Today's Message Index:
----------------------
1. 08:54 AM - Re: Re: RF Antenna Help (Jeff Luckey)
2. 11:20 AM - No-name-fuses (Robert L. Nuckolls, III)
3. 04:42 PM - Re: No-name-fuses (Bob Kuc)
4. 05:23 PM - Re: No-name-fuses (xl)
5. 06:02 PM - Re: No-name-fuses (Robert L. Nuckolls, III)
6. 06:17 PM - Re: No-name-fuses (Matthew S. Whiting)
7. 07:06 PM - Re: AeroElectric-List Digest: 1 Msgs - 11/11/23 (David Carter)
8. 07:06 PM - Re: AeroElectric-List Digest: 1 Msgs - 11/11/23 (David Carter)
Message 1
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| Subject: | Re: RF Antenna Help |
Thanks Bob for taking the time to explain and to Don also...
I ended up doing as I described in my previous post and it seems satisfacto
ry.=C2- (I did that work before seeing BobN's post)
I have not transmitted with the radio yet.=C2- That will come next week.
On Saturday, November 11, 2023 at 08:07:42 AM PST, Robert L. Nuckolls,
III <nuckolls.bob@aeroelectric.com> wrote:
At 10:38 AM 11/10/2023, you wrote:
Don,
Your explanation helps me understand some of the practical considerationswi
th respect to coax antenna lines.=C2- Thank you. (RF has always beenkind
of a mysterious subject for me)
Next question:
As you can see from the photos, the center conductor is un-insulated andif
I install the C-ring, they will touch - that would be bad.=C2- Can Iinsta
ll a very short length of the center conductor insulation over thatexposed
center conductor?
I'm thinking that I could cut a ~3/16" piece of insulation (from thecore of
a length of RG-400), cut a slit in it axially, and press it overthe expose
d center conductor.=C2- And then, to keep it from possiblyslipping off du
e to vibration (I don't think it will, but just to besafe), can a put a dro
p of CA super glue on it?=C2- Would thatwork?
TIA
-Jeff
On Friday, November 10, 2023 at 08:19:11 AM PST, Don Pansier<dpansier1@new.
rr.com> wrote:
The C shaped device is there to prevent an Impedance Bump. ImpedanceBumps c
an cause high VSWR, weak return loss, and poor system performance.
Coaxial transmission lines rely on a ratio between the diameter of thecente
r conductor and the ID of the outer conductor, in this case theratio is siz
ed for 50 ohms impedance.
Due to size limitations of the connector, it would be very difficult tomake
the connection from the coax to the center pin of the connectorwithout a r
emovable section. Reinstalling the C shaped section returnsthe transmission
line back to the correct ratio.
Impedance Bumps in Coaxial cables can also be caused by pinching,crushing a
nd bending beyond the min radius,=C2- all changing the ratiobetween the I
D and the OD of the transmission line.
=C2- Yeahhhh . . . sort of. The practical effects of 'bumps','kinks'
=C2- and sharp bends in perhaps 20' of coax are worries only
=C2- an academic could appreciate.=C2- These are things easilydetected
=C2- and measured in a lab with sophisticated equipment.
=C2- But can one demonstrate effects of these anomalies whilecruising
=C2- at 10K in your RV? Not so much.
=C2- Consider the attached drawings that illustrate variations in
=C2- coax cable terminations. In Figure 1, we see two techniques
=C2- commonly found in countless production aircraft. (a) crimp
=C2- some terminals on the ends of the conductors and (b) install
=C2- a righteous coax connector.=C2- In Figure 2 we see one ofBob
=C2- Archer's famous, wing-tip VOR antennas tailored to RV
=C2- aircraft. Note that it features crude coax termination as in1(A).
