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.

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!

on the next  page are   more images of the a618    

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mod record : date Mon May  5 19:15:32 EST 2008