ADDENDUM: RACAL RA-237B Low Frequency Converter, Serial Number 179,
Restoration and Schematic Notes - Gerry O’Hara, VE7GUH, August, 2011
Background:
Racal RA-117 Serial Number ‘N8’ was one of a batch of 3 donated to the SPARC Museum,
Coquitlam, BC in 2007. The Museum already owned two RA-117s, acquired in the late-1990’s from
the Canadian Navy on scrapping a destroyer. These receivers were part of two racks of Racal
equipment which included synthesizers, tuning units and exciters. One of the rack-mounted units
was Serial Number ‘N16’ and, being close in sequence to ‘N8’, has similar variances to the later-
serial number RA-117 units. The Museum decided to retain 2 units and to de-acquire three units.
Serial Number ‘N8’ was on the de-acquisition list and was bought for a donation by Gerry O’Hara in
August, 2008, together with a commitment to restore one of the RA-117’s retained by the Museum
at a later date. Brent Hilpert, another SPARC member, has been working on a later unit, Serial
Number ‘N0115’ (see
http://www.cs.ubc.ca/~hilpert/e/radio/RacalRA117/
).
The 5 receivers were in various states of completeness/cosmetic condition – some with missing and/or
broken tag strips, capacitors removed, broken knob skirts, missing decals etc. The two ‘best shape’
receivers were to be retained for the Museum’s collection. ‘N8’ was ascertained to be the 4
th
‘worst
shape’ overall and was the oldest (earliest Serial Number). However, I selected this one of the two
remaining (Brent was already working on one) due to it having the 0.5 – 1MHz pre-selector, this only
being present in the two earliest models.
Serial Number ‘N8’ was given a general clean-up on arrival at the VE7GUH shack in August,
2008 and was broken down into its component modules for storage and later restoration.
Restoration work finally commenced in late-February, 2009 and Stage 1 (described below) was
completed by April 5, 2009, this rendering the set to working order and presentable cosmetic
condition (but not fully re-aligned/performance-tested).
Performance below 1MHz was ok, but not stellar – (nor is it claimed to be by RACAL). Without the
pre-selector (below 500KHz) the set becomes increasingly prone to noise. In addition, several
spurious responses were noted
1
, viz:
-38kHz (weak)
-200kHz (strong)
-465kHz (very strong)
-534kHz (strong)
-665kHz (fairly strong)
-732kHz (weak)
-800kHz (very strong)
- ‘0’ and 1MHz (v.weak)
1
Explanation provided by Brent and Peter Holtham in ‘N8’ notes
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