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Old May 8th 08, 11:03 PM posted to rec.radio.amateur.antenna
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Default Field day station isolation

K7ITM wrote:
...(I've built several somewhat similar filters using
copper clad for the shielding, and they work quite well.)
Would a suggested design be helpful?..


I would like to hear of your designs, please.
Particularly how you physically work the
copper fabrication/solder etc.

Thanks -

Craig 'Lumpy' Lemke

www.n0eq.com





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Old May 9th 08, 12:06 AM posted to rec.radio.amateur.antenna
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Default Field day station isolation

On May 8, 3:03 pm, "Lumpy" wrote:
K7ITM wrote:
...(I've built several somewhat similar filters using
copper clad for the shielding, and they work quite well.)
Would a suggested design be helpful?..


I would like to hear of your designs, please.
Particularly how you physically work the
copper fabrication/solder etc.

Thanks -

Craig 'Lumpy' Lemke

www.n0eq.com


Hi Lumpy,

I'm fortunate to have access to a shear that cuts fiberglass/epoxy
board stock reasonably cleanly. I use all double-sided stock, copper-
clad on both sides. I typically set up the stop for, say, 2 inches,
and make a bunch of square pieces. They'll become end pieces and
partitions between "cells". Then I cut a couple 2 inch wide strips
using the same setup; these will be the sides, and they are whatever
length I need. The base piece is typically a quarter inch wider (or a
bit more) and the same length as the sides. I plan out where I need
holes, and punch them in the partitions and end pieces (or sides, if
that's what I want). Then I tack one of the square pieces just short
of the end of the base, so I can solder it to the base on both sides.
Same on the other end. Then side pieces go in, tack-soldered to the
base and the two end pieces. Avoid tacking where partitions will go.
Put in partitions where you want, and tack them. Then run a bead of
solder along each place where two pieces of copper-clad come
together. Occasionally I'll also put in something to support coils or
wires, too. Then I built the filter...soldering some parts to the
copper clad for ground.

Some filters I can get by with a minimum of partitions. I would
expect for a sharp cutoff filter like the "FD adjacent band" filter
that I'd need to use a partition to separate any two adjacent
resonators.

When I first started making filters this way, I was expecting to have
to seal off the open end of each cavity. The description above only
puts copper-clad on five of the six sides of each cell. I was amazed
to find that it's practically never necessary to do that. For
example, I have a 1MHz bandpass filter that has stops specifically at
2MHz and 3MHz. I used it to clean up the output of a signal generator
so I can test for harmonic distortion. That filter shows about 120dB
attenuation at 2 and 3 MHz, in spite of the open-topped cells.

If a picture would help, I'd be happy to send one via email.

Cheers,
Tom
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Old May 9th 08, 03:37 AM posted to rec.radio.amateur.antenna
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Default Field day station isolation

K7ITM wrote:

I'm fortunate to have access to a shear that cuts fiberglass/epoxy
board stock reasonably cleanly. . .


For those of us who don't, I've found that tin snips do a good job and
without the irritating dust you get if you saw it.

Roy Lewallen, W7EL
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Old May 9th 08, 04:09 AM posted to rec.radio.amateur.antenna
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Default Field day station isolation

Roy Lewallen wrote:
K7ITM wrote:

I'm fortunate to have access to a shear that cuts fiberglass/epoxy
board stock reasonably cleanly. . .


For those of us who don't, I've found that tin snips do a good job and
without the irritating dust you get if you saw it.

Roy Lewallen, W7EL


I've also used a table saw with a VERY fine-pitch blade, set just above the
table. It makes nice 90° corners. A Shop-Vac keeps the dust from getting
out of hand.

73,
Bryan WA7PRC


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Old May 9th 08, 05:56 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Feb 2008
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Default Field day station isolation

K7ITM wrote:
...(I've built several somewhat similar filters using
copper clad for the shielding, and they work quite well.)
Would a suggested design be helpful?..


If a picture would help, I'd be happy to send one via email.


I'd like to see pics please.
My return is valid.

Thanks mucho


Craig 'Lumpy' Lemke

www.n0eq.com




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Old May 12th 08, 09:25 PM posted to rec.radio.amateur.antenna
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Default Field day station isolation

On May 8, 9:56 pm, "Lumpy" wrote:
K7ITM wrote:
...(I've built several somewhat similar filters using
copper clad for the shielding, and they work quite well.)
Would a suggested design be helpful?..

If a picture would help, I'd be happy to send one via email.


I'd like to see pics please.
My return is valid.

Thanks mucho

Craig 'Lumpy' Lemke

www.n0eq.com


I've posted some pix at http://mysite.verizon.net/bruhnstv/. They'll
be there for a short time.

Cheers,
Tom
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