Hello Bob,
I have used the published velocity factors for years.
I made a 4:1 balan for my Telrex 20M546 a few years ago with RG14 coax. After I
cut it, I checked it
with my GDO and all was fine.
73 Price W0RI
Hi it's still flooded here but I wanted to fire up one of my verticals by
Let's do some quick math 234/1.82=128.57 gives us the length in feet of a
quarter wave at 1.820 mHz. Multiply that by a velocity factor ( say 85% for
LMR-400) and you get a length of 109.29 feet. The math will tell you that for
every percentage point of velocity factor, it equates to 1.28
On 9/10/2012 9:23 AM, Jim Hoge wrote:
Let's do some quick math 234/1.82=128.57 gives us the length in feet of a
quarter wave at 1.820 mHz. Multiply that by a velocity factor ( say 85% for
LMR-400) and you get a length of 109.29 feet.
That math is a bit too simple, because Vf VARIES as
Let's do some quick math 234/1.82=128.57 gives us the length in feet
of a quarter wave at 1.820 mHz.
That's not correct. The number is 245.8926/F, which is rounded to 246/F.
A quarter wave in freespace is 245.8926/1.82 = ~135.1 feet, not 128.57
234/F is a long way off.
My apologies to the group. I stand corrected. My incorrect constant and overly
simplified math clouded the point I was trying to make. The point was intended
to be that at top band frequencies, each degree of electrical phase winds up
being a little over a foot in length. With relatively
On 9/10/2012 10:44 AM, Tom W8JI wrote:
I firmly do not believe that is true.
Velocity factor in cable is the square root of the inverse of
dielectric constant.
Tom,
Respectfully, I suggest that you go back to your college textbook on the
fundamentals of Transmission Lines. The equations
I thought we were talking about RF.
73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000
Likewise, Zo is only sqrt (L/C) at VHF. The more complete equation is
sqrt [ (R+J omega L) /( G + J omega C) ] At VHF, the equation SIMPLIFIES
to sqrt (L/C) At low audio frequencies, and up to VHF, G is insignificant
(leakage) so the complete practical equation is sqrt [(R+ j omega L) / j
Just spoke to the 10 meter NH8S operator and he told me that as soon as
the sun goes down they will be on TB till the sun comes up. He said
everything is in place and tested and they will definitely be on solid
tonight.
Herb Schoenbohm, KV4FZ
___
wow, I had better get my ### in gear and finish getting my inverted L back up.
thanks Herb,
Bob
K6UJ
On Sep 10, 2012, at 2:58 PM, Herb Schoenbohm wrote:
Just spoke to the 10 meter NH8S operator and he told me that as soon as the
sun goes down they will be on TB till the sun comes up. He
Run the numbers and for RG-6 we see that sq root of L/C is good above a
couple hundred kHz.
Dave WX7G
On Sep 10, 2012 2:37 PM, Jim Brown j...@audiosystemsgroup.com wrote:
On 9/10/2012 10:44 AM, Tom W8JI wrote:
I firmly do not believe that is true.
Velocity factor in cable is the square
On 09/10/2012 07:42 PM, DAVID CUTHBERT wrote:
Run the numbers and for RG-6 we see that sq root of L/C is good above a
couple hundred kHz.
Does that have any consequences when planning phasing lines
for a receive 4-square that is to be used on eg. 137 kHz?
Are there types of coax that are more
Run the numbers and for RG-6 we see that sq root of L/C is good above a
couple hundred kHz.
Dave WX7G
I just ran it in MathCAD and it showed a Zo and Vf slope starting down
around 150 kHz, but I assumed the conductors were solid copper. Conductors
have to be in the thousands of a inch range
Bob, don't worry about the inv-l. From where you are, a loaded window
screen should work just fine.
Good luck/73,
John, W4GD
-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bob K6UJ
Sent: Monday, September 10, 2012 7:08 PM
To: Topband
Subject: Re:
hihihi !
Bob
K6UJ
On Sep 10, 2012, at 7:06 PM, John Morris wrote:
Bob, don't worry about the inv-l. From where you are, a loaded window
screen should work just fine.
Good luck/73,
John, W4GD
-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On
Tom I think everything is real quiet while a bunch of folks are busy
looking at manuals and crunching numbers with their analyzers. Someone
wants to find a mistake in your opinion.
Stand by.
- Wes Attaway (N5WA) ---
1138 Waters Edge Circle, Shreveport, LA
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