4 "D" cell Batt Adapt, FT-501, Voice Silence & Manual
The SCR-536 Radio set is the BC-611 and batteries?
3.5 to 6 Mc, single channel 360 mW RF output (typo in manual says 36 mw)
(24 ma * 103.5 Volts = 2.48 Watts Tx DC input power, TM 11-235 paragraph 115 says average RF output power is 255.3 mw, minimum RF output is 170 mw.)
It looks like the "E" is an overlay, i.e. this radio was upgraded form some earlier version.
With label "3885" on PTT side.
The battery box cover says : Place batteries in position with + (POS) end out" and
Use only BA-37 "A" Battery (1.5 V @ 250 mA Rx, 300 mA Tx, can use "D" battery and empty 0.5" shell casing)
Use only BA-38 "B" Battery (103.5 V @ 11 mA Rx, 35 mA Tx)
in this radio,. (BA-1, BA-4, BA-30 or
Flashlight cells will either burn
out or not operate
Range is 1 to 3 miles. The ON switch is activated by pulling up the bottom antenna section. The FT-501 battery adapter takes two BA-30 ("D" cells) and connects them in parallel yielding a longer lasting 1.5 Volt battery.
The "-F" version has a jack for external audio accessories like the HS-30 headphones, T-30 throat microphone, T-45 lip microphone.
The Homing Modification Kit MC-619 allows the AN-190() direction finding loop antenna to be fitted to the BC-611.
Frequency Conversion Kit MC-534 contains 400 crystals and 72 antenna coils and 60 tank coils. This allows using any of 50 frequencies in the radio. To change frequencies the Rx and Tx crystals are changed along with the load and tank coils. No alignment is needed when changing frequency. The Rx crystal is 455 kHz lower (or higher) than the Tx crystal which is on the channel frequency.
For use on 3885 kHz the C-371 tank coil is the correct one. Mine was marked 4035. Note that the C-371 covers 3825 to 4225 kHz per TM 11-235 page 41.
BC-611 with PRC-6 -
BX-49 Box with Coils & Crystals (12 frequencies)
BX-49 Box Labels
Signal Corps, BOX BC-49, 2038 CGG 31393 PHILA-43
CAUTION, Channel Change Requires, Realignment of Radio Set
Voice Privacy PTT cover -The BC-611 is turned by raising the antenna. The Push To Talk switch is very convenient, maybe too convenient such that someone might transmit without intending to. This device covers the PTT switch so you can still hear, but not mistakenly transmit.
PTT Switch is long and has many contacts whose function is labeled on plastic overlay -
Coil Side - There is a plug in coil that is part of what needs to be changed when changing channels, you can see the tops of the tubes
Socket Side - the tube sockets and point to point wiring
Back Plate - There is a hole so you can see the crystal frequency (3885 kc)
Inside Bottom - When removing the chassis unplug the red and green wires. There is a Black plug in jumper and what appears to be two places for attaching 1/4 fasteners, this was probably used in the manufacturing or re-channeling process.
AN-190 (eBay photo) - DF loop antenna, may be for use with the BC-611 since it has a matching frequency range
The BC-611 needs two voltages. "A" battery for the filaments and "B" battery for the plates.
A thought: If the batteries were to last for 24 hours with 2.4 hours of Tx and 21.6 hours of Rx (this might be 3 calendar 8 hour days.) Then for transmit you would need about 33 Watt hours of B+ (8 AA cells) and 6.12 AH of A filament (a single "C" cell will provide 8.3 AH or a single "D" cell 18 AH). Using 8 each AA cells costs about $5.60 compared to using 10 each 9 Volt batteries for $22.50. The tradeoff is that the Switching Mode Power Supply (SMPS) has a higher initial cost.
A BatteryThe tube filaments need 1.5 Volts. This was originally supplied by a single BA-37 battery. This was about the diameter of a modern "D" cell but a little more than twice as long. Do Not Use 2 series connected "D" Cells, this will burn out the filaments. The TM does suggest that you can use one "D" cell and an empty 0.50 shell casing.
The FT-501 adapter allows using 2 "D" cells in parallel. Note that a modern "D" cell has a little more capacity than the BA-37 so you could use a single "D" cell in the FT-501 adapter and it would last about as long as most "B" battery options.
2449550 Battery Adapter, Robert L. Eichberg & Homer R. Montague, Sep 21 1948, 429/1 ; 429/99; 439/627; 439/638 - Replaces BA-37 with two BA-30 common "D" cells.
2036088 Hand Lantern, Roy L. Darling (Bond Electric Corp), Mar 31, 1936, 362/191 ; 362/197; 429/97 - uses "U" shaped battery contact to prevent reversed polarity.
2293354 Constant Polarity Holder for Dry Cells, Leland A. Munchow (Ray-O-Vac), Aug 18 1942, 429/1 ; 429/99; 439/500 - works whichever way cells are installed
2377161 Electric Safety Water Light, Augustus J. Le Strange, May 29 1945, 441/17 ; 340/321; 362/158; 429/99; 43/17 - uses series connected dry cells
B BatteryThe Plate voltage of 103.5 Volts was supplied by a BA-38. The two modern ways of supplying the B+ are either a string of 10 each 9 Volt batteries or a SMPS that runs from a few "D" cells.
