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1941 NARBA Radio PSAs from RCA

Ah, yes make sure to call a professional radio serviceman to have all those buttons retuned,
and while you're at it, make sure and have him check all the tubes and replace any weak ones with genuine
RCA Radiotronic tubes.....

Those buttons needed retuning by various methods, some quite kooky.
The best had a trimmer coil and variable cap for each button...with very good selectivity but touchy to adjust.
 
Tom Wells said:
Ah, yes make sure to call a professional radio serviceman to have all those buttons retuned,
and while you're at it, make sure and have him check all the tubes and replace any weak ones with genuine
RCA Radiotronic tubes.....

Those buttons needed retuning by various methods, some quite kooky.
The best had a trimmer coil and variable cap for each button...with very good selectivity but touchy to adjust.
Click to expand...

And I thought they were as simple as programming an AM car radio.......
 
Perversely, these individualally tuned circuits of seperate L and C gave a seemingly impossible balance between high selectivity and a high-fidelity (hi-end response), depending on your professional radio serviceman.

They depended on accurate peaking by "da guy" and really could sharp tune a dx of particular interest or side a bit off to the side on a local power house and give 15 khz.
 
Glad to see you liked this rare record of mine...

Wish someone would write a comment in my blog...or, better, donate a few bucks. I've got the financial miseries (bad!) lately.

I have two complete Tastyeast Jesters shows from 1930-31 that I could post if there's enough intere$t. Of course, I'd give your board a plug...
 
My Westinghouse from 1938 had the little circular inserts with the call letters. The buttons had separate oscillator and and radio frequency antenna adjustments. Our area was a little different. We had two stations with major freqeuncy adjustments-CKLW moved from 1030 to 800 staying as a 5000 watt Class II, and WFDF upgraded from a Class IV to a Class III, going from 100 watts on 1310 to 1000 watts at 910. So the order of the stations (WJR 750, WWJ 920, CKLW 1030, WFDF 1310, WBCM 1410) changed to (WJR 760, CKLW 800, WFDF 910, WWJ 950, WBCM 1440). Hence to tune all the stations, they had to make new inserts for the changed button order. The new inserts were typed on the sticker master sheets with circular cutouts.

I had a lot of fun and frustration restringing the dial on that set.

The selectivity curve was bimodal, giving it and incredible frequency response and sound, but sacrificing selectivity. I think the bimodality was accomplished with the IF transformer adjustments being tuned to slightly different frequencies. As you tuned across the frequency, the tuning eye narrowed, widened slightly, and narrowed again before widening off on either side of the carrier.
 
The good sets with three section tuning capacitors ( and at that price range, pushbuttons, too) were normally peaked in the IF section as S Cat says, one a little high and one a little low of the center IF design freq.
If this was done right, the combined response of the stagger-tuned IF gave a flat-top curve,
which gave less peaky-sounding audio, and a better balance of sound with more high frequency audio response.
The tuning eye opening a little as you tune across a signal could be the IFs a little too far apart, or it could be a normal
AVC effect. Anyway, it's a touchy thing to do and greatly affects the tradeoff of frequency response vs selectivity.

It was not an advantage at all when such sets went to the shortwave bands, where the 15 khz bandwidth
sounded great on good signals, but was not very good once SW stations got realy packed in every 5 khz.

On my Philcos, the range of the osc coils were limited, "lo" or "hi".
I think 3 of them only tuned 520-1200, and the other 4 tuned 900 to 1600 or some split like that.
So you had put the lower end stations down with the "lower end" buttons.

I'll bet there were situations where not all desired choices could be set up after the change.

Many of the simple ones had mechanical stops, where the regular dial would tune until hitting a stop.
The dials were rotated much like an old rotary telepohne dial.
These were often not very precise, and the user was still required to fine tune.

The better sets with "electronic" push button tuning were more expensive but the tuning was perfect every time.
 
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