Over the past few years, I’ve been buying these old multi-band portable receivers, especially when I find them cheap. They are not difficult to get, as it seems that they are not a popular collector item for the most part. A few like the Radio Shack Patrolman SW-60 and Sony SRF-59 have achieved cult status, and cost more. Most, like that Lafayette Guardian, are less than $20 at hamfests, and often less than $10. These units are pretty easy to hack around with, and not being especially collectible are not going to give some antique radio aficionado his final stroke if you extensively modify it from stock.
The receivers are generally pretty sensitive, and don’t mind short antennas. The tuning on a lot of them however can best be described as coarse. I’ve got a Radio Shack 12-456 that uses all of 2 inches of dial space to tune from 108-175 MHz.
A few nights ago I was reading my Lindsay reprint of the 1936 Frank C. Jones Radio Handbook Receiver Chapters. The same information, by the way, is in the 1938 5th. Edition which you can download here. Radio hobbyists had similar issues back then with the tek of those days, and used a technique called bandspreading to get finer tuning. One way to bandspread, mechanical, is with a slow-speed vernier dial. Those are like unobtanium. The second way, shown below, is electrical bandspreading with trimmer capacitors.
Good trimmer caps are a lot easier to come across. I usually find a couple when I search through the “make offer” parts tables at a hamfest. Seems there are precious few of us who build things any more.
On the topic of cheap radio mods, I found this on Instructables. Not only can you walk the FM band up the VHF-Aircraft band, but you can also walk the AM broadcast band up to receive some Shortwave frequencies. I published an article on how to do that in Issue #9 of Cybertek – Cybertek_09, and Bob Grove’s book Communications Monitoring had some other useful info of this sort.
Anyway, it’s getting dark out here. The sun’s setting over the Rockies and I’m listening to the steel guitar reaching out on KDNO to all us old cowboys, even those of the Brooklyn type. Soon it will be midnite, in New York. Maybe some of you RTL-SDR types will go look for a couple of cheap radios at your local thrift store and go talk a walk on the analog dark side. Until next time…
New Sparks31 Class: Electronic Interception, Communications Monitoring, and Signals Intelligence (SIGINT) For the 3%er, Prepper, or Survivalist – October 20th to 21st, 2018 – Denver, Colorado
I’ve received enough emails asking me to do a class on electronic interception, that I decided to make one available. If there remains sufficient interest after this first one, I’ll schedule another.
Electronic Interception, Communications Monitoring, and Signals Intelligence (SIGINT) For the 3%er, Prepper, or Survivalist
October 20th to 21st, 2018
This is a two day class focused on the needs of the 3%er, survivalist, or prepper. It teaches the basics of intelligence versus information, electronic communications monitoring, signals intelligence (SIGINT), and open source intelligence (OSINT) in support of SIGINT. It has been my observation that these skills are important and needed. Until now instruction was unavailable in the 3%, survivalist, and prepper communities. This class has been developed to provide access to this valuable information, and help those who would like to learn. It is based upon my 30 years of experience…
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WHY I WROTE MY BOOKS:Guide to Wild Foods and Useful Plants[Nyerges’ “Guide to Wild Foods” book, originally published in 1978, was published in full color as of 2014. The book, now titled “Guide to Wild Foods and Useful Plants,” is available at bookstores, Amazon, and at http://www.SchoolofSelf-Reliance.com. It has been adopted for use as a…
WHY I WROTE MY BOOKS:URBAN WILDERNESS: An Urban Survival Guide[cover of first edition][current cover]“Urban Wilderness” is the third book I wrote, published in 1979. A few years earlier, I had started writing outdoor columns for the Pasadena Star News and other papers, and I thought the collected columns could make a good book. But I…
Broke out the RTL-SDR this afternoon, and ran dump1090 for a bit to see what’s above.
Performance was surprisingly good with the stock RTL-SDR antenna placed on top of a metal toolbox on the bench. Was able to track high-altitude (>30,000 ft) aircraft out to about 120 miles or so.
Not a big fan of dump1090’s Google Maps interface as it won’t display a track, and requires you to have an Internet connection. ADSBScope is much nicer in that regard, but is Windows software.
Was surfing the RTL-SDR website and found a hobbyist who had did some software for the Raspberry Pi that has some nice analytical tools. That seems like the next step for keeping an eye on the sky.