Photo at left shows the 4 "D" cell battery adapter from Pietro in Italy.
|Mitchell was aware of
Murphy's Law (Wiki),
probably didn't call it that, when it comes to getting the
polarity reversed when making DC power wiring connections
and that's the subject of patent 2439409. The exact
same problem was present when the first Fuzz Busters were
being made. In that case the answer was to install a
full wave bridge rectifier inside the Fuzz Buster so that
it did not matter which way the input wires are
connected. Silicon bridge rectifiers were not
available in 1942.
TM 11-235 Radio Sets, SCR-536-A, -B, -D, -E, and -F War Department, May 1945
C 1 15 Dec '43
C 2 18 Oct '44
TB 11-235-1 31 May '44
TB 11-235-2 22 Jul '44
TB 11-235-3 8 Aug '44
TB 11-235-4 11 Aug '44
TB 11-235-5 16 Sep '44
TB 11-235-6 14 Nov '44
TB 11-235-7 Nov '44
TB 11-235-8 25 Jan '45
This manual is available on a CD-ROM for $10 + postage. It has the following enhancements over the stock government issue manual:
- 125 pages
- 9 color Photos
- All Bookmarks changed from something like "PART 2" to "Part 2 - Operating Inst" making it much much easier to use.
- The key patents above (not the references).
|U.S. mailing address $
|International Air mail $
Removing the Chassis
Remove the screw from the top cover, and in my case so as to not strain the web strap, remove the screw that holds the strap to the top cover.
Lift the top cover up and off. Note the porcelain antenna insulator comes off with the top cover.
loosen the screw that holds the bottom battery cover on and swing it out and open the door to the bottom.
Unplug the red and green wires and slide the chassis out the bottom.
Tips on Alignment -------------------------------
Date: Sat, 7 Apr 2001 00:26:17 -0500
From: "ROBERT W. DOWNS" <RWDowns_WA5CAB@compuserve.com>
Subject: [MilSurplus] BC-611-F Trivia
As a few of you know, the ferrite slugs in the IF transformers of the BC-611-F are tender", and the adjusting slot often breaks off when you try to do an IF alignment. I've been fighting with what initially looked like a mint condition chassis for the last two days. So far, I've discovered the following. The remainder of the slug (which can no longer be adjusted) is simple to drill out with a 1/8" HS drill bit. Most (but not all) of the remainder of the slug can be pushed out or blown out with LP air. The slug and beeswax residue that won't come out using those methods means certain death to the first replacement slug that you try to install. The solution is to run a bottoming tap into both ends of the transformer, turning it only with your fingers (do NOT use a tap wrench) until it contacts the unthreaded area in the middle of the transformer. The trivia is that the threads are #12-28, probably the least commonly available thread in North America. However, some of the larger machine tool supply houses still seem to have a small number of the taps in stock. I bought a set this morning, along with a die (JIC).
Another BC-611 tip not mentioned in any of the manuals. It is much easier to align the IF's (no noise to contend with) if you do it with the coils and crystals removed.
Date: Sat, 16 Jun 2001 09:31:39 -0400
From: "ROBERT W. DOWNS" <RWDowns_WA5CAB@compuserve.com>
Subject: [MilSurplus] BC-611 DC-DC Converter Spacer
By now, quite a few of you have bought C. Litrico's converters for the BC-611, either directly from him or off the web site in the UK. I have several here and other than in the late BC-611-F (with the thick bottom cover), they all work OK. However, when you shake the set, because the original BA-38 was rectangular in cross section rather than square, there is enough room for everything to rattle around pretty severely, sometimes enough to cause the inverter to stop. I fixed the problem by making a spacer from 1/4" plywood that goes between the three D-cells and the gray fibre or aluminum battery spacer/wire protector. Width is the width of the protector. Length is the length of the three D-cells. Bevel the end toward the bottom cover so that the D-cells will drop in without catching on the spacer. Notch the bottom to clear the B-battery ground spring and the two bosses cast into the top cover.
1/4" phenolic, other plastic, or aluminum would also work and probably last longer than the plywood because of the notching at the top.
My laptop, ordered on Monday for delivery on Wednesday, still hasn't arrived, so I'll be totally out of touch for a while from tomorrow (Sunday).
BC-611 Main Page by Crusty old Joe Stevens
WA4KCY - photo of BC-611 collection -
Military Equipment List - Photo - Schematic Circuit Diagram -
Signal Corps US Army BC611 Transceiver by Nicolas Ducor
Surplus Stuff - Technical Manual -
eBay photo of a BC-721 -
K4CHE Military Radio and Boat Anchors - BC-611 B+ battery Box - Build a BC-611 Filament Battery Supply - home brew details
Pietro in Italy - Inverting type battery adapter that uses 4 "D" cells
[11.1] Tactical Radio Communications -
BC-611 & BC-721 - Pogo Stick Radio SCR-511 BC-745 -
BC-611 Tube Substitution using FETs and then running from 4 each 9 volt batteries.
BC-611 Inverter Power Supply -
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Page Created 11 March 2001.