[HBR] eBay NOS NATIONAL VELVET VERNIER DIAL ICN, Ham Radio (item 26002332...

[Bob AH7I]

On Thu, 24 Aug 2006 N2EY at aol.com wrote:

> In a message dated 8/24/06 9:32:21 AM Eastern Daylight Time,
> waltah at earthlink.net writes:
>
>
> > >  I found this National ICN type on "that E site"...
> > >
> > > It's number 260023324900
> >
> > That's a nice one, all right.   It was at $24 when I looked, last
> > night.
> >
> > The issue with these dials is that they have a 5:1 ratio which is
> > fine for coverage of the usual ham band if you are building a
> > receiver for AM and CW only as was the usual case ~1960 but gives a
> > VERY fast tuning rate for SSB -- over 200 kcs/revolution if covering
> > all of 80-75M, for example.
>
> IMHO. 200 kc per revolution is way too fast for CW as well as SSB. In fact 20
> kc. per revolution is almost too fast. This is particularly true if the
> receiver has decent selectivity.
>
> I suspect that many classic receivers had such fast tuning rates for two
> reasons:
>
> 1) Good slow dial drives were expensive and scarce.
>
> 2) The way hams operated back then was very different. Many hams used rigs
> that were not very frequency-agile, and operating split was the rule rather than
> the exception. You would call CQ and tune the entire band looking for
> replies. (This is also why old-time operating used such long calling sequences - they
> gave time for you to find answers). With such operation, you needed to be
> able to get across the band fast.
>
> All that is changed now.
>
> >
> > I like the JB/Miller 6:1/36:1 two speed drives for this sort of
> > application.   You can use them with a modified National dial or make
> > your own dial, which could be as simple as a metal frame with a
> > cardboard face.
> >
> > Or, with a few more hours of work (hey, it's a hobby ...) you can
> > make a sandwich consisting of a piece of your dial face, a 1/4"
> > plastic spacer around the edges, a 1/32" plastic cover, and a metal
> > frame as before.   Cut the metal frame so it overhangs the dial face
> > at the upper corners, you can drill through the panel behind the
> > overhangs to put in lamps (or LED's?).  A 3/32" plastic pointer fits
> > easily in the 1/4" allowed by the spacer.   With careful work and a
> > nice paint job (TEST ON A SCRAP BEFORE PAINTING PLASTIC) it will
> > equal the best of them for both looks and function.
> >
>
> Or, use a disk of plastic and a fixed pointer.
>
> --
>
> But there's an easier way.....
>
> The tuning capacitors from surplus ARC-5 transmitters and receivers, as well
> as the LM and BC-221 series of frequency meters, will do a better job than
> almost anything else. They all have integrated antibacklash gear-drives, and
> built-in dials.
>
> Best of all, you can usually get a junker-but-good-for-parts ARC-5 or
> LM-BC-221 for less than $24.
>
> 73 de Jim, N2EY
> ************************************
> Visit the HBR Receiver Web Site with over 100 pictures of receivers and
> construction notes...... via http://www.qsl.net/k5bcq/
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>
>
> Retrieve reflector archived data via http://mailman.qth.net/mailman/listinfo/hbr
>
>
I like the National PW and gearbox. One needs a logging scale but hey,
what's so tough about that? As for sliderule dials, DO NOT underestimate
the power of string and a long linear scale.

-Bob AH7I ex WB4MNF, 3D2MD, A35MD