What is Impedance of Carl's Antennas?

[HiTower]

Just out of curious city. Which exactly is the resistance/impedance of the "Antenna Guy Karl" kind of the antenna? Is the resistance adjusted if you co-ordinate the coil for minimum reflected power, or does adjusting on tunig of the coil affect the straight reflected energy and not the resistance/impedance. Can you bring Thwiderstand together of the antenna like then easily? How to do easily making adjustment of the correct resistance/impedance match of antenna and transmitter?

 

[pbolyn]

The series inductance and capacitance of a base loaded antenna cancel each other at resonance leaving only the loss resistances that are primarily the coil loss and the ground loss. If you have a "perfect" coil and "perfect" ground, the impedance is zero! In the real world, you might expect 5 ohms for the coil and 10 ohms for ground (15 ohms total). These numbers vary widely (particularly the ground resistance). So, you might get anywhere from 0 ohms to say 30 ohms. Note that this wacky impedance range is something we are forced to live with when complying with the 3 meter rule. Full sized commercial broadcast antennas with really good ground radial systems have close to 50 ohms impedance which is almost all "radiation resistance", a good thing. Not so the lowly 3-meter base loaded antenna with its 0.1 ohm radiation resistance fighting way higher loss resistances. The FCC knew what they were doing when they wrote the 3-meter rule!



> Just out of curious city. Which exactly is the
> resistance/impedance of the "Antenna Guy Karl" kind of the
> antenna? Is the resistance adjusted if you co-ordinate the
> coil for minimum reflected power, or does adjusting on tunig
> of the coil affect the straight reflected energy and not the
> resistance/impedance. Can you bring Thwiderstand together of
> the antenna like then easily? How to do easily making
> adjustment of the correct resistance/impedance match of
> antenna and transmitter?
>
<P ID="signature">______________
Phil B
</P>

 

[radio8z]

Hi,

I have little to add to the fine technical explaination from Phil B, but I have a few comments.

What we try to do with part15 AM antennas is to cancel the reactance of the antenna, leaving only resistance. If we minimize the resistance of the tuning coil and ground, we maximize the power delivered to the "radiation resistance". This is not a practical science so to answer your question about the particular antenna resistance you mentioned is not possible because it depends on where and how it is installed. The general approach is to provide a tuned system with the lowest resistance possible in the coil and in the ground. The actual numbers will in practice vary greatly with each unique installation.

You asked about reflected power. A SWR meter or a directional coupler is used to measure this. A SWR reading can be misleading in this situation. SWR meters are designed to give a 1:1 reading when the load is a perfect match to the transmission line regardless of the impedances involved and there is therefore no reflected power. A 797.2 ohm antenna on a 797.2 ohm transmission line will give a 1:1 match. This only measures the match of the antenna to the transmission line, not to the transmitter, therefore using one with a part15 system doesn't make sense unless the system has a transmission line, which is not common in these setups. There is a misconception that a 1:1 SWR is a perfect match to the transmitter. Not true unless the transmitter output impedance is the same as the transmission line and antenna impedance. If this is so, as is the case with amateur and CB transmitters which are designed to have a 50 Ohm output impedance, then at 1:1 you have maximum power transfer, but a 20 Ohm transmitter feeding a perfectly matched (1:1) 50 Ohm line and antenna is still mismatched even though the reflected power is zero AT THE POINT OF MEASUREMENT. My advice is to abandon SWR as a valid indicator of antenna tuning without a transmission line because you can have zero reflected power (1:1 SWR) and still have a mismatch between the transmitter and the antenna and submaximum power transfer. Even those transmitters which have the reverse power detection built into the final stage are still not measuring the impedance match, just the reflected power. These are useful, because high reflected power caused by a mismatch can damage the transmitter (watts, not milliwatts), so they throttle back power here, but they do not indicate that maximum power is being transferred.

Usually, when tuning a transmitter system, we adjust the antenna for a minimum SWR (reflected power), then we adjust the loading circuit in the transmitter for maximum forward power. (Watching Specified final amplifier current). This matches the transmitter to the transmission line.

The best and simplest way to get things adjusted overall for a modestly equipped experimenter is to use field strength as the measurement and adjust the antenna and transmitter for a maximum.

Adjust to maximize field strength.

