Like Robert, I also started out with the SRF-59 and due to my
arthritic thumbs found the analog tuning troublesome. I have mostly
used a SRF-T615e as my primary ULR. The majority of the 581 stations
I've heard was with the "tiny giant". I've heard stations from across
the Atlantic and Pacific on the T615 using only its internal antenna.
Besides sensitivity, one of the receiver's pluses is its antenna,
allowing for very tight nulls - often better than larger loops. As
with any receiver I've used there is always a downside. The T615
doesn't handle strong adjacent frequency signals as well as say the
E100. This is mostly a problem during the daytime, for I rarely
encounter it at night.
There are lower cost alternatives to the T615. The one most often
mentioned is the Etón E100. It offers the possibility of future
modification. Another is the Sangean DT-400W.
For more on the subject I suggest you look at the www.dxer.ca website.
It contains a wealth of information on the ultralight receivers.
Unfortunately the perfect receiver has yet to be marketed
Best wishes and good DX.
36°22'51"N / 97°26'36"W
(near Perry OK USA)