Antennas: Best Mini-Whip ?? Grounds discusssion


Tony_AD0VC
 

The mini-whip and other e-field probe antennas are, by their nature, high impedance measuring devices. Like the  voltmeter on your test bench, they are intended to measure without loading. So, how good of a ground do you think you need? The answer is "not very good". The coax laying on the ground is often good enough for a mini-whip. A few hundred picofarads is quite large compared to the <1pf the sensing pad. For the mini-whip, I think a good ground has more value for noise suppression than it does for antenna operation. I always ground a mini-whip at the base of the antenna myself, but I use a 4 foot rod. 

For me, the achilles heel of active e-field antennas is overload. I live near an AM BC station and I have not found an active e-field antenna that doesn't have IMD spurs scattered about in the waterfall. I use a passive e-field antenna with an impedance of 50k-100k ohms. A 4 foot rod is still fine for this.

Tony


jdow
 

In general a rod in the ground is a safety ground. For RF you use radials to get a good ground. And they should be 1/4 wave at the lowest frequency of interest. That will lower the main lobe on your radiation pattern.

{^_^}

On 20210919 08:12:26, Tony_AD0VC wrote:

The mini-whip and other e-field probe antennas are, by their nature, high impedance measuring devices. Like the  voltmeter on your test bench, they are intended to measure without loading. So, how good of a ground do you think you need? The answer is "not very good". The coax laying on the ground is often good enough for a mini-whip. A few hundred picofarads is quite large compared to the <1pf the sensing pad. For the mini-whip, I think a good ground has more value for noise suppression than it does for antenna operation. I always ground a mini-whip at the base of the antenna myself, but I use a 4 foot rod. 

For me, the achilles heel of active e-field antennas is overload. I live near an AM BC station and I have not found an active e-field antenna that doesn't have IMD spurs scattered about in the waterfall. I use a passive e-field antenna with an impedance of 50k-100k ohms. A 4 foot rod is still fine for this.

Tony



Kriss Kliegle KA1GJU
 

My 4' ground rod (half of an 8' one) at the 9:1 Unun  of my 210' long EFW drops the noise floor on 160 and 80M by 1 1/2 S-units, not so noticeable on upper bands.
Somewhere on a laptop, I have SDRC images of the before and after grounding. This is installed on KA1GJU Super Station #1 Server BTW. Since then, I have done the same to Super Station #2, which feeds 4 SDR's when that was installed over a year ago.

YMMV
73 Kriss KA1GJU


Tony_AD0VC
 

In general maybe. But in specific, there are hundreds of us LF DXers (world wide) out here who use rods with our e-probe types of antennas. If only we had thought to use radials instead. At least we are safe.

Also, I have not gotten my mini-whip to radiate yet. Maybe thats why.

Irked,

Tony


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of jdow <jdow@...>
Sent: Sunday, September 19, 2021 7:48 PM
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] Antennas: Best Mini-Whip ?? Grounds discusssion
 
In general a rod in the ground is a safety ground. For RF you use radials to get a good ground. And they should be 1/4 wave at the lowest frequency of interest. That will lower the main lobe on your radiation pattern.

{^_^}

On 20210919 08:12:26, Tony_AD0VC wrote:

The mini-whip and other e-field probe antennas are, by their nature, high impedance measuring devices. Like the  voltmeter on your test bench, they are intended to measure without loading. So, how good of a ground do you think you need? The answer is "not very good". The coax laying on the ground is often good enough for a mini-whip. A few hundred picofarads is quite large compared to the <1pf the sensing pad. For the mini-whip, I think a good ground has more value for noise suppression than it does for antenna operation. I always ground a mini-whip at the base of the antenna myself, but I use a 4 foot rod. 

For me, the achilles heel of active e-field antennas is overload. I live near an AM BC station and I have not found an active e-field antenna that doesn't have IMD spurs scattered about in the waterfall. I use a passive e-field antenna with an impedance of 50k-100k ohms. A 4 foot rod is still fine for this.

