---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 06/03/19: 21 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:04 AM - Re: THE FASCINATING WORLD OF SOLDER ALLOYS AND METALLURGY (Robert L. Nuckolls, III) 2. 07:20 AM - Re: Antenna Ground Plane (Ernest Christley) 3. 08:58 AM - Re: Antenna Ground Plane (Roger Curtis) 4. 09:16 AM - Re: Antenna Ground Plane (Jared Yates) 5. 10:56 AM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 6. 11:02 AM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 7. 11:03 AM - Re: Antenna Ground Plane (Ernest Christley) 8. 11:04 AM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 9. 12:13 PM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 10. 01:18 PM - Re: Antenna Ground Plane (Charlie England) 11. 01:25 PM - Re: Antenna Ground Plane (Joe Keenan) 12. 01:27 PM - Re: Antenna Ground Plane (Kelly McMullen) 13. 02:08 PM - Re: Antenna Ground Plane (Charlie England) 14. 02:39 PM - Re: Antenna Ground Plane (Joe Keenan) 15. 04:08 PM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 16. 04:09 PM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 17. 08:32 PM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 18. 08:32 PM - Re: Antenna Ground Plane (Robert L. Nuckolls, III) 19. 10:12 PM - Re: Antenna Ground Plane () 20. 10:31 PM - Re: Antenna Ground Plane () 21. 10:58 PM - Re: Antenna Ground Plane (James kale) ________________________________ Message 1 _____________________________________ Time: 06:04:55 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: THE FASCINATING WORLD OF SOLDER ALLOYS AND METALLURGY At 09:01 PM 6/2/2019, you wrote: >I just ran across this very interesting article > >THE >FASCINATING WORLD OF SOLDER ALLOYS AND METALLURGY Good find! Thanks . . . Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:20:54 AM PST US From: Ernest Christley Subject: Re: AeroElectric-List: Antenna Ground Plane I can answer this with some real world experience.=C2- I mounted my COM antennae just behind the canopy on my 601XL, and then I put the ELT about h alfway between the COM and the rudder.=C2- There was about 18 inches or s o separation between each. In there air, I could not reliably communicate with KRDU once I got out of their airspace. Once I moved the ELT to the bottom of the fuselage (and away from the COM a ntennae), performance has been like every other plane I've ever flown in. On Sunday, June 2, 2019, 7:48:30 PM EDT, wrote: Just out of interest why should the ELT antenna be separated from the com a ntenna =C2- =C2- | | Virus-free. www.avast.com | ________________________________ Message 3 _____________________________________ Time: 08:58:57 AM PST US Subject: Re: AeroElectric-List: Antenna Ground Plane From: Roger Curtis CiAgICAKSXNuJ3QgdGhlIEVMVCB0dXJuZWQgb2ZmIChub3QgdHJhbnNtaXR0aW5nKSBhbGwgdGhl IHRpbWUgZHVyaW5nIGZsaWdodD/CoCBJZiB0aGlzIGlzIHRoZSBjYXNlIHBsZWFzZSBleHBsYWlu IHdoeSBpdCB3b3VsZCBhZmZlY3QgdGhlIENvbSBwZXJmb3JtYW5jZS5Sb2dlclNlbnQgZnJvbSBt eSBWZXJpem9uIFdpcmVsZXNzIDRHIExURSBzbWFydHBob25lCgotLS0tLS0tLSBPcmlnaW5hbCBt ZXNzYWdlIC0tLS0tLS0tCkZyb206IEVybmVzdCBDaHJpc3RsZXkgPGVjaHJpc3RsZXlAYXR0Lm5l dD4gCkRhdGU6IDA2LzAzLzIwMTkgIDEwOjIwICAoR01ULTA1OjAwKSAKVG86IGFlcm9lbGVjdHJp Yy1saXN0QG1hdHJvbmljcy5jb20gClN1YmplY3Q6IFJlOiBBZXJvRWxlY3RyaWMtTGlzdDogQW50 ZW5uYSBHcm91bmQgUGxhbmUgCgoKICAgICAgICBJIGNhbiBhbnN3ZXIgdGhpcyB3aXRoIHNvbWUg cmVhbCB3b3JsZCBleHBlcmllbmNlLsKgIEkgbW91bnRlZCBteSBDT00gYW50ZW5uYWUganVzdCBi ZWhpbmQgdGhlIGNhbm9weSBvbiBteSA2MDFYTCwgYW5kIHRoZW4gSSBwdXQgdGhlIEVMVCBhYm91 dCBoYWxmd2F5IGJldHdlZW4gdGhlIENPTSBhbmQgdGhlIHJ1ZGRlci7CoCBUaGVyZSB3YXMgYWJv dXQgMTggaW5jaGVzIG9yIHNvIHNlcGFyYXRpb24gYmV0d2VlbiBlYWNoLkluIHRoZXJlIGFpciwg SSBjb3VsZCBub3QgcmVsaWFibHkgY29tbXVuaWNhdGUgd2l0aCBLUkRVIG9uY2UgSSBnb3Qgb3V0 IG9mIHRoZWlyIGFpcnNwYWNlLk9uY2UgSSBtb3ZlZCB0aGUgRUxUIHRvIHRoZSBib3R0b20gb2Yg dGhlIGZ1c2VsYWdlIChhbmQgYXdheSBmcm9tIHRoZSBDT00gYW50ZW5uYWUpLCBwZXJmb3JtYW5j ZSBoYXMgYmVlbiBsaWtlIGV2ZXJ5IG90aGVyIHBsYW5lIEkndmUgZXZlciBmbG93biBpbi4KICAg ICAgICAKICAgICAgICAKICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAKICAgICAgICAgICAg ICAgIAogICAgICAgICAgICAgICAgICAgIE9uIFN1bmRheSwgSnVuZSAyLCAyMDE5LCA3OjQ4OjMw IFBNIEVEVCwgIDxtaWtlQHZpc2lvbjQ5OS5jb20+IHdyb3RlOgogICAgICAgICAgICAgICAgCiAg ICAgICAgICAgICAgICBKdXN0IG91dCBvZiBpbnRlcmVzdCB3aHkgc2hvdWxkIHRoZSBFTFQgYW50 ZW5uYSBiZSBzZXBhcmF0ZWQgZnJvbSB0aGUgY29tIGFudGVubmEgwqDCoCAKVmlydXMtZnJlZS4g d3d3LmF2YXN0LmNvbQoJCSAKICAgICAgICAgICAgCiAgICAgICAg ________________________________ Message 4 _____________________________________ Time: 09:16:53 AM PST US From: Jared Yates Subject: Re: AeroElectric-List: Antenna Ground Plane If you ring a tuning fork of a certain pitch on one side of the room, a tuning fork of the same pitch will vibrate across the room. Both are as turned off as can be. I had a case where transmissions on 121.7 were bleeding onto 121.5. Moving the ELT antenna farther away fixed it. The story we told ourselves was that it must have been a resonance through the inactive ELT's circuit. On June 3, 2019 12:04:40 Roger Curtis wrote: > > > Isn't the ELT