Radio Preppers

Both the 'A99' and the Imax antennas are single band antennas with a built in impedance matching device (the rings) at the base.  The 'A99' is a 1/2 wave antenna, the Imax is a 5/8 wave, both were originally designed for 11 meters.  Because of the impedance matching built in, both can be 'skootched' to close bands without much trouble.  They can also be made to 'work' on bands as far away fron the design frequency as 20 meters.  That doesn't mean that they will work well, but they will work.  How far they can be moved depends on the tuner used and the setting of the built-in matching device (rings).  There are some combinations of those two 'tuners' settings that result in it not working at all.
Most of the 'reviews' of both of these antennas are purely 'subjective' and very seldom ever 'objective'.  (And like any antenna, there are going to be 'lemons'.) 
One thing about both of them is that the feed line is used as the 'other half' of the antenna, or the counterpoise.  How and were the feed line is run can and will make a difference in how they perform.  Typically, adding a "groundplane" or counterpoise to either of them isn't going to do much of benefit since there's already one there.  It usually doesn't hurt anything, but it seldom helps it either.  If you want to try one, do so.
Both the 'A99' and the Imax are sort of the 'standard' antennas for 11 meters.  There's certainly a lot of them in use.  The typical gain figures quoted for either of them are what is spread on a garden to make things grow better.  The Imax does have some slight gain, but not very much at all.  Why'z that?  Because 'gain' figures are determined by reference to a standard antenna, which is a 1/2 wave length.  Since the 'A99' is a 1/2 wave length, how can it have gain over a 1/2 wave length antenna?  A 5/8 wave antenna typically has something like 1.5 - 2 dBd of gain over a 1/2 wave.  The biggy is the shape of the radiation patterns!, which can make a big difference at times.
Lot's of 'myths' concerning both the 'A99' and Imax antennas...
- Paul

Thanks Paul, nothing magical here I am sure. I have been reading numerous antenna reviews on Eham, and indeed, lots of them seems to be based on feelings rather than hard facts. There are always a couple reviews though by Hams who know their antennas, that provide valuable information. Eham does help. When I wanted an end-fed dipole, I saw that the PAR had a 5.0 rating, with 23 pages of reviews! There had to be something there.. So I bought one, and like it.

I might try one quarter wave counterpoise with the I-Max, just as an experiment.. Otherwise, it works, so I won't bother.. I almost never use my CB anyway. It's just an emergency radio, just in case. Sometimes I put the I-Max up and listen, but I'd rather listen to 20 and 40m. Even on 38LSB, CB is not so "civilized."

Have a great day,

Gil.

The radiation angle on the A99 and the Imax is a low angle - around 15 to 20 degrees shooting toward the horizon which does well on skip,  For NVIS work you need a low horizontal antenna and low frequency like 40 & 80 meters, not 10 and 11 meters.

I'm sorry Gil, but you are talking in circles.

10 meters is upper side band only.

11 meters - there is no such thing as full legal power.. CB only allows for 5 watts AM - with a tube type transmitter and brand new tubes, or 12 watts PEP Single Side Band.

The Solorcon A99 and Antron, Anttron, and Imax are all basically the same antenna.
The company was sold several times and there was patent issues that made them change their name.

The antenna works on the principal of having a portion of a wavelength over another portion of a wavelength.  The two portions equals some type of gain over a dipole antenna - which is a known radiation pattern and performance - so we use the dipole to measure other types of antenna.

No Vertical antenna can exhibit true gain due to the fact that the only way to create real gain is to cause rejection in one direction which pushes the remaining power in the opposite direction, and when you cause rejection in one direction you reduce multipath which causes the remaining signal to have a better spectral purity.  A multipath signal is corrupt.

The coax has but one job, to transfer the power from point A to point B - like a garden hose it is just a conductor.  When you make the shield reactive, you defeat the purpose of the coax.  The waY TO reduce the current on the shield is to coil about 20 turns of RG 8X in a 12 inch coil which will create a choke.
I have noticed lot's of RF being reflected back into my shack with this antenna.

The IMAX should have the option of using 4 counterpoises, at a 45* angle, that can take the place of multiple ground radials.  The counterpoise is mounted directly below the antenna within about a foot.
I think the counterpoises are at least 9 feet long, and the antenna requirement is at least 30' - preferably 36 feet minimum.

With a good tuner, you can tune a salty wet noodle up on any band, but making it effective it has to be a portion of a wavelength long beyond a half a wave length.  It does no good to be able to transmit if it won't receive you won't hear anything other then the very strongest signals.

On 17 meters with my Kenwood TS 590 - my input is about 100 watts and the output after the internal antenna tuner is about 15 watts.
15 watts will talk half way around the world when the band is open and won't talk across the street when the band is not open.