=C2- However, Bob's design also features a matching section
=C2- intended to optimize impedance matching between the antenna
=C2- and feedline. In Figure 3, we see a VOR antenna that was used
=C2- on hundreds of thousands of aircraft for decades. It too uses
=C2- terminals-on-conductors ('bumpy') and no attempt to optimize
=C2- impedance matching or correct for conditions posed by
=C2- connecting an 'unbalanced' feedline (coax) directly to
=C2- a 'balanced' antenna (dipole).
=C2- Hmmmm . . . if one scans these two antennas with a network
=C2- analyzer or time domain reflectometer, I suspect that the
=C2- Archer antenna would present 'nicer' characteristics
=C2- than the legacy 'rabbit ears' used for a century or so.
=C2- However, in terms of practical performance, it would not
=C2- surprise me to discover that the whiskers outperform
=C2- the wing-tip antenna in terms of receiver sensitivity
=C2- as measured in a circle around the airplane.
=C2- Now, does that bode ill for Mr. Archer's brainchild?
=C2- I suspect not . . . there are many examples flying
=C2- today. We're not hearing/reading of operator-owners
=C2- replacing them with 'something better'.
=C2- I cite this as one of countless examples of variations
=C2- in performance among similar systems. The market-place
=C2- question is, does Bob's antenna perform adequately to
=C2- the pilot's needs?=C2- The answer to that must be 'yes'.
=C2- This in spite of theoretical anomalies (like a 'bumpy'
=C2- coax termination) having no demonstrable shortcoming inpractice.
=C2- The little c-ring under discussion in this thread
=C2- is one such example. Your market-place question is,
=C2- 'would I KNOW that it were or were not present by
=C2- observing stuff on my panel? You've noticed that it might
=C2- prove unhandy should it not hold proper position
=C2- within the connector and cause a short.
=C2- I'd pitch the thing and not give it another thought.
=C2-
=C2- Bob . . .
=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2
-=C2-=C2-=C2-=C2-=C2-////
=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2
-=C2-=C2-=C2-=C2-(o o)
=C2-=C2- ===========o00o=(_)=o00o====
=====
=C2-=C2- < Go ahead, make my day . . .=C2-=C2- >
=C2-=C2- < show me where I'm wrong.=C2-=C2-=C2-=C2-=C2->
=C2-=C2- ====================
============
=C2-
=C2-=C2- In the interest of creative evolution
=C2-=C2- of the-best-we-know-how-to-do based
=C2-=C2- on physics and good practice.
Message 2
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At 11:13 PM 11/6/2023, you wrote:
>Here is another illustrative test of no-name
>Chinese fuses. I would think twice before using
>these in an airplane. I wouldn=99t use these in lawn equipment.
>
><https://youtu.be/apQU_VuJlFU>Bad Fuses
><https://youtu.be/apQU_VuJlFU>youtu.be
>
>
>Sent from my iPad
>
>>On Nov 6, 2023, at 11:56=AFPM, Matthew S.
>>Whiting <m.whiting@frontier.com> wrote:
>>
>>=EF=BBI can no longer find the video that actually
>>tested the fuses to failure, but this one shows
>>the problem using fuse resistance as the surrogate.
>>
>><https://youtu.be/nELwmfAOz_I>youtu.be
>><https://youtu.be/nELwmfAOz_I>
>>[]
This is an unfortunate posting to youtube. Especially
sad given what has to be thousands of hours effort in
the balance of learned gentleman's content. In this instance,
he does not demonstrate or explain the physics of
fusible protective devices.
The advice offered in conclusion of his demonstration
is not 'bad' in that one us quite safe to
favor name brand, legacy products supported
by specification documents. That's what a large
proportion of aviation design and manufacturing is
all about. But to broadly brush competing products
with lesser data based on his ill-conceived,
bench-top demonstration is beneath the quality
of his other works.
I've got a gaggle of 'amazon' fuses on order. I
have the tools to quickly quantify critical
characteristics for these devices. Don't need
another project but this one would yield some
measured and demonstrated data for coming to
a more refined judgement.
By the way, in this video, he held up a bottle
of 'test articles?' from a prior demonstration.