turned off (not transmitting) all the time during flight? If > this is the case please explain why it would affect the Com > performance.RogerSent from my Verizon Wireless 4G LTE smartphone > > -------- Original message -------- > From: Ernest Christley > Date: 06/03/2019 10:20 (GMT-05:00) > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Antenna Ground Plane > > > I can answer this with some real world experience. I mounted my COM > antennae just behind the canopy on my 601XL, and then I put the ELT about > halfway between the COM and the rudder. There was about 18 inches or so > separation between each.In there air, I could not reliably communicate with > KRDU once I got out of their airspace.Once I moved the ELT to the bottom of > the fuselage (and away from the COM antennae), performance has been like > every other plane I've ever flown in. > > > > > > On Sunday, June 2, 2019, 7:48:30 PM EDT, wrote: > > Just out of interest why should the ELT antenna be separated from the com > antenna > Virus-free. www.avast.com > > > ________________________________ Message 5 _____________________________________ Time: 10:56:03 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Antenna Ground Plane At 06:46 PM 6/2/2019, you wrote: >Thank you very much for the help. > >The aircraft is a KIS made from honeycomb and fiberglass > >On the dipole antenna what length should the folded balun be and do >I make the toroid balun with 3 toroids as in the instruction? This antenna can't use a coax balun . . . it's a dual frequency configuration that precludes using a resonant piece of coax cable to improve feedline performance. Unfortunately the highest frequency of operation (402Mhz) precludes the use of broad-band magnetics. Jim was fond of the string-of-beads approach to reducing effects of mismatch on the feedline but I researched that in the EMC lab at Beech about 30 years ago . . . minimally effective. The most effective decoupling technique using ferrite beads or toroids was utilized in this product a few years ago . . . https://tinyurl.com/y4qpkqoc Talked with this fellow by email and phone. Made some questionable claims including the assertion that the thing was 'patented'. Never could find that patent . . . nonetheless, here's what was inside the 'miracle box': http://www.aeroelectric.com/articles/Antennas/AirWhip/AirWhip_Inside.jpg This de-coupling technique wound several turns on a common core. Inductance goes up as the square of turns. In the photo we count 7 turns or 49 times the inductance of a same core with one turn. Jim's string- of-beads gives 1x potential inductance/per/core or perhaps 8-12x depending on how many cores are strung onto the coax. Played with this in the EMC lap at RAC/Beech and determined that the string of beads wasn't worth the trouble. So . . . how about the airwhip technique for multiple turns on a single core? Not a bad choice. I've seen it done with antennas over a broad spectum of frequencies . . . within limits. Seems that ferrite inductive qualities versus attenuation qualities swap duties at about 200 Mhz or so . . . that's why they are effective for EMC management at vhf/uhf frequencies, not so much as transformers at 402 Mhz . . . but still worth investigating with the right test equipment. I've got a uhf vector analyzer sitting on the shelf above my desk (sigh) . . . someday maybe . . . Given that this antenna is intended to operated on two, unchanging discrete frequencies, one COULD consider fabricating a passive components matching network to transfer feedline energy to the two antennas effectively . . . but I'd bet that the performance differences between uncle Jim's shade-tree engineering approach an one by Dorne-Margolin would be observable only in the lab and of little advantage in practice. In the mean time, fabricating uncle Jim's paralleled dipoles arrangement is easy. Attaching directly to this antenna with coax is also easy. Emacs! It seems that your airplane (epoxy/glass) is a likely candidate for an all internal ELT antenna which would, I suspect, be less vulnerable to damage by unintended arrivals with the earth. Best yet, no ground plane . . . > >Just out of interest why should the ELT antenna be separated from >the com antenna Kelly offered the strongest rationale for separation . . . ELT's are particularly susceptible to cross-modulation products because unlike receivers, there are 'high power', non-linear components continuously connected to the antenna. I suspect that modern ELTs with FET output stages might be better in this regard but the risks are not zero. Having said that, there is zero risk for damaging anything. I'd recommend you install for convenience and see if you have problems. The problems will be nothing worst than an occasional nuisance with a high probability that you'll not suffer the effects at all. Bob . . . ________________________________ Message 6 _____________________________________ Time: 11:02:13 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Ground Plane At 11:16 AM 6/3/2019, you