I'd be glad to compare results and methodologies with anyone else who
has measured this coax. It would be particularly interesting and
educational if someone else's results are significantly different from mine.

Roy Lewallen, W7EL

Charlie wrote:
If Davis 9914 has the center conductor suspended by a thin spiral

thing like 9913,

Davis BuryFlex 9914 does not have the center conductor suspended by a thin
spiral.
1. http://www.davisrf.com/ham1/coax.htm#buryflex

It amazes me that no one else (that I can find) has found Davis BuryFlex to
be "bad coax". It has been in production well over 10 years.
Moreover I am amazed how many of you are non-thinking lambs following along
head-to-tail after your shepherd.
And also Davis emphasizes in it's data that this coax is flexible enough for
rotator loops and yet one guy says it is "bad coax" and so everyone falls to
their knees and worships accordingly?

And as far as data goes...is this guys data more accurate then the Davis RF
company that has been in the wire and cable business
with engineering professionals on the payroll since 1980? Sheesh......take
off the blinders people.....thousands of miles of Davis 9914 have been
installed by government,commercial and amateur stations and just now we find
out it's "bad coax" after more than 10 years?

Somebody is asleep at the switch.......

I have emailed Davis RF and asked them to send me their test results. Yes
it will be interesting.

Roy..doesn't seem a bit odd that NO ONE ELSE in over 10 years of BuryFlex
production has cited these same alarming "test results".


--

Charlie


"Roy Lewallen" wrote in message
...
I'd be glad to compare results and methodologies with anyone else who has
measured this coax. It would be particularly interesting and educational
if someone else's results are significantly different from mine.

Roy Lewallen, W7EL

Charlie wrote:
If Davis 9914 has the center conductor suspended by a thin spiral

thing like 9913,

Davis BuryFlex 9914 does not have the center conductor suspended by a
thin spiral.
1. http://www.davisrf.com/ham1/coax.htm#buryflex

It amazes me that no one else (that I can find) has found Davis BuryFlex
to be "bad coax". It has been in production well over 10 years.
Moreover I am amazed how many of you are non-thinking lambs following
along head-to-tail after your shepherd.
And also Davis emphasizes in it's data that this coax is flexible enough
for rotator loops and yet one guy says it is "bad coax" and so everyone
falls to their knees and worships accordingly?

And as far as data goes...is this guys data more accurate then the Davis
RF company that has been in the wire and cable business
with engineering professionals on the payroll since 1980?
Sheesh......take off the blinders people.....thousands of miles of Davis
9914 have been installed by government,commercial and amateur stations
and just now we find out it's "bad coax" after more than 10 years?

Somebody is asleep at the switch.......

Charlie wrote:
I have emailed Davis RF and asked them to send me their test results. Yes
it will be interesting.

Roy..doesn't seem a bit odd that NO ONE ELSE in over 10 years of BuryFlex
production has cited these same alarming "test results".

No. My experience is that the vast majority of amateurs don't have the
ability and/or confidence and/or interest and/or equipment to make good
measurements. And lacking the ability to measure it, very few would be
able to discern the difference in loss. If my measurements are typical,
commercial and government users (if there indeed are any for this
particular cable type) would quietly reject the stuff on incoming
inspection and order something else.

I do have a high degree of confidence that my measurements are accurate.
I took a lot of care in characterizing the cable before using it for
making remote antenna impedance measurements in the course of a
consulting job. But it's entirely possible that the particular piece of
cable I have is defective. That would just point to a quality control
problem rather than overzealous specsmanship.

In your query of Davis, I hope you asked them if they routinely test
production batches for loss, and if so how often and when the last test
was run. It's possible that something in their process changed
relatively recently.

If no other reader of this newsgroup has some of this cable and the
ability to test it, I'll see if I can arrange for someone else to make
measurements and post results.

