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Old 12-15-2011, 4:14 PM
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Default Setting up I-maxx 2000, How can I set it up to be most efficient?

Ordered an I-max 2000 Friday and still waiting for it to get here even though I opted for 2 day delivery, Anyway, What is the most efficient way I can set this antenna up? Its going to be mounted to a 13 ft. fence post. Really, 8 ft. then with 2 huge @55 u-bolts to a 5 ft. post in the ground. All galvanized. In January I'm planning on driving a 4-6 ft. copper rod into the ground and grounding the whole setup to it. Anything I should do besides that? Why until January you ask? The I-max wiped my budget for radio until then.
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Old 12-15-2011, 6:56 PM
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Quote:
Originally Posted by Cruiseomatic View Post
Ordered an I-max 2000 Friday and still waiting for it to get here even though I opted for 2 day delivery, Anyway, What is the most efficient way I can set this antenna up? Its going to be mounted to a 13 ft. fence post. Really, 8 ft. then with 2 huge @55 u-bolts to a 5 ft. post in the ground. All galvanized. In January I'm planning on driving a 4-6 ft. copper rod into the ground and grounding the whole setup to it. Anything I should do besides that? Why until January you ask? The I-max wiped my budget for radio until then.
IF possible i would mount it on the side of your house and then running the ground wire to the rod [remember the higher the better] 13 feet is not a good height for a base. You can mount it on a chimney or on the eve of your house [again IF possible] with 10 to 20 feet of mast and it would be better.

Just curious WHAT radio are you gonna get? Are you thinking a mobile rig with a power supply or are you thinking or spending the big bucks and getting one of them export rigs with oodles of illegal extra channels? Best thing is to get a simple radio [Sideband on it if you wish] and call it good.
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Old 12-15-2011, 8:27 PM
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If you want to ground the antenna to code the ground rod will have to be bonded to the house ground point with #6 wire. Check NEC article 810 for antenna grounding.

Getting the antenna at multiples of 1/2 wavelength above ground will help concentrate the radiated signal closer to the horizon and about 18ft would be the lowest for that with 36ft being the next goal for CB band.
prcguy
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Old 12-15-2011, 9:49 PM
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13 feet is not really high enough to mount an antenna like an Imax 2000. You can do it, but you're just asking for SWR and RFI issues. I use an Antron 99 and had my antenna mounted at that height for about a year or so. Once I pushed it up to about 22 feet to the base of the antenna my receive and transmit improved a lot. As prcguy said, the closer you get to 36ft. the better; every little bit that gets you closer to 36ft. makes a difference.

If I were you I'd mount it to sections of fencing top rail if you're looking for a budget setup. Use cement to put the bottom 2.5 feet of a section of top rail in the ground. Top rail is about $10 per 10ft section at Lowe's. You can use it up to about 25 feet in height without it bending. One of the locals here managed to get 36ft with nothing but top rail, although I definitely wouldn't reccomend it at all. Conduit also works and is somewhat stronger. It really just depends on where you're putting the antenna. You may be able to mount it to your house instead.
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Old 12-16-2011, 12:01 AM
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The Imax 2000 is a 5/8 wave vertical, so mounting 1/4 wave above the ground will work. This isn't VHF, where you need line-of-sight. The post in the ground will ground the mast (and the antenna if you bond the coax shield to the mast). But as prcguy said, if you want it to code, mount it insulated from the ground and run a ground braid to your house ground. You could use a PVC pipe in the ground, or you could mount the mast to the house. Just don't mount a metal pipe in the ground and bond it to the house ground. If anything survives the fire (when you get hit by lightning), the insurance company won't pay.
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Old 12-16-2011, 9:21 AM
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I didn't say to insulate the antenna or mast from house ground. I don't have the NEC in front of me but TV and CB antennas, satellite dishes, etc are supposed to be grounded to the main house ground with no more than about 25-30ft of #10 copper wire. A mast on the side of a house is usually not considered a ground rod but it would not hurt to bond that to a nearby ground rod with the NEC specified method which includes bonding the ground rod to the house ground with #6 copper wire.