wrote: >If you ring a tuning fork of a certain pitch on one side of the >room, a tuning fork of the same pitch will vibrate across the room. >Both are as turned off as can be. I had a case where transmissions >on 121.7 were bleeding onto 121.5. Moving the ELT antenna farther >away fixed it. The story we told ourselves was that it must have >been a resonance through the inactive ELT's circuit. Close . . . big bears in the woods are the solid state devices with matching networks that feed their energies to the antenna. In transceivers, a relay disconnects that path except while transmitting. In ELTs the pathway is enduring. One could just connect a diode across the BNC connector at the base of the ELT antenna and create a really whippy cross-mod generator. Take the final stage transistor out of the ELT and the problem would go away . . . Bob . . . ________________________________ Message 7 _____________________________________ Time: 11:03:13 AM PST US From: Ernest Christley Subject: Re: AeroElectric-List: Antenna Ground Plane The ELT is "off", meaning that the circuits that produce and amplify a sig nal then apply it to the antennae are not working.=C2- It is "off" in the sense that the circuits that detect and amplify an incoming signal are not working.=C2- But, measuring from the antennae to ground, and you will no tice that the resistance is not infinite.=C2- In fact, it will read a dea d short if I'm not mistaken.=C2- The antennae is still "sensing" electrom agnetic fluctuations and supplying them for reading.=C2- There's just not hing there to read them.=C2- The only way for the antennae to "sense" the fluctuations is for the fluctuations to do the work of producing a current in the antennae.=C2- When the ELT is off, that "work" just gets dumped a s heat. By placing the antennas very close,=C2- my COM was providing a VERY large signal to the ELT.=C2- The ELT could hear me clear as day.=C2- The ELT then proceded to convert that clear signal into heat.=C2- That heat came from my COM radio, which cut out a major part of the energy that was meant to propagate to ATC and other pilots. It's worth noting that with the ELT antennae next to my COM, my ability to communicate with ATC was very much dependent on which direction I was flyin g.=C2- If I flew directly to or away from the airport, the signal was eve n weaker. On Monday, June 3, 2019, 11:59:33 AM EDT, Roger Curtis wrote: Isn't the ELT turned off (not transmitting) all the time during flight? =C2- If this is the case please explain why it would affect the Com perfo rmance. Roger | | ________________________________ Message 8 _____________________________________ Time: 11:04:34 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Ground Plane At 09:20 AM 6/3/2019, you wrote: >I can answer this with some real world experience. I mounted my COM >antennae just behind the canopy on my 601XL, and then I put the ELT >about halfway between the COM and the rudder. There was about 18 >inches or so separation between each. > >In there air, I could not reliably communicate with KRDU once I got >out of their airspace. > >Once I moved the ELT to the bottom of the fuselage (and away from >the COM antennae), performance has been like every other plane I've >ever flown in. Interesting! That would have been a fascinating installation to study in the lab. Bob . . . ________________________________ Message 9 _____________________________________ Time: 12:13:56 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Ground Plane At 01:02 PM 6/3/2019, you wrote: >The ELT is "off", meaning that the circuits that produce and amplify >a signal then apply it to the antennae are not working. It is "off" >in the sense that the circuits that detect and amplify an incoming >signal are not working. But, measuring from the antennae to ground, >and you will notice that the resistance is not infinite. In fact, >it will read a dead short if I'm not mistaken. The antennae is >still "sensing" electromagnetic fluctuations and supplying them for >reading. There's just nothing there to read them. The only way for >the antennae to "sense" the fluctuations is for the fluctuations to >do the work of producing a current in the antennae. When the ELT is >off, that "work" just gets dumped as heat. > >By placing the antennas very close, my COM was providing a VERY >large signal to the ELT. The ELT could hear me clear as day. The >ELT then proceded to convert that clear signal into heat. That heat >came from my COM radio, which cut out a major part of the energy >that was meant to propagate to ATC and other pilots. > >It's worth noting that with the ELT antennae next to my COM, my >ability to communicate with ATC was very much dependent on which >direction I was flying. If I flew directly to or away from the >airport, the signal was even weaker. Not sure I can grok the heat thing. While the comm signal is 'strong', comm power measured at the base of the ELT antenna cannot be more than a tiny fraction of total comm output power. But the 'lensing' effects