Here's the patent abstract for the nonradiating aircraft band receiver. It's not exactly a world-class technical advance. United States Patent <http://patft.usp o.gov/netacgi/nph-Parser?Sect1=PTO1&Sec 2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO 2Fsrchnum.htm&r=1&f=G&l=50&s1=5361405.PN.&OS=PN/5361405&RS=PN/5361405#h0> <http://patft.uspto.gov/netacgi/nph-Par er?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u %2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G l=50&s1=5361405.PN.&OS=PN/5361405&RS=PN/5361405#h2> 5,361,405 Ramsey November 1, 1994 ________________________________
Aircraft band radio receiver which does not radiate interfering signals Abstract A broadband radio receiver monitors transmissions over a broadband of frequencies, and especially over the aircraft band, between aircraft and control towers or between the cockpit and ground stations at an airport. The radio utilizes an earphone having a lead which provides an antenna. The lead is AC coupled to an amplifier having band-pass filters connected to the input and to output thereof to provide selectivity while passing the entire band. An AM detector is connected to the output filter and produces an audio signal which is coupled, via an RF blocking inductor, to the earphone by way of the earphone lead. A miniaturized self-contained radio is therefore provided which does not utilize a local oscillator or other radiating signal generator and may be used on board or nearby aircraft without violating regulations for the use of electronic equipment. It's a crystal radio with a bandpass filtered RF amp in front. Orin Laney On Thu, 24 Sep 2009 12:08:37 -0400 ibmken <[email protected]> writes: I would suspect they designed the circuit correctly to suppress those oscillations, but I don't know. I don't think Ramsey provides a schematic on their site, but there is a patent associated with the product, so maybe some information about the circuit could be gleaned from the patent description. It might be interesting to take a sniff of this device with a spectrum analyzer... On Thu, Sep 24, 2009 at 9:44 AM, John Woodgate <[email protected]> wrote: In message <[email protected]>, dated Thu, 24 Sep 2009, American Idle <[email protected]> writes: I have always wanted to buy and use the Ramsey 'Passive Airband Monitor' on a plane trip http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key= ABM1 but I don't think I'd ever be able to successfully explain the finer points of the local oscillator-free design to the flight crew, and probably end up getting ejected from the flight for not complying with their instructions to turn it off during takeoff... Amplified crystal set, I suppose. But how do you know the audio amp isn't oscillating at VHF? Some of the BTL chips are very intolerant of capacitive load. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
