[ARC5] (no subject)

[WA5CAB at cs.com]

Comments interleaved...

In a message dated 11/10/2015 15:38:22 PM Central Standard Time, 
kk5f at earthlink.net writes: 
> The CDA-T is actually a 20 channel crystal-controlled MF/HF oscillator, 
> with a separate 4 channel crystal-controlled LF/MF oscillator included.
> 
> >It appears from the way it is written, that the ART-13B is not compatible
> >with VFO MF modules.
> 
> The CDA-T occupies semi-permanently the space for a LF/MF oscillator.



The T-412 schematic still includes the MX-128/ART-13 as an alternate to the 
CDA-T. Although several modifications (such as K-106) would remain in place 
in the transmitter, I don't actually see any reason why if the CDA-T were 
removed and an O-16 or O-17 plugged in, it wouldn't still work. You would of 
course want to remove the Low B+ jumper. Further careful study of the 
AN/ART-13B manual turned up the following in the section on the T-412:

        (2) VFO OPERATION -- LOW FREQUENCY
This operation requires the use of Oscillator O-17/ART-
13A.  Circuit operation is outlined in paragraph 2.g.(1)
of this section.

Therefore, you can reinstall the O-17 (or O-16) in the modified 
transmitter.

> 
> FWIW, the T-412/ART-13B also has a LF EXTENDED FREQUENCY switch below the 
> front panel instruction plate. However, it has nothing to do with LF 
> operation. It adds capacitance to allow an amp stage to tune to about 1640 kHz if 
> there are crystals installed for that in the MF/HF portion of the CDA-T.


S-117 is on the T-412 schematic, along with C-151. But aren't a part of the 
original CDA-T conversion as they are not mentioned in the original Gables 
Engineering documentation.. They were apparently added by USAF as part of 
the T-412 contract. The actual figure given in the manual is down to 1670 
kilocycles. Nowhere in the manual can I find how or what operates the switch. 
And I no longer have a T-412 (or any of the CDA-T's).

> 
> >The companion receiver for for MF operation is the BC-348-E . the earlier 
B
>and C models did not have the 200-500 KHZ band.

>I suspect there was never a BC-348-E used with these transmitters. By the 
time the USAAF adopted the design, the BC-348-R and -Q >models were the 
dominant versions, and "on paper" (not on the receiver itself) they were 
JAN-designated AN/ARR-11.


I agree.

> 
> Mike / KK5F
> 


Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480