w4jle wrote:
Arrrg! Your making my stomach hurt reading this misinformation...

Well, let's add a few words to make his statement correct.

Get the aerial resonant,

with a 50+j0 ohm feedpoint impedance,

and it doesn't matter what length of coax you use
as the SWR will not change.
--
73, Cecil http://www.qsl.net/w5dxp



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Now you are getting technical, beyond the understanding of most of today's
hams.

(I looked everywhere on my SWR's meter and couldn't find a J knob and isn't
a 50 to 0 SWR kinda high)

"Cecil Moore" wrote in message
...
w4jle wrote:
Arrrg! Your making my stomach hurt reading this misinformation...

Well, let's add a few words to make his statement correct.

Get the aerial resonant,

with a 50+j0 ohm feedpoint impedance,

and it doesn't matter what length of coax you use
as the SWR will not change.
--
73, Cecil http://www.qsl.net/w5dxp



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http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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w4jle wrote:



(They told me all I had to do to become a ham was to memorize these
questions.)



SNIP That's absolutely TRUE if all you want is to "...become a ham..."

However, if you want to install and operate an efficient short wave
radio station you need to learn quite a bit!

DD, W1MCE

Keven Matthews wrote:

I recently moved my shack from an upstairs room to downstairs, much closer
to the garden and antennas.

SNIPPED

Kevin, there have been numerous responses to your original post. Let me
be an Elmer for a short moment.

An example of antenna resonance and VSWR follows.

In my mobile I have a resonant 40 meter Hamstick. Resonance means there
is NO Reactance in the antenna impedance. My antenna analyzer indicates
approximately 12 + j0 ohms at 7.225 MHz. This is almost a 5:1 VSWR and
that's what a meter indicates. Now, I added an ICOM AH-4 automatic
antenna tuner at the antenna. The antenna is still 12 + j0 ohms but the
tuner transforms the impedance to 50 + j0 ohms. So, the VSWR from the
antenna/tuner to the 706, approximately 16 feet of coax, is now
approximately 1:1.

Since the length of coax in your installation changes the measured VSWR,
the coax is part of the antenna system and is radiating. So, you need to
isolate the coax from the antenna. There are several ways to accomplish
this. The most direct way is to make a coil of coax about 4 to 6 inches
diameter and having 8 to 10 turns and install it directly at the base of
the antenna. If you have a ground radial system make sure the coax is
underneath [lower] than the radial system. Finally, install some clamp
on ferrites, available from Radio Shack for less than $10, at the 1/4
and 1/2 wavelength on the coax from the antenna feedpoint.

Hopefully this will clean up the RF on the coax.

With a vertical antenna a reasonable VSWR at antenna resonance should be
somewhere between 1.5:1 and 2.0:1.

Deacon Dave, W1MCE

Well said Sir!

Even the "appliance operators" of old had to know how the appliance worked.

Were I the FCC, your first transmitter and receiver would be built from
scratch and a minimum of 25 CW contacts confirmed before the use of a
purchased rig would be allowed.

Next no one would be permitted to apply for extra class without 5 years
experience and 250 confirmed contacts.Also participation in a public
service capacity, (i.e. traffic net, weather warning net, charity races etc)
and have elemered 5 new hams.

I have a friend that has an extra and has never been on the air. He took the
exams at a hamfest just to see if he could pass them. He said he studied the
question pools for a couple of days on-line. He spent 20 years in the Navy
as a Chief Radioman, so the code was a joke for him.

"Dave Shrader" wrote in message
news:XnFJb.49405$I07.151812@attbi_s53...
w4jle wrote:



(They told me all I had to do to become a ham was to memorize these
questions.)



SNIP That's absolutely TRUE if all you want is to "...become a ham..."

However, if you want to install and operate an efficient short wave
radio station you need to learn quite a bit!

DD, W1MCE

"w4jle" W4JLE(remove this to wrote in message
...
Well said Sir!

Even the "appliance operators" of old had to know how the appliance
worked.

Were I the FCC, your first transmitter and receiver would be built from
scratch and a minimum of 25 CW contacts confirmed before the use of a
purchased rig would be allowed.

Careful, one of the local Ham "Channelmasters" will dub you a
CBPlusser for using the term "contact". It's a pet peeve of his.

Harold Burton
KD5SAK

Just like I had some "newby" attempt to chastise me on a 2 meter repeater
for using "handle". He told me that that word was only used on 11 meters.

I had to admit, I did use it on 11 meters when it was a ham band. But thanks
for the lesson Good Buddy!



"Harold Burton" wrote in message
...

"w4jle" W4JLE(remove this to wrote in message
...
Well said Sir!