of parasitic radiators is another matter . . . distortion of the comm radiation pattern would be my first guess. Would be fun to 'sniff' it in the lab . . . Bob . . . ________________________________ Message 10 ____________________________________ Time: 01:18:23 PM PST US Subject: Re: AeroElectric-List: Antenna Ground Plane From: Charlie England On 6/3/2019 2:12 PM, Robert L. Nuckolls, III wrote: > At 01:02 PM 6/3/2019, you wrote: >> The ELT is "off", meaning that the circuits that produce and amplify >> a signal then apply it to the antennae are not working. It is "off" >> in the sense that the circuits that detect and amplify an incoming >> signal are not working. But, measuring from the antennae to ground, >> and you will notice that the resistance is not infinite. In fact, it >> will read a dead short if I'm not mistaken. The antennae is still >> "sensing" electromagnetic fluctuations and supplying them for >> reading. There's just nothing there to read them. The only way for >> the antennae to "sense" the fluctuations is for the fluctuations to >> do the work of producing a current in the antennae. When the ELT is >> off, that "work" just gets dumped as heat. >> >> By placing the antennas very close, my COM was providing a VERY >> large signal to the ELT. The ELT could hear me clear as day. The ELT >> then proceded to convert that clear signal into heat. That heat came >> from my COM radio, which cut out a major part of the energy that was >> meant to propagate to ATC and other pilots. >> >> It's worth noting that with the ELT antennae next to my COM, my >> ability to communicate with ATC was very much dependent on which >> direction I was flying. If I flew directly to or away from the >> airport, the signal was even weaker. > > Not sure I can grok the heat thing. While the > comm signal is 'strong', comm power measured > at the base of the ELT antenna cannot be more > than a tiny fraction of total comm output power. > But the 'lensing' effects of parasitic radiators > is another matter . . . distortion of the > comm radiation pattern would be my first guess. > > Would be fun to 'sniff' it in the lab . . . > > Bob . . . > OK, show of hands: How many of you had to google 'grok'? (Brag mode on; I didn't... If you had to google it, don't stop there; read the book. It's *great*.) I wonder if a better way of talking about the interference would be in SWR terms. Was the ELT antenna causing parasitic degradation/reflection of the comm transmission? Charlie --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 11 ____________________________________ Time: 01:25:43 PM PST US From: Joe Keenan Subject: Re: AeroElectric-List: Antenna Ground Plane > On Jun 3, 2019, at 4:17 PM, Charlie England wrote: > > On 6/3/2019 2:12 PM, Robert L. Nuckolls, III wrote: >> At 01:02 PM 6/3/2019, you wrote: >>> The ELT is "off", meaning that the circuits that produce and amplify a signal then apply it to the antennae are not working. It is "off" in the sense that the circuits that detect and amplify an incoming signal are not working. But, measuring from the antennae to ground, and you will notice that the resistance is not infinite. In fact, it will read a dead short if I'm not mistaken. The antennae is still "sensing" electromagnetic fluctuations and supplying them for reading. There's just nothing there to read them. The only way for the antennae to "sense" the fluctuations is for the fluctuations to do the work of producing a current in the antennae. When the ELT is off, that "work" just gets dumped as heat. >>> >>> By placing the antennas very close, my COM was providing a VERY large signal to the ELT. The ELT could hear me clear as day. The ELT then proceded to convert that clear signal into heat. That heat came from my COM radio, which cut out a major part of the energy that was meant to propagate to ATC and other pilots. >>> >>> It's worth noting that with the ELT antennae next to my COM, my ability to communicate with ATC was very much dependent on which direction I was flying. If I flew directly to or away from the airport, the signal was even weaker. >> >> Not sure I can grok the heat thing. While the >> comm signal is 'strong', comm power measured >> at the base of the ELT antenna cannot be more >> than a tiny fraction of total comm output power. >> But the 'lensing' effects of parasitic radiators >> is another matter . . . distortion of the >> comm radiation pattern would be my first guess. >> >> Would be fun to 'sniff' it in the lab . . . >> >> Bob . . . >> > OK, show of hands: How many of you had to google 'grok'? (Brag mode on; I didn't... If you had to google it, don't stop there; read the book. It's *great*.) Nope, been in my vocabulary since my teens. Was my very first password on a multi-user computer in college. joe ________________________________ Message 12 ____________________________________ Time: 01:27:48 PM PST US Subject: Re: AeroElectric-List: Antenna Ground Plane From: Kelly McMullen While I don't doubt that this configuration contributed to the