I was unable to locate the video where he
produced these carcasses. I'd appreciate a
head-up on his (or any other) study of
off off-label fuses.
Thanks!
Bob . . .
////
(o o)
===========o00o=(_)=o00o=======
=
< Go ahead, make my day . . . >
< show me where I'm wrong. >
========================
========
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 3
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| Subject: | Re: No-name-fuses |
Thanks Bob.
That was very interesting and eye opener.
I was looking at the ones in Amazon but I could not find 1 and 2 and 3 amp
ones and I didn't think I would need a lot of 30 amp ones. I did buy some
of the 1,2 and 3 amp ones from digikey. Those were all littelfuse ones.
Bob
On Sun, Nov 12, 2023, 2:23=AFPM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 11:13 PM 11/6/2023, you wrote:
>
> Here is another illustrative test of no-name Chinese fuses. I would thin
k
> twice before using these in an airplane. I wouldn=C3=A2=82=AC=84
=A2t use these in lawn
> equipment.
>
> Bad Fuses <https://youtu.be/apQU_VuJlFU>
>
> youtu.be <https://youtu.be/apQU_VuJlFU>
>
>
> Sent from my iPad
>
> On Nov 6, 2023, at 11:56=C3=A2=82=AC=C2=AFPM, Matthew S. Whiting <m.wh
iting@frontier.com>
> wrote:
>
> =C3=AF=C2=BB=C2I can no longer find the video that actually tested the
fuses to
> failure, but this one shows the problem using fuse resistance as the
> surrogate.
>
> youtu.be <https://youtu.be/nELwmfAOz_I>
> [image: []] <https://youtu.be/nELwmfAOz_I>
>
>
> This is an unfortunate posting to youtube. Especially
> sad given what has to be thousands of hours effort in
> the balance of learned gentleman's content. In this instance,
> he does not demonstrate or explain the physics of
> fusible protective devices.
>
> The advice offered in conclusion of his demonstration
> is not 'bad' in that one us quite safe to
> favor name brand, legacy products supported
> by specification documents. That's what a large
> proportion of aviation design and manufacturing is
> all about. But to broadly brush competing products
> with lesser data based on his ill-conceived,
> bench-top demonstration is beneath the quality
> of his other works.
>
> I've got a gaggle of 'amazon' fuses on order. I
> have the tools to quickly quantify critical
> characteristics for these devices. Don't need
> another project but this one would yield some
> measured and demonstrated data for coming to
> a more refined judgement.
>
> By the way, in this video, he held up a bottle
> of 'test articles?' from a prior demonstration.
> I was unable to locate the video where he
> produced these carcasses. I'd appreciate a
> head-up on his (or any other) study of
> off off-label fuses.
>
> Thanks!
>
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o======
==
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> =======================
=========
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
>
Message 4
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| Subject: | Re: No-name-fuses |
fyi, known bad fuses,
For example, a safety recall:
https://tinyurl.com/3ekjatdh]
Joe
On Sun, 12 Nov 2023, Bob Kuc wrote:
> Thanks Bob.
>
> That was very interesting and eye opener.
>
> I was looking at the ones in Amazon but I could not find 1 and 2 and 3 amp
> ones and I didn't think I would need a lot of 30 amp ones. I did buy some
> of the 1,2 and 3 amp ones from digikey. Those were all littelfuse ones.
>
> Bob
>
> On Sun, Nov 12, 2023, 2:23PM Robert L. Nuckolls, III <
> nuckolls.bob@aeroelectric.com> wrote:
>
>> At 11:13 PM 11/6/2023, you wrote:
>>
>> Here is another illustrative test of no-name Chinese fuses. I would think
>> twice before using these in an airplane. I wouldnt use these in lawn
>> equipment.