All antennas, vertical or horizontal, 1/4 wave, half wave, 5/8, etc will put more signal at the horizon when mounted at multiples of a half wavelength above ground. This is good for local and DX contacts and height is just as important for line of site CB range as higher VHF and UHF frequencies.
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Originally Posted by W2PMX View Post
The Imax 2000 is a 5/8 wave vertical, so mounting 1/4 wave above the ground will work. This isn't VHF, where you need line-of-sight. The post in the ground will ground the mast (and the antenna if you bond the coax shield to the mast). But as prcguy said, if you want it to code, mount it insulated from the ground and run a ground braid to your house ground. You could use a PVC pipe in the ground, or you could mount the mast to the house. Just don't mount a metal pipe in the ground and bond it to the house ground. If anything survives the fire (when you get hit by lightning), the insurance company won't pay.
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Old 12-16-2011, 11:59 AM
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Quote:
Originally Posted by prcguy View Post
IAll antennas, vertical or horizontal, 1/4 wave, half wave, 5/8, etc will put more signal at the horizon when mounted at multiples of a half wavelength above ground. This is good for local and DX contacts and height is just as important for line of site CB range as higher VHF and UHF frequencies.
prcguy
With VHF and up, the higher (within limits, but 500 feet AAT isn't too high) the better. At 30MHz and below, halfwave multiples are more important than absolute height. (Too high is actually worse than too low.) So is the ground under the antenna. (VHF and above antennas usually have their own ground planes, so soil conductivity is irrelevant. At 27MHz it makes a difference.)
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Old 12-16-2011, 9:02 PM
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I have never had an antenna that was 'too high' (except in cost). I have to think that there are specific reasons for not getting an antenna as high as possible, but in general, I honestly can't think an HF antenna can be too high. It can certainly change the radiation characteristics, but that's not such a bad deal in all cases. I can also see that there are practical aspects that can determine the 'usable' height of any antenna. I figure something on the order of a 1/4 mile would 'do' me just dandy! But the practical a$pect$ of that are daunting, $ort of...
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Old 12-16-2011, 9:11 PM
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"13 feet is not really high enough to mount an antenna like an Imax 2000. You can do it, but you're just asking for SWR and RFI issues."

I doubt SWR would be a significant issue but at that height you have a grass burner. Simply put you really don't want electronics in the near field where they can radiate noise into the antenna and transmitted signals can interfere with them.

"As prcguy said, the closer you get to 36ft. the better; every little bit that gets you closer to 36ft. makes a difference."

Agreed, technically an antenna mounted one wavelength above ground or more won't have ground reflections skewing the vertical radiation angle. What you have here is a .64 wavelength antenna that has a low angle to begin with, ground reflections recombining with the direct wave will only serve to raise it wasting energy skyward. The whole idea behind an omnidirectional antenna having "gain" is in the ground hugging angle, why ruin it?

Hint; a low angle over the horizon refracting off the ionosphere comes back to Earth much farther away, really great for long distance skip during a band opening. Use power efficiently and you won't need an illegal amplifier, remember if you can't hear 'em you can't work 'em.

"I use an Antron 99 and had my antenna mounted at that height for about a year or so."

That's the antenna that inspired the Imax and frankly is a vast improvement. Being an "antenna specialist" for many years <blush> it comes as no surprise that sooner or later the CB market would copy what the broadcast industry has known for years. Here, you may find this interesting:
The Imax 2000 EXPOSED!
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Old 12-16-2011, 11:20 PM
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Very interesting, Warren.
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Old 12-17-2011, 1:13 PM
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Got it up and installed, Man the skip its picking up this morning is killer! Problem is, On AM, SWRs are all 1.1or below. However, On SSB they go to 1.1 or 1.2 with only 12 watts maybe higher if I were pushing more than 12. Could this be coax leaking or extreme loss? I've got a balun directly under the feedpoint. If I were to replace my coax, What should I go with? Also, Is it bad that I can hear the outer shield or braid when I flex the coax?
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Old 12-17-2011, 1:36 PM
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If it were me, I wouldn't worry about it. Generally anything less than around 1.5 is acceptable. If you're hovering around 1.1 on AM then I wouldn't worry about it. Also, checking your SWR in SSB mode is really a waste of time. To check your SWR you need to have a steady unvarying tone which you have on AM, but not on SSB. The reason you're getting a higher SWR in SSB is because the radio is putting out more power in SSB mode which will sometimes give you a slightly higher SWR. So check the SWR on AM and if it's fine there, then it will be fine on SSB too.

What kind of coax are you using? Clearly there's not a problem with it since your SWRs are normal, but I'm still curious.
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Old 12-17-2011, 2:05 PM
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At first, RG-58/U Foam with a barrel connector in it, then to a RG-8 mini with barrel connector going to the balun which feeds the antenna. Basically:

RG-58/U Foam - Barrel connector - RG-58/U Foam - Barrel connector - RG-8X mini - Barrel connector - RG-8X mini balun - antenna
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Old 12-17-2011, 2:08 PM
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SWR is not a function of operating mode and if your calibrated the meter in AM mode then it will show a proportionately higher SWR reading on SSB peaks because your putting out 2 or 3 times more power than you calibrated with. That would be normal.

Even at 1 wavelength above ground all antennas will still have the radiating pattern skewed upward a little compared to "free space" but 1 wavelength high is a whole lot better for putting signal at the horizon than lower.