Roy Lewallen, W7EL

Roy the kind of test results you cited would be extremely evident whether
someone has a network analyzer or just an swr meter.
That defense is sorely transparent in my opinion. To suggest that most
amateurs would not even have any interest if their bent or coiled 9914
suddenly jumped off the scale for loss and mismatch is ludicrous to say the
least.

Let me be clear ...I am not disputing what you claim you got as test
results. My conclusion is either the 100ft length you had was bad or
something skewed your calibrated setup. My career was in microwave r&d and
I know that it takes repeatable test results to form a valid, verifiable and
publishable data.
This is not personal Roy....but it is somewhat stimulating.


--

Charlie


"Roy Lewallen" wrote in message
...
Charlie wrote:
I have emailed Davis RF and asked them to send me their test results.
Yes it will be interesting.

Roy..doesn't seem a bit odd that NO ONE ELSE in over 10 years of BuryFlex
production has cited these same alarming "test results".

No. My experience is that the vast majority of amateurs don't have the
ability and/or confidence and/or interest and/or equipment to make good
measurements. And lacking the ability to measure it, very few would be
able to discern the difference in loss. If my measurements are typical,
commercial and government users (if there indeed are any for this
particular cable type) would quietly reject the stuff on incoming
inspection and order something else.

I do have a high degree of confidence that my measurements are accurate. I
took a lot of care in characterizing the cable before using it for making
remote antenna impedance measurements in the course of a consulting job.
But it's entirely possible that the particular piece of cable I have is
defective. That would just point to a quality control problem rather than
overzealous specsmanship.

In your query of Davis, I hope you asked them if they routinely test
production batches for loss, and if so how often and when the last test
was run. It's possible that something in their process changed relatively
recently.

If no other reader of this newsgroup has some of this cable and the
ability to test it, I'll see if I can arrange for someone else to make
measurements and post results.

Roy Lewallen, W7EL

Charlie wrote:
Roy the kind of test results you cited would be extremely evident whether
someone has a network analyzer or just an swr meter.
That defense is sorely transparent in my opinion. To suggest that most
amateurs would not even have any interest if their bent or coiled 9914
suddenly jumped off the scale for loss and mismatch is ludicrous to say the
least.

Would you really notice if your cable loss was about 3 dB higher than
specified at 400 MHz and if it varied by a dB or two when the cable is
flexed and bent? What measurement equipment do you use which would cause
this amount of extra loss to "jump off the scale"? And what causes you
to think that increased loss would cause mismatch to "jump off the
scale"? Increased loss will improve, not degrade, the impedance match.

Let me be clear ...I am not disputing what you claim you got as test
results. My conclusion is either the 100ft length you had was bad or
something skewed your calibrated setup.

What you have as evidence is Davis' spec on the one hand, and my
measurement report on the other. You've chosen to believe that Davis'
cable all meets its published specifications. I have exactly the same
evidence, but know my capabilities and that of my equipment, so I
believe my measurements -- but always keeping in mind that it's a single
sample. Additional measurements made by someone else on another piece of
the cable would increase the knowledge base, although I'm sure there are
people who would choose to ignore the evidence no matter how much is
presented.

My career was in microwave r&d and
I know that it takes repeatable test results to form a valid, verifiable and
publishable data.

That's great! Then you have the background to be able to make decent
measurements, and you said you're using some of the cable. Why not just
measure the loss in a length of it and report your results?

This is not personal Roy....but it is somewhat stimulating.

I hope it's caused a few people to think a bit about how they evaluate
evidence to determine the truth of a matter. It's something which too
many people are woefully unable or unwilling to do.

Roy Lewallen, W7EL

To find ALL electrical characteristics and performance of
solid-polyethylene transmission line, use program COAXPAIR, from audio
frequencies to UHF.

Accuracy is of the same order as physical dimensions can be measured.
Use a micrometer to measure inner conductor diameter and diameter over
insulant. Or just guess at it. No need to unwind the cable off the
drum!

