RE: Emissions or not?
Could it be a Radar Jammer, which receives radio waves and re-transmits them to fool the Radar Gun? A poorly designed Radar Jammer could repeat in a very broadband fassion, especially since most are home built kits. Just an idea. - Randy Flinders EMC Test Engineer Emulex Network Systems randall.flind...@emulex.com -- From: Tim Haynes G-Net 701 3239 / 3455 Sent: Wednesday, June 17, 1998 9:57 AM To: emc-pstc Subject: Re: Emissions or not? WoW! Replies! Rather than respond in person I acknowledge all replies with thanks and comment here. BTW the 144.8 MHz tx is 100W e.r.p. Reflections from the Green Italian car? Why not all the other cars? Over all the other days, weeks, years that I have been using these frequencies? Too much coincidence. I like the idea that it might be the radio receiver in the Italian car kicking out a spurious response. Fault on my receiver? NEVER! :-) Oh well - possibly, but why only in relation to this Italian car? Third harmonic? 144.8 x 3 = 434.4 + 3xdeviation... not equal 433.325 by a long way. BTW 3rd harmonic is neg 74dBc on my old HP 8566a. I think it rules out the rusty bolt syndrome as well. The idea that it is an alarm system (the "here I am - I've been stolen" type) is possible though the chances are pretty low - there are not too many users of that alarm system here in the UK. Resonating car...? Hmm? Possibly but I streaches my imagination. Duff (Duff is UK slang for faulty/bad) electronics! Well - this was my first thought. Nice processor with lots of harmonics of clock frequencies and the subdivisions. Lots of switches changing the terminating impedance of the tracks (don't forget I am assuming a duff design). Now that really would modulate an incoming signal! Rating of the proposed causes? No I will let you all decide which is the most likely. Me? I am looking for a Green Italian car to experiment on. Oh, the make? I do't want to upset Fiat so I won't tell you..:-) Regards to all Tim
Re: Emissions or not?
Isn't 433 MHz a common frequency for unlicensed emitters? It is entirely possible that the occupant of that vehicle was using one. COrtland == Original Message Follows >> Date: 17-Jun-98 02:09:23 MsgID: 1061-9447 ToID: 72146,373 From: Tim Haynes G-Net 701 3239 / >INTERNET:tim.hay...@gecm.com Subj: Re: Emissions or not? Chrg: $0.00 Imp: Norm Sens: StdReceipt: NoParts: 1 Sender: owner-emc-p...@majordomo.ieee.org Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) by hil-img-1.compuserve.com (8.8.6/8.8.6/2.12) with ESMTP id FAA15450; Wed, 17 Jun 1998 05:09:19 -0400 (EDT) Received: by ruebert.ieee.org (8.8.8/8.8.8) id FAA17294 for emc-pstc-resent; Wed, 17 Jun 1998 05:07:14 -0400 (EDT) Disclose-Recipients: prohibited List-Post: emc-pstc@listserv.ieee.org Date: Wed, 17 Jun 1998 09:57:21 +0100 (BST) From: Tim Haynes G-Net 701 3239 / 3455 Subject: Re: Emissions or not? To: emc-pstc Message-Id: <6621570917061998/A02205/PLANET/11C68A791500*@MHS> Autoforwarded: false Mime-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Content-Transfer-Encoding: 7BIT Importance: normal Priority: normal Ua-Content-Id: 11C68A791500 X400-Mts-Identifier: [;6621570917061998/A02205/PLANET] Hop-Count: 2 Sender: owner-emc-p...@majordomo.ieee.org Precedence: bulk Reply-To: Tim Haynes G-Net 701 3239 / 3455 X-Resent-To: Multiple Recipients X-Listname: emc-pstc X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org WoW! Replies! Rather than respond in person I acknowledge all replies with thanks and comment here. BTW the 144.8 MHz tx is 100W e.r.p. Reflections from the Green Italian car? Why not all the other cars? Over all the other days, weeks, years that I have been using these frequencies? Too much coincidence. I like the idea that it might be the radio receiver in the Italian car kicking out a spurious response. Fault on my receiver? NEVER! :-) Oh well - possibly, but why only in relation to this Italian car? Third harmonic? 144.8 x 3 = 434.4 + 3xdeviation... not equal 433.325 by a long way. BTW 3rd harmonic is neg 74dBc on my old HP 8566a. I think it rules out the rusty bolt syndrome as well. The idea that it is an alarm system (the "here I am - I've been stolen" type) is possible though the chances are pretty low - there are not too many users of that alarm system here in the UK. Resonating car...? Hmm? Possibly but I streaches my imagination. Duff (Duff is UK slang for faulty/bad) electronics! Well - this was my first thought. Nice processor with lots of harmonics of clock frequencies and the subdivisions. Lots of switches changing the terminating impedance of the tracks (don't forget I am assuming a duff design). Now that really would modulate an incoming signal! Rating of the proposed causes? No I will let you all decide which is the most likely. Me? I am looking for a Green Italian car to experiment on. Oh, the make? I do't want to upset Fiat so I won't tell you..:-) Regards to all Tim == End of Original Message =
Re: Emissions or not?
