When Tandy sold out to another one gone [AST Research], I was working on a midnight emissions site trying to find how a computer's RF was getting "out" on our outdoor site with a LOT of broadcast RF.
I added another antenna to the test equipment coax with caox, a "T" connector, and an adjustable attenuator to move the "stranger" to null and until I got a low broadcast spur on the screen and got down under the broadcaster's RF. Interesting, but very useful, if only to see if any of the product's failing RF was anything under the BC noise. It turned out to be a too-thin conductive paint on the plastic "floor" -- and I had to write up how to fix it of course -- with a better way to put on the spray applied paint, this time, all axis sprayed. Cortland Richmond Retired from the Grand Rapids GE at 67 Some Belcan contracts til' age 70 or so. -----Original Message----- From: Brent DeWitt Sent: May 6, 2022 9:49 PM To: Subject: Re: [PSES] Dual antenna during RE test ? Brings back memories! MANY moons ago, I ran an OATS in the foothills of Colorado with lots of radio and TV ambients. Thought I'd give the two antenna cancellation thing a quick experiment. I had one antenna on out 10 meter test mast and put a second one on the edge of our 3 meter diameter turntable with a preamp and attenuator on one of them. With that arrangement, I could adjust both the relative amplitude and phase of FM and TV signals over a pretty good range, to get the best null. After a day or so of playing around, I found that I could poke a 15-20 dB hole in some signals, but barely change some others. After scratching my head for a while, I realized that the ones I could cancel were almost line-of-sight from Cheyenne, and the ones I couldn't were from Denver. The light went on. I was in a narrow mountain canyon, so the signals from Denver had so much multi-path reflection, that whatever one you canceled stll left three or four others with different phase relationship. With that realization😉, I went down to Lyons and had a beer. On 5/6/2022 1:57 AM, Bill Owsley wrote: Tried the dual antennas to subtract out the ambients, several times since the explanation was good. About 20 years ago. Unsat !!! On Monday, May 2, 2022, 02:23:26 PM EDT, Ken Javor (mailto:[email protected]) wrote: Likely a totally different application than yours, but a long time ago on OATS measurements, there was development of a two-antenna test where one was for the actual measurement, but the other was pointed away to pick up the ambient, and the idea was to subtract the ambient out, and leave only the EUT emissions. It was controversial. MIL-STD-826 (1964 – 1967) had radiated emission antenna set-up drawings showing all antennas deployed simultaneously. In the days when each antenna had its own receiver, if you had enough techs that could speed up the test significantly. It should be noted that was unique to MIL-STD-826 and it did not survive into MIL-STD-461. I’m thinking in your specific application, the antennas should be separated by some distance, so that they don’t affect each other. What that separation needs to be will depend on the desired uncertainty in the measurement. -- Ken Javor (256) 650-5261 From: Patrick (mailto:[email protected])Reply-To: Patrick (mailto:[email protected])Date: Monday, May 2, 2022 at 2:00 PMTo: (mailto:[email protected])Subject: [PSES] Dual antenna during RE test ? Hi All - I'm wondering if there is any academic or practical literature on the use of two antennas during an emissions test. For example, research or experiments on the use of two DRH's above 1.0 GHz, side-by-side, one vertical, the other horizontal. Have any researchers looked at this? Are there any experimental studies? Thank you. -Patrick ----------------------------------------------------------------- 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) (http://www.ieee-pses.org/)List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators:Scott Douglas Mike Cantwell For policy questions, send mail to:Jim Bacher David Heald -----------------------------------------------------------------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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) (http://www.ieee-pses.org/)List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators:Scott Douglas Mike Cantwell For policy questions, send mail to:Jim Bacher David Heald - ---------------------------------------------------------------- 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - ---------------------------------------------------------------- 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - ---------------------------------------------------------------- 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) 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]>
