RadioBanter - X-terminator antenna

RadioBanter (https://www.radiobanter.com/)

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- - X-terminator antenna (https://www.radiobanter.com/cb/30126-x-terminator-antenna.html)

On Sat, 25 Oct 2003 07:09:10 -0500, Neil Down
wrote:

wrote in :

On Sat, 25 Oct 2003 02:21:12 -0400, wrote:

On Fri, 24 Oct 2003 22:23:48 -0700, Frank Gilliland
wrote:

In , lancer
wrote:

snip
Chrome has about the same conductivity that Stainless does, or at
least from the info I found. 3-15% for Stainless, 19% for chrome,
relative to copper.

For a conductor 102" long with a diameter of 0.625", the following
metals have the following AC resistance at 27 MHz:

Chromium .0194 ohms
Copper .00711 ohms
S. Steel .0451 ohms

http://www.amm.com/index2.htm?/ref/conduct.HTM

Chrome has 55% the conductivity of copper

Steel (all types ) 3% - 15%

17-7 ph stainless steel is used for most stainless antennas

Its resistivity compared to the standard (copper) can be found here
http://www.hpmetals.com/elec_resist.asp

Copper = 1.71 microohm-cm

17-7 ph = 83 microohm-cm

In other words stainless antenna stock has 2% the conductivity of
copper.

What type of material is the whip of the exterminator? SS right, the few
inches of copper or chrome material of that antenna will make little or
no difference what so ever, you guys are nit picking about something that
in this application is un noticeable.

The top section of that antenna is made from stainless steel. The top
section also has very little current flowing in it. The bottom
section has a majority of the current flow and does most of the
radiation. It maybe nit picking, but in theory the difference can be
seen. If you would see it in the real world is another question.

On Fri, 24 Oct 2003 15:49:41 -0500, Neil Down
wrote:

lancer wrote in
:

On Thu, 23 Oct 2003 17:23:26 -0500, Neil Down
wrote:

"(Scott Unit 69)" wrote in
:

I wish someone who knew what they were talking about would tell the
truth about this antenna.There is enough BS on this group as it is
without more myths being spread.

The funniest part this antenna is made by workman it is junk, the
coils are low Q. No way on gods green earth it beats a full 1/4 wave.

No, the coils aren't low Q

Yes they are compared to a high q coil.

What do you consider high Q?

Q (Quality factor) is equal to the inductive reactance/the resistance
or loss

Capacitive coupling between the turns is part of the loss.

The coils for that antenna are large diameter tubing, less resistance.

They are spaced from eath other by at least a diameter, less
capacitive coupling.

They are "air wound", less loss due to the coil form.

The coils on that antenna have a Q of 100-300

In a typical tank circuit of a transmitter, smaller wire wound closer
together on a ceramic form, a Q of 20 is considered very good.

You make think that those coils look like they do for show, there is a
proven reason why large diameter, large gauge material is used for the
coils. And its not just for the power handling capability.

In , Frank Gilliland
wrote:

In , lancer wrote:

snip
Chrome has about the same conductivity that Stainless does, or at
least from the info I found. 3-15% for Stainless, 19% for chrome,
relative to copper.

For a conductor 102" long with a diameter of 0.625", the following metals have
the following AC resistance at 27 MHz:

Chromium .0194 ohms
Copper .00711 ohms
S. Steel .0451 ohms

By golly, I made -another- mistake in my math, which is not such a suprise. But
when I was double-checking my work this time I ran across something that
everyone should find VERY significant. So from the beginning.....

S = Skin depth in meters = sqrt(2/(2*pi*f*u*q)), where

q = conductivity of conductor (mhos/m), and
u = 4piE07 * relative permeability of medium

This is what's interesting. Stainless steel comes in many varieties. Some of
them aren't even steel but use the term because they are used for the same
applications. Regardless, some stainless steel is ferromagnetic and some is not.
The nonferromagnetic steel will have a relative permeability close to that of
copper, or 1 for all practical purposes. OTOH, ferromagnetic steel will have a
relative permeability much higher, and the value of 500 was used in the
calculations below.

