Mike,
I just built this filter from kit I had acquired couple years ago. All AM
interference is gone with this filter online before my RX antenna preamp. I
also tried it on my transmit antenna (to listen without preamp) and it
attenuates AM interference better than my transmit BPF (Hamation) when
listening with main atenna (top fed sloper on 160). I think my interference
was also coming from some station around 1400MHz at least when I tuned
around couple years ago. I don't see it at all with this filter online,
without there is lots of artifacts on SDR. It has very sharp drop below
1.8MHz, like -35 dB at 1.5 MHz and -45 dB at 1.4 MHz. There is some
attenuation already on 160 m band, like couple dBs at low end of the band,
and one could try to tune it by squeezing/spreading wire on toroids but I
have not tried it. I will send you couple pictures of measurements in
direct email. I don't know how fast one can get these shipped from VK land,
but price is reasonable.
https://www.minikits.com.au/electronic-kits/filter-kits/hf-highpass-filters
I also have 7 or 8 pole filter from same Aussie guys and it also almost gets
rid of AM interference but is not quite as sharp. I don't see that 7 or 8
pole filter on website so probably not available any more.
73 de Marko N5ZO
------------------------------
Message: 3
Date: Sun, 30 Jan 2022 16:57:46 -0500
From: "Mike Ryan" <mryan001@tampabay.rr.com>
To: "'towertalk'" <towertalk@contesting.com>
Subject: [TowerTalk] Broadcast Band AM Transmiiter Intererence on 160M
Message-ID: <000001d81624$6b762c10$42628430$@tampabay.rr.com>
Content-Type: text/plain; charset="us-ascii"
There have to be dozens of readers here who have or HAVE HAD AM broadcast
AM radio interference on 160m and even on 80m. I found some old
contributions to the subject where the DLW filter was suggested. I have a
friend who uses one by K7FP. I wonder if anyone would care to share their
experience here. I need to pick up something asap but before buying I just
thought I would ask for feedback on actual experience with any brand or kind
of filter. By FAR my greatest offender is at 1420AM which is less than one
mile from my qth. Thanks. - Mike, K4CVL
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