Ok i am having a strange issue.I have a wilson 1000 mag mount on my truck and best swr i can get from it is about 1.3 channel 1 1.2 or 1.4 depending on where im parked channel 40.I did clip a quarter inch on that whip.I took out my old imax99 which sat under my deck for 3 years and mounted it to the side of my camper.I hooked up with a cable that was left outside as well for 3 years under the deck.My swr was 1 on channel 1 and 1.1 on channel 40.So as a experiment i messed with the tunning rings five clicks up and the swr does not really change much at all.Going 5 down brought it to 1.2 on 40.Im using my galaxy 979 swr meter.Now why would my swr remain low with such a drastic ring change on my imax99?Is my imax screwed up?I talked to a guy about 80 miles from me on lsb clear as day on the imax99 today.Tried on my 1000 and couldnt hear him.The reason i am asking all this is i am buying a 2950dx peaked and tuned.I wanna make sure i dont screw up the radio if the antennas are faulty.Also i wanna ask if a pyramid 14amp 12 amp continous will power that radio efficiently.
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Antenna Tuning Issues
- Thread starter 123kid
- Start date
1) Those SWR numbers are typical and normal for a Wilson 1000. Make sure you re-calibrate the SWR meter before checking on each ch: 1, 20, & 40. Make sure that you vehicle has the doors closed and you aren't around other cars or metal buildings when you test it.
2) Either it is a Imax 2000 or a Solacon A-99. It can't be both. The Imax is 22 1/2 ft long and is in three ~8 ft sections and the A-99 is 18 ft long and has three 6 ft sections.
3) You cannot compare a mobile antenna with a length of 5 1/2 ft to a 18 or 22 ft base antenna. Like comparing a $20 bill to a $100 bill. They are both paper currency; but they both spend differently. Don't they? A mobile antenna isn't truly resonant with a short length and a base antenna is resonant with a longer length (1/4 wave=~9 ft, 1/2 wave=18 ft, 5/8 wave=~22.5 ft). A mobile antenna is a compromise antenna; but they will work. A 1/4 wave mobile antenna is the best; but difficult to work with.
4) Put the tuning rings back to where they were on your base antenna before you messed with it. Probably will still need to re-tune it anyway - now.
5) Both the Imax and the A-99 need to have a ground plane kit - or 10ft of steel support mast to act as a ground plane - to radiate properly. If you talked to someone that far away, that was just luck of the draw. These antennas aren't efficient until they have some kind of ground plane - either a ground plane kit or 10-20 ft of steel mast to work with. They will use the coax as a ground plane if there is nothing else; but that isn't dependable and will only cause interference with consumer electronics devices. eg: a TV set or even your CB.
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Here are some general truths about antennas.
The shorter an antenna is the less usable SWR bandwidth it will have, it will be more 'picky' than a 'full sized' antenna.
You can make almost any length resonant on almost any frequency. That deals with the definition of resonance, which can be determined by length, but that's certainly not the only way of making an antenna resonant! Resonance is defined as the absence of reactance in the antenna. One way of achieving that 'absence of reactance' is by selecting the length of conductor which contains equal and opposing reactances which equals zero. Another way to achieve resonance is by adding the correct 'size' and type/polarity (either + = inductive reactance, or - = capacitive reactance). With short antennas which are capacitive in nature, you make then resonant by adding inductive reactance which is a coil (loading coil). For antennas that are too long or having too much inductive reactance, you add the appropriate amount of capacitive reactance to neutralize that inductive reactance, which make reactance 'zero' or resonant. (You don't see many 'too long' antennas on a mobile especially at HF.) So those shorty mobile antennas ARE resonant. Resonance has nothing to do with input impedance or SWR, it's an entirely different animal.
- 'Doc
The shorter an antenna is the less usable SWR bandwidth it will have, it will be more 'picky' than a 'full sized' antenna.
