[ARC5] MF and the ARC-8 system

[J Mcvey]

Does the ART-13B also need the external tank? Is it totally Chrystal controlled for HF and MF? Is there still a HF VFO in the B series?This is getting to sound expensive and complicated already. Finding all of the parts will probably take a long time.
It looks like I'm going to take one of the badly Ham hacked SCR-274 transmitters and converting it for MF operation. it will look "semi-legit" sitting there with the BC-453.

 


     On Tuesday, November 10, 2015 4:32 PM, Mike Morrow <kk5f at earthlink.net> wrote:
   

 
> I was looking at some art-13's and noticed that not all of them had the
> VFO for MF. Many just have a blank plate installed in that position...

Most of these transmitters lack the O-16 or 0-17.

> ...they describe the ART-13 and ART-13A using the VFO MF modules . Module
> 016/ART-13 appears to be the most desirable, allowing the the tuning range
> of 200-1500 KHZ while the 017/ART-13 tunes 200-600KHZ.

Strictly speaking, the O-16/ART-13 is associated with the USN's T-47/ART-13, while the O-17/ART-13A is associated with the USAAF's T-47A/ART-13.  That's what is historically proper to the AN/ARC-8, a USAAF set consisting of the AN/ART-13A and the AN/ARR-11 (BC-348-*).  But...there's nothing that prevents either LF/MF oscillator being installed in any transmitter (except a AN/ART-13B which has the CDA-T crystal oscillator installed).

The T-47A is an improved T-47, built by Stewart-Warner.  It has a vernier scale on HF VFO dial B that facilitates setting frequencies at 1 kHz intervals, plus a DC control power safety-interlock switch that opens when the top cover is removed.

But NOTE THIS!  The AN/ART-13-series have NO PA TANK CIRCUITRY FOR LF/MF in the transmitter.  That is provided externally.  For 472 kHz operation you need either of the following:

(1) The CU-25/ART-13 PA tank.  It would be useful to have the SA-22/ART-13 antenna switch/relay as well.  This is a USN approach.

--- OR ---

(2) The CU-32/ART-13A PA tank and antenna switch.  This is the USAAF approach and is the superior device, except that the CU-32 is almost as large as the transmitter.  Ultimately the USN used the CU-32 too.

> The ART-13B variant used the crystal controlled MF oscillator module CDA-T
> which tunes 200-1500 KHZ, but with 4 slectable channels.

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.

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.

> 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.

Mike / KK5F
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