I am in need of tuning information on the Avanti Moon Raker 4
As some of you know I am in the process of putting up a new tower and antenna,( moonraker 4 on a tower, top of antenna calculated to be at 74')
I have the Avanti construction book and it gives very detailed construction details but little tuning information, any one with experience ???
Also i need to know if there are 2 versions of gamma matches for the MR4.. The set of gamma matches on my MR 4 are different from the ones shown in the assembly manual, mine are pre bent and don't use the adjustment studs/bolts as shown...... this makes it difficult to find a starting point to tune from...
also the measurements in the manual are way off..compared to where mine are mounted currently...
I have the antenna assembled ( on a 10' pole for assembly and tuning), after partial dis-assembly for take down, transportation, and light maintenance.
During re-assembly, I have noticed a few differences between the manual and the actual antenna.......gamma matches shape, mounting measurements, and adjustments are the main ones that I am concerned with........
Also need to know, when adjusting the gamma matches for SWR adjustment, if the MR4 will respond to the adjustments on the ground ( on a 10' pole for assembly and tuning)
Also would like to hear from other MR4 owners for any " do this on the ground before raising " issues
what kind of SWR reading should i have when tuned properly?
the initial SWR readings are not off the scale, but are a little higher than i had expected....
Thanks in advance for all of the help form the forum members
RANGER
Need tuning information on MOONRAKER 4
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ranger6900
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231
Re: Need tuning information on MOONRAKER 4
linx would be a good one to ask on this too by the way. So if you don't see him post, PM him.
First off you can download the Antenna Specialist version of the instruction manual (they bought out Avanti) at cbtricks.com. I would do that and compare them to the instruction manual you currently have.
It's been a little while, but the only gammas on the MR4 I've ever seen bolted to the hub via a bracket and swivel over to the element. You adjust the length of the gamma itself and element connection point to the driver element to adjust for minimum SWR. The element lengths can be slightly adjusted to suit the portion of the band you want to run, but typically factory recommended lengths are pretty good for the entire 11m band.
As far as tuning on the ground, that is the way I do it...on a 10-12' pole secured and away from reflective items (i.e. metal roofs, pole barns, wire fences, etc.). I've always been able to get the MR4 under 1.5:1 on the horizontal, maybe a tad more (1.6:1?) on vertical or so. Usually the standing wave will drop some once in the air.
I usually will leave my beams down for a week or so to make sure the f/b and f/s ratios are working properly...or rather, as well as can be expected being it's not in free space. That allows me to make minor adjustments to it as I go along. The Antenna Specialist instructions are pretty good, and the last "new" MR4 I put together is still up and in tact after 15 years.
First off you can download the Antenna Specialist version of the instruction manual (they bought out Avanti) at cbtricks.com. I would do that and compare them to the instruction manual you currently have.
It's been a little while, but the only gammas on the MR4 I've ever seen bolted to the hub via a bracket and swivel over to the element. You adjust the length of the gamma itself and element connection point to the driver element to adjust for minimum SWR. The element lengths can be slightly adjusted to suit the portion of the band you want to run, but typically factory recommended lengths are pretty good for the entire 11m band.
As far as tuning on the ground, that is the way I do it...on a 10-12' pole secured and away from reflective items (i.e. metal roofs, pole barns, wire fences, etc.). I've always been able to get the MR4 under 1.5:1 on the horizontal, maybe a tad more (1.6:1?) on vertical or so. Usually the standing wave will drop some once in the air.
I usually will leave my beams down for a week or so to make sure the f/b and f/s ratios are working properly...or rather, as well as can be expected being it's not in free space. That allows me to make minor adjustments to it as I go along. The Antenna Specialist instructions are pretty good, and the last "new" MR4 I put together is still up and in tact after 15 years.
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ranger6900
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mr4 adjsutments
231 I have the antenna specialist assembly manual same as your reference any idea where i can find the other ?
also do you know which way the gamma's should move to lower swr the adjustments on mine are fragile and i don't want to move them over and over
my swr's are generally higher on the low side both vert and hor.
all help appreciated
Ranger
also do you know which way the gamma's should move to lower swr the adjustments on mine are fragile and i don't want to move them over and over
my swr's are generally higher on the low side both vert and hor.
all help appreciated
Ranger
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linx
Hi there,
Ranger, is there any chance you can take a picture of what your gamma matches look like? They could have come off of anything from a Gizmotchy to a Maco and work on the MR4. I am running the stock gamma matches and mine are set about half way down the rod.
That manual on CBTricks is identical to the ones that ship with the MR4. My BEST recommendation I can give you is to put it together perfectly as that manual says. If it says an element needs to be 96 1/8th of a inch long, then be sure it's 96 1/8th of an inch long and not 96 1/4 inch long. If you set the beam up to be exactly as Avanti recommends then you will have a lot less problems. Also, when putting it together, be gentle with the hubs...once you break one of them you are out of commission. You can usually find them used, but not always.