You can make almost any length resonant on almost any frequency. That deals with the definition of resonance, which can be determined by length, but that's certainly not the only way of making an antenna resonant! Resonance is defined as the absence of reactance in the antenna. One way of achieving that 'absence of reactance' is by selecting the length of conductor which contains equal and opposing reactances which equals zero. Another way to achieve resonance is by adding the correct 'size' and type/polarity (either + = inductive reactance, or - = capacitive reactance). With short antennas which are capacitive in nature, you make then resonant by adding inductive reactance which is a coil (loading coil). For antennas that are too long or having too much inductive reactance, you add the appropriate amount of capacitive reactance to neutralize that inductive reactance, which make reactance 'zero' or resonant. (You don't see many 'too long' antennas on a mobile especially at HF.) So those shorty mobile antennas ARE resonant. Resonance has nothing to do with input impedance or SWR, it's an entirely different animal.
- 'Doc
antenna
Its a imax99 not the 2000 imax makes the 99s now not antron anymore.So your saying i need a 10 foot mast?My plan is to mount it on the roof 30 feet up on my house using a sat dish mount thats up there im taking off the sat dish.Will the sat dish mount be a efficient enough gp?I always thought with these antennas gps were not neccessary.Also i was talking with another guy about 35 miles from me crystal clear and i heard him on my 1000 before barely but he was louder on the 99.
Its a imax99 not the 2000 imax makes the 99s now not antron anymore.So your saying i need a 10 foot mast?My plan is to mount it on the roof 30 feet up on my house using a sat dish mount thats up there im taking off the sat dish.Will the sat dish mount be a efficient enough gp?I always thought with these antennas gps were not neccessary.Also i was talking with another guy about 35 miles from me crystal clear and i heard him on my 1000 before barely but he was louder on the 99.
Doc:
Yes; resonance is having neither capacitive reactance nor inductive reactance unequal.
Guess I was just trying to simplify things a bit too much for the level of the question asked. Point taken. Getting a bit ahead of ourselves here - ya think?
123kid said:
10 ft of mast -minimum- seems to work out. Sure, put it up 30 feet if you can. So long that it is secure and won't come down on any power lines during a wind storm!
Wasn't aware that the company changed the name. My bad.
Few antennas don't need ground planes.
However, these work best with them.
Yes; resonance is having neither capacitive reactance nor inductive reactance unequal.
Guess I was just trying to simplify things a bit too much for the level of the question asked. Point taken. Getting a bit ahead of ourselves here - ya think?
123kid said:
10 ft of mast -minimum- seems to work out. Sure, put it up 30 feet if you can. So long that it is secure and won't come down on any power lines during a wind storm!
Wasn't aware that the company changed the name. My bad.
Few antennas don't need ground planes.
However, these work best with them.
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This is absolutely correct, especially when talking about mobile antennas. Even the "no ground plane" antennas that are available have a built in ground plane of sorts, usually in the form of a custom coax cable.
About the only antennas that don't require some form of ground plane are balanced antennas, such as dipoles. With these antennas the counterpoise is a part of the radiating antenna, and not a groundplane.
The DB
hmmm
Well im gonn aput it on the roof.There are power lines nearby on the street but im gonna mount it with the u bolts right to the sat dish angle mast.I gott make sure the ubolts can get around that or im gonna have to buy a smaller mast to bolt to the other.It had no problems holding my direct tv dish and i get alot of wind on this lake im sure it will be fine.AS for the ground plane i have had this antenna a long time and various models of it antrons etc.Never used a ground plane.I used to operate one from 40 feet up above boston in a suburb in the hills with awesome results.The only loss i ever got was i interference with a cab antenna system on the same building.Got my ass reamed for that many times.As far as tvi im not worried this day in age with everyone having flat screens and cable its kinda a thing of the past.Im sure if i mount it right and have a good swr it wont be a issue.I just dont wanna drop money on a gpk and i dont wanna spend money on antenna mast.Im sure the sat dish mount will work fine if i get complaints i will take a look into other options.I ran this antenna 3 years ago out here off my deck with no complaints with a magnum 257.