In a few seconds, download COAXPAIR from website below and run
immediately.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Reg Edwards wrote:
To find ALL electrical characteristics and performance of
solid-polyethylene transmission line, use program COAXPAIR, from audio
frequencies to UHF.

Accuracy is of the same order as physical dimensions can be measured.
Use a micrometer to measure inner conductor diameter and diameter over
insulant. Or just guess at it. No need to unwind the cable off the
drum!

In a few seconds, download COAXPAIR from website below and run
immediately.

Have you compared the results to any measurements of real cables?

Roy Lewallen, W7EL

On Sat, 10 Dec 2005 17:15:44 -0800, Roy Lewallen
wrote:

If no other reader of this newsgroup has some of this cable and the
ability to test it, I'll see if I can arrange for someone else to make
measurements and post results.

Roy, this seems a case of brand loyalty vs objective measurement and
evaluation (albeit on a single sample).

You will change your mind based on more measurement data, either
strengthening your existing opionion or changing it.

Those with brand loyalty already know all they need to know, life is
comfortable.

You are talking different languages, and the only way there will be
agreement is if you capitulate (which would be unprincipled in the
absence of evidence).

Owen

I remember the fierce debates over 9913, there were nearly as many
words written about how fabulous it was, as there were words written
on how to keep water out of it.
--

Owen it is NOT brand loyalty. It is the publicly published data by RF Davis
(for the past 10+ years) vs. Roy's one-shot test setup some years ago. I'm
not out to discredit Roy...I even shook his hand once at a Hamfest.



--

Charlie


"Owen Duffy" wrote in message
...
On Sat, 10 Dec 2005 17:15:44 -0800, Roy Lewallen
wrote:

If no other reader of this newsgroup has some of this cable and the
ability to test it, I'll see if I can arrange for someone else to make
measurements and post results.

Roy, this seems a case of brand loyalty vs objective measurement and
evaluation (albeit on a single sample).

You will change your mind based on more measurement data, either
strengthening your existing opionion or changing it.

Those with brand loyalty already know all they need to know, life is
comfortable.

You are talking different languages, and the only way there will be
agreement is if you capitulate (which would be unprincipled in the
absence of evidence).

Owen

I remember the fierce debates over 9913, there were nearly as many
words written about how fabulous it was, as there were words written
on how to keep water out of it.
--

On Sat, 10 Dec 2005 19:46:15 -0600, "Charlie"
wrote:

Owen it is NOT brand loyalty. It is the publicly published data by RF Davis
(for the past 10+ years) vs. Roy's one-shot test setup some years ago. I'm
not out to discredit Roy...I even shook his hand once at a Hamfest.

We should be a little suspicious of manufacturers claims. Davis' can
be expected to support their product.

Roy's single poor experience is concerning, indicating either a
quality control issue, or more general non-compliance with spec (both
are issues for Davis). An independent test of stock cable and possibly
Roy's sample would be most interesting.

I know I have made measurements and adjustments at times and in
searching for possible explanations, the cable quality is on the
radar. In one of those cases, a mobile installation could not be
trimmed properly, and the Taiwanese RG58 centre conductor was so far
off centre, it was nearly touching the braid.

We have all cut cables up and found inconsistent braid weave, open
braid weave, voids in the dielectric, faulty stranding of inner
conductor, off centre centre conductors. It is those kind of issues
that downgrade a suppliers reputation, not their ability to select a
good cable sample for laboratory measurement.

Perhaps if you're a whiz, you should perform some measurements so you
can report first hand your experience.

We don't see the Davis stuff on this side of the world. The concept
seems a good one, PE sheath, braid+foil outer, foam dielectric,
stranded inner, but you have to ask yourself why they haven't
displaced Heliax and its copies. I suspect the reasons include IM and
noise issues associated with the braid+foil, mechanical issues with
the foam, and resistance to water. Experience with noise and IM
problems with braid+foil coax in fixed installations makes me wonder
how it stands up in a rigorous test of flexing for a rotator loop, not
anecdotal evidence, but a structured test.

Owen
--