[MRCA] Looking for BC-AL-430 Transmittter Info and Related Items

[Mike Hanz]

On 5/14/2014 5:47 PM, Christopher Bowne wrote:
> Picked up an apparently un-hacked BC-AL-430 at Near-fest. Missing 
> tubes, but otherwise in good condition.  Looking for info on getting 
> it on the air, figure I can run about 400 VDC for B plus, I believe it 
> uses 12V DC for filaments, even though it is designed for use in 28V 
> DC aircraft.

The tube filaments are nominal 7.5 volts but obviously they are 
connected for 28v by series-ing them.  I hear that you can substitute 
much less expensive type 45 tubes if you reduce the low voltage to 24 
volts and check to make sure the series string is providing equal 
voltage to each tube filament.  I haven't tried it personally.  The 
design B+ should be 300 volts DC.  AB5S has done some groundbreaking 
work in substituting newer tubes, but I don't believe his tests are 
collected in a single web page as yet.  He has a beautiful complete 
operating system that he displayed at HamComm in Dallas a couple of 
years ago, but I don't have the web page he placed it on right at hand.

> Surprised that the original application was voice only, with no CW or 
> MCW mode.

I'm a little puzzled here, as the system diagram and transmitter control 
box has provisions for CW and MCW.  Do you have a manual for it?  If 
not, you can download the -AR manual at 
http://aafradio.org/docs/SCR-AR-183-283_manual.pdf - I don't believe 
it's significantly different.

> Can it be made run on CW without bad chirp?

Yes.

> I came with a 4 to 4.something megacycle TU, can it be pulled down 
> into the 80/75 meter band with that TU?  I would definitely be 
> interested in a TU that actually covers the 3.5 to 4 mc.

There are quite a lot of these TUs out there.  I suspect one will turn 
up with the folks on this list, or if you widen your request to the 
ARC-5 and milsurplus lists, I would certainly think so.

73,
  - Mike  KC4TOS

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