There are times when you want a low dipole for saturating an area out to a few hundred miles on HF using NVIS, but thats not possible on CB are rarely below about 10MHz. The ideal height for NVIS is about 1/4 wavelength above ground or lower.
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Old 12-17-2011, 4:55 PM
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Quote:
Originally Posted by Cruiseomatic View Post
At first, RG-58/U Foam with a barrel connector in it, then to a RG-8 mini with barrel connector going to the balun which feeds the antenna. Basically:

RG-58/U Foam - Barrel connector - RG-58/U Foam - Barrel connector - RG-8X mini - Barrel connector - RG-8X mini balun - antenna
That's quite a bit of connections there. If the SWR is fine then that setup should be fine. If I were you I'd try and waterproof any of your exposed connections just to keep water from getting in.
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Old 12-17-2011, 6:00 PM
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Quote:
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That's quite a bit of connections there. If the SWR is fine then that setup should be fine. If I were you I'd try and waterproof any of your exposed connections just to keep water from getting in.
Believe me I know, Lol. Reason is, The RG-8U/Foam had to be cut to be removed then the remainder was eventually recovered. Had new PL-259 connectors put on them and re-used them. It was to short so I needed anouther "jumper" to reach the pole then it was to short to make the balun so ANOTHER jumper was needed to make it. I wrapped all the connections in electrical tape so in a lightning storm, even with the 10awg wire to 6ft. ground rod, before when or if lightning hits, I can disconnect the last barrel connector before the pole and let it swing and the house be fine. I would love to get it above the house but is out of the question. House needs a new roof and it would cost little over $5,000. Can't walk on it. And would also love to have one piece coax run from a outside disconnect to the feedpoint but coax the caliber I'm wanting to get is expensive. Believe it or not, Even with the "Maxx2000" only 15 actual ft. from dirt level, I have low SWRs and no RFI. I did figure out from reading the previous post about SSB. I sent a continuous tone and re-calibrated the meter, Peak SSB was the same as AM. And according to solarcon's box and book, It is a Maxx2000 not IMax. And it looks like the Antron 99 is now Maxx99.
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Old 12-18-2011, 8:55 AM
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Hello Warren: Need some clarification here:

You said: "That's the antenna that inspired the Imax and frankly is a vast improvement. Being an "antenna specialist" for many years <blush> it comes as no surprise that sooner or later the CB market would copy what the broadcast industry has known for years. Here, you may find this interesting: The Imax 2000 EXPOSED! "

Just what is it the Broadcast Industry has known for years?

Jay Mojave

Added in here: Here is a good web site that talks about the end feed antennas
http://www.w8ji.com/end-fed_vertical.htm

Last edited by JayMojave; 12-18-2011 at 9:19 AM.. Reason: adding in more good stuff
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Old 12-18-2011, 11:25 AM
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I'll take a stab and say he's probably referring to a .64 wavelength antenna, which puts the most signal at the horizon for a non collinear vertical. However there is no ground plane with the Imax, so it will not achieve the maximum benefit of of the .64 wavelength.
prcguy

QUOTE=JayMojave;1663338]Hello Warren: Need some clarification here:

You said: "That's the antenna that inspired the Imax and frankly is a vast improvement. Being an "antenna specialist" for many years <blush> it comes as no surprise that sooner or later the CB market would copy what the broadcast industry has known for years. Here, you may find this interesting: The Imax 2000 EXPOSED! "

Just what is it the Broadcast Industry has known for years?

Jay Mojave

Added in here: Here is a good web site that talks about the end feed antennas
End-fed Vertical and J-pole[/QUOTE]
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Old 12-18-2011, 2:08 PM
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Well, prcguy pretty much said it plus a little more that's been on my mind but haven't said until now as not to confuse the issue prematurely. A set of 1/4 wave radials would complete the package but make for a HUGE and rather cumbersome antenna. Seems to me they sacrificed just a tiny bit of performance for marketability but leave it up to some enterprising CBer to complete the package with fence wire and duct tape. (;->)

As a footnote, when it comes to AM broadcast towers the .64 wavelength is not the ultimate market blanket. When KDKA replaced their tower they experienced severe audio distortion in a portion of their regional coverage area at night where ground wave and sky wave recombined. That was a few years ago, probably fixed by now after wrangling with the FCC red tape. It only goes to show that what looks good on paper doesn't always work in practice or to put it another way, the best laid plans of mice and men sometimes get pregnant.
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Old 12-18-2011, 4:10 PM
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Yup, looks like my radio brother Warren and I are thinkin the same these days. Must of been that trip I had through NJ last week....
prcguy


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Well, prcguy pretty much said it plus a little more that's been on my mind but haven't said until now as not to confuse the issue prematurely. A set of 1/4 wave radials would complete the package but make for a HUGE and rather cumbersome antenna. Seems to me they sacrificed just a tiny bit of performance for marketability but leave it up to some enterprising CBer to complete the package with fence wire and duct tape. (;->)

As a footnote, when it comes to AM broadcast towers the .64 wavelength is not the ultimate market blanket. When KDKA replaced their tower they experienced severe audio distortion in a portion of their regional coverage area at night where ground wave and sky wave recombined. That was a few years ago, probably fixed by now after wrangling with the FCC red tape. It only goes to show that what looks good on paper doesn't always work in practice or to put it another way, the best laid plans of mice and men sometimes get pregnant.
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