Tony



Kriss Kliegle KA1GJU
 

Once my Bovine friends are gone for the winter, I could lay out some radials and compare noise floors of none, ground rod, and radials. Superstation #1 is inside one of the pastures and they will surely get anything I put down on the ground torn up and wrapped around their hooves. Hence I buried, welded together sheets of concrete reinforcing wire around my 160M vertical:


73 Kriss KA1GJU


Wes Stewart
 

There is no need to make radials 1/4 wave.  They have little to do with pattern but a lot to do with efficiency.  A wire on or buried in the ground is much longer electrically than it is physically.  Some of the best info to be found is on Rudy's site  http://rudys.typepad.com/files/chapter-5-.pdf

Wes  N7WS


On Sun, Sep 19, 2021 at 06:48 PM, jdow wrote:
In general a rod in the ground is a safety ground. For RF you use radials to get a good ground. And they should be 1/4 wave at the lowest frequency of interest. That will lower the main lobe on your radiation pattern.

{^_^}

On 20210919 08:12:26, Tony_AD0VC wrote:
The mini-whip and other e-field probe antennas are, by their nature, high impedance measuring devices. Like the  voltmeter on your test bench, they are intended to measure without loading. So, how good of a ground do you think you need? The answer is "not very good". The coax laying on the ground is often good enough for a mini-whip. A few hundred picofarads is quite large compared to the <1pf the sensing pad. For the mini-whip, I think a good ground has more value for noise suppression than it does for antenna operation. I always ground a mini-whip at the base of the antenna myself, but I use a 4 foot rod. 
 
For me, the achilles heel of active e-field antennas is overload. I live near an AM BC station and I have not found an active e-field antenna that doesn't have IMD spurs scattered about in the waterfall. I use a passive e-field antenna with an impedance of 50k-100k ohms. A 4 foot rod is still fine for this.
 
Tony
 


Siegfried Jackstien
 

hey kriss

how long will those iron mats survive in the ground and outside in the weather?!?

would it be worth using stainless instead?!? or at least galvanized ones?!?

dg9bfc sigi


Am 20.09.2021 um 16:22 schrieb Kriss Kliegle KA1GJU:

Once my Bovine friends are gone for the winter, I could lay out some radials and compare noise floors of none, ground rod, and radials. Superstation #1 is inside one of the pastures and they will surely get anything I put down on the ground torn up and wrapped around their hooves. Hence I buried, welded together sheets of concrete reinforcing wire around my 160M vertical:


73 Kriss KA1GJU


Gedas
 

Yup exactly right Wes. I think it goes WAY back when ops were making radials for ground plane antennas where having 1/4-wave radials provided efficiency and helped provide a good match to 50-ohm coax. Broadcast stations use even longer radials (usually 1/2-wave) but this is FCC mandated. Once the wires are on the ground the dielectric constant kicks in and they become longer electrically. And of course much better to have a boat load of shorter radials than a few long ones.

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 9/20/2021 10:51 AM, Wes Stewart via groups.io wrote:

There is no need to make radials 1/4 wave.  They have little to do with pattern but a lot to do with efficiency.  A wire on or buried in the ground is much longer electrically than it is physically.  Some of the best info to be found is on Rudy's site  http://rudys.typepad.com/files/chapter-5-.pdf

Wes  N7WS

On Sun, Sep 19, 2021 at 06:48 PM, jdow wrote:
In general a rod in the ground is a safety ground. For RF you use radials to get a good ground. And they should be 1/4 wave at the lowest frequency of interest. That will lower the main lobe on your radiation pattern.

{^_^}

On 20210919 08:12:26, Tony_AD0VC wrote:
The mini-whip and other e-field probe antennas are, by their nature, high impedance measuring devices. Like the  voltmeter on your test bench, they are intended to measure without loading. So, how good of a ground do you think you need? The answer is "not very good". The coax laying on the ground is often good enough for a mini-whip. A few hundred picofarads is quite large compared to the <1pf the sensing pad. For the mini-whip, I think a good ground has more value for noise suppression than it does for antenna operation. I always ground a mini-whip at the base of the antenna myself, but I use a 4 foot rod. 
 
For me, the achilles heel of active e-field antennas is overload. I live near an AM BC station and I have not found an active e-field antenna that doesn't have IMD spurs scattered about in the waterfall. I use a passive e-field antenna with an impedance of 50k-100k ohms. A 4 foot rod is still fine for this.
 
