[ARC5] BC-221 and LM on eBay

[Mike Morrow]

I am unfamiliar with the AN/ARC-25A.  How does it differ from the AN/ARC-25?
 
USN AN/ARC-25 employs the AN/ART-13 and the AN/ARR-15, each of which is capable of accurately setting channel frequency without use of an external CFI like an LM-*.
 
USAAF AN/ARC-8 employs the AN/ART-13A (T-47A) that has VFO dial B with vernier scale and improved calibration book for setting 1 kHz intervals.  The associated AN/ARR-11 (BC-348-*) is tuned to the transmitter using the system's MONITOR-NORMAL switch.  The AN/ARC-8 has little need for an external CFI like SCR-211-* (BC-221-*).
 
These systems minimized the value of LM-* and SCR-221-* frequency meters in aircraft HF liaison systems well before the end of WWII.
 
Mike / KK5F
 
-----Original Message-----
From: Doran Platt 
Sent: Mar 28, 2022 8:08 AM
To: ARC-5 Mail List 
Subject: Re: [ARC5] BC-221 and LM on eBay
 
In my ARC-25A acft re-creation here, I have the requisite LM meter. In this case, more for looks. But, in the ARC-8 setup, the other LM does a nice job as a calibrator for the BC-348.  One has the external supply with the voltage adjust toggle switches, the other is the tall metal cabinet version with an internal a.c. supply.  
Jeep K3HVG

On 03/28/2022 8:38 AM Bob kb8tq  wrote:
Hi
 
As an “all in one” gizmo for keeping a pile of HF radio gear tuned up,
I still would put the LM / BC-221 pretty close to the top of the list. Yes,
there would be other things on the list as well. With care, you can do a
lot of things with one of them.
 
The fact that I can fire the typical example up and it still zeros is mind
boggling. Do this and to that properly and they still seem to deliver good
accuracy. I can pretty much guarantee that the examples I’ve played
with haven’t seen a cal shop for a *very* long time.
 
Are there more accurate ways to check your transmitter output? Sure
there are. Do I *need* to know that I’m 0.0000003 Hz high on 10M? I
can’t think of any practical reason why. The gear that checks the transmitter
to that level isn’t going to be of any help setting the receiver to frequency.
The pile of gear to do it all to that level makes a BC-221 look small and light.
(the BC-221 also warms up faster … :) ).
 
I would say that they have withstood the “test of time” pretty darn well.
Very few instruments out there still do a proper job 60+ years after their
last full calibration.
 
Bob
On Mar 27, 2022, at 7:41 PM, Richard Knoppow  wrote:
 
Of course the same argument could be made for virtually everything discussed on this list. Too old, lets just smash it up and dump it in the ocean.
I am not so sure the _method_ of making frequency measurements is so obsolete. Comparing a well calibrated standard against an unknown source. Of course using a BC-221 as an alignment generator leaves something to be desired but, it CAN do a lot of the job.
I happen to have a BC-221, a K I think, have to look. Mine is in a wooden case with an AC power supply in the bottom in place of batteries. Has a modulator. It is still surprisingly useful and I am far from ready to toss it in the trash. Of course, one must have some knowledge of history to understand what it is and what it does. A lot of "younger" people wouldn't know how to work a dial telephone if they had to so the decision as to whether something is useful or not may depend as much on experience and knowledge as on reality.
 
On 3/27/2022 4:08 PM, J Mcvey via ARC5 wrote:
I've seen some 221's "repurposed" as radio projects of various types.
Unless it's part of a historical display, they are a very antiquated way of doing alignments, so not of much practical value anymore.
On Sunday, March 27, 2022, 06:59:52 PM EDT, Roy Morgan  wrote:
(Years go now) a friend put an LM out at his spot at the big Gaithersburg Hamfest. When he came back, someone had left two more to join it. I think none of them sold!
I have dug into the "needs repair" power supply here - it is Coast Guard Power Pack for LM-7 Type GF-118, 1942:
-Original iron replaced by newer non-military transformer and two chokes
-Rectifier jumpered by diodes
-One of three oil bathtub caps clipped out of service (2uF 600v)
-Two-prong line connector has line cord soldered on
-Original power outlet connector still present
This thing needs overhaul but will serve well once set right.
Roy Morgan
K1LKY Western Mass
K1LKY68 at gmail.com (mailto:K1LKY68 at gmail.com) 
Hubert Miller  wrote:
 
I think hamfest price is around $10, not much more, for LM and BC-221.
 
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