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
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| Subject: | Re: 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
>
><https://hackaday.com/2019/05/30/the-fascinating-world-of-solder-alloys-and-metallurgy/>THE
>FASCINATING WORLD OF SOLDER ALLOYS AND METALLURGY
Good find! Thanks . . .
Bob . . .
Message 2
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| Subject: | Re: 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, <mike@vision499.com> wrote:
Just out of interest why should the ELT antenna be separated from the com a
ntenna
=C2-
=C2-
| | Virus-free. www.avast.com |
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| Subject: | Re: Antenna Ground Plane |
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Message 4
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| Subject: | Re: 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 <rnjcurtis@charter.net> 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 <echristley@att.net>
> 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, <mike@vision499.com>
wrote:
>
> Just out of interest why should the ELT antenna be separated
from the com
> antenna
> Virus-free. www.avast.com
>
>
>
Message 5
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| Subject: | 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
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| Subject: | Re: 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
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| Subject: | Re: 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 <rnjcurtis@chart
er.net> 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
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| Subject: | Re: 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
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| Subject: | Re: 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
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| Subject: | Re: Antenna Ground Plane |
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
---
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Message 11
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| Subject: | Re: Antenna Ground Plane |
> On Jun 3, 2019, at 4:17 PM, Charlie England <ceengland7@gmail.com>
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
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| Subject: | Re: Antenna Ground Plane |
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
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| Subject: | Re: Antenna Ground Plane |
On 6/3/2019 3:25 PM, Joe Keenan wrote:
>
>
>> On Jun 3, 2019, at 4:17 PM, Charlie England <ceengland7@gmail.com
>> <mailto:ceengland7@gmail.com>> 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?
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| Subject: | Re: 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.
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| Subject: | Re: 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 . . .
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| Subject: | Re: Antenna Ground Plane |
>Great book, right?
Arguably his best
Bob . . .
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| Subject: | Re: 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 . . .
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| Subject: | 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
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| Subject: | 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
<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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| Subject: | 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
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| Subject: | 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
<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
<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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