Measured Velocity Factor of balanced line
 

Thanks to all for the advice on measuring velocity factor.

I suspended 53.25 feet of JSC #1317 18-AWG balanced line in the
backyard.

At a velocity factor of 1, the MFJ 269 claimed an electrical length of
59.5 feet, which would give an actual velocity factor of .89.

After four or five more tries, I nearly replicated it with an
electrical length of 59.6 feet.

To verify the results, I tried entering the .89 velocity factor to get
the length of the line, and it kept coming in at a 26.6 foot length --
oh, well.

Bob
k5qwg

Measured Velocity Factor of balanced line
 

Bob Inscribed thus:

Thanks to all for the advice on measuring velocity factor.

I suspended 53.25 feet of JSC #1317 18-AWG balanced line in the
backyard.

At a velocity factor of 1, the MFJ 269 claimed an electrical length of
59.5 feet, which would give an actual velocity factor of .89.

After four or five more tries, I nearly replicated it with an
electrical length of 59.6 feet.

To verify the results, I tried entering the .89 velocity factor to get
the length of the line, and it kept coming in at a 26.6 foot length --
oh, well.

Bob
k5qwg

That sounds pretty close to half of the physical line length you
mentioned.

--
Best Regards:
Baron.

Measured Velocity Factor of balanced line
 

Bob wrote in
:
....

To verify the results, I tried entering the .89 velocity factor to get
the length of the line, and it kept coming in at a 26.6 foot length --
oh, well.

"Oh, well" means you didn't understand something, a problem to be resolved.

It is a long time since I used one of these.

I assume you are using the Distance to Fault mode.

Did you find the first X=0 point to be around 4MHz? If you mistakenly found
the first at a higher frequency, it will give a harmonically related
result.

Owen

Measured Velocity Factor of balanced line
 

On Tue, 06 Apr 2010 21:44:12 GMT, Owen Duffy wrote:

Bob wrote in
:
...

To verify the results, I tried entering the .89 velocity factor to get
the length of the line, and it kept coming in at a 26.6 foot length --
oh, well.

"Oh, well" means you didn't understand something, a problem to be resolved.

It is a long time since I used one of these.

I assume you are using the Distance to Fault mode.

Did you find the first X=0 point to be around 4MHz? If you mistakenly found
the first at a higher frequency, it will give a harmonically related
result.

Owen

I am using the Distance to Fault mode. I've tried several frequencies
for X=0, and sometimes get the 26.6 foot figure, other times
non-sensical answers in the thousands of feet.

Bob
k5qwg

Measured Velocity Factor of balanced line
 

On Tue, 06 Apr 2010 22:08:45 +0100, Baron wrote:
Bob Inscribed thus:

Thanks to all for the advice on measuring velocity factor.

I suspended 53.25 feet of JSC #1317 18-AWG balanced line in the
backyard.
... -snip-
To verify the results, I tried entering the .89 velocity factor to get
the length of the line, and it kept coming in at a 26.6 foot length --
oh, well.

That sounds pretty close to half of the physical line length you
mentioned.

Yep. For selected values of 1/2 ...... HI!HI!

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm

Measured Velocity Factor of balanced line
 

Any chance the 2:1 error is related to the incorrect measurement
procedure described in some versions of user manual:

http://lists.contesting.com/_topband.../msg00017.html

73,
Steve G3TXQ

Measured Velocity Factor of balanced line
 

On Wed, 7 Apr 2010 08:28:27 -0700 (PDT), steveeh131047
wrote:

Any chance the 2:1 error is related to the incorrect measurement
procedure described in some versions of user manual:

http://lists.contesting.com/_topband.../msg00017.html

73,
Steve G3TXQ

That's very interesting. The newest online manual has a slightly
different procedure for measuring Distance to Fault. When it stops
raining (and the balanced line dries off) I'll go and measure again
with the newer procedure.

Bob
k5qwg

Measured Velocity Factor of balanced line
 

On Wed, 07 Apr 2010 10:50:42 -0500, Bob wrote:

When it stops
raining (and the balanced line dries off) I'll go and measure again
with the newer procedure.

Hi Bob,

This rain is an opportunity to astonish youself about the measurement
variability of line operation in real-life.

73's
Richard Clark, KB7QHC

Measured Velocity Factor of balanced line
 

On Wed, 7 Apr 2010 08:28:27 -0700 (PDT), steveeh131047
wrote:

Any chance the 2:1 error is related to the incorrect measurement
procedure described in some versions of user manual:

http://lists.contesting.com/_topband.../msg00017.html

73,
Steve G3TXQ

I finally got it to work properly. The trick is getting Xs=0 at a
second frequency -- I couldn't get it on the same band as the first
frequency but had to go to a second band, either up or down, and once
the second frequency was found with Xs=0, it came up with the correct
distance to fault, 53.2 feet.

Bob
k5qwg