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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