WoW! Replies! Rather than respond in person I acknowledge all replies with thanks and comment here. BTW the 144.8 MHz tx is 100W e.r.p. Reflections from the Green Italian car? Why not all the other cars? Over all the other days, weeks, years that I have been using these frequencies? Too much coincidence. I like the idea that it might be the radio receiver in the Italian car kicking out a spurious response. Fault on my receiver? NEVER! :-) Oh well - possibly, but why only in relation to this Italian car? Third harmonic? 144.8 x 3 = 434.4 + 3xdeviation... not equal 433.325 by a long way. BTW 3rd harmonic is neg 74dBc on my old HP 8566a. I think it rules out the rusty bolt syndrome as well. The idea that it is an alarm system (the "here I am - I've been stolen" type) is possible though the chances are pretty low - there are not too many users of that alarm system here in the UK. Resonating car...? Hmm? Possibly but I streaches my imagination. Duff (Duff is UK slang for faulty/bad) electronics! Well - this was my first thought. Nice processor with lots of harmonics of clock frequencies and the subdivisions. Lots of switches changing the terminating impedance of the tracks (don't forget I am assuming a duff design). Now that really would modulate an incoming signal! Rating of the proposed causes? No I will let you all decide which is the most likely. Me? I am looking for a Green Italian car to experiment on. Oh, the make? I do't want to upset Fiat so I won't tell you..:-) Regards to all Tim
Re: Emissions or not?
Tim, I agree that Mike's theory is very likely (since nobody makes a perfectly clean transmitter), but I will offer a different theory on how your transmitted 2 meter signal was received on the 70 cm band. To begin with, your ham radio equipment will have far superior sensitivity (and usually a much lower noise floor due to tighter bandwidth) than the typical EMI receiver can attain without significant preamplification. The signal you detected would not pose any risk of failing a CISPR emission standard, especially since it's range was obviously very limited. I believe that your 2 meter signal, likely with an effective radiated power in excess of 50 to over 100 Watts (and at close range). This would by a very strong signal at the Italian car's broadcast receiver (hereafter Radio X). It could be strong enough to perturb Radio X's local oscillator (LO) or maybe (for more modern equipment) the phase lock loop (PLL) - that is synthesizing the LO signal. The LO must be coupled to the first mixer stage - with only one stage, usually a mediocre wideband preamp, providing some isolation from the antenna. (Say maybe 30 to 60 dB worth of isolation, depending on design, quality, age/condition, and proper adjustment of Radio X.) There is a good chance that your signal arrived at Radio X with sufficient strength to modulate/mix with the LO at the mixer stage. Now to 70 cm. I have personally observed that my Jeep's stock FM/AM/Cassette radio, in FM mode, places a CW harmonic in the 70 cm band that is present only at one broadcast frequency. I tune to another broadcast FM station - it is gone - I tune back, there it is again. This is a clearly a harmonic of the LO, strong enough to be notable on a hand-held radio with a poor antenna. So, if that LO harmonic is present, and your 2 meter signal is indeed strong enough to surpass the LO rejection, then you were accidentally forcing Radio X to act as a upconverter for 70 cm (and likely a couple other bands as well). But then, even a rusty tailpipe or bumper (metal) can act as a harmonic upconverter if the Italian car had the wrong two metals in contact (rectifying your 2 meter RF). I've seen AM radio stations in the 0.5 to 1.6 MHz band upconverted to the 2 meter band just by corrosion of the towers guywire cables; a very irksome problem when it happens on a remote mountaintop at 10,500 feet. Best Regards, Eric Lifsey - Callsign AC7K "Tim Haynes G-Net 701 3239 / 3455" on 06/16/98 09:39:43 AM Please respond to "Tim Haynes G-Net 701 3239 / 3455" To: emc-pstc cc: (bcc: Eric Lifsey/AUS/NIC) Subject: Emissions or not? Hello everybody! Isn't experience a wonderful thing? Well, I have just experienced something that makes me wonder about the validity of EMC emission regulations... I am a radio ham and operate on VHF and UHF bands from the car. The other night I was transmitting on 144.8MHz while the UHF receiver was tuned to 433.325MHz (my local UHF repeater). Suddenly, I started hearing a weak signal on UHF and, as it got rapidly stronger, I realised that it was me! At first I thought that somebody was fooling around, but that thought went when I realised that every time I caught up with the green Italian sports machine the signal got stronger and when it pulled away, the signal got weaker. When I stopped transmitting, there was no signal on UHF - no repeater or spurious. I have two thought on this... 1 The Italian car mixed my 144.8 with something internal to it, and retransmitted the resulting product. 2 It has a strong emission that caused mixing in the UHF receiver. I tend to discount the third theory, that the VHF transmitted signal overloads the UHF radio, because I use a duplexer and can receive very weak UHF signals while transmitting VHF. So - any ideas on this matter - and should we start doing emission measurements during immunity tests so that we know what the real world performance of the products will be? Regards Tim tim.hay...@gecm.com
RE: Emissions or not?
