Best coax for aircraft radios

ELIPPSE wrote:

I worked with an X-band extreme-accuracy Atlas guidance radar at
Vandenberg AFB. It was necessaspecializedt least 150dB isolation to
prevent interference in our test simulator. Solid jacket cable was the
only thing that would allow this kind of performance. The Andrew cable
was also the only kind that did not generate noise when flexed or
vibrated, which was very important in our test operations. Remember
that the transponder puts out 100W-400W peak. Leaking cables in close
proximity can cross couple. Cable leakage also effects the apparent
radiation pattern of antennas, generating undesired sidelobes and
cancellations. Consider the 20' long com run from the instrument panel
to the antenna buried in the tip sail of the VariEZ or LongEZ that
passes near the extreme RFI generated by the engine's ignition. Has
anyone ever had spark noise in their com radio?


Your x-band does not compare with homebuilt even when talking about
transponders and dme. Even 20 foot run for a com radio doesn't require that
high a caliber cable. You will probably find that most of the noise from
ignition isn't from the center conductor but from the shield and also then
antenna itself. Most people do not run there coax next to their ignition
wires anyway! Use a little common sense, it's a heck of a lot cheaper!
John


PS my background is in microwave measurements etc that doesn't mean I need
to engineer my homebuilt around top end specialized cable.

I really like RG142 as well, especially the low loss and low leakage
in a fairly small and light cable. But for short runs, it is still overkill
for much of anything besides a radio altimeter.

Peter

wrote in message
oups.com...
Andrew Heliax is fine cable - just what you need to run
up a tower (it comes in many sizes). But in an airplane?
Like the man said - it's overkill. I'd recommend RG142.

As for the isolation - engineers have an inside joke that
goes something like this:

Oh say can you see.....
Three Hundred Dee Bee....

This is a range greater than that between the smallest
detectable signal to an unimaginable amount of power.
In other words, it doesn't exist in the natural world.
AFAIK, nobody makes anything with "300 dB of isolation".
Any engineers out there who would care to comment?

David Johnson

Sorry that you think this is a marketing ploy. I thought that this was
a forum for information exchange. I just wanted to pass along my
experiences working with all kinds of coax under a lot of extreme
conditions, and the lessons learned from them.
As far as the props, If you had designed a prop that gave performance
so far beyond the others available and this performance was
demonstrated in the best way, wouldn't you want to share that with
others? I don't sell cables or props or ignitions; I leave that to
others. I guess there are some of you who don't care that there is a
revolution in prop design that can give you markedly better
performance. Or coax that will up your radio's performance. Perhaps you
don't also want me to share with you the research I and another have
done to keep your prop bolts tensioned regardless of temperature or
humidity. When all you do is put down others who want to share, you can
suppress that sharing!

I have rarely read such unmitigated horsepuckey in my engineering career.

Jim



"ELIPPSE" wrote in message
oups.com...
If you would like to have the finest low-loss, light-weight coax cable
for your aircraft radio installations

Horsepuckey, unmitigated or otherwise, does not constitute a cogent
review of the technical information presented. It would be much more
enlightening to all if the respondent had replied with a discussion of
the technical merits as he sees them from his own perspective of
theoretical and practical experience, rather than to launch into the
vitriol of an ad hominem attack. This type of attack is often a shield
for the attacker's own ignorance or incompetence! I presented the
specs; he, for his part, should show how and in what way they are not
applicable, along with his own recommendations, especially with
practical examples of received and transmitted power levels and cable
lengths. It would also be interesting to see, from his vantage point,
what testing he has done on the effect of signal leakage in coax on the
their concomitant creation of sidelobes resulting in attenna pattern
distortion and signal dropout. Only in this way may all who are
interested in the proper selection of cabling for their aircraft be
able to intelligently make, what is for them, the proper choice of
cable and connector type based on performance and economics. We report,
they decide!

Double horsepuckey, and I don't appreciate your snide side emails. If you
have something to say to me, have the intestinal fortitude to post it in the
newsgroup.

What you recommended was a howitzer to kill an ant. Showing how and why 300
dB is a meaningless number is meaningless to somebody who doesn't have a
concept of how impossible that is to measure.

Signal leakage distortion of the antenna pattern is possible to measure on
the pattern range. With the coax inside of a metal structure the concept is
meaningless, as is it meaningless when the coax is bundled with other
wires...a 99+% probability.

Plonk.

Jim




"ELIPPSE" wrote in message
oups.com...
Horsepuckey, unmitigated or otherwise, does not constitute a cogent
review of the technical information presented. It would be much more
enlightening to all if the respondent had replied with a discussion of
the technical merits as he sees them from his own perspective of
theoretical and practical experience, rather than to launch into the
vitriol of an ad hominem attack. This type of attack is often a shield
for the attacker's own ignorance or incompetence! I presented the
specs; he, for his part, should show how and in what way they are not
applicable, along with his own recommendations, especially with
practical examples of received and transmitted power levels and cable
lengths. It would also be interesting to see, from his vantage point,
what testing he has done on the effect of signal leakage in coax on the
their concomitant creation of sidelobes resulting in attenna pattern
distortion and signal dropout. Only in this way may all who are
interested in the proper selection of cabling for their aircraft be
able to intelligently make, what is for them, the proper choice of
cable and connector type based on performance and economics. We report,
they decide!

