Another IMAX 2000 question

[Captain Kilowatt]

We are indeed getting better weather. It has been raining the better part of the last 24 hours and is supposed to continue for the next 24 hours. It's not often we look forward to rain but at this point it is better than snow. Just have to be watchful of flooding in some areas however. As long as the rain is slow it shouldn't be too bad. Temps were around +10C the other day and are supposed to be on the plus side a couple degrees for the next several days. It looks like I may have an ice free driveway before the first of the week at this rate. Now to get rid of the 6-7 foot high snow banks in the yard.

 

[fourstringburn]

Why not go with a 43 ft ground mounted vertical. Put that up with at least 2 each 1/4 wavelength radials for each band and use a tuner and be done with it. That would be much better than trying to push an Imax far beyond it's range. These effectively cover 6 thru 40 meters and even 80 meters with some of them.

 

[Heavy Metal]

Why not go with a 43 ft ground mounted vertical. Put that up with at least 2 each 1/4 wavelength radials for each band and use a tuner and be done with it. That would be much better than trying to push an Imax far beyond it's range. These effectively cover 6 thru 40 meters and even 80 meters with some of them.

Hmmm 45.725 rounded and 16.725 radials can input 4 each or that over kill? Just need to find something to attach radials and I think I have that covers for a few bucks their think takes 8 or so.


Question does the radials have to be tuned as the radiator itself or be close enough to freq?

 

[Captain Kilowatt]

Why not go with a 43 ft ground mounted vertical. Put that up with at least 2 each 1/4 wavelength radials for each band and use a tuner and be done with it. That would be much better than trying to push an Imax far beyond it's range. These effectively cover 6 thru 40 meters and even 80 meters with some of them.

Can someone please explain the magic behind a 43 foot vertical? What makes a 43 foot vertical any better than a 33 foot 1/4 wave on 40m or a 55 foot vertical. I see a few 43 foot pieces of pipe sold comercially as antennas and a lot of people suggest a 43 foot vertical but since it requires a tuner to work anyway what is so special about 43 feet? It is nothing special in terms of wavelength. Just curious as I and many others, including a couple engineers, cannot figure that one out.

 

[Heavy Metal]

Like on com ports why is com 2 faster than the others loathe world may never know it is a take it as it is and enjoy lol but sure why not why is 43'?

 

[wavrider]

CK from my understanding, it is the magic length, not resonant any where near any of the amateur bands, thus it does not tend to have any 2nd or 3rd order harmonics. that may effect other amateur bands.
( just guessing here)

COPY & PASTE from L.B. Cebik's site
(Table 2 provides the most convenient lengths and the bands included. Table 2. Broadside Doublet Lengths and Amateur Band Coverage Length (feet) Bands covered
44' -10, 12, 15, 17, 20, 30, 40 meters
66' -15, 17, 20, 30, 40, 60 meters
88'- 20, 30, 40, 60, 80 meters )

Looks like it is one leg of an ZEP on 10 meters, thus the 43' length, 1.25 WL on highest frequency of use. [sort of).

Really do not need to lay tuned radials down for this antenna as it it not resonant anywhere on the amateur bands.

Just put down as many radials as you can, the more ground radials the better the antenna will be.

Reccomend minimum of at least 24 radials, 30' or longer

 

[Captain Kilowatt]

Harmonically related lengths are a good thing in most antenna and meaningless in others. Yes sometimes a nonresonant length is good as it eliminates trying to load into a resonant half wave on one band which can be several thousand ohms and a shortened quarter wave on another band which can be only 10 ohms or so, so yes a nonresonant length can be good sometimes however if the matching system is made properly a harmonically related antenna is much easier to predict the pattern of as well as use on different bands. FWIW you could use an antenna that is 50 feet high and it would not be resonant in any amateur band......I think.....if I did my math right. LOL

 

[fourstringburn]

Can someone please explain the magic behind a 43 foot vertical? What makes a 43 foot vertical any better than a 33 foot 1/4 wave on 40m or a 55 foot vertical. I see a few 43 foot pieces of pipe sold comercially as antennas and a lot of people suggest a 43 foot vertical but since it requires a tuner to work anyway what is so special about 43 feet? It is nothing special in terms of wavelength. Just curious as I and many others, including a couple engineers, cannot figure that one out.