Neil

 

[JasonW]

Neil, the Talking House ATU and TalkingSign ATU (plus the TalkingSign transmitter itself) have RF current meters that indicate (I presume) the forward power going into the antenna--one adjusts the ATU for a maximum reading.

Could a Field Strength Meter in the near field (if you don't have a helper) give a better indication of radiated power than the built-in RF current meters? A dummy load looks perfect to an SWR meter when an ATU is properly adjusted, but that doesn't mean it's radiating any RF worth mentioning. -- Jason

 

[radiopilot]

> The series inductance and capacitance of a base loaded
> antenna cancel each other at resonance leaving only the loss
> resistances that are primarily the coil loss and the ground
> loss. If you have a "perfect" coil and "perfect" ground, the
> impedance is zero! In the real world, you might expect 5
> ohms for the coil and 10 ohms for ground (15 ohms total).
> These numbers vary widely (particularly the ground
> resistance). So, you might get anywhere from 0 ohms to say
> 30 ohms. Note that this wacky impedance range is something
> we are forced to live with when complying with the 3 meter
> rule. Full sized commercial broadcast antennas with really
> good ground radial systems have close to 50 ohms impedance
> which is almost all "radiation resistance", a good thing.
> Not so the lowly 3-meter base loaded antenna with its 0.1
> ohm radiation resistance fighting way higher loss
> resistances. The FCC knew what they were doing when they
> wrote the 3-meter rule!
>
>
>
> > Just out of curious city. Which exactly is the
> > resistance/impedance of the "Antenna Guy Karl" kind of the
>
> > antenna? Is the resistance adjusted if you co-ordinate the
>
> > coil for minimum reflected power, or does adjusting on
> tunig
> > of the coil affect the straight reflected energy and not
> the
> > resistance/impedance. Can you bring Thwiderstand together
> of
> > the antenna like then easily? How to do easily making
> > adjustment of the correct resistance/impedance match of
> > antenna and transmitter?
> >
>


Phil,

The impedance for Carls antenna as measured by my antenna is as follows (for 1700khz):

L= 350uh
R= 0.5 ohms resistance of the coil
C= 25-30 pf for the antenna (copper)
f= 1700khz
calculates to approx. Z= 3.77 ohms of impedance.

Z = R^2+(2PI*fL)^2 squared

This does not include ground losses only the impedance seen at the coil.

Radiopilot

<P ID="edit"><FONT class="small">Edited by radiopilot on 12/12/05 05:38 PM.</FONT></P>

 

[rfry]

> The impedance for Carls antenna as measured by my antenna is
> as follows (for 1700khz):
>
> L= 350uh
> R= 0.5 ohms resistance of the coil
> C= 25-30 pf for the antenna (copper)
> f= 1700khz
> calculates to approx. Z= 3.77 ohms of impedance.

______________

These values seem unexpected. What exact configurations were you measuring?

Below is a squashed table showing some calculated values for a system on 1.7 MHz, using a coil about 4" long and 2" in diameter (eyeball guess from looking at Carl's antenna design). I set the ground loss very high just to wash it out of the numbers, as you said you weren't including ground losses.

The ~15 ohm coil loss is much higher than you are reporting.

Also, if you have your loading coil set for zero reactance at its input while connected to the 3-meter section, then your "Z" at the feedpoint would consist only of resistance. So if you say that is 3.77 ohms, and that the coil loss is 0.5 ohms, and given that radiation resistance is 0.1 ohm and there is no connection to ground (very high loss) -- then how do we get to 3.77 ohms?


H. Height overall, metres 3.00 J. Coil diameter, mm .......... 50.0
L. Lower antenna dia, mm. 13.0 P. Coil height as percent of Ht 1.0
U. Upper antenna dia, mm. 13.0 G. Ground loss resistance, ohms 10000.0
C. Coil length, mm ...... 100 F. Frequency, Megahertz ....... 1.70

Overall antenna height 0.017 wavelengths.
Height of coil midpoint 0.08 metres above antenna base.
Coil inductance 287.28 microhenries
Number of turns on coil 119
Coil wire diameter 0.55 millimetres = 23 AWG
Self-resonant frequency of coil 5.57 MHz, with self-capacitance.
Coil Q 222 incl effect of self-capacitance.

