[ARC5] Fwd: Re: [MRCA] SCR-274-N receiver bandwidth spec

[J. Forster]

It is almost certainly at AC ground. It also shields between the coils to
prevent capacitive coupling, which might be significant, depend9ng on the
geometry.

-John

==================
>
>
>
> -------- Original Message --------
> Subject: 	Re: [MRCA] SCR-274-N receiver bandwidth spec
> Date: 	Sun, 23 Mar 2014 14:09:02 -0400
> From: 	D. Platt <jeepp at comcast.net>
> Reply-To: 	jeepp at comcast.net
> To: 	Military Radio Collectors Association <mrca at mailman.qth.net>
>
>
>
> Yes, the washer is metallic (Al) and has a "pan handle" that attaches to
> one of the vertical leads. I'm assuming its the ground lead, as all the
> coils are buttoned up, just now.
>
> Jeep
>
> On 3/23/2014 1:32 PM, J. Forster wrote:
>> If the washer is metalic, even brass or aluminum, it will decrease the
>> mutual inductance between the coils, thus narrowing the 'rabbit ears'
>> response curve or narrowing the BW.
>>
>> -John
>>
>> ===============
>>
>>
>>> Gentlemen,
>>>
>>> Continuimg with my ARC-5/SCR-274-N receiver IF coil mod investigation,
>>> I
>>> just completed yet another coil set, this one from an ARC-5/R-26.  In
>>> doing so, I find yet another mechanical set-up in these coils.  This
>>> one
>>> has the long brass screw (up from the bottom) and threading into the
>>> phenolic spacer bar (vice using a nut).  All else is the same as other
>>> coil sets and I find that coils sets are, so far,  interchangeable.
>>> The
>>> question for today is what is the original published (sic) receiver
>>> bandwidth of this receiver?  I'd like to know what the starting point
>>> should be, even though I'll be measuring unmodified and modified sets.
>>> At this point, I can again say that there /is/ a detectable improvement
>>> in selectivity.  What remains is to quantify things and, as we speak,
>>> I'm proceeding with the procurement of a suitable sweeper.
>>>
>>> Another point of possible interest is the fact that in each and every
>>> coil set there appears a 1/2" disk "shield" positioned between the
>>> upper
>>> and lower coil bobbins.  Could this be what others have spoken of as a
>>> method of providing electrical separation (read: increased selectivity)
>>> between these coils?  If so, then someone back then was
>>> thinking.........
>>>
>>> Regards    Jeep - K3HVG
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