Hello Guys,

 

     The Sony ICF-SW7600GR is compact digital SSB portable with reasonably good MW performance, using a stock 4.75" x .37" fixed-coil loopstick for the 530-1700 kHz frequencies.  At $134.80 plus shipping from Amazon.com (via Gigabargain), it has excellent Synch detector function for a portable, as well as decent shortwave performance.

 

     Having a sudden need for a very compact SSB-equipped MW portable to use as a "spotting receiver" for South Pacific DX targets during a short Ultralight Radio DXpedition to Grayland, Washington, I became intrigued with the idea of replacing the SW7600GR's stock loopstick with a 7.5" Amidon ferrite bar, wound with 40/44 Litz wire.  This combination of MW frequency-optimized ferrite and Litz wire has provided huge sensitivity gains not only in the SRF-39FP and E100 Ultralight models, but also in the larger ICF-2010 traditional DX portable.  Upon checking the stock SW7600GR loopstick, it was found to be a smaller-sized copy of the ICF-2010 loopstick system, having a fixed (non-alignable) larger coil and a smaller tickler coil, to optimize spurious signal rejection.

 

     The SW7600GR loopstick was easily replaced with a 7.5" x .5" Amidon ferrite bar-based antenna, wound with 40/44 Litz wire to match the 983 mh inductance of the stock main coil.  The sensitivity improvement was very dramatic, boosting the weak-signal performance of this compact portable past that of a stock ICF-2010.  This was a total reversal of its performance prior to the modification, in which the SW7600GR was clearly inferior to the stock 2010 on all MW frequencies.

 

     At Grayland, the newly hot-rodded SW7600GR performed very well as an SSB "spotting receiver," with different TP station frequencies stored in memory, easily accessed by pushing single buttons.  SSB carrier strength of the "targets" could be quickly checked, and the direction of the received signal could be easily determined by the new loopstick's excellent nulling ability.

 

     On the domestic frequencies, the newly modified SW7600GR provided lots of sensitivity, with easy loggings of KPUA-670 and KGU-760 in Hawaii.  For the 9 kHz split targets in the South Pacific, however, the modified SW7600GR's sensitivity alone wasn't quite adequate to keep up with the modified Eton E100 Ultralight, which had a Murata CFJ455K5 premium ceramic IF filter installed (the same narrow filter as in the Eton E1).  The modified E100 could split off Fiji-639, Tonga-1017, 2ZB-1035 and 2YA-567 significantly better than could the modified SW7600GR, which had to contend with more domestic slop.

 

     Despite this, the compact Sony's function as an SSB "spotting receiver" was excellent, and it directed the AM-mode only Eton E100 to the "hot" frequencies very well.  9 kHz SSB carrier strength can usually be checked even in the presence of domestic splatter, and the SW7600GR was great for this purpose.

 

     For domestic DXers, this modified ICF-SW7600GR would provide a great sensitivity improvement over the stock model, for a very reasonable cost in parts (under $30 for the ferrite bar, Litz wire and other items).  The modification is easy to perform, and the unit remains very compact (a photo is on the Ultralightdx Yahoo group site in the "Roll Your Own DXing Monster" album).  Nulling ability is excellent, and the loopstick's external mounting provides extremely quiet reception compared to the stock antenna, crammed as it is inside a cramped cabinet next to the SW whip antenna.  The full modification article should be written shortly, for those interested in this impressive performance upgrade. 

 

     For serious 9 kHz split-frequency DXers, however, a premium IF filter upgrade would be very helpful in chasing TP's and TA's next to domestic splatter.  The good news is that with an IF of 455 kHz, the ICF-SW7600GR can be modified with the same premium ceramic filter that has transformed the tiny E100 into a DXing sensation this summer.  Well, there's always a nice-to-do project that is on the drawing board...

 

73,  Gary DeBock