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

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'd ten to agree and most take cable on faith as well.

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.

There are a number of things that can or possibly happen.

When you test coax connectors and termination effects are part
of the system and need to be considered.

I bought 250ft, then tested the 50ft sections I made up for the tower.
All five tested the same at 440mhz and my confidence factor was
good. The test setup was 0.100 Watt RF source, 3DB attenuator,
RLB, cable section, termaline watmeter. All check on spec
and I was doing to verify connectors installed as well. I only tried
one section for bening effects near the end as I was interested in
how it would behave for rotor loops. I saw now ill efects until I
reduced the bend radius to under 4 inches where it developed
a definitate bump that showed on a TDR. Like most foam cored
cables you can overbend it with bad results. The damaged length
was removed (only 4ft) and the cable placed in service.

Expected 2.9db @ 400mhz. But that does not allow for connectors
or measurment setup. Half that should be 1.45db (50ft).

However my testing was at 440mhz. All loss testing I did was
at 440 because small things look bigger there.

To the limits of the attenuators and meter calibration I'd call the
losses including the connectors right where I'd expect 50ft with
PL259s on at least one end would be. I got at 440, greater
than 1.6db but less than 1.8db. The loss was determined by
removing cable and substituting a known attenuators of .2db
steps as that was as fine as I had. Calculated was 1.66db
based on measurements. Allowing for test error and
connectors the there is some range of error. The RLB was
used to verify there were no visible bumps over the 6m, 2m and
420-450mhz range of the source.

The same setup for 50ft or both RG58A/U, RG8X and RG213
gave me 7db(pl259/ug174), 4.6-4.8(pl259/ug175), 2.4-2.6(pl259).
The RG213 was a suprize as I'd expected losses to be lower.
But the results were consistant. Where I give a range in loss
it is because the lower and higher attenuateors used were
either too low or too high meaning the exact result was somewhere
in between. The loss substitution is likely more accurate than
analog meters. Also I tried to minimize the error from adaptors
and cable transitions where needed though te test method tends
to zero them out by substiution.

I did during installation notice one thing over RG213. The 2M antenna
I'd tuned with a length of RG213 showed a higher VSWR when using the
Buryflex. Further tests reveled the losses of the 213 made the SWR
look better than it was. Antenna was readjusted and all was happy.

Allison
Kb1GMX