problem, a much more common situation is when the aircraft is near a high powered facility broadcasting on VHF. For instance, it is common for TV and FM broadcast towers to be located near each other, especially if there is convenient high ground. They can put out thousands of watts. They will cause the ELT output stage to oscillate and re-radiate to nearby com antennas. I experienced this in Phoenix, where 90% of broadcast antennas are on "South Mountain", which is 7-8 miles south of Phoenix Sky Harbor Airport. When flying the VFR transition over the top of PHX, I would get terrible squelch break on both com radios, making communications with the Tracon difficult on both frequencies they used (120.7 and 123.7). I verified this by flying under the class B on the south side of the mountain, with and without the ELT antenna connected. Without ELT connected, no problem. I then removed one of my 2 com antennas from the topside of the fuselage to the belly. Problem was 95% eliminated. On 6/3/2019 12:12 PM, Robert L. Nuckolls, III wrote: > At 01:02 PM 6/3/2019, you wrote: >> The ELT is "off", meaning that the circuits that produce and amplify a >> signal then apply it to the antennae are not working. It is "off" in >> the sense that the circuits that detect and amplify an incoming signal >> are not working. But, measuring from the antennae to ground, and you >> will notice that the resistance is not infinite. In fact, it will >> read a dead short if I'm not mistaken. The antennae is still >> "sensing" electromagnetic fluctuations and supplying them for >> reading. There's just nothing there to read them. The only way for >> the antennae to "sense" the fluctuations is for the fluctuations to do >> the work of producing a current in the antennae. When the ELT is off, >> that "work" just gets dumped as heat. >> >> By placing the antennas very close, my COM was providing a VERY large >> signal to the ELT. The ELT could hear me clear as day. The ELT then >> proceded to convert that clear signal into heat. That heat came from >> my COM radio, which cut out a major part of the energy that was meant >> to propagate to ATC and other pilots. >> >> It's worth noting that with the ELT antennae next to my COM, my >> ability to communicate with ATC was very much dependent on which >> direction I was flying. If I flew directly to or away from the >> airport, the signal was even weaker. > > Not sure I can grok the heat thing. While the > comm signal is 'strong', comm power measured > at the base of the ELT antenna cannot be more > than a tiny fraction of total comm output power. > But the 'lensing' effects of parasitic radiators > is another matter . . . distortion of the > comm radiation pattern would be my first guess. > > Would be fun to 'sniff' it in the lab . . . > > Bob . . . > ________________________________ Message 13 ____________________________________ Time: 02:08:53 PM PST US Subject: Re: AeroElectric-List: Antenna Ground Plane From: Charlie England On 6/3/2019 3:25 PM, Joe Keenan wrote: > > >> On Jun 3, 2019, at 4:17 PM, Charlie England > > wrote: >> >> On 6/3/2019 2:12 PM, Robert L. Nuckolls, III wrote: >>> At 01:02 PM 6/3/2019, you wrote: >>>> The ELT is "off", meaning that the circuits that produce and >>>> amplify a signal then apply it to the antennae are not working. It >>>> is "off" in the sense that the circuits that detect and amplify an >>>> incoming signal are not working. But, measuring from the antennae >>>> to ground, and you will notice that the resistance is not >>>> infinite. In fact, it will read a dead short if I'm not mistaken. >>>> The antennae is still "sensing" electromagnetic fluctuations and >>>> supplying them for reading. There's just nothing there to read >>>> them. The only way for the antennae to "sense" the fluctuations is >>>> for the fluctuations to do the work of producing a current in the >>>> antennae. When the ELT is off, that "work" just gets dumped as heat. >>>> >>>> By placing the antennas very close, my COM was providing a VERY >>>> large signal to the ELT. The ELT could hear me clear as day. The >>>> ELT then proceded to convert that clear signal into heat. That >>>> heat came from my COM radio, which cut out a major part of the >>>> energy that was meant to propagate to ATC and other pilots. >>>> >>>> It's worth noting that with the ELT antennae next to my COM, my >>>> ability to communicate with ATC was very much dependent on which >>>> direction I was flying. If I flew directly to or away from the >>>> airport, the signal was even weaker. >>> >>> Not sure I can grok the heat thing. While the >>> comm signal is 'strong', comm power measured >>> at the base of the ELT antenna cannot be more >>> than a tiny fraction of total comm output power. >>> But the 'lensing' effects of parasitic radiators >>> is another matter . . . distortion of the >>> comm radiation pattern would be my first guess. >>> >>> Would be fun to 'sniff' it in the lab . . . >>> >>> Bob . . . >>> >> OK, show of hands: How many of you had to google 'grok'? (Brag