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Old November 3rd 03, 10:25 PM
Tom Bruhns
 
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So, Reg, I note that (1) YOUR table shows more variation in VF over
the HF ham bands (especially so if you allow it to be extended down to
the 1.8MHz ham band, which I assume the MFJ analyzer would cover) than
the three significant digits of 0.665 would allow (the table showing
only 0.65 at 10MHz, and I suppose you'd go for about 0.64 at 2MHz,
maybe even 3.5MHz), (2) your posting in this thread of 0.665 did NOT
qualify the VF as being HF only, and (3) my posting DID say something
that SHOULD have indicated to you and anyone else who read it that I
was thinking beyond the bounds of HF with respect to large VF
variation. I'd STILL say there are instances where one should not
assume 0.665 for solid polyethylene at HF. There are instances where
0.64 and 0.665 are different enough to want to get the right value.
You're welcome to get all bent out of shape over that if you wish.

Cheers,
Tom

"Reg Edwards" wrote in message ...
Tom,

It should be obvious when somebody asks how to find VF by using an HF
antenna analiser he is interested, like every other radio amateur, in the HF
value of VF.

If you agree with the table in the other posting, which gives VF vesus
frequency, and you are aware VF decreases with frequency, then how come you
didn't realise you had taken the value of 0.665 out of its HF context.

All my figures are correct.

(As we noted at the time of the original posting, the numbers in the
table are rough approximations...certainly they're correct as
approximations...)
----
Reg

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'''''''''''''''
"Tom Bruhns" wrote in message
m...
"Reg Edwards" wrote in message

...
"Tom Bruhns" wrote "Reg Edwards"
The velocity factor of ALL solid polyethylene coax cable, regardless

of
impedance, is 0.665

================================

And this comes from someone who I could swear posted not long ago a
table that had velocity factors for solid polyethylene cable that were
significantly different from this magic number?

...
Freq Ro jXo Angle VF
------ ------ ------ ------ ------
50 Hz 967 -965 -44.95 0.034
1 kHz 220 -213 -44 0.151
10 kHz 80 -58 -36 0.41
100 kHz 56 -9.3 -9.5 0.59
1 MHz 52.4 -2.4 -2.7 0.63
10 MHz 50.7 -0.76 -0.86 0.65
100 MHz 50.2 -0.23 -0.27 0.66

Smith Chart calculations begin to be inaccurate around 2 MHz and
below. So
do SWR meters.