Radiation resistance 0.11 ohms transformed to feedpoint.
Coil wire loss 15.26 ohms .. .. ..
Antenna conductor loss 0.01 ohms .. .. ..
Feedpoint resistance10015.38 ohms
Feedpoint reactance 0.1 ohms
//

 

[radio8z]

> Neil, the Talking House ATU and TalkingSign ATU (plus the
> TalkingSign transmitter itself) have RF current meters that
> indicate (I presume) the forward power going into the
> antenna--one adjusts the ATU for a maximum reading.
>
> Could a Field Strength Meter in the near field (if you don't
> have a helper) give a better indication of radiated power
> than the built-in RF current meters? A dummy load looks
> perfect to an SWR meter when an ATU is properly adjusted,
> but that doesn't mean it's radiating any RF worth
> mentioning. -- Jason
>
Hi Jason,

I don't know exactly how these units are metered. Generally, antenna current is a good measure of the output, but it will not give the power unless the load is known. Adjusting for peak antenna current or voltage works because if they are peaked, then so is the current and voltage at the radiation resistance in a series circuit, but I prefer to adjust for peak field strength since this includes all the system parts working together. I was just trying to point out that SWR does not tell all by itself and that a good SWR does not mean optimum signal strength. Carrying your dummy load example one step further, you will measure a 1:1 SWR with the transmitter turned off.

Neil

 

[radiopilot]

> > The impedance for Carls antenna as measured by my antenna
> is
> > as follows (for 1700khz):
> >
> > L= 350uh
> > R= 0.5 ohms resistance of the coil
> > C= 25-30 pf for the antenna (copper)
> > f= 1700khz
> > calculates to approx. Z= 3.77 ohms of impedance.
>
> ______________
>
> These values seem unexpected. What exact configurations
> were you measuring?
>
> Below is a squashed table showing some calculated values for
> a system on 1.7 MHz, using a coil about 4" long and 2" in
> diameter (eyeball guess from looking at Carl's antenna
> design). I set the ground loss very high just to wash it
> out of the numbers, as you said you weren't including ground
> losses.
>
> The ~15 ohm coil loss is much higher than you are reporting.
>
>
> Also, if you have your loading coil set for zero reactance
> at its input while connected to the 3-meter section, then
> your "Z" at the feedpoint would consist only of resistance.
> So if you say that is 3.77 ohms, and that the coil loss is
> 0.5 ohms, and given that radiation resistance is 0.1 ohm and
> there is no connection to ground (very high loss) -- then
> how do we get to 3.77 ohms?
>
>
> H. Height overall, metres 3.00 J. Coil diameter, mm
> .......... 50.0
> L. Lower antenna dia, mm. 13.0 P. Coil height as
> percent of Ht 1.0
> U. Upper antenna dia, mm. 13.0 G. Ground loss
> resistance, ohms 10000.0
> C. Coil length, mm ...... 100 F. Frequency, Megahertz
> ....... 1.70
>
> Overall antenna height 0.017 wavelengths.
> Height of coil midpoint 0.08 metres above
> antenna base.
> Coil inductance 287.28 microhenries
> Number of turns on coil 119
> Coil wire diameter 0.55 millimetres =
> 23 AWG
> Self-resonant frequency of coil 5.57 MHz, with
> self-capacitance.
> Coil Q 222 incl effect of
> self-capacitance.
>
> Radiation resistance 0.11 ohms
> transformed to feedpoint.
> Coil wire loss 15.26 ohms ..
> .. ..
> Antenna conductor loss 0.01 ohms ..
> .. ..
> Feedpoint resistance10015.38 ohms
> Feedpoint reactance 0.1 ohms
> //
>


Rfry,

I just measured my coil to get the results I posted above...

I coil is 2.5 inches diameter
the length is 7.25 inches
Inductance = 350uh
Resistance measured is .5-.6 ohms as measured with ohmmeter
The capacitance of the copper antenna is 28-35pf depending on how tall or short you happen to have the antenna set to... for this equation I have it set for
28pf.

The 16 gauge magnet wire = 4.018 ohms per 1000 ft.

Try plugging those numbers in....

