I put a mount on my Dodge pickup, bolted to the bed rail with 4 stainless
steel bolts. I placed a 20M Hamstick on the mount and the lowest I could get
the SWR to drop at my desired frequency was 1.7 to 1. So I placed a small
matching coil at the base of the antenna (also made by the same manufacturer
as the antenna). As I started trying to bring the SWR down I noticed that
anywhere that I touched the coil with the shorting wire would make the SWR
rise. At the very end of the coil - away from the mounting point, the rise
was minimal. As I moved the clip closer to the coil mounting point the SWR
rose.

The same thing happens with my 40M hamstick.

What does this tell me? Am I doing something incorrectly in the matching
process?

Thanks for any and all advice.

WB5CYS
Texas

Well, judging from the description, I'd say you need a cap
instead of the coil. It's sorta telling me you have enough
coil already. Part of your loading coil in the whip is
already acting as a matching coil. I think you probably
need a cap to tune out some reactance. I often use a
simple MFJ random wire tuner as a mobile matcher.
That would dial that down pretty low I would think.
But this is just a guess, being I can't see it...
In my trucks, I have the small tuner, and also a "dollar
special" matching coil. I use the tuner more often I
think...Most of my antenna setups with the glass stick
bases, have a few turns of matching coil wound into
the base. MK

wb5cys wrote:
I put a mount on my Dodge pickup, bolted to the bed rail with 4 stainless
steel bolts. I placed a 20M Hamstick on the mount and the lowest I could get
the SWR to drop at my desired frequency was 1.7 to 1. So I placed a small
matching coil at the base of the antenna (also made by the same manufacturer
as the antenna). As I started trying to bring the SWR down I noticed that
anywhere that I touched the coil with the shorting wire would make the SWR
rise.

Anything you do to a resonant antenna will usually raise the
SWR. For the coil to work, you need to start with an antenna
that is too short. You need to adjust the stinger as well as
adjusting the coil. First adjust the stinger to resonance
without the coil. Then shorten the stinger to raise the SWR
by making the antenna capacitive. Then add the coil. Alternate
between stinger adjustment and coil adjustment until satisfied.
--
73, Cecil http://www.qsl.net/w5dxp


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First, I would say that 1.7 to 1 is fine, leave it alone. It is what is
expected.

That being said, the strident need to be 1:1 can be met in several ways. The
antenna will probably be around 35 ohms. giving you the 1.7:1 you observe.
You can wind a toroid (t-106-2) with 14 turns of wire. tap one of the wires
at 11 turns and feed the antenna. A 50pf cap between the antenna and ground
might also prove usefull.

to wind the toroid, start with a black and white wire, wind 14 times through
the hole. Connect the black start end to the coax center. Connect the white
start to the black finish. Connect the white finish to the coax shield, and
vehicle ground. At turn 11 of the black wire, put a tap. This tap goes to
the antenna.

The SWR meter should now read 1:1 and you won't get out one bit better.

The SWR on my base feedlines are 9:1 by design. I run a screwdriver on the
car and once I am below 2:1, the radio is happy and so am I.



"wb5cys" wb5c ...
I put a mount on my Dodge pickup, bolted to the bed rail with 4 stainless
steel bolts. I placed a 20M Hamstick on the mount and the lowest I could
get
the SWR to drop at my desired frequency was 1.7 to 1. So I placed a small
matching coil at the base of the antenna (also made by the same
manufacturer
as the antenna). As I started trying to bring the SWR down I noticed that
anywhere that I touched the coil with the shorting wire would make the SWR
rise. At the very end of the coil - away from the mounting point, the rise
was minimal. As I moved the clip closer to the coil mounting point the SWR
rose.

The same thing happens with my 40M hamstick.

What does this tell me? Am I doing something incorrectly in the matching
process?

Thanks for any and all advice.

WB5CYS
Texas

Fred W4JLE wrote:
First, I would say that 1.7 to 1 is fine, leave it alone. It is what is
expected.

That being said, the strident need to be 1:1 can be met in several ways. The
antenna will probably be around 35 ohms. giving you the 1.7:1 you observe. . .

I'm curious -- how did you determine from the SWR that the antenna
impedance would be resistive, and assuming it is, that it would be less
than 50 ohms rather than greater? Perhaps you've measured a Hamstick on
a typical mobile mount?

Roy Lewallen, W7EL

Roy Lewallen wrote:
I'm curious -- how did you determine from the SWR that the antenna
impedance would be resistive, and assuming it is, that it would be less
than 50 ohms rather than greater? Perhaps you've measured a Hamstick on
a typical mobile mount?

It's impossible to bring an impedance greater than 50
ohms down to 50 ohms by installing a shunt reactance
so the resonant feedpoint resistance of any mobile antenna
using a shunt reactance to achieve 50 ohms is, by definition,
less than 50 ohms.

if Rs = 50 and Xs 0 then Rp 50

Assume one can adjust the feedpoint impedance of a 40m
bugcatcher to 25+j25 or 25-j25 by adjusting the length
of the stinger. If one shunts 25+j25 with a -j50 cap,
the feedpoint impedance will be 50+j0 ohms. If one shunts
25-j25 with a +j50 coil, the feedpoint impedance will
be 50+j0 ohms.
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil Moore wrote:
It's impossible to bring an impedance greater than 50
ohms down to 50 ohms by installing a shunt reactance ...

