I might have said it badly Bob. I didn't mean you weren't convinced with what W8JI wrote, I meant that you didn't agree with my idea about what he wrote. That's why I said at the end of the sentence, "...like I was, so I could be wrong."
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IMAX 2000 ?
- Thread starter IDIeselman
- Start date
I might have said it badly Bob. I didn't mean you weren't convinced with what W8JI wrote, I meant that you didn't agree with my idea about what he wrote. That's why I said at the end of the sentence, "...like I was, so I could be wrong."
Well it looks like I will be going up a couple more times, as I have no test equipment and must rely on trial and error:redface: I will eliminate the balum and look for any change before I ground the antenna. With my limited knowledge and equipment I wish I would have just followed the manufacturers directions in the first place, although I do have 4 102" whips leaning in the corner of the garage I could install and really cause myself more misery. Here is a pic of the antenna/balum incase something stands out as incorrect.
Well it looks like I will be going up a couple more times, as I have no test equipment and must rely on trial and error:redface: I will eliminate the balum and look for any change before I ground the antenna. With my limited knowledge and equipment I wish I would have just followed the manufacturers directions in the first place, although I do have 4 102" whips leaning in the corner of the garage I could install and really cause myself more misery. Here is a pic of the antenna/balum incase something stands out as incorrect.
I can't tell from the image, but is the choke a part of the feed line, or does it use connectors top and bottom to connect to the antenna and the feed line?
If that coax loop hanging down is the lead wire to the feed point, then it is way too long and is probably radiating like gangbusters, even if the choke below is working like intended which I doubt.
IMO the lead end of the coaxial choke does need to be right at the feed point and the closer the better.
Some PVC also has iron ore or some other metal in the mix to add strength and conductivity, and for sure maybe with schedule 40 type, but I'm not sure. I would check this PVC in a microwave for a few seconds to see if it gets hot. I don't know what it will do to your antenna system, but I have heard this caution and it is worth checking.
Let us know if you check OK?
The choke is part of the feedline and the loop you see coming down is coming from the feed point, It is as it appears....incorrect as I am learning. I did do one thing right though. I placed all the PVC pieces in the microwave with a shot glass of water for 50 seconds, the water boiled but the PVC remained cold. Should I move the choke as close to the feed point as possible or negate it all together? I could use the extra length.
Most people just stick there Imax 2000 in the air and use it for 3 or 4 yrs until it starts falling apart and then they throw it in the garbage. Why all this over analyzing?
I agree with Thirsty, it is best to start with the basics and get the antenna to working as intended.
If you want to try and modify, then establish a base line, recording results first, and then modify one thing at a time to some conclusion.
To be sure, duplicate such tests and results.
If you move the choke, and the antenna, choke, or feed line is the problem, you still won't know the reason for your dubious results, because you haven't fixed the problem. IMO, it is best to get the antenna working in the simplest setup and then start to modify.
Doc, you seem to have a downer on GP kits for Antrons and Imax's. Don't you understand that using your mast or your coax as a counterpoise for any antenna is just simply taking a stab in the dark? Think of all the possible arrangements you could have with different masts, coax and so forth which could affect the performance of any antenna. Wouldn't it be great if we had an industry standard way of mounting antenna's so that they could all be compared with at least comparable parameters?
What is the point is suggesting that one antenna is better than another if mounting poles and coax location is too much part of the equation?
I've just mounted a custom GP kit on my Antron 99. The custom kit is a design that i've used before that myself and Bob-85 were tinkering with a couple of year ago - the imfamous spiderplane.
Firsty, to make sure we get all the currents we need flowing in the right places, I isolated the antenna from the mast. Not by taping the mast and mounting the antenna on the tape because this creates capacitance between the mast and the antenna. Isolated it by driving a piece of strong ash into the end of the mounting pole and mounting the antenna directly onto that. The antenna is choked with five turns of my RG213 on a four inch former, directly below the feed point. The GP kit bolts directly onto the base of the Antron about an inch below the tuning rings and consists of a 3 sided clamping system similar to the basket clamp on a Sigma 4.
There are three Sirio 827 radials attached to this but with a twist, the electrical length is increased to full quarter wave by attaching wire to the end of each radial which is aimed in free space towards the next radial tip and secured to it using strong nylon thread. The general shape of this kit if I were using four radials instead of three would resemble a swastika if you get what I mean. So its general sort of shape would resemble a three leg swastika with each leg secured to the next leg with nylon wire.
I will post pics up later.
When I first tried this method about two years ago on an half wave GP it worked tremendous and i had TX signal increases ranging from S2 to S4 over the standard GP. RX went up hell of a lot and I was hearing stations i'd never have dreamed of with the standard GP.
The Antron is a slightly different animal and seems to work better than a standard GP out of the box but it didn't stop me from trying to improve it.
An increase of one S point at 25 miles was my first result and an immediate increase in RX was apparant.
I worked 333 Tennessee and New Jersey yesterday from Central England using 5 watts when the skip was not very good.