Radiopilot

 

[rfry]

> I just measured my coil to get the results I posted above...
> I coil is 2.5 inches diameter
> the length is 7.25 inches
> Inductance = 350uh
> Resistance measured is .5-.6 ohms as measured with ohmmeter
> The capacitance of the copper antenna is 28-35pf depending
> on how tall or short you happen to have the antenna set
> to... for this equation I have it set for
> 28pf.
>
> The 16 gauge magnet wire = 4.018 ohms per 1000 ft.
>
> Try plugging those numbers in....
_____________

Here's what I get now, letting your physical dimensions for the coil and wire gauge drive some of the other parameters...

F. Frequency, MHz ...... 1.700 C. Coil length, mm .... 184.2
H. Radiator hgt, metres .. 2.816 L. Coil former dia, mm. 63.5
D. Diameter, millimetres 4.0 R. Ratio wire dia/pitch 0.930

Antenna height 0.016 wavelengths = 9.24 feet
Antenna diameter 0.156 inches
Base input resistance 0.10 ohms (Add ground loss ohms)
Base input reactance -3733.2 ohms = capacitive reactance

Base loading coil inductance 349.51 microhenries

Loading coil length 7.25 inches
Loading coil diameter 2.50 inches
Number of turns on coil 134.2

Coil wire diameter 1.28 millimetres = 16.2 AWG
Winding pitch 1.37 millimetres = 0.054 inches
Coil wire length 27.31 metres = 89.60 feet
//

 

[radiopilot]

> > I just measured my coil to get the results I posted
> above...
> > I coil is 2.5 inches diameter
> > the length is 7.25 inches
> > Inductance = 350uh
> > Resistance measured is .5-.6 ohms as measured with
> ohmmeter
> > The capacitance of the copper antenna is 28-35pf depending
>
> > on how tall or short you happen to have the antenna set
> > to... for this equation I have it set for
> > 28pf.
> >
> > The 16 gauge magnet wire = 4.018 ohms per 1000 ft.
> >
> > Try plugging those numbers in....
> _____________
>
> Here's what I get now, letting your physical dimensions for
> the coil and wire gauge drive some of the other
> parameters...
>
> F. Frequency, MHz ...... 1.700 C. Coil length,
> mm .... 184.2
> H. Radiator hgt, metres .. 2.816 L. Coil
> former dia, mm. 63.5
> D. Diameter, millimetres 4.0 R. Ratio wire
> dia/pitch 0.930
>
> Antenna height 0.016 wavelengths =
> 9.24 feet
> Antenna diameter 0.156 inches
> Base input resistance 0.10 ohms (Add
> ground loss ohms)
> Base input reactance -3733.2 ohms =
> capacitive reactance
>
> Base loading coil inductance 349.51 microhenries
>
> Loading coil length 7.25 inches
> Loading coil diameter 2.50 inches
> Number of turns on coil 134.2
>
> Coil wire diameter 1.28 millimetres =
> 16.2 AWG
> Winding pitch 1.37 millimetres =
> 0.054 inches
> Coil wire length 27.31 metres =
> 89.60 feet
> //
>

Rfry,

The inductor/impedence calculates to:

Z= 3.73849 ohms and a Q of 7.47699 ohms for the above coil...

Not sure what values you are plugging in.... anyway the impedence is very small and if the ground losses are small, less than 10 ohms with a good radial system, I can't see why anyone is having trouble making their system work, other than poor ground conductance, which there are remedies for... Carl's antenna if built correctly and installed correctly should have no problem getting the desired results, and if the transmitter is set high 30-50 feet, then they are also benefitting from added ground wire radiation, which as you say goes contrary to part15 rules....

Radiopilot

 

[carlvanorden]

