[CQ-Contest] Yaesu FT1000MP Filters

[Ron M.Philip]

I would appreciate some advice on the advisability of using INRAD
filters as opposed to the filters available from Yaesu in a stock
FT1000MP which I hope to acquire shortly.

Many thanks

Ron
VE7NS



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>From N7RX" <n7rx at arrl.net  Sun Mar 12 17:46:19 2000
From: N7RX" <n7rx at arrl.net (N7RX)
Date: Sun, 12 Mar 2000 09:46:19 -0800
Subject: [CQ-Contest] Band pass filters for M/M


W7LT runs 4A QRP M/M for Field Day. We typically split modes 2 & 2. One of
the stations runs 40 & 20 CW, while another runs 40 & 20 PH (a 3rd and 4th
run 80/10/15 CW and PH, respectively). Problem is that the 40 CW station has
been blanking the 40 PH station, practically disabling it entirely. We've
tried different rigs, antennas and spacing:

1998: CW Icom 725 with a 40M loop; PH Kenwood 440 with a double extended
zepp. The stations and antennas were about 20 feet apart. 40M blanking was
really bad and I don't remember about 20.

1999: CW Icom 706mkII with a 40M loop; PH Icom 765 with a bobtail curtain.
The stations were 100 feet apart. 40M blanking was semi-tolerable; 20M
blanking intolerable.

2000: CW Icom 706mkII with a 40M loop; PH Elecraft K2 with Lazy H on 40.
(This station will go to 10M CW during the day this year with a 10M monoband
yagi. The 20 PH station will be about 150 feet away with a tri-band yagi).

We've got to eliminate this problem. The following has been suggested:

1. Bandpass filters to reduce intra-band mode interference - we don't have a
cross band problem
2. Improve earth grounds at each station (we've had none to speak of).
3. More spacing.

I'm particularly interested in #1. How does/can a bandpass filter be tuned
to deal with mode interference? Bear in mind that we're running QRP, and I'm
having a hard time understanding what's cause this in the first place. I
think its the 40M loop.

The good folks at the Portland Amateur Radio Club thank you.

73 Neal N7RX
W7LT FD Site Boss





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