[ARC5] ATD Transmitter Longwave Tuning Unit Repair

[Mike Morrow]

Thanks Dave for the intersting details of operating your ATD on the 630m band.

CRR-47207 TUs should have PA PLATE SWITCH position 4 (360-450 kHz) wired to a higher inductance tap than than the tap for position 3 (295-360 kHz).  That's what the CRR-47207 schematic shows, and that is how my #317 is wired.  When the PA circuit is switched from 5 or 4 to 3, 2, or 1 the PA capacitance in parallel with the PA inductance is doubled.  Position 4 with one PA cap needs more inductance than position 3 with 2 PA caps.

I like how you've put a semi-exotic unit on the 630m band and I like your report on its signal quality.  What antenna did you use and how many RF amps are typically indicated?

The fact that the ATD was not supplied with the 200-540 kHz tuning unit but was supplied standard instead with the CRR-47208 540-1500 kHz tuning unit seems to indicate that someone told Bendix to make operation in that band of higher importance than operation on 200-540 kHz and the important naval and maritims frequency of 500 kHz.  Perhaps that had the same motivation which the T-15, T-16, T-17/ARC-5 and the O-16/ART-13 had.

73,
Mike / KK5F

-----Original Message-----
>From: David Stinson <arc5 at ix.netcom.com>
>Sent: Jan 4, 2021 9:32 PM
>
>Howdy, Mike.
>On 1/4/2021 12:21 PM, Mike Morrow wrote:
> >Interesting, Dave.  Do you use the ATD dynamotor to power your ATD?
>Yes; I haven't tried it on HF CW.  I did make some contacts
>on 630 Meters (473 KC CW) and it had a good note.
>Oh HF, I've only used it on 75M phone.  Yesterday,
>I didn't get any audio and smelled something hot.
>Haven't looked into that yet.
>
> >Position 5 on PA Switch J must go to the lowest coil inductance tap on 
>the PA coil.  Position 5 (max >clockwise) on OSC GRID G and OSC PLATE H 
>capacitance and PA PLATE J inductance switches set the TU for >450 to 
>540 kHz operation.  I am missing the "error" or quirk in this 
>configuration. :-)
>In this unit as-found, the PA coil taps match
>the switch positions as they should, with the
>exceptions of taps 3 and 4, which are reversed
>from where it would seem they should be.
>
> >Have you tried the CRR-47206 antenna coil?
>Yes; both stand-alone for my 630 Mtr digital
>station and with the ATD on Longwave.
>It does work, but introduces some signal
>attenuation due to circulating currents
>between the internal coil and its grounded
>metal case.  I need to do a real comparison
>to my unshielded variometer.  One of these days...
>
>GL OM ES 73 DE Dave AB5S