I would like to know too. I do see it as another compromise multiband antenna but I suggested that over trying to load up a Imax 2000 on bands beyond it's range. I don't see it as anything special, but it does work if setup properly and it is a good solution for people in HOA neighborhoods to put up one antenna you can hide by trees or do the flagpole thing.

Who said it was better than a 1/4 antenna on any band?

What some people don't seem to get is even though you can load up nearly any antenna for multiple bands, it's the effective radiated power (ERP) that suffers the most. But as long as they can make a contact, all is well, or so they may seem to believe.

There is one guy I read on this forum uses a tuner for a 1/4 mobile CB antenna on 40 meters. I responded back as that falls under the category of "tuning a rain gutter".

 

[Captain Kilowatt]

I would not even consider extending an Imax for other bands for all the reasons I have already mentioned regarding height and matching network required. As for the CB antenna on 40m well that would suck. I ran such an antenna on the mobile with a remote mounted auto tuner with proper feedline attachment (six inches of HEAVY strap) and it worked great 20m and up. On 40m it was pretty deaf and all but useless and on 80m my Hamstick worked better even without the tuner so that should tell you something. LOL

 

[Heavy Metal]

COPY & PASTE from L.B. Cebik's site
(Table 2 provides the most convenient lengths and the bands included. Table 2. Broadside Doublet Lengths and Amateur Band Coverage Length (feet) Bands covered
44' -10, 12, 15, 17, 20, 30, 40 meters
66' -15, 17, 20, 30, 40, 60 meters
88'- 20, 30, 40, 60, 80 meters )

Looks like it is one leg of an ZEP on 10 meters, thus the 43' length, 1.25 WL on highest frequency of use. [sort of).

So these numbers are for vertical and bands they cover Hmm wow

 

[Captain Kilowatt]

So these numbers are for vertical and bands they cover Hmm wow

Those lengths require a tuner to cover those bands however as a licensed amateur you should know that already.

 

[BJ radionut]

CK: I am with you on this. Best I can figure 43 ft. is very close to a 3/8 th's length at 7.2 MHz....and roughly .64 wave on 20 meters (14.0 MHz) ....Then to almost a full wave on 15 m (.96 at 21.05 MHz)
I know couple op's that have run that length with a unun set-up by DX Eng or one of Zero Fives matching networks and bunch of tuned radials on 40/20/15 meters and they can do well...???? Depending on the length of the tuned radials they can operate segments of each band without a tuner...Again ???? So I've been told...
Personally I've had good luck with 33 ft. on 40/15 meters with as little as 4 radials per band(field day set-up)....
But the one I had up years ago here really came to life with like 30 radials...
Did "OK" on Phone band but it did Well on the bottom end CW sections
Go figure
All the Best
Gary

Went back after my original post and realized the numbers were wrong. These should be closer...
To much Coffee today I guess

 

[wavrider]

http://www.eham.net/articles/21272

The 43' Vertical -- a Theoretical Analysis

 

[Captain Kilowatt]

CK: I am with you on this. Best I can figure 43 ft. is very close to a 3/8 th's length at 7.2 MHz....and roughly .64 wave on 20 meters (14.0 MHz) ....Then to almost a full wave on 15 m (.96 at 21.05 MHz)
I know couple op's that have run that length with a unun set-up by DX Eng or one of Zero Fives matching networks and bunch of tuned radials on 40/20/15 meters and they can do well...???? Depending on the length of the tuned radials they can operate segments of each band without a tuner...Again ???? So I've been told...
Personally I've had good luck with 33 ft. on 40/15 meters with as little as 4 radials per band(field day set-up)....
But the one I had up years ago here really came to life with like 30 radials...
Did "OK" on Phone band but it did Well on the bottom end CW sections
Go figure
All the Best
Gary

Went back after my original post and realized the numbers were wrong. These should be closer...
To much Coffee today I guess

LOL Gary you should have seen how well a top loaded 96 foot vertical with 120 radials worked on 80 and 160m. When I decommissioned an old AM site we loaded the antenna up for some fun one fine January night and had a ball blasting into Europe with 100 watts. Prior to that we loaded a 160 foot vertical also with 120 radials but a much better site. It was to become the new AM site and we tried it before we moved and the other site after the move. 100 watts was 40/9 into western Europe on both 80 and 160m . We had a ball those couple nights.

 

[DainBramage]

Can someone please explain the magic behind a 43 foot vertical?... It is nothing special in terms of wavelength. Just curious....

I dunno about the number either,........ but it will load up nicely on 60 meters w/o a tuner.