Marconi testing the Sigma4 vs. Gain Master

[HomerBB]

You have a valid point with testing with one antenna, but again the miniscule difference isn't going to be seen with his S-meter collecting more useless data in this regard is like :bdh: .

I thought we already went over that chapter? Relying on others to get a accurate test isn't the way I would like to go, I like to be in control of all the parameters.

By gathering info from the controls I only meant from the stations HE was monitoring.

This is just my theory on what may if it was even going to effect his radiation pattern in certain directions if the antennas are to close.

Ant A talking to Station #1 No interaction from Ant B ,
Station B talking to Ant #2, no interaction from Ant A
Ant A or Ant B talking to Station 3# would no interaction between antennas.
Ant A talking to Station #2 would possibly get interaction from Ant B
Ant B talking to Station #2 would possibly get interaction from Ant A

Who On First? :blink:

Just kidding. Good graphical representation of your point.

 

[HomerBB]

Clearly there is better receive on the antenna out back. Too bad it is noisier.

Gain Master & A99 Signal Reports compared on mounts.pdf

 

[Henry HPSD]

Shockwave....

Your methode is not valid to my opinion.
The way you are describing things.

QUOTE:
The reason why he won't have to change coax length and rotate the pattern to see a change is because there is going to be a noticeable change in the pattern as soon as the second antenna is made active regardless of phase. This is all that's needed to show they are close enough to interact.
END OF QUOTE

Just by connecting them with one coax you have made that the situation always interacts.
Due to that coax, not for the single reason the antennas are closed spaced
and have a "electric" influence on each ohter.
And that was the question. can we verify if they interact as two single antennas under test.

As soon as you phase antennas the power will be devided. Because of that simple fact the signal will be different.
Only that fact will cause a change in report. ALWAYS
(unless there is a situation where due to the phasing there is a 3dB gain in that direction, so it may look like it isnt the case..but still is.)

IAnother reason to prove they dont interact with each other in the way 2 antennas closed spaced can do.
Imagine a 4 square antenna for 27mhz for example. Place the vertical monopoles 1000 feet apart.
They still have a different radiation pattern.
Though im sure you would agree with me :while in a testing situation that 1000 feet apart is more then sufficient.

Another example:
What do you think SWR does whit a random length cophasing coax length?
Although SWR is overrated, it still can be a indication of loss.

and with co/phasing the antennas it would be possible to actually get "gain" if they interact in a correct way it would also be possible to get loss depending on how they interact.
with that said it is also possible to achieve the exact same signal amount in that direction.
This although the entire pattern may be different then before

Oke, so im saying the way you put they will always interact.


sorry m8, cant agree with you on this one.

Regards,

Henry
11 meter Dx antenna systemx

ps MrS. your possible way of interaction is truly a possible way..though the other options you mentioned would also be suitable for the term`possible interaction`.
This cause there is no way of telling how things would go.
A antenna pattern is 3D.
As soon as you have a noticable difference in one direction it means it has changed somewhere else too

 

[MrSuburban]

Shockwave....

Your methode is not valid to my opinion.
The way you are describing things.

QUOTE:
The reason why he won't have to change coax length and rotate the pattern to see a change is because there is going to be a noticeable change in the pattern as soon as the second antenna is made active regardless of phase. This is all that's needed to show they are close enough to interact.
END OF QUOTE

Just by connecting them with one coax you have made that the situation always interacts.
Due to that coax, not for the single reason the antennas are closed spaced
and have a "electric" influence on each ohter.
And that was the question. can we verify if they interact as two single antennas under test.

As soon as you phase antennas the power will be devided. Because of that simple fact the signal will be different.
Only that fact will cause a change in report. ALWAYS
(unless there is a situation where due to the phasing there is a 3dB gain in that direction, so it may look like it isnt the case..but still is.)

IAnother reason to prove they dont interact with each other in the way 2 antennas closed spaced can do.
Imagine a 4 square antenna for 27mhz for example. Place the vertical monopoles 1000 feet apart.
They still have a different radiation pattern.
Though im sure you would agree with me :while in a testing situation that 1000 feet apart is more then sufficient.

Another example:
What do you think SWR does whit a random length cophasing coax length?
Although SWR is overrated, it still can be a indication of loss.

and with co/phasing the antennas it would be possible to actually get "gain" if they interact in a correct way it would also be possible to get loss depending on how they interact.
with that said it is also possible to achieve the exact same signal amount in that direction.
This although the entire pattern may be different then before

Oke, so im saying the way you put they will always interact.


sorry m8, cant agree with you on this one.

Regards,

Henry
11 meter Dx antenna systemx

ps MrS. your possible way of interaction is truly a possible way..though the other options you mentioned would also be suitable for the term`possible interaction`.
This cause there is no way of telling how things would go.
A antenna pattern is 3D.
As soon as you have a noticable difference in one direction it means it has changed somewhere else too

Henry, I agree with what you say, when you provide facts and good theory the truth it is hard for anyone to argue. No matter if they like the person delivering the message or not...

 

[Shockwave]

Shockwave....

