Fw: Fw: [HBR] coil shields

Mon, 15 Apr 2002 12:34:10 -0400

>Maybe some thin walled tubing... fence top rail tubing?
>Might not look too bad if you could cut it square and shoot
>it with aluminum paint. How far from the coil does the shield=
 need
>to be?
>John

Did some thinking about the shields at work yesterday.  Soda cans=
 are 
way too thin, took one apart.  I went into tools and parts and 
started looking around at electrical conduit but it's too thick. =
 I 
ran the situation past my friend Paul.  This guys really good for=

ideas.  You can give him a pile of crap and a couple of paper=
 clips 
and he'll make something useful out of it.  So he thinks for=
 about 5 
minutes and and says why don't you cut the bottom off of some=
 large 
caps, like the ones you replaced in one of the machines last=
 week.  I 
tossed them out I replied.  No problem, Paul says, I pulled them=
 out 
of the garbage can and saved them.  These caps are about 10=
 inches 
tall and 3 inches in dia.  We cut 4 inches off the bottom and=
 viola!  
All I have to do now is punch a hole in the bottom to clear the=
 coil 
socket, a little polish and I think I'm in business.

>PS: The "new" HBR11 works (albeit with some ferocious hum=
 that's
>modulating the CW...which brings me to a question:

>What's an acceptable ripple on the B+ line? I am seeing about=
 10V 
PTP
>AC on top of B+

10 volts is way too much.  If your using a choke and cap type=
 filter 
the ripple should be in the millivolt range.

Does the hum start when the BFO is turned on?   If so the BFO 
oscillator signal is getting back into the B+ supply.  Or=
 sometimes 
the AC on the filament needs to be bypassed with a .01 mfd cap. =
 A 
good idea to do to on any oscillator.  Or like you said a bad=
 ground. 

.... I did jumper in replacement caps, but made no
>difference.
>I think there's a lot of grounds that "arent" . Off to go=
 tighten up
>a lot
>of screws!
>
>
>
>At 01:17 PM 4/14/02 -0500, you wrote:
>>They used to have manufactured coil shields ...James Millen ?
>>but would be impossible to find today. Can't think of really=
 thin
>>aluminum that size ....yes, I can.....soft drink cans (maybe=
 too
>>thin). Take the paint off with MEK ? flatten the base and cut=
 a
>>hole in it for the socket. Figure out some way to dull the=
 edge
>>a little ...maybe "glue on" split wire insulation or "roll" it.=
 If
>>you
>>need a larger shield, "Foster's" makes a larger one.  Other
>>than that, take thin aluminum sheet stock, bend it over a=
 mandril,
>>and pop rivit it into cylinders. Tabs on the bottom for=
 mounting.
>>
>>73s  Kees K5BCQ
>>
>>
>>--------- Forwarded message ----------
>>From: Helmut Usbeck <[email protected]>
>>To: <[email protected]>
>>Date: Sun, 14 Apr 2002 12:56:59 -0400 (EDT)
>>Subject: [HBR] coil shields
>>Message-ID: <Pine.LNX.4.33.0204141248390.271-
>>[email protected]>
>>
>>
>>I did a little touring around the web last night looking for a
>>source of
>>shields for plug in coils.  Didn't find anything.  The first
>>thought I
>>had
>>was was Campbell soup cans but they look pretty mickey mouse to=
 me
>>after
>>sitting one on a receiver chassis.  Anyone ever try making=
 some
>>that have
>>that professional zing to them.
>>
>>Regards,
>>Helm.  WB2ADT
>>
>>
>>************************************
>>Visit the HBR Receiver Web Site with over 100 pictures of=
 receivers
>>and
>>construction notes...... via http://www.qsl.net/k5bcq/
>>
>>Retrieve reflector archived data via http://mailman.qth.net
>>
>>
>>HBR mailing list
>>[email protected]
>>http://mailman.qth.net/mailman/listinfo/hbr
>>
>>
>>************************************
>>Visit the HBR Receiver Web Site with over 100 pictures of=
 receivers
>>and
>>construction notes...... via http://www.qsl.net/k5bcq/
>>
>>Retrieve reflector archived data via http://mailman.qth.net
>>
>>
>>HBR mailing list
>>[email protected]
>>http://mailman.qth.net/mailman/listinfo/hbr
>>
>
>************************************
>Visit the HBR Receiver Web Site with over 100 pictures of=
 receivers
>and
>construction notes...... via http://www.qsl.net/k5bcq/
>
>Retrieve reflector archived data via http://mailman.qth.net
>
>
>HBR mailing list
>[email protected]
>http://mailman.qth.net/mailman/listinfo/hbr

-- 
Helmut Usbeck, [email protected] on 04/15/2002