Tony
 


Gedas
 

Kriss that will be a fascinating experiment. I hope you are able to do it as it would be very educational and not many people can do. Nothing like empirical data !

Now I know this is probably not going to be possible, and you already know this, but it is not enough to just know that the noise level dropped x dB when using ground system A vs. ground system B. What we really need to know is what happened to the strength of desired signals as well when you noted that drop in noise. It's all about that S/N.

Again I know you won't be able to make those kinds of comparisons, not unless you have identical receive setups separated some distance apart and each one using a different grounding scheme.....that is the only way I could think of to run real-time A/B tests and know for sure what is going on. Thanks for running the tests that you have and will be. 73

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 9/20/2021 10:22 AM, Kriss Kliegle KA1GJU wrote:

Once my Bovine friends are gone for the winter, I could lay out some radials and compare noise floors of none, ground rod, and radials. Superstation #1 is inside one of the pastures and they will surely get anything I put down on the ground torn up and wrapped around their hooves. Hence I buried, welded together sheets of concrete reinforcing wire around my 160M vertical:


73 Kriss KA1GJU


Gedas
 

Sigi the resistance of SS or steel wires is much poorer than that of copper. Significant when one is trying to cut every 1/10th of an ohm to maximize efficiency.

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 9/20/2021 11:59 AM, Siegfried Jackstien wrote:

hey kriss

how long will those iron mats survive in the ground and outside in the weather?!?

would it be worth using stainless instead?!? or at least galvanized ones?!?

dg9bfc sigi


Am 20.09.2021 um 16:22 schrieb Kriss Kliegle KA1GJU:
Once my Bovine friends are gone for the winter, I could lay out some radials and compare noise floors of none, ground rod, and radials. Superstation #1 is inside one of the pastures and they will surely get anything I put down on the ground torn up and wrapped around their hooves. Hence I buried, welded together sheets of concrete reinforcing wire around my 160M vertical:


73 Kriss KA1GJU


jdow
 

That is a lot of rebar if you are running out the optimal distance of 131' for each radial. It should make a significant difference. Comments I have seen suggest burying it a few inches won't make much difference; but, burying it below what bovines might churn the ground when it gets really muddy might make it less effective. Your sheet layout may mitigate that. And hooboy is that gonna be expensive.

{O.O}

On 20210920 07:22:07, Kriss Kliegle KA1GJU wrote:

Once my Bovine friends are gone for the winter, I could lay out some radials and compare noise floors of none, ground rod, and radials. Superstation #1 is inside one of the pastures and they will surely get anything I put down on the ground torn up and wrapped around their hooves. Hence I buried, welded together sheets of concrete reinforcing wire around my 160M vertical:


73 Kriss KA1GJU


jdow
 

He hared off in the efficiency direction. Efficiency is important, to be sure. But you also must look at the pattern. With a ground rod the radiation pattern's lobe is very much like a bubble. The antenna spends watts on clouds. For regional communications that is good. If DX is your goal you want to shape that into a low to the ground doughnut. The lower the better. Are there ruminations there regarding power delivered to various elevation angles or power delivered to the first lobe's peak and its elevation angle?

Modeling with EZNEC is a good way to get a feel for what transpires with radials, efficiency, and radiation angle. (The paid for version of course. The modeling within the free version is too limited to go a good job.)

{^_^}

On 20210920 07:51:37, Wes Stewart via groups.io wrote:

There is no need to make radials 1/4 wave.  They have little to do with pattern but a lot to do with efficiency.  A wire on or buried in the ground is much longer electrically than it is physically.  Some of the best info to be found is on Rudy's site  http://rudys.typepad.com/files/chapter-5-.pdf

Wes  N7WS

On Sun, Sep 19, 2021 at 06:48 PM, jdow wrote:
In general a rod in the ground is a safety ground. For RF you use radials to get a good ground. And they should be 1/4 wave at the lowest frequency of interest. That will lower the main lobe on your radiation pattern.