mode >> on; I didn't... If you had to google it, don't stop there; read the >> book. It's *great*.) > > Nope, been in my vocabulary since my teens. Was my very first > password on a multi-user computer in college. > > joe > > Great book, right? --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 14 ____________________________________ Time: 02:39:06 PM PST US From: Joe Keenan Subject: Re: AeroElectric-List: Antenna Ground Plane >> > Great book, right? He was my go-to author growing up. And Ive named characters in many computer games after his characters. My two original World of Warcraft characters are Mycroft and Wyoming. ________________________________ Message 15 ____________________________________ Time: 04:08:53 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Ground Plane At 03:25 PM 6/3/2019, you wrote: > >While I don't doubt that this configuration contributed to the >problem, a much more common situation is when the aircraft is near a >high powered facility broadcasting on VHF. For instance, it is >common for TV and FM broadcast towers to be located near each other, >especially if there is convenient high ground. They can put out >thousands of watts. They will cause the ELT output stage to >oscillate and re-radiate to nearby com antennas. I experienced this >in Phoenix, where 90% of broadcast antennas are on "South Mountain", >which is 7-8 miles south of Phoenix Sky Harbor Airport. When flying >the VFR transition over the top of PHX, I would get terrible squelch >break on both com radios, making communications with the Tracon >difficult on both frequencies they used (120.7 and 123.7). I >verified this by flying under the class B on the south side of the >mountain, with and without the ELT antenna connected. Without ELT >connected, no problem. I then removed one of my 2 com antennas from >the topside of the fuselage to the belly. Problem was 95% eliminated. I'm certain that this is a classic demonstration of inter-modulation of multiple strong signals that mix and remix in a cacophony of of new signals all of which carry vestiges of the original modulation. Got some real hard lessons in this phenomenon back in my two-way radio days when EVERYBODY wanted to put their company's repeater on top of the tallest buildings in the city. Some building owners would hold roof-leases in their hip-pocket and dole them out to all comers irrespective of proposed operating frequencies and equipment. I was anointed with several calls from a new client who complained that a brand new $kilo$ repeater we had just installed became unusable at certain times of the day. Of course, it was our fault . . . in fact it was the uncoordinated exploitation of premium rooftop real estate. That rooftop radio farm could have as many as ten, 50-100 watt uhf and vhf transmitters talking simultaneously into antennas with 6 to 9 db of gain. In one case, an intermod problem had nothing to do with the local electronics . . . was traced to corroded joints in a very old Decibel Products antenna that wasn't even in service! It was sitting up there with nobody knowing that the associated radio had been off the roof for years . . . hence the antenna's mechanical condition deteriorated to the point of becoming a nuisance neighbor. Those problems were materially eliminated by leasing such juicy spots to a single, talented re-leasing company that coordinated all suitable tenants by conducting a potential intermod products study . . . by hand . . . no whippy desktop computers back then. Of course, flying past an antenna farm of television and FM broadcast stations can wreak havoc in a lowly vhf comm radio, a condition you can fly out of in a matter of seconds. Bob . . . ________________________________ Message 16 ____________________________________ Time: 04:09:56 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Ground Plane >Great book, right? Arguably his best Bob . . . ________________________________ Message 17 ____________________________________ Time: 08:32:08 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Ground Plane > Of course, it was our fault . . . in fact it > was the uncoordinated exploitation of premium > rooftop real estate. That rooftop radio farm > could have as many as ten, 50-100 watt uhf > and vhf transmitters talking simultaneously > into antennas with 6 to 9 db of gain. Just for grins, snatched a recent photo of that building Emacs! It's still got an aluminum whisker-farm growing out the top . . . brings back memories. Last time I was up there it was over 100F and no breeze . . . Bob . . . ________________________________ Message 18 ____________________________________ Time: 08:32:28 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Antenna Ground Plane At 06:46 PM 6/2/2019, you wrote: >Thank you very much for the help. > >The aircraft is a KIS made from honeycomb and fiberglass > >On the dipole antenna what length should the folded balun be and do >I make the toroid balun with 3 toroids as in the instruction? > >Just out of interest why should the