[ARC5] Selectivity and the BC-455

[Ian Wilson]

Measured inductance of the pie-wound coil is about 176uH
(assuming that the measurement frequency of the AADE L/C
meter is well below 2833kHz).

This resonates with about 18pF at 2833kHz, so this would look
like a tuned winding, given typical 12SK7 input capacitance and
wiring capacitance (not an untuned winding, as I initially thought).

Measured inductance of the solenoidal coil is about 16uH, which
needs about 200pF to resonate at 2833kHz.

73, ian K3IMW


On Fri, Oct 24, 2014 at 1:52 PM, WA5CAB--- via ARC5 <arc5 at mailman.qth.net>
wrote:

> Here is, as saliors used to say, the "straight skinny".  I have and have
> just gone through the manuals on all Type-K derived Command Sets.  All
> IFT's
> in all models of all sets have two coils in all IFT's.  In all IFT's up
> through 1415 KC, both the primary and the secondary coils are pie-wound
> and both
> are tuned.
>
> In all 4200 KC and all 2830 KC IFT's except those in R-27/ARC-5, the
> primary coil is single layer close wound and is tuned.  The secondary is
> pie-wound
> and untuned (or fix tuned).  In all IFT's in all R-27/ARC-5 (both before
> and after 01 January 1945), the primary and secondary are both pie-wound
> and
> both are tuned.
>
> Probably someone with the necessary parts and the time should take a
> BC-455, carefully alingn it, and measure the 6db and 60db bandwidths.  Then
> substitute all three IFT's with a set from an R-27, re-align it and repeat
> the
> bandwidth tests.
>
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
>
> In a message dated 10/24/2014 13:15:36 PM Central Daylight Time,
> jeepp at comcast.net writes:
> > Ken,
> >
> > Now that's a new twist on the subject.  Truth told, I have never seen a
> > single-coil ARC-5/274-N receiver, but then again, its only recently that
> > I've been actually disassembling them.   If there is only one coil, no
> > wonder the selectivity is "less than what might be desired".   Which
> > manual carries that design, if you or anyone can pass on?
> >
> > Regards
> >
> > Jeep - K3HVG
> >
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