Even the "appliance operators" of old had to know how the appliance
worked.

Were I the FCC, your first transmitter and receiver would be built from
scratch and a minimum of 25 CW contacts confirmed before the use of a
purchased rig would be allowed.

Careful, one of the local Ham "Channelmasters" will dub you a
CBPlusser for using the term "contact". It's a pet peeve of his.

Harold Burton
KD5SAK

Note that well-engineered broadcast stations do not accept ANY significant
affect of the length of their transmission line(s) on the SWR/impedance
match of their antenna system, as seen by the transmitter.

Greatest antenna system efficiency and least stress on the transmission
hardware are achieved when transmission line impedance is matched to antenna
input impedance. When that condition exists then the length of the
transmission line is unimportant except for the power lost due to
transmission line attenuation, and the cost to use the length and type of
transmission line selected.

The match of the antenna input to its input transmission line is a function
of their design, AND the installation environment. The physical environment
near the antenna can change its input impedance from the assumed value, and
create an impedance mismatch with a transmission line selected to match the
input impedance assumed for the antenna.

This is usually corrected by an impedance-matching network installed at the
junction of the antenna and its input transmission line. Virtually every
AM, FM and TV broadcast antenna in the US has some means of adjusting the
match between the antenna and its input line to optimise system SWR.

Impedance adjustments can be done at the input end of the transmission line
to the antenna, but will be more narrow-band. Trimming the length of the
main transmission line is another approach, but again, is more
frequency-sensitive than adjusting the match directly at the antenna input
connector.

RF

Visit http://rfry.org for FM broadcast RF system papers.

________________

"Dave Shrader" wrote in message
news:5bzJb.113315$VB2.290693@attbi_s51...
Kevin, the resonance of the antenna is determined by the length of the
antenna! It is not related to the VSWR!!!

If you are using VSWR as an indicator of resonance it is meaningless!

Since your VSWR is changing with length of Coax, I suspect you have RF
on the braid of the coax. Install a series of Chokes or ferrites.

W1MCE

Keven Matthews wrote:
SNIP
The SWR was pretty good across the band. Regardless I started my
evening doing a tidy job with some of that nice 5DFB japanese coax all
ready
for the following day. Guess what ? I put on the nice new cable and
plugs
and the antenna is no longer anywhere near resonant on 80M. So why am I
getting a better result with a long length of still coiled cable sitting
on
my patio rather that a much shorter brand new piece.

SNIP

"Keven Matthews" a écrit dans le message de news:
...
I recently moved my shack from an upstairs room to downstairs, much
closer
to the garden and antennas. All the antennas previously had a long run of
coax to the old shack. The obvious thing was to have a nice new short
run
of coax to my HF vertical which is now only 15' away. So I cut the coax
and
since then the antenna is no longer resonant on 40 Metres. Also this week
I
was putting up a new HF wire antenna, it was getting dark and raining by
the
time I was hoisting it up but so I could just have a listen that night a
grabbed an old (15 years) large coiled up of quantity RG213 coax
complete
with rotten oxydized pl259 plugs on each end which had just sat on the
garage wall for years. I just slung the coil down and plugged in at each
end. The plugs looked so rotten it was shameful but it pitch dark by
then!
However The SWR was pretty good across the band. Regardless I started my
evening doing a tidy job with some of that nice 5DFB japanese coax all
ready
for the following day. Guess what ? I put on the nice new cable and
plugs
and the antenna is no longer anywhere near resonant on 80M. So why am I
getting a better result with a long length of still coiled cable sitting
on
my patio rather that a much shorter brand new piece. Please could some
one
explain to me if the coax length does matter, it has certainly never been
a
problem for me in the past on VHF and Six but I am new to HF frequencies.
If you do need to have a certain size run, what can you do with the cable
if
you phisically dont need it ?


Many Thanks & 73 for 2004

Keven G7UUD


Hello and happy new year.

It would always be necessary to tune the coaxial feeder
to the frequency of work.


For your problem it is necessary :

To measure the ros in one 1/2 length of cable feeder.
To tune the coaxial fededer with the frequency of work
on multiple of one 1/2 wavelength.
[Certain vertical antenna (as 5/8 lambda) have necessarily
to have 1 wavelength of cable feeder at least].
To control the ros and connect your installation.

Although it is it, value read in one 1/2 longuer of wave is
the same that that read to all the multiple of 1/2 lamda (3 or 10.5 lamda
for example).

Good luck


GG, amateur of radio for 19 years

Low SWR for
the
Wrong Reasons".

=========================
Should be required reading for all hams.

Why? ;-)
73 Gary N4AST