ELT antenna be separated from >the com antenna > >Thanks again The antenna is two dipoles . . . one centered on 121.5 MHz, the other on 402 MHz. Bob . . .z ________________________________ Message 19 ____________________________________ Time: 10:12:04 PM PST US From: Subject: RE: AeroElectric-List: Antenna Ground Plane Bob Thank you very much for the detailed explanation, I'm not sure that I understand it all, took a Ham radio course a while back so will go back to my notes. If I understand you correctly I must make Jim's dipole antenna as per instruction and attach the core of the coax to one "leg" and the braid to the other "leg" without a balun or toroid. I found the remains of the copper tape that I got (I think) from Jim in 1998, will sen a photo before I install. Thanks Mike From: owner-aeroelectric-list-server@matronics.com On Behalf Of Robert L. Nuckolls, III Sent: June 3, 2019 10:55 AM Subject: RE: AeroElectric-List: Antenna Ground Plane At 06:46 PM 6/2/2019, you wrote: Thank you very much for the help. The aircraft is a KIS made from honeycomb and fiberglass On the dipole antenna what length should the folded balun be and do I make the toroid balun with 3 toroids as in the instruction? This antenna can't use a coax balun . . . it's a dual frequency configuration that precludes using a resonant piece of coax cable to improve feedline performance. Unfortunately the highest frequency of operation (402Mhz) precludes the use of broad-band magnetics. Jim was fond of the string-of-beads approach to reducing effects of mismatch on the feedline but I researched that in the EMC lab at Beech about 30 years ago . . . minimally effective. The most effective decoupling technique using ferrite beads or toroids was utilized in this product a few years ago . . . https://tinyurl.com/y4qpkqoc Talked with this fellow by email and phone. Made some questionable claims including the assertion that the thing was 'patented'. Never could find that patent . . . nonetheless, here's what was inside the 'miracle box': http://www.aeroelectric.com/articles/Antennas/AirWhip/AirWhip_Inside.jpg This de-coupling technique wound several turns on a common core. Inductance goes up as the square of turns. In the photo we count 7 turns or 49 times the inductance of a same core with one turn. Jim's string- of-beads gives 1x potential inductance/per/core or perhaps 8-12x depending on how many cores are strung onto the coax. Played with this in the EMC lap at RAC/Beech and determined that the string of beads wasn't worth the trouble. So . . . how about the airwhip technique for multiple turns on a single core? Not a bad choice. I've seen it done with antennas over a broad spectum of frequencies . . . within limits. Seems that ferrite inductive qualities versus attenuation qualities swap duties at about 200 Mhz or so . . . that's why they are effective for EMC management at vhf/uhf frequencies, not so much as transformers at 402 Mhz . . . but still worth investigating with the right test equipment. I've got a uhf vector analyzer sitting on the shelf above my desk (sigh) . . . someday maybe . . . Given that this antenna is intended to operated on two, unchanging discrete frequencies, one COULD consider fabricating a passive components matching network to transfer feedline energy to the two antennas effectively . . . but I'd bet that the performance differences between uncle Jim's shade-tree engineering approach an one by Dorne-Margolin would be observable only in the lab and of little advantage in practice. In the mean time, fabricating uncle Jim's paralleled dipoles arrangement is easy. Attaching directly to this antenna with coax is also easy. It seems that your airplane (epoxy/glass) is a likely candidate for an all internal ELT antenna which would, I suspect, be less vulnerable to damage by unintended arrivals with the earth. Best yet, no ground plane . . . Just out of interest why should the ELT antenna be separated from the com antenna Kelly offered the strongest rationale for separation . . . ELT's are particularly susceptible to cross-modulation products because unlike receivers, there are 'high power', non-linear components continuously connected to the antenna. I suspect that modern ELTs with FET output stages might be better in this regard but the risks are not zero. Having said that, there is zero risk for damaging anything. I'd recommend you install for convenience and see if you have problems. The problems will be nothing worst than an occasional nuisance with a high probability that you'll not suffer the effects at all. Bob . . . --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 20 ____________________________________ Time: 10:31:14 PM PST US From: Subject: RE: AeroElectric-List: Antenna Ground Plane The antenna is two dipoles . . . one centered on 121.5 MHz, the other on 402 MHz. You have lost me here, I do not understand two dipoles concept. Please explain in more detail if you don't mind Thanks Mike --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 21 ____________________________________ Time: 10:58:41 PM PST US From: "James kale" Subject: RE: AeroElectric-List: Antenna Ground Plane I am working on an antenna for a homebuilt and I read from the AEROLECTRIC column in KITPLANES about using ferrite toroid's for a balun arrangement. However, I seem to remember that the material used in the toroids must be of a certain mixture to get the desired effect for RF signals. Can anyone tell me which toroids to use and which ones not to use. Apparently some work for RF and some work better for audio frequencies. From: owner-aeroelectric-list-server@matronics.com On Behalf Of mike@vision499.com Sent: Tuesday, June 4, 2019 12:11 AM Subject: RE: AeroElectric-List: Antenna Ground Plane Bob Thank you very much for the detailed explanation, I'm not sure that I understand it all, took a Ham radio course a while back so will go back to my notes. If I understand you correctly I must make Jim's dipole antenna as per instruction and attach the core of the coax to one "leg" and the braid to the other "leg" without a balun or toroid. I found the remains of the copper tape that I got (I think) from Jim in 1998, will sen a photo before I install. Thanks Mike From: owner-aeroelectric-list-server@matronics.com On Behalf Of Robert L. Nuckolls, III Sent: June 3, 2019 10:55 AM Subject: RE: AeroElectric-List: Antenna Ground Plane At 06:46 PM 6/2/2019, you wrote: Thank you very much for the help. The aircraft is a KIS made from honeycomb and fiberglass On the dipole antenna what length should the folded balun be and do I make the toroid balun with 3 toroids as in the instruction? This antenna can't use a coax balun . . . it's a dual frequency configuration that precludes using a resonant piece of coax cable to improve feedline performance. Unfortunately the highest frequency of operation (402Mhz) precludes the use of broad-band magnetics. Jim was fond of the string-of-beads approach to reducing effects of mismatch on the feedline but I researched that in the EMC lab at Beech about 30 years ago . . . minimally effective. The most effective decoupling technique using ferrite beads or toroids was utilized in this product a few years ago . . . https://tinyurl.com/y4qpkqoc Talked with this fellow by email and phone. Made some questionable claims including the assertion that the thing was 'patented'. Never could find that patent . . . nonetheless, here's what was inside the 'miracle box': http://www.aeroelectric.com/articles/Antennas/AirWhip/AirWhip_Inside.jpg This de-coupling technique wound several turns on a common core. Inductance goes up as the square of turns. In the photo we count 7 turns or 49 times the inductance of a same core with one turn. Jim's string- of-beads gives 1x potential inductance/per/core or perhaps 8-12x depending on how many cores are strung onto the coax. Played with this in the EMC lap at RAC/Beech and determined that the string of beads wasn't worth the trouble. So . . . how about the airwhip technique for multiple turns on a single core? Not a bad choice. I've seen it done with antennas over a broad spectum of frequencies . . . within limits. Seems that ferrite inductive qualities versus attenuation qualities swap duties at about 200 Mhz or so . . . that's why they are effective for EMC management at vhf/uhf frequencies, not so much as transformers at 402 Mhz . . . but still worth investigating with the right test equipment. I've got a uhf vector analyzer sitting on the shelf above my desk (sigh) . . . someday maybe . . . Given that this antenna is intended to operated on two, unchanging discrete frequencies, one COULD consider fabricating a passive components matching network to transfer feedline energy to the two antennas effectively . . . but I'd bet that the performance differences between uncle Jim's shade-tree engineering approach an one by Dorne-Margolin would be observable only in the lab and of little advantage in practice. In the mean time, fabricating uncle Jim's paralleled dipoles arrangement is easy. Attaching directly to this antenna with coax is also easy. It seems that your airplane (epoxy/glass) is a likely candidate for an all internal ELT antenna which would, I suspect, be less vulnerable to damage by unintended arrivals with the earth. Best yet, no ground plane . . . Just out of interest why should the ELT antenna be separated from the com antenna Kelly offered the strongest rationale for separation . . . ELT's are particularly susceptible to cross-modulation products because unlike receivers, there are 'high power', non-linear components continuously connected to the antenna. I suspect that modern ELTs with FET output stages might be better in this regard but the risks are not zero. Having said that, there is zero risk for damaging anything. I'd recommend you install for convenience and see if you have problems. The problems will be nothing worst than an occasional nuisance with a high probability that you'll not suffer the effects at all. Bob . . . 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