Base New Imax wont tune 11m....this sucks

[Marconi]

Here is a link to an article done by W9Ji using an Imax model that produces a similar pattern to the Imax I just posted in post #240 above...if you want to see the rest of the information, click the link below and scan down to the topic "I-Max 2000 Solarcon A-99 Antenna"..

https://www.w8ji.com/end-fed_vertical.htm#IMAX

 

[HomerBB]

Looks like a butterfly that did a nose dive into the concrete...

 

[357]

I did not talk with Charlie.
I copied and pasted a post from Coppers Electronics Forum from 30 August 2007. There is a pile of discussions, issues and complaints relating to the 2000 going way back to 2007.

I bet thats when they put the capacitor in the middle section!
2007

 

[Recon]

I bet thats when they put the capacitor in the middle section!
2007

View attachment 33391

For what purpose?

 

[357]

For what purpose?

not sure, I think to stop electrocution if it hits a line

 

[The DB]

When modeled, this capacitor has the opposite effect of a loading coil on a mobile antenna. It has the effect of lengthening the antenna beyond a half wavelength, yet still providing the feed point impedance of a half wavelength antenna. This has several effects. 1, it lets them use a similar (if not the same) matching section as the a99 antenna, and 2, itt has the effect of, unlike other end fed antennas of this length, keeping the entire length of the antenna in phase with itself.

I have not seen any models from anywhere but this forum that includes the capacitor in the model, and that includes the W8JI models linked to above.


The DB

 

[HomerBB]

@The DB
Cool

 

[357]

When modeled, this capacitor has the opposite effect of a loading coil on a mobile antenna. It has the effect of lengthening the antenna beyond a half wavelength, yet still providing the feed point impedance of a half wavelength antenna. This has several effects. 1, it lets them use a similar (if not the same) matching section as the a99 antenna, and 2, itt has the effect of, unlike other end fed antennas of this length, keeping the entire length of the antenna in phase with itself.

I have not seen any models from anywhere but this forum that includes the capacitor in the model, and that includes the W8JI models linked to above.


The DB

https://www.worldwidedx.com/threads/imax-2000-continuity-query.170384/#post-561527

I think Marconi did somewhere in this thread

 

[Riverman]

I talked with a tech at Bell's. He told me that one customer who has a short MAX 2000 added a 3/8" X 10" long (K-40?) shaft between the top and center sections. He probably had to adjust the tuning rings to get a decent VSWR, but it worked!

Could use one of these. Just screw it in between the two sections. And paint white if desired. The 11” version is $15. https://www.buddipole.com/exanar.html

 

[Marconi]

This has several effects. 1, it lets them use a similar (if not the same) matching section as the a99 antenna, and 2, itt has the effect of, unlike other end fed antennas of this length, keeping the entire length of the antenna in phase with itself.

Very good description DB.

In the PDF file below I've added images for a rough idea of what DB is describing as highlighted above in bold.

 

[The DB]

https://www.worldwidedx.com/threads/imax-2000-continuity-query.170384/#post-561527

I think Marconi did somewhere in this thread

I had the models in that thread as well, unfortunately I lost those models a while back and can't repost them.

Maybe I should remake said models...


The DB

 

[The DB]

Redid my lost models for this. All of these images can be clicked to show larger versions.

The current distribution for the Imax with no capacitor (left) and the Imax with the capacitor (right).

[photo=medium]6129[/photo][photo=medium]6130[/photo]

As we can see, the imax with a capacitor is completely in phase. Marconi's model above also shows this as well. In the model without the capacitor we have a typical 5/8 wavelength current distribution, and in the model with the capacitor we do not.

Here we see a comparison between the Imax with and without the capacitor in free space.

[photo=medium]6131[/photo]

As we can see, the Imax with the capacitor has a superior horizontal gain in free space. This tells us that the model with the capacitor will be superior for making local contacts in most (but not all) cases.

Now a look at comparisons for just the Imax (first), the Imax with a mast but no choke (second), and the imax with a mast and a choke mounted 9 feet below the feed point (third). In these models, the Imax is mounted 20 feet above the earth.

[photo=medium]6132[/photo]

[photo=medium]6134[/photo]

[photo=medium]6136[/photo]


Now we do the same for the antenna mounted at 30 feet. Again, just the antenna (first), antenna with mast but no choke (second), and antenna with mast and choke mounted 9 feet below the feed point (third).

[photo=medium]6133[/photo]

[photo=medium]6136[/photo]

[photo=medium]6137[/photo]


I will let you make your own judgements on these last six models, and the change caused by the addition of the capacitor.


The DB

 

[357]

The capacitor was an after thought. I think the SWR problem happened awhile after the capacitor was added but thats a mystery too.
The Imax when it was done right got out like stink and I'd buy 10.
Whatever happened is a shame because it was a kickass antenna.

Now other companies are coming back because it sucks, thats whats really going on.
Other companies will get my cash unless I can find an original Imax, which will probably get $300 on Ebay now

 

[Recon]

The capacitor was an after thought. I think the SWR problem happened awhile after the capacitor was added but thats a mystery too.
The Imax when it was done right got out like stink and I'd buy 10.
Whatever happened is a shame because it was a kickass antenna.

Now other companies are coming back because it sucks, thats whats really going on.
Other companies will get my cash unless I can find an original Imax, which will probably get $300 on Ebay now

Have you tried calling the sellers and ask if they would measure the antenna prior to shipping?

 

[Riverman]

Could use one of these. Just screw it in between the two sections. And paint white if desired. The 11” version is $15. https://www.buddipole.com/exanar.html
View attachment 33439

I discovered I have a spare one of these left over from my Buddistick days.
If anyone wants it for their Imax, let me know.