[AMRadio] Stewart Warner, old radio

John E. Coleman (ARS WA5BXO) wa5bxo2006 at pctechref.com
Thu Nov 2 12:35:52 EST 2006

Hi Charlie - 
	I guess it might be called an airplane dial.  It is circular with AM
at the top and two SW bands at the bottom.  In addition to the large double
pointer it also has a single pointer which spins around the center as a band
spread (mechanical reduction vernier).  

Thanks to Darrell, WA5VGO, for the link to where I found a schematic. 
I was right.  It is wired wrong in a number of places and has some of the
wrong component values.

As for the filter capacitors cans.
They were the round cans with a single ping coming out of the bottom.  They
were mounted with a large nut, which threaded onto the protruding threads
surrounding the single terminal post on the bottom of the can.  I cut the
crimped top off of the cans to gain access to the inside and there was no
oil, chemical or anything inside except the metal foil.

The perforated material which lined the inside of the can may be made of
some type ceramic as an insulator to keep the foil from shorting against the
can yet allowing the electrolyte to pass through.  

There are some pictures of the inside stuff removed from the can.  The
perforated material in the picture was in a complete circle lining the
inside of the can but it was broken taken it out so that only half is left
to show.

Pictures here

So it is my understanding that the electrolyte bonds with the foil on both
sides.  The molecules which bond to the aluminum, form an insulating barrier
and the molecules which are farther away from the foil are still conductive
and become the other conductor of the capacitor so it must pass through the
perforated insulator to reach the aluminum can as the other terminal.

So basically, the capacitor is made of a metal foil and a conductive liquid
separated by an insulating material which is;

1. A result of a chemical change at the surface of the foil.


2. The metal foil is already coated with an insulating paint which is not
penetrated by the electrolyte?  

I think it is the first 

John, WA5BXO

Using the term "2nd Detector" really shows my age doesn't it? HIHI

For the new guys;
The regenerative and TRF receivers of long ago had a detector stage to
convert the CW signal to audio signal.  This type of detection is
technically a heterodyne/mixer device, detector became the word all
heterodyne/mixer devices.  Later when the super heterodyne receivers
arrived, the RF to IF heterodyne/mixer device was called the first detector
and IF to Audio device circuit was called the second detector. 

Now if I can just adjust the "cat whisker" a little looser for those weak
signals. HIHI

Thanks, 73
John, WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of k0ng at inebraska.com
Sent: Wednesday, November 01, 2006 7:51 PM
To: amradio at mailman.qth.net
Subject: Re: [AMRadio] Stewart Warner, old radio

Hey John, you forgot to list the 1st Detector??  (just kidding)

Is it a nice airplane type dial ??

73, Charlie,  K0NG

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