My meaning above may not have been 100% clear.
I meant to say: It's impossible to bring an impedance,
having a resistive component greater than 50 ohms, down
to 50 ohms by installing a shunt reactance.
--
73, Cecil http://www.qsl.net/w5dxp

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Only going from the last one I fooled with. I was unable to persuade the
owner he would be better off tuning for field strength than SWR and the
solution I purposed is one of many that will make a SWR meter happy along
with those folks who are cult members of the church of no reflections.

I make no claims that any other antenna in like or different circumstances
will ever exhibit exactly 35 +j0 Ohms. If I gave that impression to the
learned members of this conference, I humbly apologize for once again making
a broad statement with out a list of qualifiers. Mea Culpa :)

The ubiquitous SWR meter, the greatest generator of misinformation since
Baghdad Bob.





"Roy Lewallen" wrote in message
...
Fred W4JLE wrote:
First, I would say that 1.7 to 1 is fine, leave it alone. It is what is
expected.

That being said, the strident need to be 1:1 can be met in several ways.
The
antenna will probably be around 35 ohms. giving you the 1.7:1 you
observe. . .

I'm curious -- how did you determine from the SWR that the antenna
impedance would be resistive, and assuming it is, that it would be less
than 50 ohms rather than greater? Perhaps you've measured a Hamstick on
a typical mobile mount?

Roy Lewallen, W7EL

Fred:

I wonder if most arent really aware that SWR is not real in a lot of
cases where the term "swr" is bandied about (big deal, I don't believe
in time either)--I have experienced large feedline radiation on almost
perfect reading swr meters--I accept this as real--and still run with it
(even if I lose 10 watts of 100, I don't sweat it anymore, heck, if
Cecil splits his bottle of wine with me--I could careless about 20 watts
grin)...

.... however, I have noticed that it (the swr meter) slows the need to
keep soldering new mrf4?? mosfets into the finals and linears of this
new age--it is a cheap quick fix--and if transmitter loading is good,
the finals are cool, I am good with it... and some just wanna get on the
air... I will mess with an ant for best received signal--from there on
out it is just crank power till we are at max--if needed--and if that
fails a gentlemans admission of failure... and a gentleman ALWAYS uses
minimum power for effective communication!!! sly grin

.... the true art of dancing fairies on pins, and speaking in shakespeare
to obfuscate the ideas which I express, and beginning to hold myself as
superior in intelligence and mind games--I hold for a later date--which
seems to be approaching far to fast for my liking... check back with me
next week, I may have changed my mind... grin

Warmest regards,
John
"Fred W4JLE" wrote in message
...
Only going from the last one I fooled with. I was unable to persuade
the
owner he would be better off tuning for field strength than SWR and
the
solution I purposed is one of many that will make a SWR meter happy
along
with those folks who are cult members of the church of no reflections.

I make no claims that any other antenna in like or different
circumstances
will ever exhibit exactly 35 +j0 Ohms. If I gave that impression to
the
learned members of this conference, I humbly apologize for once again
making
a broad statement with out a list of qualifiers. Mea Culpa :)

The ubiquitous SWR meter, the greatest generator of misinformation
since
Baghdad Bob.





"Roy Lewallen" wrote in message
...
Fred W4JLE wrote:
First, I would say that 1.7 to 1 is fine, leave it alone. It is
what is
expected.

That being said, the strident need to be 1:1 can be met in several
ways.
The
antenna will probably be around 35 ohms. giving you the 1.7:1 you
observe. . .

I'm curious -- how did you determine from the SWR that the antenna
impedance would be resistive, and assuming it is, that it would be
less
than 50 ohms rather than greater? Perhaps you've measured a Hamstick
on
a typical mobile mount?

Roy Lewallen, W7EL

snip

I'm curious -- how did you determine from the SWR that the antenna
impedance would be resistive, and assuming it is, that it would be
less
than 50 ohms rather than greater? Perhaps you've measured a Hamstick
on
a typical mobile mount?

Roy Lewallen, W7EL





Roy spurred me to type:

I use a screwdriver matched with a simple toroidal autoformer.
I tuned the antenna for a purely resistive load using an analyzer.
Turns out it was 20 - 30 ohms on 40 meters, IIRC.
Then I wound 14 turns of copper wire around a toroid, connecting one end to
the coax center
and the other to coax shield and chassis ground.
Then I tapped the antenna on to the autoformer such that,
looking down the coax, the analyzer saw 50 ohms.
I use this matching configuration for 160 - 20.
I get the best VSWR and field strength of many variations I've tried over
the years.
On the higher bands I just hook up the coax and tune for minimum VSWR at the
transceiver.

73, H.,

H. Adam Stevens
NQ5H