AC resistance in ohms = l / (q * S * 2 * pi * r), where

l = length of conductor (in meters)
r = radius of conductor (in meters)

Note that there are two different listings for the conductivity of chromium. The
first value is based on the information that it is 55% of the conductivity of
copper, and the second value (as well as the values for copper and stainless
steel) is based upon CRC's HC&P:

Cu Cr #1 Cr #2 S.S. S.S. (ferro)
Conductivity: 5.80E07 3.19E07 .769E07 .166E07 .166E07
Skin depth: 12.7E-06 17.1E-06 34.9E-06 75.2E-06 3.36E-06
AC resistance: .0705 ohms .0952 ohms .194 ohms .161 ohms 9.31 ohms!!!

Notice that the differences in the resistance are all insignificant except for
the ferromagnetic stainless steel. This is because of it's high relative
permeability. Now when I realized this issue I put a magnet to my whip it
doesn't stick. So I went to the shop this morning and checked a number of SS
whips of different lengths. Some were magnetic and some were not. The magnetic
whips are now all in a pile for other uses.

So even old farts like me can learn something new. From now on I'll recommend to
everyone to check an antenna with a magnet before buying it, because that's what
I intend to do myself.

Now, back to the X-terminator. Comparing the difference in radiation efficiency
with regards to length and polarization, the 102" whip has 102" that are
vertical. Everything is sent vertically polarized. Nothing is wasted in
horizontal polarization. OTOH, the X-terminator has 9.5" vertical, followed by
74" of coil, then 3.75" vertical, 41.23" of coil, 5.5" vertical, and 32" of
(gasp!) stainless steel. So you have a total of 166" of conductor, with 50.75"
of it radiating the desired vertically polarized radiation, but 115" of it
dumping horizontal hash. Let's disregard for the moment that 32" (or 63%) of the
vertical total is made of that infamous stainless steel, and forget the extra
overall resistance due to the additional length of conductor needed to wind the
coils. Let's concentrate instead on the fact that the coils consume 69% of the
total 'wire' in this antenna. Now if the current distribution was even
throughout the length of the antenna, that would mean the coils are radiating
69% of the power as multi-phasic mush. But that's not the case, as the coils are
positioned near the base of the antenna, where the antenna's current
distribution is the greatest. That means the coils are radiating -more- than if
the current was evenly distributed, and therefore -more- than 69%! And that
means the efficiency of the X-terminator is less than 31%!!!

And if that isn't bad enough, let's take a look at an el-cheapo 102" stainless
steel whip of -magnetic- persuasion. If the whip has an AC resistance of 9.31
ohms, and the input impedance is an ideal 50 ohms, that translates into a loss
of only 19%. If the input impedance is 36.5 ohms, the wire diameter is 0.25",
and accounting for power reflected back to the radio due to mismatch, loss is
still well below 30%. Both scenarios are a -hell- of a lot better than the 69%
waste caused by the X-terminator's loading coils, and we didn't even go into
absorbtion, reflection, hysteresis and eddy current losses caused from the
vehicle roof right below those coils!!!

So yes, stainless steel -is- more resistive than chromium. But the difference is
not significant. So I'll say it again -- there is no way that this antenna will
outperform an unloaded 102" whip whether it's made of fiberglass, stainless
steel OR ferromagnetic steel!

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Very nice job Frank............................................. .....
Now, go buy a 7 foot SkipShooter and out talk the 102".
Train
LOL

"Frank Gilliland" wrote in message
...
In , Frank Gilliland
wrote:

In , lancer
wrote:

snip
Chrome has about the same conductivity that Stainless does, or at
least from the info I found. 3-15% for Stainless, 19% for chrome,
relative to copper.

For a conductor 102" long with a diameter of 0.625", the following metals
have
the following AC resistance at 27 MHz:

Chromium .0194 ohms
Copper .00711 ohms
S. Steel .0451 ohms

By golly, I made -another- mistake in my math, which is not such a
suprise. But
when I was double-checking my work this time I ran across something that
everyone should find VERY significant. So from the beginning.....

S = Skin depth in meters = sqrt(2/(2*pi*f*u*q)), where

q = conductivity of conductor (mhos/m), and
u = 4piE07 * relative permeability of medium

This is what's interesting. Stainless steel comes in many varieties. Some
of
them aren't even steel but use the term because they are used for the same
applications. Regardless, some stainless steel is ferromagnetic and some
is not.
The nonferromagnetic steel will have a relative permeability close to that
of
copper, or 1 for all practical purposes. OTOH, ferromagnetic steel will
have a
relative permeability much higher, and the value of 500 was used in the
calculations below.

