Topband: Transmit High Pass Filters for BCB Interference

[Mark Schoonover]

Mark,

I had the same problem - I live a mile from 760 AM at 50KW 24/7. I used a
homebrew highpass filter and that helped but didn't quite reduce it enough.
What I figured out was the signal was also on the coax braid! I put two mix
71 toroids, wound 6 turns of coax through them as close to the rig as
possible. Made a huge difference in interference. The signal went from 60
over 9 down to a manageable S8 on the fundamental. Harmonics don't fall
into ham bands so not worried about them. Mostly I suffered from severe
overload and distortion across the low bands.

HTH

73! Mark KA6WKE

Website: https://www.ka6wke.net
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On Mon, Jul 29, 2019 at 9:29 AM Mark K3MSB <mark.k3msb at gmail.com> wrote:

> A friend of mine in our local radio club sent me the following email
>
> "I'm 6/10's of a mile from an AM 910 KHz. transmitter. They operate with 5k
> daytime and 2k at night.
>
> They're S9+45db on 160 meters with clear audio and S9+35db on 80 meters.
> have an inverted "V" resonant at 3.715 MHz. orientated east-west, towards
> their reflector tower."
>
> The station is willing to pay for a filter for my friends station,  and he
> has looked at notch and band pass filters but has concerns.
>
> I recommended he look at transmit high pass filters to knock out signals
> below 1.8 Mhz and provided him with various links:
>
> https://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html
>
> http://www.kf7p.com/KF7P/Morgan_Filters.html
>
>
> https://www.dxengineering.com/search/part-type/transmit-high-pass-filters/product-line/dlw-associates-am-broadcast-band-brick-wall-high-pass-filters?autoview=SKU&sortby=Default&sortorder=Default
>
> I have no practical experience with any of these filters and was wondering
> what the TB Gang thought.
>
> He would prefer one that handled 1.5 KW but I told him he may have to
> settle for 200W.
>
> He prefers an "out of the box" solution.
>
> Thanks
>
> Mark K3MSB
> _________________
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>