> > > The impedance for Carls antenna as measured by my> antenna> > is> > > as follows (for 1700khz):> > > > > > L= 350uh > > > R= 0.5 ohms resistance of the coil> > > C= 25-30 pf for the antenna (copper)> > > f= 1700khz> > > calculates to approx. Z= 3.77 ohms of impedance.> > > > ______________> > > > These values seem unexpected. What exact configurations> > were you measuring?> > > > Below is a squashed table showing some calculated values> for> > a system on 1.7 MHz, using a coil about 4" long and 2" in> > diameter (eyeball guess from looking at Carl's antenna> > design). I set the ground loss very high just to wash it> > out of the numbers, as you said you weren't including> ground> > losses.> > > > The ~15 ohm coil loss is much higher than you are> reporting.> > > > > > Also, if you have your loading coil set for zero reactance> > > at its input while connected to the 3-meter section, then> > your "Z" at the feedpoint would consist only of> resistance. > > So if you say that is 3.77 ohms, and that the coil loss is> > > 0.5 ohms, and given that radiation resistance is 0.1 ohm> and> > there is no connection to ground (very high loss) -- then> > how do we get to 3.77 ohms? > > > > > > H. Height overall, metres 3.00 J. Coil diameter, mm> > .......... 50.0> > L. Lower antenna dia, mm. 13.0 P. Coil height as> > percent of Ht 1.0> > U. Upper antenna dia, mm. 13.0 G. Ground loss> > resistance, ohms 10000.0> > C. Coil length, mm ...... 100 F. Frequency,> Megahertz> > ....... 1.70> > > > Overall antenna height 0.017 wavelengths.> > > Height of coil midpoint 0.08 metres above> > > antenna base.> > Coil inductance 287.28 microhenries> > > Number of turns on coil 119> > Coil wire diameter 0.55 millimetres> => > 23 AWG> > Self-resonant frequency of coil 5.57 MHz, with> > self-capacitance.> > Coil Q 222 incl effect> of> > self-capacitance.> > > > Radiation resistance 0.11 ohms> > transformed to feedpoint.> > Coil wire loss 15.26 ohms ..> > > .. ..> > Antenna conductor loss 0.01 ohms ..> > > .. ..> > Feedpoint resistance10015.38 ohms> > Feedpoint reactance 0.1 ohms> > //> > > > > Rfry,> > I just measured my coil to get the results I posted above...> > > I coil is 2.5 inches diameter> the length is 7.25 inches> Inductance = 350uh> Resistance measured is .5-.6 ohms as measured with ohmmeter> The capacitance of the copper antenna is 28-35pf depending> on how tall or short you happen to have the antenna set> to... for this equation I have it set for > 28pf.> > The 16 gauge magnet wire = 4.018 ohms per 1000 ft.> > Try plugging those numbers in....> > Radiopilot> Except my coil is wound around 3" pvc, not 2", and the length of the wind is more like 10-11", without going to find one and measure it right now.Phil is kind of on the money: when we discussed this in terms of how well it would work with other transmitters, and looked at what other transmitters required, and...figured that a good ground system would be employed, we came up with a very very low resistance.......I also do build Radio Pilots' coil, and I have buyers for it, and in that case I would have to say he is correct: he designed it.Carl<P ID="signature">______________
[email protected], [email protected],[email protected]</P>

 

[radiopilot]

> > > > The impedance for Carls antenna as measured by my>
> antenna> > is> > > as follows (for 1700khz):> > > > > > L=
> 350uh > > > R= 0.5 ohms resistance of the coil> > > C= 25-30
> pf for the antenna (copper)> > > f= 1700khz> > > calculates
> to approx. Z= 3.77 ohms of impedance.> > > > ______________>
> > > > These values seem unexpected. What exact
> configurations> > were you measuring?> > > > Below is a
> squashed table showing some calculated values> for> > a
> system on 1.7 MHz, using a coil about 4" long and 2" in> >
> diameter (eyeball guess from looking at Carl's antenna> >
> design). I set the ground loss very high just to wash it> >
> out of the numbers, as you said you weren't including>
> ground> > losses.> > > > The ~15 ohm coil loss is much
> higher than you are> reporting.> > > > > > Also, if you have
> your loading coil set for zero reactance> > > at its input
> while connected to the 3-meter section, then> > your "Z" at
> the feedpoint would consist only of> resistance. > > So if
> you say that is 3.77 ohms, and that the coil loss is> > >
> 0.5 ohms, and given that radiation resistance is 0.1 ohm>
> and> > there is no connection to ground (very high loss) --
> then> > how do we get to 3.77 ohms? > > > > > > H. Height
> overall, metres 3.00 J. Coil diameter, mm> >
> .......... 50.0> > L. Lower antenna dia, mm. 13.0
> P. Coil height as> > percent of Ht 1.0> > U. Upper
> antenna dia, mm. 13.0 G. Ground loss> > resistance,
> ohms 10000.0> > C. Coil length, mm ...... 100 F.
> Frequency,> Megahertz> > ....... 1.70> > > >
> Overall antenna height 0.017 wavelengths.> > >
> Height of coil midpoint 0.08 metres above> > >
> antenna base.> > Coil inductance
> 287.28 microhenries> > > Number of turns on
> coil 119> > Coil wire diameter 0.55
> millimetres> => > 23 AWG> > Self-resonant frequency of
> coil 5.57 MHz, with> > self-capacitance.> >
> Coil Q 222 incl effect> of> >
> self-capacitance.> > > > Radiation
> resistance 0.11 ohms> > transformed to feedpoint.> >
> Coil wire loss 15.26 ohms ..> > >
> .. ..> > Antenna conductor loss 0.01
> ohms ..> > > .. ..> > Feedpoint
> resistance10015.38 ohms> > Feedpoint
> reactance 0.1 ohms> > //> > > > > Rfry,> > I just
> measured my coil to get the results I posted above...> > > I
> coil is 2.5 inches diameter> the length is 7.25 inches>
> Inductance = 350uh> Resistance measured is .5-.6 ohms as
> measured with ohmmeter> The capacitance of the copper
> antenna is 28-35pf depending> on how tall or short you
> happen to have the antenna set> to... for this equation I
> have it set for > 28pf.> > The 16 gauge magnet wire = 4.018
> ohms per 1000 ft.> > Try plugging those numbers in....> >
> Radiopilot> Except my coil is wound around 3" pvc, not 2",
> and the length of the wind is more like 10-11", without
> going to find one and measure it right now.Phil is kind of
> on the money: when we discussed this in terms of how well
> it would work with other transmitters, and looked at what
> other transmitters required, and...figured that a good
> ground system would be employed, we came up with a very very
> low resistance.......I also do build Radio Pilots' coil, and
> I have buyers for it, and in that case I would have to say
> he is correct: he designed it.Carl
>


