[Racal] RA-17 knobs n info

[David Craft]

Hi Paul,

Racal didn't seem to like providing inductor info; I've always supposed they were manufactured specifically for racal rather than commercial-off-the-shelf and thus had part numbers that would not be helpful even if you knew them.

So here's my two-cents worth:

I would get a T180-2 (or thereabouts) powdered iron toroidal core and wind it with more than 200 turns of #28 awg enamel coated wire, and less than 300 turns.  It's a bother, but you should get more than a milliHenry and more than 200 milliamps and still be inductive at 30 MHz.  I suspect this would be a better part than Racal had, as toroids were either uncommon or unavailable in those days. Amidon might be a source for the toroid, at about $ 5 US.

I hope you discover a commercial part that needs less effort, but the original worked well at 1 MHz, so you need to find a substitute with a resonant frequency lower than that.
J.W. Miller company might be a good place to start.  If you were not really interested in frequencies near 1 MHz, the 6300 series might work.

I don't have an RA-17, but I've always wished for one.  I've spent some time looking over its map, in times past.  The above guess is based on the assumption the filter following that stage has a high input impedance.

Hope it helps.

Dave


On Dec 31, 2010, at 10:00 AM, racal-request at mailman.qth.net wrote:

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> Message: 1
> Date: Thu, 30 Dec 2010 22:06:50 +0200
> From: "Paul Galpin" <galpinp at absamail.co.za>
> Subject: [Racal] RA17 knobs and info wanted
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> Can anyone help?
> 
> I need 
> (a) The value of the RF choke in the anode of V3, the RF amplifier. It's not in the list at the end of my manual. 
> I want to use this cascode circuit to make a wideband antenna distributor (one in, several out, a couple of dB gain)
> (b) some of the switch knobs for the RA17- not the circular skirt ones, the "pointer" type.
> 
> Paul Galpin
> ZS2PG
> 
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