>>
>> Bad Fuses <https://youtu.be/apQU_VuJlFU>
>>
>> youtu.be <https://youtu.be/apQU_VuJlFU>
>>
>>
>> Sent from my iPad
>>
>> On Nov 6, 2023, at 11:56PM, Matthew S. Whiting <m.whiting@frontier.com>
>> wrote:
>>
>> I can no longer find the video that actually tested the fuses to
>> failure, but this one shows the problem using fuse resistance as the
>> surrogate.
>>
>> youtu.be <https://youtu.be/nELwmfAOz_I>
>> [image: []] <https://youtu.be/nELwmfAOz_I>
>>
>>
>> This is an unfortunate posting to youtube. Especially
>> sad given what has to be thousands of hours effort in
>> the balance of learned gentleman's content. In this instance,
>> he does not demonstrate or explain the physics of
>> fusible protective devices.
>>
>> The advice offered in conclusion of his demonstration
>> is not 'bad' in that one us quite safe to
>> favor name brand, legacy products supported
>> by specification documents. That's what a large
>> proportion of aviation design and manufacturing is
>> all about. But to broadly brush competing products
>> with lesser data based on his ill-conceived,
>> bench-top demonstration is beneath the quality
>> of his other works.
>>
>> I've got a gaggle of 'amazon' fuses on order. I
>> have the tools to quickly quantify critical
>> characteristics for these devices. Don't need
>> another project but this one would yield some
>> measured and demonstrated data for coming to
>> a more refined judgement.
>>
>> By the way, in this video, he held up a bottle
>> of 'test articles?' from a prior demonstration.
>> I was unable to locate the video where he
>> produced these carcasses. I'd appreciate a
>> head-up on his (or any other) study of
>> off off-label fuses.
>>
>> Thanks!
>>
>>
>> Bob . . .
>>
>> ////
>> (o o)
>> ===========o00o=(_)=o00o========
>> < Go ahead, make my day . . . >
>> < show me where I'm wrong. >
>> ================================
>>
>> In the interest of creative evolution
>> of the-best-we-know-how-to-do based
>> on physics and good practice.
>>
>
Message 5
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| Subject: | Re: No-name-fuses |
At 07:22 PM 11/12/2023, you wrote:
>fyi, known bad fuses,
>For example, a safety recall:
>https://tinyurl.com/3ekjatdh]
I read about this incident . . . unfortunately,
not very informative. Without having
exemplar fuses to test, the recall contributes
nothing to understanding.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 6
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| Subject: | Re: No-name-fuses |
What understanding are you seeking?
=46rom my perspective as an airplane builder, the only understanding I reall
y care about is knowing that the fuses I buy will perform according to the c
urrent/time curves that the manufacturer publishes. If a given fuse manufac
turer either doesn=99t provide performance data for its fuses or doesn
=99t produce fuses that perform according to spec, then I won=99
t use them.
I have been unable to find the first video I saw on these fuses (I think it w
as about the Harbor Freight fuses prior to the recall), but I wish I could a
s, if memory serves, the video maker took close-up pictures of the fuses and
it was pretty clear that the fuse element in them was identical for every f
use size in the box and even the 5 A fuse would easily handle 30 A.
As a retired EE, I have some intellectual curiosity about fuse performance a
nd how they are made, etc., but as a builder I am mainly concerned about hav
ing assurance of the fuse performance and understanding the physics is in th
e =9Cnice to know=9D category, but not essential.
Matt
Sent from my iPad
> On Nov 12, 2023, at 9:05=AFPM, Robert L. Nuckolls, III <nuckolls.bob
@aeroelectric.com> wrote:
>
> =EF=BB At 07:22 PM 11/12/2023, you wrote:
>
>> fyi, known bad fuses,
>> For example, a safety recall:
>> https://tinyurl.com/3ekjatdh]
>
> I read about this incident . . . unfortunately,
> not very informative. Without having
> exemplar fuses to test, the recall contributes
> nothing to understanding.
>
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o=======
=
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ========================
========
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
Message 7
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| Subject: | Re: AeroElectric-List Digest: 1 Msgs - 11/11/23 |
Different topic: Are Lithium ion batteries affected by low ambient
temperature like, or any where close to, what lead acid batteries suffer
down around zero F and below?