Carl,

The larger the coil diameter the better the coil is in terms of inductance/reactive resistance, etc.... infact if the coil was wound on a diameter of 12 inches or better the transmitter would forward it's signal better, I have seen people wind the coil on 5 gallon paint buckets, but it's a ground installation, it'll be funny seeing that bucket 30 feet high, nice coversation piece though.

The ground resistance and good conductivity is the best we can do for these antennas... go try it, bury the ground rods in cat litter clay, or in moist salty soil, bury as many radials and as long as you can muster and see how well the signal transmits... tuning is the biggest obstacle and my new antenna will solve that as there are no taps to solder and the only adjustment will be the adjusting the height of the copper tube...

Those that can't employ a good radial system, try adding not one ground rod but many ground rods tied to one another, any ground system as long as you reduce the ground resistance to it's lowest, ie, less than 10 ohms!

Radiopilot

 

[JasonW]

For a ground-mounted antenna, how about burying a large metal object such as an old electric stove and connecting the ground lead to it? The stove would have more soil contact than a ground rod (or even several). -- JasonW

> Carl,
>
> The larger the coil diameter the better the coil is in terms
> of inductance/reactive resistance, etc.... infact if the
> coil was wound on a diameter of 12 inches or better the
> transmitter would forward it's signal better, I have seen
> people wind the coil on 5 gallon paint buckets, but it's a
> ground installation, it'll be funny seeing that bucket 30
> feet high, nice coversation piece though.
>
> The ground resistance and good conductivity is the best we
> can do for these antennas... go try it, bury the ground rods
> in cat litter clay, or in moist salty soil, bury as many
> radials and as long as you can muster and see how well the
> signal transmits... tuning is the biggest obstacle and my
> new antenna will solve that as there are no taps to solder
> and the only adjustment will be the adjusting the height of
> the copper tube...
>
> Those that can't employ a good radial system, try adding not
> one ground rod but many ground rods tied to one another, any
> ground system as long as you reduce the ground resistance to
> it's lowest, ie, less than 10 ohms!
>
> Radiopilot
>

 

[JasonW]

Hello Neil,

The load is a bit of a mystery on these units. The TalkingSign remote antenna (ATU) output on the back of the transmitter is marked "50 ohms," yet it uses 75 ohm RG-59 coax. The Talking House uses 75 ohm RG-6 coax to connect its ATU.

On top of that, these Talking House and TalkingSign "ATUs" are really "remote tank circuits" that are connected to their transmitters by lengths of coax. This arrangement satisfies the FCC's Part 15 certification requirements while allowing the "ATU"/whip antenna to be mounted outdoors in the clear.

