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

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

No Spam wrote:
I'm trying to come up with some ideas for multi-op field day station
isolation. Main problem will be front end desens between Voice and CW
portion of the same band. Main concern is on 20M

I'm thinking simple stub filters. Though they are wide, I would think
that there would be a few DB of isolation 100Khz away. Perhaps several in
parallel to narrow it up a bit.

Would a simple LC resonant circuit with perhaps 20-30Khz of BW work?

Any thing else I should be considering?


Thanks You!

I considered stubs and lumped-element filters but last year with the Machias
Radio Group, we ran two stations w/o any filters... an FT1000MP on CW and
TS430 on fone (http://www.geocities.com/bswadener/fd2007/). The tents were
separated by about 1000'. We had almost nonexistent issues with
interference.

If you want to work through design of lumped-element filters, Jim Tonne
WB6BLD (http://tonnesoftware.com/) has some nifty software available. Stubs
are covered in a book written by George Cutsogeorge W2VJN, "Managing
Interstation Interference - Coaxial Stubs and Filters", available he
http://www.qth.com/inrad/book.htm.

73 es gl,
Bryan WA7PRC

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

On Wed, 07 May 2008 01:29:18 -0500, No Spam wrote:

I'm trying to come up with some ideas for multi-op field day station
isolation. Main problem will be front end desens between Voice and CW
portion of the same band. Main concern is on 20M

I'm thinking simple stub filters. Though they are wide, I would think
that there would be a few DB of isolation 100Khz away. Perhaps several
in parallel to narrow it up a bit.

Would a simple LC resonant circuit with perhaps 20-30Khz of BW work?

Any thing else I should be considering?

I've used stubs to clear things up. I've been surprised how well they
work. Just remember what band you're on.

Another possibility is a beverage antenna. Get that as far from the
transmitting antennas as you can - though keep in mind the real estate
limitations in Field day

--
-73 de Mike N3LI -

On Wed, 07 May 2008 21:35:21 +0000, Dave wrote:

"No Spam" wrote in message
. ..
I'm trying to come up with some ideas for multi-op field day station
isolation. Main problem will be front end desens between Voice and CW
portion of the same band. Main concern is on 20M

I'm thinking simple stub filters. Though they are wide, I would think
that there would be a few DB of isolation 100Khz away. Perhaps several
in parallel to narrow it up a bit.

Would a simple LC resonant circuit with perhaps 20-30Khz of BW work?

Any thing else I should be considering?


Thanks You!

coax stubs are too broad...

I thought so too, until I tried one. I was working 20 meters on a
tribander ans a KW, teh guy beside me was on a 40/30 meter fan dipole
running legal limit. Antennas were less than 50 feet apart. Without th
stub, I couldn't work period, with it, it knocked the 40 meter signal
completely out, FAPP.

-73 de Mike N3LI -

On Wed, 07 May 2008 16:05:47 -0600, Larry Benko wrote:

I have done exactly what you want to do and you will not accomplish it
with LC filters and stubs alone.

I would suggest that No Spam might try an experiment, making a stub as a
first try. It's simple enough that if it doesn't work, there isn't much
effort wasted.

Can't say for sure why some say a stub won't work, while the one I made
worked gangbusters, and cured the exact problem No Spam was looking at.

-73 de Mike N3LI -

Mike Coslo wrote:
I would suggest that No Spam might try an experiment, making a stub as a
first try. It's simple enough that if it doesn't work, there isn't much
effort wasted.
=====
Mike , Was that a single or treble stub (Pi shape) ?

Frank GM0CSZ / KN6WH

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

Highland Ham wrote:
Mike Coslo wrote:
I would suggest that No Spam might try an experiment, making a stub
as a first try. It's simple enough that if it doesn't work, there
isn't much effort wasted.
=====
Mike , Was that a single or treble stub (Pi shape) ?

It was a single stub. The situation was during a contest, so I had to
come up with something quick. I can only imagine something like a Pi
stub would have been all that much better.

- 73 de Mike N3LI -