[ARC5] BC-453 dial calibration (continued)

[Mike Morrow]

WALDO:
>> I received two plug-in coil sets from David Stinson (thanks 
>> Dave) and tried them out using NDB MW (Moses Lake, WA) about 100 
>> miles west of Spokane at 408 kc. The results:
>>   Original coils - 413 (dial reading)
>>   Coil set one   - 413 (same reading)
>>   Coil set two   - 409 (very close to the 408)

DAVE:
>That's really interesting, since both the coil sets
>I sent have the same part number.  That the original
>and Set One give the same error while Set Two
>results in near-correct tuning calibration is, IMHO,
>unlikely to be coincidence.  The coil set with MFP
>is probably from a later-production set.  One of these
>days, if  The Almighty isn't tired of my foolishness by
>then, I'll do some "coil swapping" and see if I can find
>an oddity like this.

These are two different coil sets for the 190 to 550 kHz receivers.  All have identical RF and LO coils...only the ANT coil varies:

PART NUMBER
6184 (RAV CBY-46102 version)
- ANT coil has winding for loop antenna.

6184 (ARA CBY-46129 and SCR-274-N BC-453-A,B version)
- ANT coil has NO winding for loop antenna.
- Error was made not assigning this coil set a new part number.

9630 (R-23, R-23A/ARC-5 and R-148/ARC-5X version)
- ANT coil has winding for loop antenna.
- Identical coil to 6184 RAV version, but it needed new number to
  distinguish this coil set from the ARA and SCR-274-N version.

Such info is listed here:

 http://mailman.qth.net/pipermail/arc5/attachments/20160425/24b17647/attachment-0001.pdf

I have not followed this thread closely, but is the local oscillator failing to align properly at 210 kHz using C-9 and at 520 kHz using C-4E, with C-4G set to mid-position as the SCR-274-N manual requires?

It is not unreasonable for one coil set versus another just like it to show the less than 1 percent change in frequency reported here (409 to 413 kHz) until C-9 and C-4E have been adjusted.  (FWIW, the AN/ARC5 manual requires C-4G to be set to minimum position for the R-23*/ARC-5, rather than mid-position specified for ARA and SCR-274-N.)

Mike / KK5F