[ARC5] ARC-5 as VFO

[Mike Feher]

Right around 1960 I designed and built a BFO using an ARC-5 transmitter
capacitor. I forget the oscillator tube that I used, but I remember building
it on a small chassis and I used the gearing attached to the capacitor. This
is where all those ARC-5s went, HI. I took the dial plate from the front of
the transmitter and filled the back of it with molten solder. In a sense I
made a flywheel. I attached it to the shaft I made, and, with a good single
spin of the knob I installed, the cap would tune from start to finish. Boy
did it have smooth tuning. I used it mainly on CW and I did not notice any
drift, but, actually measuring it was way beyond my means back then. Later
in the early 70's I built a 20 meter only CW transceiver, all solid state,
with digital readout, and built in electronic keyer and the works,. Again, I
used an ARC-5 cap for the VFO, even though I was tempted to use a DDS, but
back then it would have taken way too many discrete ICs. Regardless, on this
VFO I used a FET and I soldered the FET can directly to the back plate of
the variable. This not only assured mechanical stability, but, a decent
thermal mass also. It was a beautiful little rig and I worked the world with
it. I think it put out about 10 watts. Wish I would never had scrapped it
for another project. Those ARC-5 caps are truly amazing. 73 - Mike   

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 

-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Michael St.
Angelo
Sent: Sunday, November 22, 2015 2:35 PM
To: kgordon2006 at frontier.com; Arc5 at mailman.qth.net
Subject: Re: [ARC5] ARC-5 as VFO

Ken,

I found the article on the ARRL Periodicals Search:

Linear Tuning with a War Surplus Capacitor HAM RADIO JUN 1989 (PG. 40)
Pivnichny, John, N2DCH

Mike N2MS



-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Kenneth G.
Gordon
Sent: Friday, November 13, 2015 2:13 PM
To: Arc5 at mailman.qth.net
Subject: Re: [ARC5] ARC-5 as VFO

On 13 Nov 2015 at 18:36, mstangelo at comcast.net wrote:

> There was an article in Ham Radio magazine discussing the stability of 
> the variable capacitors used in Command Set transmitters.
> 
> It did mention the tpye of metal used in the construction; I don't 
> remember if it referred to the MO capacitor or all of the variables 
> used
in the set.
> 
> I'll have to dig out that article.

Boy! Would I ever love to see that!

Ken W7EKB

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