Boatanchors II
** Amateur radio equipment mods are found in chapter B **

RCA AR8503 VLF Radio communication receiver.

Frequency coverage:

1: 15- 40 kHz 3: 100-250 kHz
2: 40-100 kHz 4: 250-600 kHz

Valves: 3x 6K7 + 6F6.
Type 1V2:
RF amplifier + Regenerative detector + Audio amplifier + Audio output stage.
Manufacturer: RCA Radiomarine Corporation of America, New York, N.Y
[From NRHF auction 2003.10.19]

RCA AR8503 chassis front, with open window

seen from above

The receiver seen from rear

It is two sets of different coils to the right, and the third set of coils to the right for
band 1 and 2. The first set of coils are tuned with the capacitor at the front, the
second are tuned with the section at rear, they are supposed to form a tuned bandpassfilter,
and the third set is tuned with the center capacitor.

The receiver seen from below.
The 3rd set of coils for the highest bands (band 3 + 4) are located at upper left side of the picture.

Connections: +90V, +22V, +6V, -BA, ANT/GND.

Simplified circuit diagram for the receiver (schematic).

Note: The set of coils are screened from the other (under chassis, while the others are above).
None of the coils have iron cores. Also note the unreasonable large value for 6F6 cathode resistor,
but I checked it. Cathode resistor for the last 6K7 is 5.5k.
The trimmer is connected to the first tuned circuit - not the 2nd as drawn.

National HRO-50T amateur radio receiver with matching speaker
[From NRHF auction 2003.10.19]

National HRO-50T seen from above

Have the following coil plug-in's:

Band code General coverage Band spread
J 50-100kHz  
H 100-200kHz  
G 180-480kHz  
C 1.7-4.0MHz 3.5-4.0MHz
D 3.5-7.3 7.0-7.3MHz
B 7.0-14.4MHz 14.0-14.4MHz
A 14.0-30MHz 27.0-30MHz
AB 25-35MHz  
AD 50-54MHz  

Wanted: "Band F" (480-960kHz), plug in coils module
Manufactured: 1951. The coverage seems to be somewhat different from what Fred Osterman claims
Circuit complement:
6BA6/EF93 1st and 2nd RF amplifier, 6BE6/EK90 mixer, 6C4/EC90 HF Osc., 6K7 (EF39) 1st and 2nd IF amplifier,
6J7(EF36) BFO, 6H6 AVC/Det, 6H6 ANL, 6SJ7 1st Audio, 6SN7 Audio, 2x 6V6 Audio output, 0B2 108V stab.
Rectifier 5V4 ++ , it seems to be somewhat unclear and printing mistakes
IF: 455kHz

HRO50T. Plug-in coilpacks with one section demounted (3.5-7.3MHz)
see pg-f12 for SSB-conversion


Hallicrafters R-274/FRR (= Hammarlund SP600)

Philips BX925 Radio communication receiver

Have been curious about this receiver, since it was seen in '67 when I was in the army at Alta.
Glad I left it to another because all decoupling capacitors were defective and must be replaced.

Philips BX925
Many of the round "electrolytic capacitor looking" boxes are supposed to be IF transformers.
The receiver is mentioned in Fred Osterman's book " Shortwave Receivers - Past and Present",
it has 75kHz IF,
Valves: 8x EF93 (6BA6), EK90 (6BE6), 3x EAA91 (6AL5), 2x EL90 (6AQ5), 5Y3GT, 0D3.

210-540kHz 9.1 - 13.7 MHz
1.45-3.6 MHz 13.7-20.7 MHz
3.5 - 9.1 MHz 20.7 -32 MHz

Couldn't resist bringing this picture of an old radio ( )
[From NRHF auction 2003.10.19]

WL117 - possibly a microwave meter(?), has micrometer tuning
Have no idea where I got it from.

HP623B, 6cm signal generator

Further notes:

Mods for Lorenz 6P203 Communication receiver on page b71 and f12
Modifications for Siemens Receiver 745 E310 on page
b72 and f12

I enjoy collecting these items and and investigate into the techniques.
I will show them on my website for others to enjoy. I am not interested in selling them,
however - please do not ask.
Instead, I hope to help others who collect this type of gear and would like to
hear from them.

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Updated: 2004.10.30