanks to the help received here, the panel is finished.

An 8 inch panel, a two hole Bird pick up line, and two meters fitted with Bird
scales. Op amps to drive the meters, because they're not 30 microamp (1mA and
27mA!) A 555 oscillator driving a charge pump to produce the negative rail for
the 741 op-amps (unnecessary if you use modern op amps that can go to zero on
input and output) and a negative regulator using VERY old transistors - MM1613
and MM1614 because they were there in the box. Shielded in a tin can that once
contained mustard powder.....

Works fine, but the paint didn't come out too well - it seems that when using
Hammerite grey hammer finish paint over the recommended primer, you need to wait
a couple of weeks for it to harden, not a couple of days. As this unit is in the
remote antenna tuning shed, I'm not worrying too much.

The holes weren't to much trouble to cut in 1/8 inch thick aluminium, using a
circle cutter that cost about $5 in Sears in Phoenix, Az. These are B-holes,
manufactured to European standards but American (inch ) size, A-holes being
apparently restricted to their natural habitat in Washington DC!

Anyhow, thanks to everyone who contributed to the request for info.

73

Peter G3RZP

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