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 <[email protected]> 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 > > _________________ > > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
