I guess one way to do it is with both antennas up check the swr , if you have a analyzer that would give you more indepth numbers than a swr bridge that would be better. Check swr of antenna 1 with both antennas up, lower antenna #2 check swr, Put up antenna #2 and lower #1 and check again. compare. Then if you have a FS meter give that a try as well with both up walk around note readings if you cant make exact circle pick a few areas around both see if anything changes when you lower one see if you get same pattern. Rinse and repeat Thats about the best I think you can do the sensitivity and accuracy of the test equipment probably will determine what you see.
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Marconi testing the Sigma4 vs. Gain Master
- Thread starter Marconi
- Start date
I guess one way to do it is with both antennas up check the swr , if you have a analyzer that would give you more indepth numbers than a swr bridge that would be better. Check swr of antenna 1 with both antennas up, lower antenna #2 check swr, Put up antenna #2 and lower #1 and check again. compare. Then if you have a FS meter give that a try as well with both up walk around note readings if you cant make exact circle pick a few areas around both see if anything changes when you lower one see if you get same pattern. Rinse and repeat Thats about the best I think you can do the sensitivity and accuracy of the test equipment probably will determine what you see.
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. Depending on the length of the coax and distance between the antennas you could have a pattern that ranges from cardioid to figure 8. Changing the length of coax (phase angle) will change the shape of the pattern.
It is important to remember if you see this interaction with both antennas active, then there is almost a guaranteed chance interaction exists when one antenna is a parasitic element and not driven with RF. Having them both active just causes a change in the pattern that is quickly noticeable and dependant on the phase delay in the coax. Pattern is effected much more then VSWR in many cases.
It is important to remember if you see this interaction with both antennas active, then there is almost a guaranteed chance interaction exists when one antenna is a parasitic element and not driven with RF. Having them both active just causes a change in the pattern that is quickly noticeable and dependant on the phase delay in the coax. Pattern is effected much more then VSWR in many cases.
Can't one make the reasonable assumption that what may affect the one antenna mounted within the 2 - 3 wl of each other will also affect the other? and if so then whatever readings one is getting due to those effects so is the other? If so, a simple cross reference would be to swap the mounting of both antennas to the the opposite masts and retest, then apply the data obtained by both tests for averages in each case?
Additionally, could the antennas not then be tested one at a time on each mast and the data be worked into the equation?
And, with respect to some stations no longer operational that were averaged into some previous data, why not compare the stations in every test, collate the data of only the stations operating in every test, and report results from those controls?
Just thinking out loud . . .
Additionally, could the antennas not then be tested one at a time on each mast and the data be worked into the equation?
And, with respect to some stations no longer operational that were averaged into some previous data, why not compare the stations in every test, collate the data of only the stations operating in every test, and report results from those controls?
Just thinking out loud . . .
Here are three Antenna Work Sheets with bandwidth curves one taken in 2009, and two taken recently in 2/2011.
The difference in the tests were the feed line in 2009, was 75'+, and the other two more recent test with the GM mounted side-by-side, and with the S4 mount by itself, used a 56'+ length. That may have affected the bandwidth difference noted, plus the 2009, test I installed a RF choke at the feed point.
I'm not sure this is a definitive answer to the question, but this is what I figured to do about the delima. I thought the match might be ill-affected in such an incident, and we could see the results in the curve presented. MrS, we at least agree on this part of the delima, as a starting point for consideration. Thanks,
I'm going to read Henry's post over again to see if I can understand what he is talking about, on first reading, it was all over my head.
View attachment Sigma4 Bandwidth Curves.pdf
Homber:
On the first part yes, you can assume that one will efect the other.
But it is how they will effect each other wich is "less predictable".
Take a look at a 2el beam.. a radiator with a longer reflector will show additional gain.
Vice versa aswell...if it is "seen" as a shorter one it will work as a director.
Now, thats just a simple explination..the goal is to get no interaction within each other.
Cross reference wont work accurate as you dont know where the system migth "dip" with closed spaced antennas under test.
The situation about testing one at a single time can only work when the receiving antenna is withing say..10..20 wl. (see my previous post).
Testing with different stations as earlier mentioned is on a "nice to know" base.
But true gain measurents should be done different (as earlier described.)
Shockwave:
To notice how the pattern changes when firing both antenna s up, you should be able to rotate the system 360 degrees. A single point reference is not usefull.
The idea of "co-phasing" is not relevant.
co-phasing can only be done with identical antennas. in this case we are comparing different antennas. Co-phasing non- identical antennas can lead to drastic loss in performance.
Neither can you just change the length of a coax cable..your rigth about changing the phasing angles but there are specific lengths for that purpose. And again you need to know what you are doing...for example the 75ohm cable i use for stacking wich should have a 0,85 velocity factor actually has 0,88 velocity factor. There are probarlby a couple guys reading this thread that could measure that but by far not all.
and yes, it is of big influence!..
But why make things more complicated?
The best way would just be to place them 2..3 wl apart.
Verify if SWR has changed and verify if your earlier gain measurments has changed.
Put the receiving antenna at 10..to 20 wl away and set a single antenna in between to pick up ground reflections.
Enjoy the weekend,
Henry
11 meter Dx antenna systemx
On the first part yes, you can assume that one will efect the other.