The Solorcon A99 works acceptably well on 15 meters.

12 meters is in the same category as 17.   Because it is not a harmonic of anything, the antenna is not resonant and the transceiver folds back the power to about 15 watts.

I have talked to South America with 15 watts many times on the Solorcon...

One way to improve the Solorcon A99 is to use a mobile whip in place of the top section of antenna.

You can cut the mobile whip to a specific length which helps tune it much better then the ring on the bottom.

Quote10 meters is upper side band only.

Where did I mention 10m? Besides, you can use any mode you want on 10m, USB is a guideline, not a rule.
When mentioning LSB I was talking about CB channel 38 LSB which is a DX calling channel for CB. Nothing to do with 10m.

Quote11 meters - there is no such thing as full legal power..

Of course there is, it's just not 1500W like Ham radio, it's 4W AM and 12W SSB. That's full legal power for CB.
FCC regulations say nothing about 5W with tubes that I know of. That might have been an older regulation when tube CBs were still being sold.
My Galaxy DX 579 outputs 4W AM. That is the full legal limit.

QuoteNo Vertical antenna can exhibit true gain

Gain is always comparing one antenna to another, whether it's between a hypothetical isotropic ideal antenna in free space (dbi), a standard dipole (dbd), a quarter wave ground plane vertical (dbq), or between any two antennas of different type. So a vertical antenna can absolutely exhibit gain. It all depends on which other antenna you compare it to.

So, no, I'm not talking in circles.

Have a great day,

Gil.

QuoteNo Vertical antenna can exhibit true gain

QuoteGain is always comparing one antenna to another, whether it's between a hypothetical isotropic ideal antenna in free space (dbi), a standard dipole (dbd), a quarter wave ground plane vertical (dbq), or between any two antennas of different type. So a vertical antenna can absolutely exhibit gain. It all depends on which other antenna you compare it to.

So, no, I'm not talking in circles.

Have a great day,

Gil.

Gain is really about concentration of radiation in a particular direction like toward the horizon verses higher up toward the sky, or north, south, east, or west.  Antennas with little or no gain exhibit radiation patterns shaped somewhat like a ball with power going out equally in all directions, but antennas with gain have sharper patterns where radiation is highest where the pattern is concentrated like a beam antenna where the pattern goes mainly in one direction.  A vertical antenna is mainly Omni directional with patterns that are basically equal 360 degrees around it but if the antenna is long enough it can have gain which concentrates the pattern at low angles toward the horizon which is good for working DX and the Imaxx 2000 is this type of antenna.  Its radiation pattern is Omni directional but at a low 15  to 20 degrees toward the horizon making it good for DX.  The Imaxx 2000 is not an NVIS type antenna, NVIS requires signals basically radiated straight up, not toward the horizon.

Quote from: Paul on June 27, 2012, 02:42:37 AM
Since the 'A99' is a 1/2 wave length, how can it have gain over a 1/2 wave length antenna?  A 5/8 wave antenna typically has something like 1.5 - 2 dBd of gain over a 1/2 wave.  The biggy is the shape of the radiation patterns!, which can make a big difference at times.
Lot's of 'myths' concerning both the 'A99' and Imax antennas...
- Paul

The info on the A99 states that it is a "half wave over a quarter wave" and I've always just thought that's nothing more than a 3/4 wave antenna !  ::)

Quote from: Lamewolf on December 02, 2014, 08:07:00 AM

Quote from: Paul on June 27, 2012, 02:42:37 AM
Since the 'A99' is a 1/2 wave length, how can it have gain over a 1/2 wave length antenna?  A 5/8 wave antenna typically has something like 1.5 - 2 dBd of gain over a 1/2 wave.  The biggy is the shape of the radiation patterns!, which can make a big difference at times.
Lot's of 'myths' concerning both the 'A99' and Imax antennas...
- Paul

The info on the A99 states that it is a "half wave over a quarter wave" and I've always just thought that's nothing more than a 3/4 wave antenna !  ::)

Marketing at it's finest ;D

Gill,
Have you tested it with 10 and 12 meters? I am interested in test results if you have them.
I can only tx / rx  from 40-15 meters because I am using a mag loop. Adding 10/12 would be nice.
Luigi

Quote from: Luigi on December 02, 2014, 02:31:24 PM
Gill,
Have you tested it with 10 and 12 meters? I am interested in test results if you have them.
I can only tx / rx  from 40-15 meters because I am using a mag loop. Adding 10/12 would be nice.
Luigi

Want some good info on the Imax 2000, check out this website: http://www.k3dav.com/solarconimax2000antenna.htm

Its a good writeup and shows that it works 10 thru 17 meters !