. . . Just wondering if electric powered cars and trucks will be
seriously affected this winter up north.
David Carter
On 11/12/2023 1:30 AM, AeroElectric-List Digest Server wrote:
> *
>
> =================================================
> Online Versions of Today's List Digest Archive
> =================================================
>
> Today's complete AeroElectric-List Digest can also be found in either of the
> two Web Links listed below. The .html file includes the Digest formatted
> in HTML for viewing with a web browser and features Hyperlinked Indexes
> and Message Navigation. The .txt file includes the plain ASCII version
> of the AeroElectric-List Digest and can be viewed with a generic text editor
> such as Notepad or with a web browser.
>
> HTML Version:
>
> http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter 23-11-11&Archive=AeroElectric
>
> Text Version:
>
> http://www.matronics.com/digest/digestview.php?Style=82701&View=txt&Chapter 23-11-11&Archive=AeroElectric
>
>
> ===============================================
> EMail Version of Today's List Digest Archive
> ===============================================
>
>
> ----------------------------------------------------------
> AeroElectric-List Digest Archive
> ---
> Total Messages Posted Sat 11/11/23: 1
> ----------------------------------------------------------
>
>
> Today's Message Index:
> ----------------------
>
> 1. 07:58 AM - Re: Re: RF Antenna Help (Robert L. Nuckolls, III)
>
>
>
> ________________________________ Message 1 _____________________________________
>
>
> Time: 07:58:12 AM PST US
> From: "Robert L. Nuckolls, III"<nuckolls.bob@aeroelectric.com>
> Subject: Re: AeroElectric-List: Re: RF Antenna Help
>
> At 10:38 AM 11/10/2023, you wrote:
>> Don,
>>
>> Your explanation helps me understand some of the practical
>> considerations with respect to coax antenna lines. Thank you. (RF
>> has always been kind of a mysterious subject for me)
>>
>> Next question:
>> As you can see from the photos, the center conductor is un-insulated
>> and if I install the C-ring, they will touch - that would be
>> bad. Can I install a very short length of the center conductor
>> insulation over that exposed center conductor?
>>
>> I'm thinking that I could cut a ~3/16" piece of insulation (from the
>> core of a length of RG-400), cut a slit in it axially, and press it
>> over the exposed center conductor. And then, to keep it from
>> possibly slipping off due to vibration (I don't think it will, but
>> just to be safe), can a put a drop of CA super glue on it? Would that work?
>>
>> TIA
>>
>> -Jeff
>>
>>
>> On Friday, November 10, 2023 at 08:19:11 AM PST, Don Pansier
>> <dpansier1@new.rr.com> wrote:
>>
>>
>> The C shaped device is there to prevent an Impedance Bump. Impedance
>> Bumps can cause high VSWR, weak return loss, and poor system performance.
>>
>> Coaxial transmission lines rely on a ratio between the diameter of
>> the center conductor and the ID of the outer conductor, in this case
>> the ratio is sized for 50 ohms impedance.
>> Due to size limitations of the connector, it would be very difficult
>> to make the connection from the coax to the center pin of the
>> connector without a removable section. Reinstalling the C shaped
>> section returns the transmission line back to the correct ratio.
>>
>> Impedance Bumps in Coaxial cables can also be caused by pinching,
>> crushing and bending beyond the min radius, all changing the ratio
>> between the ID and the OD of the transmission line.
> Yeahhhh . . . sort of. The practical effects of 'bumps', 'kinks'
> and sharp bends in perhaps 20' of coax are worries only
> an academic could appreciate. These are things easily detected
> and measured in a lab with sophisticated equipment.
>
> But can one demonstrate effects of these anomalies while cruising
> at 10K in your RV? Not so much.