AC resistance in ohms = l / (q * S * 2 * pi * r), where

l = length of conductor (in meters)
r = radius of conductor (in meters)

Note that there are two different listings for the conductivity of
chromium. The
first value is based on the information that it is 55% of the conductivity
of
copper, and the second value (as well as the values for copper and
stainless
steel) is based upon CRC's HC&P:

Cu Cr #1 Cr #2 S.S. S.S. (ferro)
Conductivity: 5.80E07 3.19E07 .769E07 .166E07 .166E07
Skin depth: 12.7E-06 17.1E-06 34.9E-06 75.2E-06 3.36E-06
AC resistance: .0705 ohms .0952 ohms .194 ohms .161 ohms 9.31 ohms!!!

Notice that the differences in the resistance are all insignificant except
for
the ferromagnetic stainless steel. This is because of it's high relative
permeability. Now when I realized this issue I put a magnet to my whip it
doesn't stick. So I went to the shop this morning and checked a number of
SS
whips of different lengths. Some were magnetic and some were not. The
magnetic
whips are now all in a pile for other uses.

So even old farts like me can learn something new. From now on I'll
recommend to
everyone to check an antenna with a magnet before buying it, because
that's what
I intend to do myself.

Now, back to the X-terminator. Comparing the difference in radiation
efficiency
with regards to length and polarization, the 102" whip has 102" that are
vertical. Everything is sent vertically polarized. Nothing is wasted in
horizontal polarization. OTOH, the X-terminator has 9.5" vertical,
followed by
74" of coil, then 3.75" vertical, 41.23" of coil, 5.5" vertical, and 32"
of
(gasp!) stainless steel. So you have a total of 166" of conductor, with
50.75"
of it radiating the desired vertically polarized radiation, but 115" of it
dumping horizontal hash. Let's disregard for the moment that 32" (or 63%)
of the
vertical total is made of that infamous stainless steel, and forget the
extra
overall resistance due to the additional length of conductor needed to
wind the
coils. Let's concentrate instead on the fact that the coils consume 69% of
the
total 'wire' in this antenna. Now if the current distribution was even
throughout the length of the antenna, that would mean the coils are
radiating
69% of the power as multi-phasic mush. But that's not the case, as the
coils are
positioned near the base of the antenna, where the antenna's current
distribution is the greatest. That means the coils are radiating -more-
than if
the current was evenly distributed, and therefore -more- than 69%! And
that
means the efficiency of the X-terminator is less than 31%!!!

And if that isn't bad enough, let's take a look at an el-cheapo 102"
stainless
steel whip of -magnetic- persuasion. If the whip has an AC resistance of
9.31
ohms, and the input impedance is an ideal 50 ohms, that translates into a
loss
of only 19%. If the input impedance is 36.5 ohms, the wire diameter is
0.25",
and accounting for power reflected back to the radio due to mismatch, loss
is
still well below 30%. Both scenarios are a -hell- of a lot better than the
69%
waste caused by the X-terminator's loading coils, and we didn't even go
into
absorbtion, reflection, hysteresis and eddy current losses caused from the
vehicle roof right below those coils!!!

So yes, stainless steel -is- more resistive than chromium. But the
difference is
not significant. So I'll say it again -- there is no way that this antenna
will
outperform an unloaded 102" whip whether it's made of fiberglass,
stainless
steel OR ferromagnetic steel!

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On Sat, 25 Oct 2003 21:33:07 GMT, "Train" wrote:

Very nice job Frank............................................. .....
Now, go buy a 7 foot SkipShooter and out talk the 102".
Train
LOL

Frank really gets into his work. Now if he could just transfer that
energy to an actual test. The paper work is interesting but does
nothing to show how a 102" SS marginally fails to beat some
shorter antennas.

Theory and formulas are fine but they will never include all the
variables. When the results are to close to call you have to go to
the end all. The actual test.

Yup, the same AOL addy that feels rejected because of their ego being
handed to them on daily basis...