But it is how they will effect each other wich is "less predictable".
Take a look at a 2el beam.. a radiator with a longer reflector will show additional gain.
Vice versa aswell...if it is "seen" as a shorter one it will work as a director.
Now, thats just a simple explination..the goal is to get no interaction within each other.
Cross reference wont work accurate as you dont know where the system migth "dip" with closed spaced antennas under test.
The situation about testing one at a single time can only work when the receiving antenna is withing say..10..20 wl. (see my previous post).
Testing with different stations as earlier mentioned is on a "nice to know" base.
But true gain measurents should be done different (as earlier described.)
Shockwave:
To notice how the pattern changes when firing both antenna s up, you should be able to rotate the system 360 degrees. A single point reference is not usefull.
The idea of "co-phasing" is not relevant.
co-phasing can only be done with identical antennas. in this case we are comparing different antennas. Co-phasing non- identical antennas can lead to drastic loss in performance.
Neither can you just change the length of a coax cable..your rigth about changing the phasing angles but there are specific lengths for that purpose. And again you need to know what you are doing...for example the 75ohm cable i use for stacking wich should have a 0,85 velocity factor actually has 0,88 velocity factor. There are probarlby a couple guys reading this thread that could measure that but by far not all.
and yes, it is of big influence!..
But why make things more complicated?
The best way would just be to place them 2..3 wl apart.
Verify if SWR has changed and verify if your earlier gain measurments has changed.
Put the receiving antenna at 10..to 20 wl away and set a single antenna in between to pick up ground reflections.
Enjoy the weekend,
Henry
11 meter Dx antenna systemx
Here you go Homer. This is not the Sigma4 vs the GM, but the GM and the A99 should do. I extracted this information from previous test with the antennas mounted by them selves on both mounts, to compare the affects of the mounts.
I'm not really reading you mind Homer.
View attachment Gain Master & A99 Signal Reports compared on mounts.pdf
Even though the mount out back does show to be a bit more noisy, it seems to show a slightly better response. Maybe that is my mistakes, or it could be because out back is well into the clear. The new mount outside of my shack the antenna is mounted over my home.
Here is my S4 by itself on the new mount.
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SW, generally I only do RX signals on my reports, so I report only the receive signals between my station and my contacts. I will tell you however, that I can TX and it will affect just about every similar antenna within its range. So, does that make this discussion the meaningless chatter part that Cebik talked about?
Plus I need to be drinking whatever you're drinking so I too can see the patterns generated by my antennas. Did I miss something? If I'm corn'fused, please somebody help me out.
I won't be checking this with an SWR meter.
Notice: the analyzer meter I will be using is not perfect either, so don't expect too much, and maybe we'll get past all of this corn'fusion.
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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. Changing coax length in one antenna line will certainly shift the pattern. It could move a lobe right into the place a null was previously. However, there should be a significant change in pattern just connecting the two together that will be apparent on his S meter.
There is also no requirement that both antennas be the same type for them to interact. The goal here is not to make them interact in a predictable and desirable way. It is to prove there is interaction. I've done this test a few times and can guarantee that if he has stations in several directions to compare against, the change in pattern will be very evident just by combining the two antennas at any phase angle when compared to one being parasitic.
The phase angle or length of coax delay line only matters when you are trying to form a specific pattern. Otherwise any changes apparent in the pattern will confirm interaction. Marconi has already confirmed there are different length cables on both antennas. That eliminates the possibility of adding calculated 90, 135, or 180 phasing sections into the cable. I agree there is no predicting what this pattern will be however, I can predict it will be quite different then either antenna alone.
Near field interaction at 1 wavelength and your RF reaching any antenna within range are not the same. I see you have spent lots of time installing and testing these antennas and this is good. You need not be drinking anything to see the effects I'm talking about.
Since you do your testing on RX all you need is that T connector. Please take a few minutes to combine both antennas together and watch the RX signals change in various directions. With the T connector you can quickly add or remove the second antenna. Seeing is believing (most of the time).
Once you do this you may find an overwhelming desire to construct a predictable phased vertical antenna. Then you can steer that gain in the direction you want it. Patterns can easily be reversed in many cases just by changing the location of the delayed coax line to the other antenna.
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.
Would you assume testing for SWR with both antennas up then lowering one ? If you saw a change in SWR to me that would that mean there is some interaction between the 2? How about a FS meter walking around his plot ? We wouldnt have to speculate there are water towers in the way or some other man made attenuator effecting his signal. Or how about as you said better yet just test with one antenna up.
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
How is he going to check the pattern? with the s meter? or by ear? talking to guys he has no idea where they are from? Unfortunaly to me more uncontrolled testing solves nothing excepts add more variables to the mix.
Don't you think if he connects both antennas together whether they are 36' apart or 200 feet will change his pattern? Whether it is acting in phase or not.
Lower one antenna and get a good way to view signal strength do some testing for a week, put up other antenna in same location check signals again using same coax etc. If for your gonna say the signals change over a week avg them over a weeks time. I dont see signals change from weeks to months at a time but I dont have all the variables you guys seem to have.
Please for the love of god Test with one antenna, one piece of coax and one location. After that If you feel the need then retest them both one at a time in your other location on your property.
Whatever the value of this may be, it sounds cool. I may play with this just for the fun of it.
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