| Author |
Message |
    
Marconi
Intermediate Member
Username: Marconi
Post Number: 329
Registered: 11-2001
| | Posted on Monday, January 24, 2005 - 3:51 pm: | 
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Has anyone ever used an MFJ type antenna analyzer when tuning a Signal Engineering beam? |
Tech808
Moderator
Username: Tech808
Post Number: 4621
Registered: 8-2002
| | Posted on Monday, January 24, 2005 - 7:37 pm: |
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Marconi,
No I did not use one when I assembled my SE White Lighting 4.
We set everything on the Ground before we even took it up the tower.
What I did use was my
Palomer Engineers R-X Noise Bridge and still have a 1:2 on Vert and a 1:1 on Horz after being up for 2 years now. 
Lon
Tech808
CEF808
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Marconi
Intermediate Member
Username: Marconi
Post Number: 330
Registered: 11-2001
| | Posted on Thursday, January 27, 2005 - 1:56 pm: |
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Hey Lon, thanks for the reply. I will get back, but I have always had a problem using a Noise Bridge to tune and unknown load.
I do know that if you could see positive type results on your beam with that device while tuning it from scratch then an analyzer should also be useful as well.
Got to run for now, but I have some thoughts, questions, and ideas on all this, if you have time later. |
Marconi
Intermediate Member
Username: Marconi
Post Number: 349
Registered: 11-2001
| | Posted on Wednesday, February 02, 2005 - 2:26 pm: |
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833, as I said earlier I have never had much luck tuning an unknown using a Noise Bridge, unless I was lucky and had the setting real close to resonance right off the bat.
I noticed that every time I made a change in line length anywhere in the system the null settings would also change. Again, unless I was real close, that told me that the line makes a big difference when trying to tune an unknown.
With this device you have to use a transmitter. That being the case you must also use a line, and therein lies my contention that this device is not practical for tuning an unknown.
I don't question that this device can indicate that you are near resonance, but if you find the very best null possible, you can then advance the frequency up or down, maybe as much as a meg or more, and still see about the same null. Plus my R-X always come in sweet to the lower end of the band width it sees, not even near the middle. How close is that? Maybe it is close enough, but I'm not convinced. It is afterall within the bandwidth of the load and maybe that is all we really need, but it is likely not the true resonance we thought. My instructions give some business about making a plot and it is suggested that the band spread for difference is on the order of 50 KHz, but I surely haven't found that to be anywhere near the case. Maybe 1000 KHz is more like it and that is not close.
Another obvious problem with using this device is that conditions must cooperate or you cannot detect the null very well due to the noise level. That can be frustrating if you are hanging off the side of a tower trying to tune.
I guess it all goes back to the old question
"Does line length matter?" For me it sure does in this case, and this device requires at least one line to the transmitter.
Am I missing something? I looking to learn something about this interesting little device. So how about some tips, how do you do it? |
Tech808
Moderator
Username: Tech808
Post Number: 4725
Registered: 8-2002
| | Posted on Wednesday, February 02, 2005 - 4:18 pm: |
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Marconi,
Maybe I did mine a little different than most.
I already had the coax assembled, run and connected to everything before the antenna went up the tower.
We assembled the antenna in the bed of our truck on a stepladder and connected all coax there, and then we drove it back across the street and raised it to the roof and clamped it to the tower for the initial settings/adjustments.
We then raised it to the top of tower and mounted it, and it took one minor adjustment, which took less than a minute at the top of the tower.
I personally found the measurements listed in the assembly instructions for the SE White Lightning to be very precise and close after assembly to start with.
This also allowed me to have the RX noise bridge inside the house at the radio so outside noise / interference was -0-
In over 2 years now they still have a 1:1 on Horz and a 1:2 on Vert on the SE's.
Recently we added another tower for the Imax and did the exact same thing by having everything assembled before it went up the tower.
When the IMAX went into the air all Redman CEF 156 had to do was bolt it to the mast pipe.
Just my personal experience using my RX Noise Bridge.
All I can say is it works for me.
Lon
Tech808
CEF808
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 |
Chad
Intermediate Member
Username: Chad
Post Number: 127
Registered: 11-2004
| | Posted on Thursday, February 03, 2005 - 9:07 am: |
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Lon,
What did you put your Imax on? I'm tower shopping!
Chad |
Tech808
Moderator
Username: Tech808
Post Number: 4729
Registered: 8-2002
| | Posted on Thursday, February 03, 2005 - 10:26 am: |
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Chad,
At first it was on the tower (Rohn 25G) at 54' with my SE Quads on a standoff.
Now it is on its own tower also (Rohn 25G) at 36'
Lon
Tech808
CEF808
N9OSN |
Chad
Intermediate Member
Username: Chad
Post Number: 128
Registered: 11-2004
| | Posted on Thursday, February 03, 2005 - 10:51 am: |
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Lon, that's about exactly as high as i was going to go. I was thinking a 40' tower sunk 4' into the ground. Where's the best place to find them? Would a used country-bumpkin TV tower work well? Not much wind load on an Imax!
No offense to the country-bumpkins, I'm one so I see them as plentiful. Just look for then new dish network antennas with the local receive, they are easy to spot  |
Tech808
Moderator
Username: Tech808
Post Number: 4731
Registered: 8-2002
| | Posted on Thursday, February 03, 2005 - 11:00 am: |
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Chad,
Just drive around and look for any towers with nothing on them and offer to take them down for the people.
Homeboy CEF #159 was moving and gave me the Second Rohn 25G tower as he had it laying behind his garage from where someone had given it to him.
With cable tv now a lot of people do not use them anymore and are glad to get rid of them.
Lon
Tech808
CEF808
N9OSN |
Marconi
Intermediate Member
Username: Marconi
Post Number: 350
Registered: 11-2001
| | Posted on Thursday, February 03, 2005 - 9:30 pm: |
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Hey Lon, what was your reason for building the antenna on the bed of a truck and for sure why did you go accross the street to do it?
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Chad
Intermediate Member
Username: Chad
Post Number: 129
Registered: 11-2004
| | Posted on Thursday, February 03, 2005 - 9:36 pm: |
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Well, It's suposed to be nice this weekend, Might be a good time to take the boy for a drive in the country and look around
That was my original plan, a little elbow grease and it could look like new!
Chad |
Tech808
Moderator
Username: Tech808
Post Number: 4749
Registered: 8-2002
| | Posted on Friday, February 04, 2005 - 4:57 pm: |
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Marconi,
The 1st Sargant and I assembled both sections in the carport and then moved them from under the carport across the street to join them together on top of the ladder in the bed of the truck.
By placing the ladder in the back of the pickup we were able to assemble the complete antenna and have it high enough off the ground that the elements were not getting dragged all over the place and check the wire tension on the spreaders.
And it allowed us to double & triple check everything before even trying to raise it.
It also made it a LOT easier to just back across the street with everything including the coax already attached and hand it to the guy's on the roof.
By having everything done before it went up the tower it took Redman, Beerman, Homeboy and Raven less than 15 minutes to get it mounted 60' up.
1 Climb & 1 Time up the tower does it all.
Lon
Tech808
CEF808
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