At our club we make certain that our dipoles are strung end-to-end at
nearly the same height. We also make liberal use of common mode chokes
on both ends the the transmission lines for each station. This seems to
work for us relatively well as we can usually operate phone and CW on
the same band without much, if any, interference. I always run CW and I
sometimes hear some trash form the phone station. This year we traced it
down to a philosophy of "all knobs to the right" on the phone
transmitter (an IC-7300). I was using my Kenwood TS-930S with the INRAD
roofing filter in the 40 MHz IF. With that mod, it has become a pretty
stout receiver, on par with my Orion II ( which I've had to FD in the
past) if the signals are ~100 kHz apart. More separation would always
help, but we'd still strive to keep the dipoles end-to end and at nearly
the same height.
Kim Elmore N5OP
On 7/3/2017 11:13 AM, Jim Thomson wrote:
Date: Mon, 3 Jul 2017 06:52:42 -0700
From: Grant Saviers <grants2@pacbell.net>
To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Field Day
<We (N7KE) haven't had the lack of interference others note re same band
<operation on FD. So am looking for ideas about what to chase or improve.
<Operating 2A on two separate generators - Honda inverter 1000EU, no
<interconnections of stations
We experience lot's of buzz from cw into ssb, need to get as far up the
band as possible. Reverse also true. About the same level of trouble
as last year with the beams 75' closer together.
Tried a new vertical 40m dipole this year on ssb and noticed less
problems, which was expected with the crossed polarization.
Any designs for 100w same band filters appreciated.
Grant KZ1W
## band pass filters, each being 7000-7300, probably are not going to do much
good,
if 2 x xcvrs used on the same band, say 40m cw..and 40m ssb. Heres a thought
though.
I see ICE and others make band pass filters for the warc bands, like 100 khz
wide for 17+12M,
and only 50 khz wide for 30M band. If they can make a 50 khz wide band pass
filter for 30M
band, they, or somebody should be able to make any BW filter you want. IE:
say 7000-7050,
or 7000-7075 for 40m CW.... then perhaps 7100-7300 for 40m ssb, or perhaps
7150-7300,etc.
## Or perhaps an LP filter for 40m CW..with a sharp cut off at whatever
upper freq u want, like perhaps
7050, 7070, etc. Then say a HP filter, again with a sharp cut off, for 40M
ssb, like 7100 khz.
## 6 or 8 pole xtal filters, custom made, might be of some benefit...on RX
only. Same deal, like 7000-7070
etc, for cw....and something similar for 40m SSB. But if the 40m SSB station
has broadband TX IMD,
the CW station will still RX the imd, but less of it.
## I believe a band pass filter is just a combo LP + HP filter in series.
Perhaps a bandpass filter for 40M
cw use, but with a sharper cut off for the LP filter portion. And a band pass
filter for 40M SSB, but with a
sharper cut off for the HP filter portion. Band pass filters that would
handle 100-200 w, with the above
narrow widths, might well chop off some of the broad band trash, hash, buzz,
imd,clicks, etc on TX.
## A stand alone, tunable high Q RX pre-selector might be of some benefit.
The TX imd on ssb, with the K3
running 100w out, will not be wonderful on the CW stations K3...on RX. This
is where you want real low TX
IMD...on ssb....and no clix at all on cw.
Jim VE7RF
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--
Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology, CCM, PP
SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)
/"In theory there is no difference between theory and practice. But, in
practice, there is." //– Attributed to many people; it’s so true that it
doesn’t matter who said it./
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