More good info here on the Imax 2000: http://tore.aasli.no/amateur_radio/cb-antenna/solarcon_imax-2000/index.php

Thank you for the link. This is perfect.
Based on the information, You can listen to wwv on 20 MHz. The SWR is really low there.
Luigi

Quote from: Luigi on December 02, 2014, 05:01:53 PM
Thank you for the link. This is perfect.
Based on the information, You can listen to wwv on 20 MHz. The SWR is really low there.
Luigi

I ordered an Imax 2000 on Saturday and its scheduled for delivery on Thursday, so as soon as I get it installed I will put it on the antenna analyzer and take some SWR readings on the various bands.  I have an old A99 up now and have used it on 20 meters before via a tuner and it worked fairly well, but not as good as my 40 meter extended double zepp.  But I can hardly wait to play with the Imax 2000, looks like it will play 10 thru 17 without a tuner and I noticed the swr should be well within the range of most autotuners on 30 meters too.  On 30 meters it's basically a quarter wave long !

Also, the A99 when I first got it the manual said you can cut the top setion off a little at a time to make it resonant on 10 meters.  With my A99 I did not have to cut it at all and only adjusted the tuning rings slightly to get a good match and was able to work 10, 12, and 15 meters on it without a tuner.  I'm also reading that you can do the same with the Imax 2000.  So if you folks get one, don't cut it down any until you check it out first - you may not need to cut it.

My Imax 2000 arrived a day early !  Gonna give it a shot of olive drab camo paint and then try to install it tomorrow evening and will get some swr measurements on it then to post here.  Then I'll give it a workout this weekend on the air and see how it performs.

QuoteHave you tested it with 10 and 12 meters?

10m works, 12 does not. I have not tried 20 or any other band. 15m works.

Gil.

Quote from: gil on December 03, 2014, 03:36:22 PM

QuoteHave you tested it with 10 and 12 meters?

10m works, 12 does not. I have not tried 20 or any other band. 15m works.

Gil.

Just curious Gil, have you checked the swr on 12 meters ?  On the page I posted a link to here: http://tore.aasli.no/amateur_radio/cb-antenna/solarcon_imax-2000/index.php  the swr graph shows about 1.5:1 on 12 meters and less than 2:1 from 17 meters and up to 30 mhz.  My old Antron 99 works super on 12 meters !  And I'm hoping the Imax 2000 I'm putting up tomorrow will do even better.

QuoteJust curious Gil, have you checked the swr on 12 meters ?

Well, it was a while ago, I'd have to check again... Tomorrow if I don't forget...

Gil.

Got the Imax installed last night, and here is my SWR measurements via the MFJ-259B analyzer.

30 meters - 20.2:1
20 meters - 12.4:1 to 13.5:1
17 meters - 6.9:1
15 meters - 1.2:1 to 1.5:1
12 meters - 2.5:1 (well within the range of most auto tuners)
10 meters - 1.1:1 @ 28mhz to 25.2mhz
                  1.2:1 @ 28.3 to 28.4
                  1.3:1 @ 28.5 to 28.6
From there it steadily climbs to 2.6:1 @ 29.7, but under 2:1 from 28 to 29, so I'm happy

Also, had to put the tuning rings all the way to the top to get these readings, but I never use 11 meters anyway - too much trash talk there anyway.

Anyway, the bands were dead when I got done last night so I'll try it out Saturday morning and afternoon while I'm off work to see how it performs on the air.  I did find the manual is a bit flakey, on one page it states 5.1 db gain and on another page it says 8.1 db gain - strange indeed !  Since its a 5/8 wave antenna, I figure it more like 3db (maybe).

Got a chance to play with the 2000 last night when I got home.  The bands had a little traffic and it was hearing real well.  My LDG Z11 Pro2 auto tuner handles it just fine on 30, 20, & 17 meters where the swr is way to high but drops it right down under 1.5:1 in a snap.  What really surprises me is that even though the swr is horrific on 30 meters, once the LDG does its thing, the 2000 hears great there.  Haven't tried any contacts yet but will tomorrow morning when I have more time.  Really wanting to try it on 30 meters since it is close to a quarter wave in length on that band.  On 10 and 15, no tuner is needed and on 12 the swr is only a 2.5:1, so no problem there with the LDG - it barely blinks then finds a match.  The Imax 2000 is only about 8' off the ground right now and fed with 20' of RG8X coax, but when I get time and better weather I will get it up to the 22' mark and get some better coax on it.

Finally got some time to work 10 meters a little on Sunday morning.  The band was open a little, and was able to work Africa and Luxemburg with 10 watts from my Icom 703.