Here's what I did. I set my MR4 about 15 ft off the ground, and actually built it about 15 ft off the ground. It was a pain, but the measurements are 100% on the money. I plugged in the coax to each side, and set the SWR's with the exact piece of coax I was going to use in service. On the ground, I got the SWR's to about 1.2. We hoisted mine in the air, and at 55 or so feet, the SWR's are about 1.1...maybe get up to 1.2 on some frequencies.
I have a friend that builds a lot of beams and he uses a big truck Rim/Tire with a 10 ft piece of pipe welded onto the center of the rim. That works real nice too.
The stock gamma matches are pretty self explanatory...all you have to do is slide the tuning ring around. 231 is right, they attach to the hub for that driven element.
I don't feel like I was much help, but show me a picture and I can be. I think this is about the best CB antenna eve made.
My Gamma's look identical to the ones in the Moonraker assembly manual. There's some replacements available via eBay that are higher power handling that work nice too.
In the MR4 manual there's a pic that pretty well shows you the numbers on where to position it to get it dead on the money...this worked great for me.
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Ranger, is there any chance you can take a picture of what your gamma matches look like? They could have come off of anything from a Gizmotchy to a Maco and work on the MR4. I am running the stock gamma matches and mine are set about half way down the rod.
That manual on CBTricks is identical to the ones that ship with the MR4. My BEST recommendation I can give you is to put it together perfectly as that manual says. If it says an element needs to be 96 1/8th of a inch long, then be sure it's 96 1/8th of an inch long and not 96 1/4 inch long. If you set the beam up to be exactly as Avanti recommends then you will have a lot less problems. Also, when putting it together, be gentle with the hubs...once you break one of them you are out of commission. You can usually find them used, but not always.
Here's what I did. I set my MR4 about 15 ft off the ground, and actually built it about 15 ft off the ground. It was a pain, but the measurements are 100% on the money. I plugged in the coax to each side, and set the SWR's with the exact piece of coax I was going to use in service. On the ground, I got the SWR's to about 1.2. We hoisted mine in the air, and at 55 or so feet, the SWR's are about 1.1...maybe get up to 1.2 on some frequencies.
I have a friend that builds a lot of beams and he uses a big truck Rim/Tire with a 10 ft piece of pipe welded onto the center of the rim. That works real nice too.
The stock gamma matches are pretty self explanatory...all you have to do is slide the tuning ring around. 231 is right, they attach to the hub for that driven element.
I don't feel like I was much help, but show me a picture and I can be. I think this is about the best CB antenna eve made.
My Gamma's look identical to the ones in the Moonraker assembly manual. There's some replacements available via eBay that are higher power handling that work nice too.
In the MR4 manual there's a pic that pretty well shows you the numbers on where to position it to get it dead on the money...this worked great for me.
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ranger6900
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MR 4
HI LINX
Thanks for responding
the gamma match that I have looks like the ones on the MR6 ( in the MR 6 assembly manual)
i have attached a file with a drawing of it ..... couldn't get a pic yet but will if needed
also the gamma matches were not removed or disturbed during the take down, transit, or reconstruction, they are in the same exact location they were in for the last 20 + years figured they would be close if they were not disturbed but the measurements in the manual and the location they are in now are 2-3" off
other than the gamma's all other parts are spot on.......and the measurements for re assembly are spot on as well ....
have not bought new coax yet (planning to ) so I'm using what i have rg8u in good shape but diff lengths
This was the first test of the antenna after re assembly..........I was expecting some issues....
thanks again
RANGER
Thanks for responding
the gamma match that I have looks like the ones on the MR6 ( in the MR 6 assembly manual)
i have attached a file with a drawing of it ..... couldn't get a pic yet but will if needed
also the gamma matches were not removed or disturbed during the take down, transit, or reconstruction, they are in the same exact location they were in for the last 20 + years figured they would be close if they were not disturbed but the measurements in the manual and the location they are in now are 2-3" off
other than the gamma's all other parts are spot on.......and the measurements for re assembly are spot on as well ....
have not bought new coax yet (planning to ) so I'm using what i have rg8u in good shape but diff lengths
This was the first test of the antenna after re assembly..........I was expecting some issues....
thanks again
RANGER
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linx
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ranger6900
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gamma matches on MR4
Linx
yes they look like that
also did more investigation this afternoon and tuning
was able to get vertical SWR down to 1.6 on 1 and 1.6 on 40 so i feel good about that
the horizontal is about 1.7 on 1 and 1.8 on 40 not to bad there either
the gamma measurements in the assembly manual were off about an inch on both vert and horiz. from where i ended up during the adjsutments
did find a piece of defective coax removed and used same coax to tune vert and hor SWR. made a huge difference ..
have Not measured the lengths of coax needed from antenna to base radio YET,
so i can probably get the SWRs lower (fine tune a bit more) just prior to tower lift and hookup after i get that measurement.
also thinking about installing a balun in both lines vert and hor .........