{^_^}

On 20210919 08:12:26, Tony_AD0VC wrote:
The mini-whip and other e-field probe antennas are, by their nature, high impedance measuring devices. Like the  voltmeter on your test bench, they are intended to measure without loading. So, how good of a ground do you think you need? The answer is "not very good". The coax laying on the ground is often good enough for a mini-whip. A few hundred picofarads is quite large compared to the <1pf the sensing pad. For the mini-whip, I think a good ground has more value for noise suppression than it does for antenna operation. I always ground a mini-whip at the base of the antenna myself, but I use a 4 foot rod. 
 
For me, the achilles heel of active e-field antennas is overload. I live near an AM BC station and I have not found an active e-field antenna that doesn't have IMD spurs scattered about in the waterfall. I use a passive e-field antenna with an impedance of 50k-100k ohms. A 4 foot rod is still fine for this.
 
Tony
 


jdow
 

Ever tried welding stainless? Rumor has it that it's not easy.
{o.o}

On 20210920 08:59:48, Siegfried Jackstien wrote:

hey kriss

how long will those iron mats survive in the ground and outside in the weather?!?

would it be worth using stainless instead?!? or at least galvanized ones?!?

dg9bfc sigi


Am 20.09.2021 um 16:22 schrieb Kriss Kliegle KA1GJU:
Once my Bovine friends are gone for the winter, I could lay out some radials and compare noise floors of none, ground rod, and radials. Superstation #1 is inside one of the pastures and they will surely get anything I put down on the ground torn up and wrapped around their hooves. Hence I buried, welded together sheets of concrete reinforcing wire around my 160M vertical:


73 Kriss KA1GJU


Gedas
 

Piece of cake. Just today I was brazing a SS U-bolt to a brass collar as I had to make my own pillow block bearing that will allow my 10 GHz dish to move up & down in elevation. Welding (as opposed to brazing) SS is also NP as long as you use the right rods and current settings. Last week I was soldering SS to SS.

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 9/20/2021 7:32 PM, jdow wrote:

Ever tried welding stainless? Rumor has it that it's not easy.
{o.o}

On 20210920 08:59:48, Siegfried Jackstien wrote:

hey kriss

how long will those iron mats survive in the ground and outside in the weather?!?

would it be worth using stainless instead?!? or at least galvanized ones?!?

dg9bfc sigi


Am 20.09.2021 um 16:22 schrieb Kriss Kliegle KA1GJU:
Once my Bovine friends are gone for the winter, I could lay out some radials and compare noise floors of none, ground rod, and radials. Superstation #1 is inside one of the pastures and they will surely get anything I put down on the ground torn up and wrapped around their hooves. Hence I buried, welded together sheets of concrete reinforcing wire around my 160M vertical:


73 Kriss KA1GJU


Kriss Kliegle KA1GJU
 

Hello Sigi,
The wire mesh is 3.175mm of regular steel, no paint or other coatings. Will last longer than I will be around on Earth! I have found chicken fence wire underground, much smaller in diameter than what I used, and it’s +50 years old. When I built my barn, I bought the wire… but decided to go with 12mm rebar for more strength. So I welded 4 sheets end to end to make a 5’ x 32’ radial. The Icom AH-4 is for higher bands, 80-10, but on 160m, it’s not needed. Was originally going to place it on the ground, but with tractors, trucks, and cows… it would get snagged or just torn up. So I scraped a few inches of soil, put down the steel, then spread the soil back on top.

73 Kriss KA1GJU


Kriss Kliegle KA1GJU
 

It’s not rebar, just wire mesh that’s used in concrete floors, sidewalks, etc. I bought enough to do my 36x48 barn/workshop, but ended up using 1/2 rebar instead. So far, no cracks in my floor! The sheets are 5x8 of 1/8 steel wire, and once welded end to end, the radials are 32’ long by 5’ wide. This is one of three 160m TX antennas on the farm, others are inverted Vees at ~90’ on two separate towers. But this one plays very well wit only 100watts to a friend 616 miles away.

73 Kriss KA1GJU 


Joe F. KC8RKL
 

Slightly OT note:
 
EZNEC (Pro/2 version) will be released to the public domain effective 1/1/2022.
 
 
SRI for the wasted bandwidth if posted here previously.
 
73,
 
Joe F. KC8RKL