For signals reaching your equipment via coax shield: I found something that
works very well to eliminate this is a pair of back to back baluns as close
to the rcvr as possible. --Mike, WV2ZOW
On Mon, Jul 29, 2019 at 1:34 PM Grant Saviers <grants2@pacbell.net> wrote:
> Here is what I used when I had the same problem 50kw line of sight 4
> miles 1MHz. Expensive, but worked very well.
> http://herostechnology.co.uk/pages/RF_Filters.html
>
> Having the filter between rig and amp worked fine for me. 200w rating
> for the Heros.
>
> My power line had ~1v of RF, so ebay Sprague 20 amp line filters were on
> the shack 120v supply and 240v amp also. Plus 240-31 ferrites on the
> green wires.
>
> It will take some proper ferrite chokes to kill the RF on the coax
> shields and any other control cables. Plus a good ground system.
>
> IMO, Dunestars have poor reliability for their HF bandpass filters when
> on DXpeditions.
>
> I always like to see the VNA sweep in the ad and then use my VNWA to
> test whatever I buy since the tuning is hand optimized. A couple went
> back for retuning.
>
> K9YC has some comments re BCB rejection for 6 band filter sets. That is
> another alternative.
> http://audiosystemsgroup.com/BandpassFilterSurvey.pdf
>
> Grant KZ1W
>
> On 7/29/2019 9:29 AM, Mark K3MSB 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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