To further complicate matters, these "ATU"/whip units are not supposed to be grounded, yet both the Talking House and TalkingSign units have ground posts for static and lightning protection. Connecting the "ATU"/whip to a ground rod or other ground (such as a grounded metal roof) will surely change the load value. -- JasonW

> Hi Jason,
>
> I don't know exactly how these units are metered.
> Generally, antenna current is a good measure of the output,
> but it will not give the power unless the load is known.
> Adjusting for peak antenna current or voltage works because
> if they are peaked, then so is the current and voltage at
> the radiation resistance in a series circuit, but I prefer
> to adjust for peak field strength since this includes all
> the system parts working together. I was just trying to
> point out that SWR does not tell all by itself and that a
> good SWR does not mean optimum signal strength. Carrying
> your dummy load example one step further, you will measure a
> 1:1 SWR with the transmitter turned off.
>
> Neil
>

 

[radiopilot]

> For a ground-mounted antenna, how about burying a large
> metal object such as an old electric stove and connecting
> the ground lead to it? The stove would have more soil
> contact than a ground rod (or even several). -- JasonW
>
> > Carl,
> >
> > The larger the coil diameter the better the coil is in
> terms
> > of inductance/reactive resistance, etc.... infact if the
> > coil was wound on a diameter of 12 inches or better the
> > transmitter would forward it's signal better, I have seen
> > people wind the coil on 5 gallon paint buckets, but it's a
>
> > ground installation, it'll be funny seeing that bucket 30
> > feet high, nice coversation piece though.
> >
> > The ground resistance and good conductivity is the best we
>
> > can do for these antennas... go try it, bury the ground
> rods
> > in cat litter clay, or in moist salty soil, bury as many
> > radials and as long as you can muster and see how well the
>
> > signal transmits... tuning is the biggest obstacle and my
> > new antenna will solve that as there are no taps to solder
>
> > and the only adjustment will be the adjusting the height
> of
> > the copper tube...
> >
> > Those that can't employ a good radial system, try adding
> not
> > one ground rod but many ground rods tied to one another,
> any
> > ground system as long as you reduce the ground resistance
> to
> > it's lowest, ie, less than 10 ohms!
> >
> > Radiopilot
> >
>

Good idea, in fact bury a car and use it as the ground, but a simple solution is to take an old car radiator fill it with water softner salt and water and bury it 2-4 feet down and use that as the 'ground rod', it's been said that works very well, or if you're close to the water main from the street, use that as the ground... there are plenty of ways to achieve an excellent ground, just don't give up, use some imagination in finding that perfect ground.

Radiopilot

 

[JasonW]

I have an old electric stove out in the back yard. Hmmm...I could fill that sucker up with copper sulfate and then bury it. The more it rains, the better the soil around it will conduct. -- JasonW

> > For a ground-mounted antenna, how about burying a large
> > metal object such as an old electric stove and connecting
> > the ground lead to it? The stove would have more soil
> > contact than a ground rod (or even several). -- JasonW
> >
> > > Carl,
> > >
> > > The larger the coil diameter the better the coil is in
> > terms
> > > of inductance/reactive resistance, etc.... infact if the
>
> > > coil was wound on a diameter of 12 inches or better the
> > > transmitter would forward it's signal better, I have
> seen
> > > people wind the coil on 5 gallon paint buckets, but it's
> a
> >
> > > ground installation, it'll be funny seeing that bucket
> 30
> > > feet high, nice coversation piece though.
> > >
> > > The ground resistance and good conductivity is the best
> we
> >
> > > can do for these antennas... go try it, bury the ground
> > rods
> > > in cat litter clay, or in moist salty soil, bury as many
>
> > > radials and as long as you can muster and see how well
> the
> >
> > > signal transmits... tuning is the biggest obstacle and
> my
> > > new antenna will solve that as there are no taps to
> solder
> >
> > > and the only adjustment will be the adjusting the height
>
> > of
> > > the copper tube...
> > >
> > > Those that can't employ a good radial system, try adding
>
> > not
> > > one ground rod but many ground rods tied to one another,
>
> > any
> > > ground system as long as you reduce the ground
> resistance
> > to
> > > it's lowest, ie, less than 10 ohms!
> > >
> > > Radiopilot
> > >
> >
>
> Good idea, in fact bury a car and use it as the ground, but
> a simple solution is to take an old car radiator fill it
> with water softner salt and water and bury it 2-4 feet down
> and use that as the 'ground rod', it's been said that works
> very well, or if you're close to the water main from the
> street, use that as the ground... there are plenty of ways
> to achieve an excellent ground, just don't give up, use some
> imagination in finding that perfect ground.
>
> Radiopilot
>

