At 08:25 PM 7/10/2007 -0400, you wrote: >Hi Ray, > >Point well taken. > >I shouldn't have described what I had in mind as splatter. "Over >modulation" would probably be more correct. > >I DX foreign medium wave stations from Asia and the Pacific, and the #1 >reason this type of DXing is a big challenge is due to the wide signals >from domestic (North American) broadcasters, especially the 50kw >flamethrowers in the vicinity. > >For instance, when I tune 1017 kHz, A3Z Tonga with my SDR-1000, I expect >some QRM from any domestics on 1020. However, even with directional >Beverages and phased arrays I sometimes have problems with KOMO 1000 >(Seattle) putting out a swath of energy and "monkey chatter" that affects >1017 kHz (noticed when tuning in LSB to avoid the nearer station on 1020). > >That's why I was thinking maybe a broad notch that I could manual "drop" on >1000 kHz (for instance) would help in this regard. > >The challenges of foreign MW DXing are not unlike those of ham radio >contesting. The SDR-1000 is the best radio I've encountered for this >purpose, when coupled with some carefully-chosen low pass filtering. > >73, > >Guy KE7MAV
Hi, Have you tried RF phasing to reduce local MF interference? For example you would be receiving A3Z on your phased array or Beverage and you can be receiving KOMO on a small loop antenna. Combine the signals and adjust the loop so its phase cancels KOMO on your DX antenna. You could also use a small whip for KOMO and use a separate combiner/phase shift circuit to do the same thing. MFJ used to market such a device ... designed for HF ... however I have heard of dxers modifying it for MF. Personally I have used this kind of 'RF phasing' for qrm rejection with my interest in Crystal Radio DXing. It takes a little getting used to but it works. I bring the antenna into the shack into a kind of 2 stage antenna tuner (2 high Q circuits in series) carefully adjust both circuits to maximize the DX and minimize the QRM. In my experience it is easier to deal with the interference of weak signals before detection. Jim VE3CI _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
