[MRCA] BC-605 Interphone Amp

[WA5CAB at cs.com]

Mike,

In a message dated 10/27/2007 12:13:59 PM Central Daylight Time, 
kk5f at earthlink.net writes: 
> >Actually, that's not the way that it came down.  Prior to mid 1943, when 
> two 
> >MWO's began to be accomplished on BC-604's (and slightly later on 
> BC-684's), 
> >SCR-508 and SCR-608 required an RC-99 in the vehicle if interphone services 
> 
> >were going to be available and SCR-528 and SCR-628 included BC-605 for the 
> >interphone function.  Or to put it another way, as a brief review of the 
> 1942 and 
> >1943 edition TM's will show, the original models of the BC-604 and BC-684 
> had no 
> >interphone capability.
> 
> That's an interesting point about the early BC-604/684 units.  I had never 
> run across that info in the later dated manuals that I have for these units.  
> The BC-605 in the RC-99 system must have been mounted on one of those rare 
> single-receiver type of mounts.  I wonder if many of the un-MWO'd early model 
> BC-604/684 units remained in service by end of WWII.

The BC-605 isn't part of RC-99.  RC-99 is a standalone interphone system.  
The interphone amp is either BC-367 (12 volt) or BC-667 (24 volt).  The other 
components are several BC-606 and one BC-739 interphone control boxes, plus 
cable & misc.

However, if you look at the early system you will find an SCR-538 which was a 
BC-603 receiver and BC-605 mounted without the BC-604 transmitter in the 
standard FT-237.  After the MWO's, the SCR-538 disappeared from the TM.  There 
were as part of AN/VRC-5 standalone transmitter mounts (FT-508) and single 
receiver mounts (FT-346), although I have never personally seen one.  I know of a 
couple of people who have or had one or the other.   

But even in the 1947 edition manuals, although the text says little about it, 
there are two or three schematics of each of the receivers and transmitters.  
The SCR-608 manual is a little easier to follow but in both of them you can 
find evidence of the trail of changes.

One last point.  As with the BC-611's, never assume that the model of the 
receivers or transmitters is what it says on the nameplates.  They are attached 
to the easily removable front guard castings, many of which have been swapped 
around over the years.

> 
> There is a SCR-508 sitting on the floor few feet from me right now.  I'm one 
> of probably very few who considers it a beautiful system.  The SCR-508 is a 
> milestone in military radio development and one of the most innovative, 
> best-designed, and capable radio sets of WWII.  I contend that it occupies the 
> place with respect to other field radios of WWII that the M1 Garand rifle 
> occupies with respect to other rifles of WWII.
> 
> The communications range of the SCR-508 in its 20 to 28 MHz band must have 
> at times produced some unintended and surprising DX for its military users.
> 
> A great mystery remains:  What has happened to all those mounting racks?  
> That essential FT-237 is a real rarity.  I owe mine to an AJ Link auction 
> several years ago, and I've not seen many before or since.   
> 

They turn up from time to time.  I found a batch of about ten a couple of 
years ago.  And a friend recently turned up about thirty but I don't know whether 
he was successful in acquiring them.  They almost never turn up among the 
usual radio people, although Fair Radio has had many of them, last batch around 
five years ago.  The vehicle people are where almost all of them turn up or end 
up.
Robert Downs - Houston
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MVPA 9480
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