 

[radiopilot]

> I have an old electric stove out in the back yard. Hmmm...I
> could fill that sucker up with copper sulfate and then bury
> it. The more it rains, the better the soil around it will
> conduct. -- JasonW
>


This is good but in no time, less than 2-3 years you'll have nothing left of the stove in terms of metal from the electrolysis of the difference in metals, which is why you want to use as much copper as you can, they resist corrosion a little better, heck you could fill a copper cooking pot with pennies and salt and use that as the ground.... I've read somewhere that one person laid out chicken wire in a circle and then used aluminum foil crimped to the chicken wire as the radials at a hamfest and it WORKED!!! There are numerous cases of wacky ways of achieving the same goals... gotta try it!

Radiopilot

 

[carlvanorden]

Funny idea, but look at it this way...

> > For a ground-mounted antenna, how about burying a large> > metal object such as an old electric stove and connecting> > the ground lead to it? The stove would have more soil> > contact than a ground rod (or even several). -- JasonW> > > > > Carl,> > > > > > The larger the coil diameter the better the coil is in> > terms> > > of inductance/reactive resistance, etc.... infact if the> > > > coil was wound on a diameter of 12 inches or better the> > > transmitter would forward it's signal better, I have> seen> > > people wind the coil on 5 gallon paint buckets, but it's> a> > > > > ground installation, it'll be funny seeing that bucket> 30> > > feet high, nice coversation piece though.> > > > > > The ground resistance and good conductivity is the best> we> > > > > can do for these antennas... go try it, bury the ground> > rods> > > in cat litter clay, or in moist salty soil, bury as many> > > > radials and as long as you can muster and see how well> the> > > > > signal transmits... tuning is the biggest obstacle and> my> > > new antenna will solve that as there are no taps to> solder> > > > > and the only adjustment will be the adjusting the height> > > of> > > the copper tube... > > > > > > Those that can't employ a good radial system, try adding> > > not> > > one ground rod but many ground rods tied to one another,> > > any> > > ground system as long as you reduce the ground> resistance> > to> > > it's lowest, ie, less than 10 ohms!> > > > > > Radiopilot> > >> > > > Good idea, in fact bury a car and use it as the ground, but> a simple solution is to take an old car radiator fill it> with water softner salt and water and bury it 2-4 feet down> and use that as the 'ground rod', it's been said that works> very well, or if you're close to the water main from the> street, use that as the ground... there are plenty of ways> to achieve an excellent ground, just don't give up, use some> imagination in finding that perfect ground.> > Radiopilot> Everyone knows placing an AM tx and radials near the ocean does a great job.....railroad tracks are perhaps the best ground system ever seen....so, if you think about railroad tracks and are considering burying cars (heard of that actually happening once at a commercial am), or a stove (funny, but...hey, don't knock it), it's worked before.....for me, I prefer radials because they extend past the antenna and out and the ground is not centered on one solid object on one side of the antenna.<P ID="signature">______________
[email protected], [email protected],[email protected]</P>

 

[radiopilot]

Re: Funny idea, but look at it this way...

Everyone knows placing an AM tx and
> radials near the ocean does a great job.....railroad tracks
> are perhaps the best ground system ever seen....so, if you
> think about railroad tracks and are considering burying cars
> (heard of that actually happening once at a commercial am),
> or a stove (funny, but...hey, don't knock it), it's worked
> before.....for me, I prefer radials because they extend past
> the antenna and out and the ground is not centered on one
> solid object on one side of the antenna.
>


Carl,

Absolutely, the train tracks are a perfect ground plane, and are probably better than buried radials.

I only think of the poor Chinese/Irish immigrants that endured many hardships in laying those tracks that I feel guilty just thinking of using them to one's advantage... similar to bidding for 'slave items' from our horrid past on Ebay or whatever.... Just my personal feeling about certain issues....

Somewhere I'll find the site about the buried car and post it here, that'll be a conversation topic indeed!

Radiopilot