Well im gonn aput it on the roof.There are power lines nearby on the street but im gonna mount it with the u bolts right to the sat dish angle mast.I gott make sure the ubolts can get around that or im gonna have to buy a smaller mast to bolt to the other.It had no problems holding my direct tv dish and i get alot of wind on this lake im sure it will be fine.AS for the ground plane i have had this antenna a long time and various models of it antrons etc.Never used a ground plane.I used to operate one from 40 feet up above boston in a suburb in the hills with awesome results.The only loss i ever got was i interference with a cab antenna system on the same building.Got my ass reamed for that many times.As far as tvi im not worried this day in age with everyone having flat screens and cable its kinda a thing of the past.Im sure if i mount it right and have a good swr it wont be a issue.I just dont wanna drop money on a gpk and i dont wanna spend money on antenna mast.Im sure the sat dish mount will work fine if i get complaints i will take a look into other options.I ran this antenna 3 years ago out here off my deck with no complaints with a magnum 257.
Actually Imax is the model name. There is no such thing as an Imax99. Solarcon is the company that makes BOTH antennas.
Given the SWR figures quoted, there's nothing wrong with them. The antenna should be useable with any radio.
There is a 'catch' though. If I'm understanding you correctly, you are using the built-in SWR meter of the radio. That's just not exactly the most reliable meter in the world, it's subject to a lot of 'mistakes' for whatever reasons.
I think when you get your new radio that you should do that checking again to see what it thinks about the antenna, that's got to be normal. Go from there.
- 'Doc
There is a 'catch' though. If I'm understanding you correctly, you are using the built-in SWR meter of the radio. That's just not exactly the most reliable meter in the world, it's subject to a lot of 'mistakes' for whatever reasons.
I think when you get your new radio that you should do that checking again to see what it thinks about the antenna, that's got to be normal. Go from there.
- 'Doc
Robb wrote
That is not strictly true Robb, if you mounted either an Antron99 or an imax on a glassfibre poll so it had no metal counterpoise it will still radiate on the coax equally as well as a 10ft metal pole. In fact if you have a 10ft pole it will still radiate on the coax detuning itself in the process, this is why it is recommended you cut your coax into electrical half waves including calculations for velocity factor of said coax. I suppose the best bet is to have both the mounting pole and coax cut into electrical half waves for a decent counterpoise. Isolating from the mast and choking together with a GP kit helps to cut the coax and pole out of the equasion to a certain degree but does not ensure we have transmition line currents and common mode currents in all the right places, that is purely subjective.
Wrong!!!!! I remember at some point that Solarcon promoted the Imax 99. Here is an old ad for the Imax 99 that shows it as discontinued:
I-Max 99
I'll just add a little to that about the subjective part. I'm glad the V4000 was mentioned in an earlier post and the phase relationship between the basket and the driven element. I strongly believe after several experiments that there may well be a phase relationship with a half wave element with quarter wave radials very similar to the vector arrangement but not quite as effective. I don't think it can happen with radials less than a quarter wave and angled down past the horizontal so standard GP kits for Imax and Antrons are a waste of money IMHO.
If you buy one, bend the elements to horizontal and increase the electrical length to a quarter wave. If you can solder a bridge from where the short piece of coax (outer braid) meets the coil inside the mounting tube and this will cut out the electrical length of the tube and the coax inside it. Then if you are skilled enough take off the SO239 and insulate it from the bottom of the mounting tube altogether. This is my plan when my A99 comes down next. Then my own spiderplane will be exactly a quarter wave where it needs to be.
Actually, my plan is to remove the SO239 altogether and have my coax soldered directly to the Antron with a bridge to boot to where my GP kit is.
If you buy one, bend the elements to horizontal and increase the electrical length to a quarter wave. If you can solder a bridge from where the short piece of coax (outer braid) meets the coil inside the mounting tube and this will cut out the electrical length of the tube and the coax inside it. Then if you are skilled enough take off the SO239 and insulate it from the bottom of the mounting tube altogether. This is my plan when my A99 comes down next. Then my own spiderplane will be exactly a quarter wave where it needs to be.
Actually, my plan is to remove the SO239 altogether and have my coax soldered directly to the Antron with a bridge to boot to where my GP kit is.
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