[ARC5] BC sets and others.

[Geoff]

The 262 kc was to sharpen the passband to minimize interference when driving 
close to a transmitter site. The RF stage contributed to image rejection 
lost by going to 262 kc.

Some home and auto radios in the early 30's were even 175kc and National 
built RAS, a WW2 HRO-Jr for the Navy with 175 kc so it would cover the 200kc 
and up range used.

In the 20's when the superhet was in its infancy IF's as low as 13 kc were 
used and many others up to 100kc were common. Technology didnt exist yet to 
make selective IF transformers.

Carl


----- Original Message ----- 
From: "Robert Eleazer" <releazer at earthlink.net>
To: <arc5 at mailman.qth.net>
Sent: Tuesday, January 21, 2014 6:38 PM
Subject: Re: [ARC5] BC sets and others.


>I have two of the BC band sets, both of which are in pretty good shape, 
>only a couple of extra holes drilled in the case on one.  One is missing 
>its BFO coil and I think I'll order one for it from Fair Radio.  And of 
>course I have that extra BC band tuning dial as well as some spare 239 KHZ 
>IF transformers from another BC set that someone had hacked up and added a 
>transformer and power supply - I turned it on only one time and it started 
>smoking, so that was the end of that.
>
> I have found two different BC band conversions for BC-453's.  One tells 
> you how to modify all the coils, including the IF transformers (but not 
> the BFO).  The other just has you modify the RF section coils and leave 
> the 85 KHZ IF alone - I wonder how the image rejection is on that one.
>
> Geoff:
>
> Yes, in general, it seems that automobile radios of any era are head and 
> shoulders above the rest of the crowd. Making even a decent AM BCB radio 
> seems to be a lost art and making a really good one is almost unheard of. 
> My NC-190 is far better than anything you are likely to find in that 
> regard, but of course it uses an external antenna.  Especially disturbing 
> is the slapdash dial calibration on so many of them.
>
> I wonder though, why was 262 KHZ  chosen for the older automobile radio 
> IF's?  Somewhere lost in all my junk is a 262 KHZ transistorized AM radio 
> IF; I would imagine those are especially rare.
>
> Wayne
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