On Tue, 11 Jan 2005 15:21:38 -0800, "RST Engineering"
wrote:

What you recommended was a howitzer to kill an ant. Showing how and why 300
dB is a meaningless number is meaningless to somebody who doesn't have a
concept of how impossible that is to measure.

Aw Jim, 0.1 microvolt to 1 Megavolt is "only" 260 dB ... g ...
assuming 50 ohms, that is good receiver sensitivity vs 20 Gigawatt ...
we have Gigahertz, why not Gigawatt ... OH, you mean that a large
power plant turbine-generator is on the order of a Gigawatt ... OH ...

Methinks he doesn't understand large (and small) numbers ...

"ELIPPSE" wrote in message
oups.com...
Horsepuckey, unmitigated or otherwise, does not constitute a cogent
review of the technical information presented. It would be much more
enlightening to all if the respondent had replied with a discussion of
the technical merits as he sees them from his own perspective of
theoretical and practical experience, rather than to launch into the
vitriol of an ad hominem attack.

His attack was not ad hominem. I may not be an engineer, but I did take
Latin.

In fact, by usenet standards I would judge his comments as only border line
rude. He likely felt free to snipe because your reputation here is already
poor due to several missteps in ettiquette.

This type of attack is often a shield
for the attacker's own ignorance or incompetence!

I also took Psych, Communications, and Logic. You made an obvious
statement and that may or may not apply, and then qualified it with "often"
so that you really didn't say anything. Which is good, because as I said
before, I took Latin, and this IS an ad hominem attack.

I presented the
specs; he, for his part, should show how and in what way they are not
applicable, along with his own recommendations, especially with
practical examples of received and transmitted power levels and cable
lengths.

Maybe he should, or maybe he doesn't need to. Remember, "they decide".

It would also be interesting to see, from his vantage point,
what testing he has done on the effect of signal leakage in coax on the
their concomitant creation of sidelobes resulting in attenna pattern
distortion and signal dropout.

Interesting to whom? If you don't respect his opinion, why do you care about
his perspective?

Only in this way may all who are
interested in the proper selection of cabling for their aircraft be
able to intelligently make, what is for them, the proper choice of
cable and connector type based on performance and economics. We report,
they decide!

Actually, I, like many aviators, tend to go with what is tried and true
until I see a desirable benefit that would result from a change. While a
seriously detailed investigation and discussion may bring about new
knowledge, its not like our we are all failing as it is.

You are obviously a bright guy, but there are lots of those folks already
here. Perhaps you should try to avoid any heavy arguments for a bit.

Hi, Dude!
It's funny! Here I post some info about a cable, and its
characteristics, that I had a lot of excellent results with, and which
I installed on my Lancair. I thought that this forum was for the
exchange of information. I expected some replies such as: "Yeah, that
cable has some good low-loss characteristics, but after checking the
prices on the mfg's. site, I decided that the performance I'm getting
with the cable I presently use is good enough for me." OK, that's
reasonable! Or: "I'm building this hot Lancair IVP and I want the best
cable I can get; money is no object! Thanks for the tip" OK, that's
reasonable too! But do I get a discussion on the relative merits of
this cable and others? No, I get a bunch of sharks and their sycophants
who want to prove to each other just how smart they are and how they
can take down this new guy."Who does he think he is, anyway?"
I've met this type over and over in the Aerospace world. Those who
can't get up a decent technical discussion and then hide their
ignorance behind insults. Too bad that they don't see that when others
see this type of diatribe over some little innocent posting, that
they're afraid of posting something themselves and incurring this type
of wrath. What a stifler of open discussion! The political world is
full of this kind; look at the last election. I expected that on a
homebuilder's site, at least, that that kind of thing would be
dispensed with so that a dialogue of builder-helping-builder would
prevail! Silly me! I guess even in homebuilding small egos prevail. Too
bad there are not more like Corky Scott and the ones who contacted me
about the ELIPPSE prop, looking for more performance. They weren't
taken-in by these egomaniacal types who can't stand it if someone
doesn't kiss their boots and acknowledge them as the pre-eminent
authorities on everything! But as for me, as I get information that I
think others may want to know, I will post it on the forum and ignore
the sharks.

Ellipse
My original post (and I think I started the replies) had more to do with the
fact you came in with your first appearance with multiple post (4 or 5)the
one with the coax was probably the most innocent with plenty of merit
( although I still believe for the vast majority of homebuilders it is
gross overkill for the money). Go back and read your post on the prop,
which has it's own merits I'm sure. The point is you flooded the news group
with it and it was written as a "look at this prop go here and get it"
post.
I believe you meant well but you came on very strong and that's were the
objections mainly came from. I'm sure you have a lot of positive input to
this group and yes I do read your post!
So I hope you'd go back a review and see where we came from. My intention
was not to make you feel unwelcome but when I do see multiple posts (more
than 2) directing me to a product, I'm skeptical.
I hope that everyone can let this thread die and go on. If people want to
discus the merits or use of the cable consider starting a new topic on it
all over!
John