You might also be getting a passive intermod product from something on the italian car reacting to your transmitter. DB > -- > From: mikonc...@aol.com[SMTP:mikonc...@aol.com] > Sent: Tuesday, June 16, 1998 12:08 PM > To: emc-p...@ieee.org > Subject: Re: Emissions or not? > > Tim: > > Your receiver frequency is very close to the third harmonic of your > transmitter frequency. Perhaps the reflection off the adjacent car > reinforced > that harmonic to just exceed the rejection characteristics of the > receiver. > You might test that with a different (reflecting) car (with the same > angular > location relative to your vehicle) to see if it was a > mixing/retransmitting > phenomena or just a reflection (or something else!). > > By the way, great question re emissions during immunity. That would > sure open > a Pandora's box! > > Mike Conn > Owner/Principal Consultant > Mikon Consulting >
Re: Emissions or not?
--- On Tue, 16 Jun 1998 15:39:43 +0100 (BST) Tim Haynes G-Net 701 3239 / 3455 wrote: > I am a radio ham and operate on VHF and UHF bands from the car. > The other night I was transmitting on 144.8MHz while the UHF receiver > was tuned to 433.325MHz (my local UHF repeater). Suddenly, I started > hearing a weak signal on UHF and, as it got rapidly stronger, I realised > that it was me! > At first I thought that somebody was fooling around, but that thought > went when I realised that every time I caught up with the green Italian > sports machine the signal got stronger and when it pulled away, the > signal got weaker. > When I stopped transmitting, there was no signal on UHF - no repeater or > spurious. > I have two thought on this... > 1 The Italian car mixed my 144.8 with something internal to it, and > retransmitted the resulting product. > 2 It has a strong emission that caused mixing in the UHF receiver. > I tend to discount the third theory, that the VHF transmitted signal > overloads the UHF radio, because I use a duplexer and can receive very > weak UHF signals while transmitting VHF. > > So - any ideas on this matter - and should we start doing emission > measurements during immunity tests so that we know what the real world > performance of the products will be? > tim.hay...@gecm.com Tim: My first thought is that 433.325MHz is darn close to being the third harmonic of 144.8MHz, so I would assume that you are simply detecting your own third harmonic energy. The requirement for proximity of the other vehicle is interesting. Perhaps it is reflecting the 433MHz signal back toward you. And maybe simple reflection isn't all. Maybe some part of that speific vehicle's structure was resonant at 433MHz. You shouldn't assume too much about your transmitter's harmonic content; why don't you drag a spectrum analyzer outside and check it out yourself? A more interesting possibility might be the generation of harmonics via current through non-linear discontinuities on the other vehicle. Having had the priviledge of owning a small Italian sports car (during a previous lifetime), I am fully informed of the number of rusty joints and loosly bonded parts which those joyous vehicles contain. This is the legendary "Rusty Bolt" problem, which is a major concern on military systems like ships. Perhaps that green patina was actually corrosion? Ed -- Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 List-Post: emc-pstc@listserv.ieee.org Date: 06/16/98 Time: 11:36:23 --
Re: Emissions or not?
Tim: Your receiver frequency is very close to the third harmonic of your transmitter frequency. Perhaps the reflection off the adjacent car reinforced that harmonic to just exceed the rejection characteristics of the receiver. You might test that with a different (reflecting) car (with the same angular location relative to your vehicle) to see if it was a mixing/retransmitting phenomena or just a reflection (or something else!). By the way, great question re emissions during immunity. That would sure open a Pandora's box! Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Emissions or not?
What if the little green Italian sports car, happened to resonate at 433. MHz? And, with a reasonable Q? Then, your weak 3rd harmonic, will retransmit from the sports car and your receiver will pick it up. I contend that it is your Tx output filter that is not performing. Do a conducted emissions test (not the powerline type but the RF type) using a spectrum analyzer and filters and attenuators to measure your actual output to the antenna. At a minimum you should see at least -60dBc as required by the FCC, for any spurious emission (97.307(e)) Hans
Emissions or not?
Hello everybody! Isn't experience a wonderful thing? Well, I have just experienced something that makes me wonder about the validity of EMC emission regulations... I am a radio ham and operate on VHF and UHF bands from the car. The other night I was transmitting on 144.8MHz while the UHF receiver was tuned to 433.325MHz (my local UHF repeater). Suddenly, I started hearing a weak signal on UHF and, as it got rapidly stronger, I realised that it was me! At first I thought that somebody was fooling around, but that thought went when I realised that every time I caught up with the green Italian sports machine the signal got stronger and when it pulled away, the signal got weaker. When I stopped transmitting, there was no signal on UHF - no repeater or spurious. I have two thought on this... 1 The Italian car mixed my 144.8 with something internal to it, and retransmitted the resulting product. 2 It has a strong emission that caused mixing in the UHF receiver. I tend to discount the third theory, that the VHF transmitted signal overloads the UHF radio, because I use a duplexer and can receive very weak UHF signals while transmitting VHF. So - any ideas on this matter - and should we start doing emission measurements during immunity tests so that we know what the real world performance of the products will be? Regards Tim tim.hay...@gecm.com