Your methode is not valid to my opinion.
The way you are describing things.

QUOTE:
The reason why he won't have to change coax length and rotate the pattern to see a change is because there is going to be a noticeable change in the pattern as soon as the second antenna is made active regardless of phase. This is all that's needed to show they are close enough to interact.
END OF QUOTE

Just by connecting them with one coax you have made that the situation always interacts.
Due to that coax, not for the single reason the antennas are closed spaced
and have a "electric" influence on each ohter.
And that was the question. can we verify if they interact as two single antennas under test.

As soon as you phase antennas the power will be devided. Because of that simple fact the signal will be different.
Only that fact will cause a change in report. ALWAYS
(unless there is a situation where due to the phasing there is a 3dB gain in that direction, so it may look like it isnt the case..but still is.)

IAnother reason to prove they dont interact with each other in the way 2 antennas closed spaced can do.
Imagine a 4 square antenna for 27mhz for example. Place the vertical monopoles 1000 feet apart.
They still have a different radiation pattern.
Though im sure you would agree with me :while in a testing situation that 1000 feet apart is more then sufficient.

Another example:
What do you think SWR does whit a random length cophasing coax length?
Although SWR is overrated, it still can be a indication of loss.

and with co/phasing the antennas it would be possible to actually get "gain" if they interact in a correct way it would also be possible to get loss depending on how they interact.
with that said it is also possible to achieve the exact same signal amount in that direction.
This although the entire pattern may be different then before

Oke, so im saying the way you put they will always interact.


sorry m8, cant agree with you on this one.

Regards,

Henry
11 meter Dx antenna systemx

Everyone keeps thinking no, it's not possible without ever trying it and looking at the changes. I say yes, it is possible and when you see the changes it will be clear to you that you can not duplicate the results with two antennas 27 wavelengths apart at 1000 feet. I'm not talking about a small 1/2 S-unit increase in signal. It's the deep null that is much more evident when the two antennas interact because they are in the approximate near field distance. You have to have your vertical spacing and phasing perfect in order to get the 3 db omni directional increase in signal.

Marconi's description and pictures show it's not possible for this setup to produce omni directional gain. When the two antennas are combined at a random phase with this horizontal spacing, it's nearly guaranteed to produce a deep null in excess of 20db in at least one direction. This 3 or 4 S-units drop is exactly the effect I wanted Marconi to experience. Of course this counted on him having at least one station close to the nulled direction.

I completely agree that connecting two antennas together at 1000 feet could cause changes up to a of couple db depending on phasing. Because the spacing is well into the far field, the antennas are now producing their own independent patterns. This will prevent them from reaching the 3db maximum omni gain and eliminates any deep nulls in the pattern. It's easier to confirm the interaction in his case looking for the deep null then it is to determine a 3db increase.

This topic was only brought up in an attempt to show Marconi there could be much more interaction between these antennas then he might expect. I ignored VSWR with the random coax length used and suggested using a "T" connector because the tests were being done on receive. If the antennas were tuned reasonably well alone, his real VSWR should not have been more then 2:1 at 15% loss. This is not a lesson on proper phasing of vertical arrays. It just uses some of the characteristics of phasing to identify interaction still exists at one wavelength.

PS. Mr. Suburban, put your tongue back in your mouth.

 

[Henry HPSD]

Hi M8, always nice to disagree with you!
hope people dont mind us doing.

quote SW:
Everyone keeps thinking no, it's not possible without ever trying it and looking at the changes. I say yes, it is possible and when you see the changes it will be clear to you that you can not duplicate the results with two antennas 27 wavelengths apart at 1000 feet. I'm not talking about a small 1/2 S-unit increase in signal. It's the deep null that is much more evident when the two antennas interact because they are in the approximate near field distance. You have to have your vertical spacing and phasing perfect in order to get the 3 db omni directional increase in signal.

ANSWER HENRY:
You can duplicate results. As the pattern of two antennas combined will have several nulls.
Therefore the gain of the antenna sytems varies, with that said it would only be logical somewhere in the pattern you come across the same amount of gain as the single omnidirectional
We are not looking for deep nulls to show interaction.
We are looking for the slightes change in antenna pattern to show there is interaction.
As that is the question from Marconi: how can I tell if there is interaction..
The last line of your first part just proofs that. Indeed you would need to have everything perfect to gain 3dB…it would be much easier to do things wrong…in such a case there is the possibility of not noticing the difference.

QUOTE SW:
Marconi's description and pictures show it's not possible for this setup to produce omni directional gain. When the two antennas are combined at a random phase with this horizontal spacing, it's nearly guaranteed to produce a deep null in excess of 20db in at least one direction. This 3 or 4 S-units drop is exactly the effect I wanted Marconi to experience. Of course this counted on him having at least one station close to the nulled direction.

REPLY HENRY:
Agreed with the above.

QUOTE SW:
I completely agree that connecting two
antennas together at 1000 feet could cause changes up to a of couple db depending on phasing. Because the spacing is well into the far field, the antennas are now producing their own independent patterns. This will prevent them from reaching the 3db maximum omni gain and eliminates any deep nulls in the pattern. It's easier to confirm the interaction in his case looking for the deep null then it is to determine a 3db increase.

