[ARC5] ATD Transmitter Longwave Tuning Unit Repair

David Stinson arc5 at ix.netcom.com
Mon Jan 4 21:32:32 EST 2021


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

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