I did have to disassemble the gamma attachment on the radials (was thinking i would, but put it off untill i had to)
also there are a few little details that i need to finish up and double check the final measurments on elements and such
getting closer
tried to add an image (photo of my antenna ) dont know if it will work or not
Ranger
yes they look like that
also did more investigation this afternoon and tuning
was able to get vertical SWR down to 1.6 on 1 and 1.6 on 40 so i feel good about that
the horizontal is about 1.7 on 1 and 1.8 on 40 not to bad there either
the gamma measurements in the assembly manual were off about an inch on both vert and horiz. from where i ended up during the adjsutments
did find a piece of defective coax removed and used same coax to tune vert and hor SWR. made a huge difference ..
have Not measured the lengths of coax needed from antenna to base radio YET,
so i can probably get the SWRs lower (fine tune a bit more) just prior to tower lift and hookup after i get that measurement.
also thinking about installing a balun in both lines vert and hor .........
I did have to disassemble the gamma attachment on the radials (was thinking i would, but put it off untill i had to)
also there are a few little details that i need to finish up and double check the final measurments on elements and such
getting closer
tried to add an image (photo of my antenna ) dont know if it will work or not
Ranger
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231
Sorry, I had to hit the road. Glad to see linx jumped in there.
Yep...he's right. Looks to me like you need to adjust the gammas a little still, too. And if the antenna has been up that long, you really need to take the gamma's (at least) and element joints apart and clean them completely...especially the SO-239 connections. That is sort of a normal thing that should be done every several years anyway. If it was just serviced prior to taking it down, then you should be okay. But the thing about aluminum is, joints that are corroded won't conduct. A good 3M pad will work on the joints and cleans them right up (typically).
And I too will stress the being careful with the hubs. They need to be tight on there to seat to the boom. BUT, it's VERY easy to over tighten the bolts and break an ear off. What I do with MR's is add a SS hose clamp around the entire two hubs where the nut/bolt are. Snug it up a little, snug the bolt a little, then the clamp, then the bolt, etc. until it's snug on the boom, but doesn't collapse the boom. This helps distribute the torgue of the bolt being tightened up to more of the entire hub assembly...not just the bolt ears (where they usually break). New hardware is recommended if there is even a hint of corrosion on the current parts. Di-electric grease on the joints, followed by shrink wrap and/or quality electrical tape will help keep the moisture (and corrosion) out...especially on the gamma's.
Just a couple of things I've done over the years that really helps it withstand the weather.
Good luck.
Yep...he's right. Looks to me like you need to adjust the gammas a little still, too. And if the antenna has been up that long, you really need to take the gamma's (at least) and element joints apart and clean them completely...especially the SO-239 connections. That is sort of a normal thing that should be done every several years anyway. If it was just serviced prior to taking it down, then you should be okay. But the thing about aluminum is, joints that are corroded won't conduct. A good 3M pad will work on the joints and cleans them right up (typically).
And I too will stress the being careful with the hubs. They need to be tight on there to seat to the boom. BUT, it's VERY easy to over tighten the bolts and break an ear off. What I do with MR's is add a SS hose clamp around the entire two hubs where the nut/bolt are. Snug it up a little, snug the bolt a little, then the clamp, then the bolt, etc. until it's snug on the boom, but doesn't collapse the boom. This helps distribute the torgue of the bolt being tightened up to more of the entire hub assembly...not just the bolt ears (where they usually break). New hardware is recommended if there is even a hint of corrosion on the current parts. Di-electric grease on the joints, followed by shrink wrap and/or quality electrical tape will help keep the moisture (and corrosion) out...especially on the gamma's.
Just a couple of things I've done over the years that really helps it withstand the weather.
Good luck.
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ranger6900
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- Joined: Feb 10 2008, 18:25
great ideas 231 thanks
should get new coax today and will see how it effects the reading tonight...
also plan on refurbishing the coax connectors on the antenna this evening also
i knew going in that this would be slow going, and have to pay great attention to detail,
only wish there were more printed information available about the antenna.
also thanks linx for the help
i tried to add a photo ........couldnt get there................lol
maybe some one can coach me thru it
Ranger
should get new coax today and will see how it effects the reading tonight...
also plan on refurbishing the coax connectors on the antenna this evening also
i knew going in that this would be slow going, and have to pay great attention to detail,
only wish there were more printed information available about the antenna.
also thanks linx for the help
i tried to add a photo ........couldnt get there................lol
maybe some one can coach me thru it
Ranger
