the A618 Naval Radio.
also known as
RECEIVE OUTFIT ACAS RAN PATTERN 16303
which was part of
LOW POWER MF-HF RADIO COMMUNICATIONS EQUIPMENT TYPE A618/ACAS
This unit was given to me by Dave
Stuart , VK3ASE 20 years ago. I dont not know where it came from
, but it is serial number 6, made by TCA Australia. It
features mid fifties technology, was built in Australia at a time when
we still did that sort of thing. I believe a sister unit still
exists aboard the museum ship HMAS Diamantena in Queensland.
There a few other vague and impartial references to this unit on the
web without manuals, details or schematics. I have been
maintaining this unit in running order
for the last 20 years and two recent failures required me to
partially reverse engineer it and derive a partial set of schematics.
If the real manual is available to me I will publish it here.
The most compelling feature of this
radio is its long wave coverage which gets as low as 37kHz. In
Melbourne suburbia there is little to hear here but with exotic loop,
ferrite rod and its very narrow crystal filter I can pick up
assorted signals, loran A , WWVB 60kHz, and myriad NDBs. Sadly, there
are almost no long wave naval stations active any more, satellites
having done away for their need. A country field trip with a beverage
long wave antenna
clearly picked up Russian and Chinese broadcast stations between
150 and 200 kHz.
The most galling and persistent maintenance requirement is the dial
cord! The original used a woven steel piano wire, long worn out. I have
found medium fishing line gives many years of dependable service,
but its a total crock to re thread. Included
here is my rethreading diagram worked out in one long hot frustrating
weekend. Periodic buffing of the turret contacts is also required.
The radio features deep long wave
coverage, 37kHz to 33Mhz in 7 bands,
dual conversion on assorted bands, bfo (no product detector just
carrier insertion which disrupts AGC) , good if bandwidth control,
wide 7khz, narrow 4khz, narrow Xtal 1khz, very narrow Xtal
and audio filter
at 800Hz, superb agc range, nice band spread and a chassis design
to facilitate maintenance. Most components are easily reachable. (the
ones that fail are always inaccessible anyway!) There is an audio
compressor that actually works and a noise limiter that actually
works. The thing is a mechanical marvel , the simple front panel
controls drive complex systems of cams, levers and gears. The designers
clearly had simple operation in mind for naval personal that did not
require a large theoretical understanding of radio electronics. All
internal wafer switch banks are driven by racks and pinions.
This radio is completely differant from another British made
military radio designated A618, differant hardware, differant circuit.
The designator for this seems to really be A618/ACAS type 15303. I dont
know what ACAS stands for. "A" for Australian ? maybe, after all
it was made in Australia.
There is some more information including some of the history of this
radio on VK2DYM military radio and radar information site
http://www.qsl.net/vk2dym/radio , but sadly, no manual.
From VK2DYM's site the official manual is known as Royal Australia Navy
ABR 5043 Instruction Manual for low power MF-HF radio communication
equipment type a616/acas 1961.
||if in khz
||37 - 85khz
||3.3 -7.8 mhz
||7 - 16 mhz
||15 - 33 mhz
See below for my reverse engineered schematics.
The A618 Naval Radio
The tuning turret of the a618 , impressive
, eh wot ?
reminds me of a James Bond movie prop, the type that expand with great alacrity!
reverse engineering notes and TECHNICAL drawings, my hand drawn schematics
mod record : date Mon May 5 19:15:32 EST 2008