Don't let anyone try to convince you that GP kits are not worth while, just make sure you Isolate the mast properly, choke it and get those currents flowing where we need them.
Nav 707 waving an hand.
Never owned an Imax, just reporting what I've learned (sometimes the ha$d way).
Ran a A99 with no problems over one summer. Strapped a 10' conduit off of the second floor 8"x8" vertical beam holding up the porch. Antenna barely cleared the top roof ridge. DX with North America became routine and frequently reached out to South Pacific, some 8K miles away.
No choke, no counter-poise / radials, no fancy grouns. LMR400 right to the radio. Just did what the manual said.
Realize A99 is a different animal than the Imax.
That said, the majority of the folks with omni's, I DX with, run the Imax. They have a very good clear signal and their stated DX contacts and reports have very good results.
Imax are what they are, a great entry level antenna that can be purchased relatively cheaply. With some tinkering, can even put a bigger smile on one's face. I currently run a Gain-Master and really enjoy it.
Much luck and be safe on your tower! Keep us informed on your findings.
Ran a A99 with no problems over one summer. Strapped a 10' conduit off of the second floor 8"x8" vertical beam holding up the porch. Antenna barely cleared the top roof ridge. DX with North America became routine and frequently reached out to South Pacific, some 8K miles away.
No choke, no counter-poise / radials, no fancy grouns. LMR400 right to the radio. Just did what the manual said.
Realize A99 is a different animal than the Imax.
That said, the majority of the folks with omni's, I DX with, run the Imax. They have a very good clear signal and their stated DX contacts and reports have very good results.
Imax are what they are, a great entry level antenna that can be purchased relatively cheaply. With some tinkering, can even put a bigger smile on one's face. I currently run a Gain-Master and really enjoy it.
Much luck and be safe on your tower! Keep us informed on your findings.
Update: cross post from another thread. Well as most know, I have been fighting with the isolation and choke/balun with my Imax at 58' in the air. Today is the day to remedy that, so here I am at the very top plate of my 40' tower, hanging on with one hand and cuting the black tape away from the mast that was under the PVC with the other when a strong gust of wind comes along and down slides my mast pinching not only my two left fingers but worse yet my new 100' of LMR 400 now has a nice gash in it I wish I would have had three fingers under it and saved my LMR. Good news it's up according to the manufacturers directions with GP kit and No.8 copper wire from mast to 8' copper ground rod. Works beautifully! I guess the people who make them have a pretty good grasp on what makes them work.<proof><proof> I swapped ends with the coax and taped up the gash that now is the indoor end and my SWR is 1.4 on 1 and 1.2 on 40.
The few I was talking with before claim I went from hard to hear at 20-30 miles to "7-9 on my meter" not very scientific but, I sure am hearing and talking to ALOT of people I never knew were out there. I can honestly say I would never recommend isolating the Imax 2000! This little experiment caused me more aggravation than I could put into words. The down side is my wife has went to bed alone for the last three nights while I stay on the radio talking untill 4:30-5:00 in the morning.
I have the coax all taped up and everything is working great......So great infact I did not make it to bed untill 6:30 this morning and momma is:angry:
The few I was talking with before claim I went from hard to hear at 20-30 miles to "7-9 on my meter" not very scientific but, I sure am hearing and talking to ALOT of people I never knew were out there. I can honestly say I would never recommend isolating the Imax 2000! This little experiment caused me more aggravation than I could put into words. The down side is my wife has went to bed alone for the last three nights while I stay on the radio talking untill 4:30-5:00 in the morning.
I have the coax all taped up and everything is working great......So great infact I did not make it to bed untill 6:30 this morning and momma is:angry:
I don't see how isolating the mast could have anything to do with your inital problem, so IMO you still don't know the truth, or what the problem was.
IDI, sorry to hear about your injury, but it's good to hear you finally got the Imax to working right, that's all that matters.
Nav2010, I think I've seen these images before, and I think Multimode 200 posted them some time back. Your discription noted above, in red, does not agree with what we see in the image below. What we see here is what I think Bob would do, place the radials down at the feed point. Can you explain this?
http://www.worldwidedx.com/attachments/cb-antennas/6489d1327595681t-imax-2000-antennaspider.jpg
Here are my Eznec5, free space models, for Bob's radial idea that we discussed some time back. I'm not sure if I posted the models, but here is what I just did using free space, rather than dealing with all of the variables we find with models over Eznec's idea for being over real Earth.
View attachment Nav's post on Bob's radial idea .pdf
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Because the Antron's feet point is not at the bottom. There is a piece of coax inbetween the feedpoint and the tuning section inside the Antron. So the radials are actually attached below the real feedpoint.
I might agree with that point, but that is not what you said. You said the radials were mounted an inch below the tuning rings. I highlighted what you said in red in my post above.
"The GP kit bolts directly onto the base of the Antron about an inch below the tuning rings and consists of a 3 sided clamping system similar to the basket clamp on a Sigma 4."
You must have made a mistake, right?
Then, tell us why the picture does not show the BS you're repeating here again.