>
> Consider the attached drawings that illustrate variations in
> coax cable terminations. In Figure 1, we see two techniques
> commonly found in countless production aircraft. (a) crimp
> some terminals on the ends of the conductors and (b) install
> a righteous coax connector. In Figure 2 we see one of Bob
> Archer's famous, wing-tip VOR antennas tailored to RV
> aircraft. Note that it features crude coax termination as in 1(A).
>
> However, Bob's design also features a matching section
> intended to optimize impedance matching between the antenna
> and feedline. In Figure 3, we see a VOR antenna that was used
> on hundreds of thousands of aircraft for decades. It too uses
> terminals-on-conductors ('bumpy') and no attempt to optimize
> impedance matching or correct for conditions posed by
> connecting an 'unbalanced' feedline (coax) directly to
> a 'balanced' antenna (dipole).
>
> Hmmmm . . . if one scans these two antennas with a network
> analyzer or time domain reflectometer, I suspect that the
> Archer antenna would present 'nicer' characteristics
> than the legacy 'rabbit ears' used for a century or so.
>
> However, in terms of practical performance, it would not
> surprise me to discover that the whiskers outperform
> the wing-tip antenna in terms of receiver sensitivity
> as measured in a circle around the airplane.
>
> Now, does that bode ill for Mr. Archer's brainchild?
> I suspect not . . . there are many examples flying
> today. We're not hearing/reading of operator-owners
> replacing them with 'something better'.
>
> I cite this as one of countless examples of variations
> in performance among similar systems. The market-place
> question is, does Bob's antenna perform adequately to
> the pilot's needs? The answer to that must be 'yes'.
> This in spite of theoretical anomalies (like a 'bumpy'
> coax termination) having no demonstrable shortcoming in practice.
>
>
> The little c-ring under discussion in this thread
> is one such example. Your market-place question is,
> 'would I KNOW that it were or were not present by
> observing stuff on my panel? You've noticed that it might
> prove unhandy should it not hold proper position
> within the connector and cause a short.
>
> I'd pitch the thing and not give it another thought.
>
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o=======
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ===============================
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
>
>
>
>
>
>
>
--
David Carter
Message 8
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| Subject: | Re: AeroElectric-List Digest: 1 Msgs - 11/11/23 |
Different topic: Are Lithium ion batteries affected by low ambient
temperature like, or any where close to, what lead acid batteries suffer
down around zero F and below?
. . . Just wondering if electric powered cars and trucks will be
seriously affected this winter up north.
David Carter
On 11/12/2023 1:30 AM, AeroElectric-List Digest Server wrote:
> *
>
> =================================================
> Online Versions of Today's List Digest Archive
> =================================================
>
> Today's complete AeroElectric-List Digest can also be found in either of the
> two Web Links listed below. The .html file includes the Digest formatted
> in HTML for viewing with a web browser and features Hyperlinked Indexes
> and Message Navigation. The .txt file includes the plain ASCII version
> of the AeroElectric-List Digest and can be viewed with a generic text editor
> such as Notepad or with a web browser.
>
> HTML Version:
>
> http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter 23-11-11&Archive=AeroElectric
>
> Text Version:
>
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> EMail Version of Today's List Digest Archive
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> AeroElectric-List Digest Archive
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> Total Messages Posted Sat 11/11/23: 1
> ----------------------------------------------------------
>
>
> Today's Message Index:
> ----------------------
>
> 1. 07:58 AM - Re: Re: RF Antenna Help (Robert L. Nuckolls, III)
>
>
>
> ________________________________ Message 1 _____________________________________
>
>
> Time: 07:58:12 AM PST US
> From: "Robert L. Nuckolls, III"<nuckolls.bob@aeroelectric.com>
> Subject: Re: AeroElectric-List: Re: RF Antenna Help
>
> At 10:38 AM 11/10/2023, you wrote:
>> Don,
>>
>> Your explanation helps me understand some of the practical
>> considerations with respect to coax antenna lines. Thank you. (RF
>> has always been kind of a mysterious subject for me)
>>
>> Next question:
>> As you can see from the photos, the center conductor is un-insulated
>> and if I install the C-ring, they will touch - that would be
>> bad. Can I install a very short length of the center conductor
>> insulation over that exposed center conductor?
