[TowerTalk] Field Day

Kim Elmore cw_de_n5op at sbcglobal.net
Mon Jul 3 22:02:41 EDT 2017

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 at pacbell.net>
> To: "towertalk at contesting.com" <towertalk at 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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