REPLY HENRY:
No, They are not producing there own individual patterns.
If both antennas are fed 1000 feet apart they will still produce a single antenna pattern.
Wich is completely different than the individual. This can be much large then a couple dB’s
As the pattern looks like a “ninja” star..(you know what I mean).
There are very deep nulls in such a pattern must be at least 50 or more..

Besides that you are speaking against yourself. How can I look for a deep null if ther antennas are producing there own omni-directional individual patterns?


QUOTE SW:
This topic was only brought up in an attempt to show Marconi there could be much more interaction between these antennas then he might expect. I ignored VSWR with the random coax length used and suggested using a "T" connector because the tests were being done on receive. If the antennas were tuned reasonably well alone, his real VSWR should not have been more then 2:1 at 15% loss. This is not a lesson on proper phasing of vertical arrays. It just uses some of the characteristics of phasing to identify interaction still exists at one wavelength.

REPLY HENRY:
M8, im not trying to give a proper lesson on phasing..not at all my appologise if you get that idea.
But you cant give marconi the idea that there is much more interaction going on by letting him phasing the antennas. With doing so you are creating interaction...not proofing it.

The thing im pointing out..:

Question Marconi: How can I tell if there is interaction.
Asnwer Shockwave: Quote:
If you want to do a simple test to see how much interaction there is, fire both antennas up (active) at once and watch how the pattern changes. You can use a co phase harness if you want the right impedance but even a simple T connector will demonstrate the changes.
Answer Henry HPSD: wrong…by phasing them you will always have “nulls” or shifts in patterns. Though the antennas when seen as individuals do not need to interact.

Again, the thing i disagree with: is you saying
"The proof of how much interactin ther is when the antennas are both phased is proof that the antennas have interaction when they are on theire own."
I disagree with that for the reasons given in this post and the previous.

Henry

 

[Shockwave]

I hate to argue this point tooth and nail but I have had two similar antennas mounted about a wavelength apart. Adding the second antenna caused slight changes in signal when it was not even connected. Connecting the two through different phasing cables allowed me to steer the signal with reasonable results and signal changes that were very pronounced. Moving the second antenna to the roof on the barn some 250 feet away eliminated my ability to cause any signal changes similar to the 1 wavelength spacing. Changes of 4 S-units were now reduced to just a few db at around 6 wavelengths. No change in signals could be noted when the antennas were not combined. Adding any 1/4 wave multiple of coax in the phasing line when combined could not steer the pattern anything like it did at 1 wavelength.

The point was to show 1 wavelength is not enough spacing to eliminate near field interaction. Phasing the two together exaggerates the interaction although it's completely unpredictable without knowing the phase angles being fed to both antennas. As spacing of the two antennas is increased outside of the near field, both parasitic and active phased interaction is reduced. The first thing I noticed was that the deep nulls that produced broader gain in other directions was the easiest thing to spot with near field spacing.

I admit I may have gone out in left field here trying to show these antennas are too close to eliminate interaction. There could have been a null in the pattern at 6 wavelengths that I missed. Perhaps a sensitive reading of the reflected power would have proven the point easier. Only objects placed in the near field of the antenna can cause a shift in the VSWR. Even if the change is slight, it would prove interaction.

 

[MrSuburban]

PS. Mr. Suburban, put your tongue back in your mouth.

Shock it is stuck...

Have a good one sir

 

[PhilipB]

Very interesting thank you.

Finaly got through reading this full thread, very interesting Marconi! I used to have a similar antenna to the sigma 4 it was called a Comtell 444 and it was 31ft tall! the neighbours were so scared of it comming down in the wind they used to walk on the other side of the road, so I took it to the caravan where the site owners who didnt mind the A99 nearly had a heart atack when they saw the thing up in the air with the base only 7ft from the ground, but boy what a performer it was, sadly we lost the caravan in a flood so the 444 was stripped down and given to a lad in Ireland as spares for his apart from the bottom tube which I still have and use for a short mast as it is unusually realy strong.

 

[Marconi]

Finaly got through reading this full thread, very interesting Marconi! I used to have a similar antenna to the sigma 4 it was called a Comtell 444 and it was 31ft tall! the neighbours were so scared of it comming down in the wind they used to walk on the other side of the road, so I took it to the caravan where the site owners who didnt mind the A99 nearly had a heart atack when they saw the thing up in the air with the base only 7ft from the ground, but boy what a performer it was, sadly we lost the caravan in a flood so the 444 was stripped down and given to a lad in Ireland as spares for his apart from the bottom tube which I still have and use for a short mast as it is unusually realy strong.

I did a modeling project recently that compared all my vertical CB models at 9' above the ground. The Sigma4 model proved to be the best performer at that height. I also raised them all to 36' feet and the advantage was a little less, but it was still the best performer.

Surprisingly, my Starduster model was very close at 36' feet and better than all others at both heights, except for the Sigma4.