>>
>> I'm thinking that I could cut a ~3/16" piece of insulation (from the
>> core of a length of RG-400), cut a slit in it axially, and press it
>> over the exposed center conductor. And then, to keep it from
>> possibly slipping off due to vibration (I don't think it will, but
>> just to be safe), can a put a drop of CA super glue on it? Would that work?
>>
>> TIA
>>
>> -Jeff
>>
>>
>> On Friday, November 10, 2023 at 08:19:11 AM PST, Don Pansier
>> <dpansier1@new.rr.com> wrote:
>>
>>
>> The C shaped device is there to prevent an Impedance Bump. Impedance
>> Bumps can cause high VSWR, weak return loss, and poor system performance.
>>
>> Coaxial transmission lines rely on a ratio between the diameter of
>> the center conductor and the ID of the outer conductor, in this case
>> the ratio is sized for 50 ohms impedance.
>> Due to size limitations of the connector, it would be very difficult
>> to make the connection from the coax to the center pin of the
>> connector without a removable section. Reinstalling the C shaped
>> section returns the transmission line back to the correct ratio.
>>
>> Impedance Bumps in Coaxial cables can also be caused by pinching,
>> crushing and bending beyond the min radius, all changing the ratio
>> between the ID and the OD of the transmission line.
> Yeahhhh . . . sort of. The practical effects of 'bumps', 'kinks'
> and sharp bends in perhaps 20' of coax are worries only
> an academic could appreciate. These are things easily detected
> and measured in a lab with sophisticated equipment.
>
> But can one demonstrate effects of these anomalies while cruising
> at 10K in your RV? Not so much.
>
> Consider the attached drawings that illustrate variations in
> coax cable terminations. In Figure 1, we see two techniques
> commonly found in countless production aircraft. (a) crimp
> some terminals on the ends of the conductors and (b) install
> a righteous coax connector. In Figure 2 we see one of Bob
> Archer's famous, wing-tip VOR antennas tailored to RV
> aircraft. Note that it features crude coax termination as in 1(A).
>
> However, Bob's design also features a matching section
> intended to optimize impedance matching between the antenna
> and feedline. In Figure 3, we see a VOR antenna that was used
> on hundreds of thousands of aircraft for decades. It too uses
> terminals-on-conductors ('bumpy') and no attempt to optimize
> impedance matching or correct for conditions posed by
> connecting an 'unbalanced' feedline (coax) directly to
> a 'balanced' antenna (dipole).
>
> Hmmmm . . . if one scans these two antennas with a network
> analyzer or time domain reflectometer, I suspect that the
> Archer antenna would present 'nicer' characteristics
> than the legacy 'rabbit ears' used for a century or so.
>
> However, in terms of practical performance, it would not
> surprise me to discover that the whiskers outperform
> the wing-tip antenna in terms of receiver sensitivity
> as measured in a circle around the airplane.
>
> Now, does that bode ill for Mr. Archer's brainchild?
> I suspect not . . . there are many examples flying
> today. We're not hearing/reading of operator-owners
> replacing them with 'something better'.
>
> I cite this as one of countless examples of variations
> in performance among similar systems. The market-place
> question is, does Bob's antenna perform adequately to
> the pilot's needs? The answer to that must be 'yes'.
> This in spite of theoretical anomalies (like a 'bumpy'
> coax termination) having no demonstrable shortcoming in practice.
>
>
> The little c-ring under discussion in this thread
> is one such example. Your market-place question is,
> 'would I KNOW that it were or were not present by
> observing stuff on my panel? You've noticed that it might
> prove unhandy should it not hold proper position
> within the connector and cause a short.
>
> I'd pitch the thing and not give it another thought.
>
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o=======
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ===============================
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
>
>
>
>
>
>
>
--
David Carter
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