I had played around a bit with a corner-fed, corner-terminated "Superloop" ( http://www.bamlog.com/superloop.htm) last fall, but foolishly tried to make it too big and unwieldy to put up and take down every time, and was still lacking in knowledge about how to really do this stuff. Broadband was the key; my tuned loops have worked very well, and even more so when phased with a tuned vertical, but don't fully take advantage of an SDR.
This time I was more practical and decided to limit the height of the antenna to 7 feet, so I can reach the top. Length-to-height ratios of about 3-to-1 or 4-to-1 give the best modeled front-to-back signal ratios for the cardioid pattern, so I've settled on a 24-foot length for now. That's about as long as I can go and still set it up in a wide range of orientations. I've always been more of a software person than a hardware person, but I'm using my renewed DXing interest to work on that. So, I put together a proper connection box for a potentiometer for the terminating resistance, and wired up a 16:1 impedance matching transformer on the recommended Fair-Rite 2873000202 binocular core for the feed line connection box. Due to the low dynamic range of my inexpensive SDR setup, I used a pair of Mini-Circuits filters to make a steep low-pass filter for my local 1450/1490 pair (and higher frequencies, of course) and thus can make use of higher amplification. For the latter, I hot-rodded a commercial upconverter with a semi-commercial low-noise amplifier on a bare PCB and my own ham-fisted soldering. The cheap RTL-SDR dongles have built-in amplifiers, but you get what you pay for. I still want to do some rigorous daytime testing to measure front-to-back ratios and such, but I had my first chance for some nighttime testing on the 25th. I decided that the most obvious test would be to point the cardioid pattern at 130 degrees into Mexico and do an SDR recording over the 10pm MST TOH (5UT). Indeed the dial was dominated by Mexican stations (including a new log of XEPRC), along with Texas and New Mexico, plus a few strong stations off the back end. Work and life (and work) got in the way. But, Saturday morning, I set up at about 280-290 degrees for the 2am TOH (9UT) and had pretty much the opposite with lots of California and Utah, a long-awaited confirmation of 920-KBAD out of Las Vegas, and several Canadians. After working through that SDR file, I swapped the antenna boxes to point to about 105 degrees, hoping to catch some stations to the east on day power at the 5am MST (12UT) TOH. That worked out insanely well with 7 new stations! Admittedly, if I'm DXing at that hour, it is almost always for trans-Pacific stations, one of the planned uses for this antenna. Thus, there's a lot of untapped potential in the eastern sunrise option. But, I was not expecting such a bounty. Using an SDR really seemed like cheating! Other pointings Sunday morning were not so fruitful, but I did pick up another new station and as often the case with TOH recordings, I added some new call recordings to my collection. So, the 10 new stations from these tests put me up to 486 stations since August 15th, 410 of which have been logged with their call letters (not always on the first log, though), and most of the rest on slogan/webcast combinations. I have recordings of about 90% of the call letters. About a dozen of the logged stations without call letters are Canadian or Cuban where it will be very difficult to ever get call letters, but the rest should eventually be amenable. Also, some of the unrecorded calls are common stations for which I'm only bothering if they are coming in particularly well. I hope to put together a blog post with pictures and other details eventually, and especially some daytime signal strength testing. May not be useful for all of the highly experienced people here, but I like putting this stuff together anyway. Brian Rachford - Prescott, AZ azswdx...@gmail.com http://azswdxing.wordpress.com/ _______________________________________________ IRCA mailing list IRCA@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: irca@hard-core-dx.com