My Imax 2k...

[Oatmeal]

Ok, I have one of these in which I bought it new a few years back and I set the swr in it for 11m band use, and the swr is good on the 10 and 11m bands....

Ok, how do I go about getting the swr set for the other meter bands, meaning I dont have a MFJ antenna anlizer to use setting the swr...far as I no thers no operators in the area who still fools with there stuff anymore.

 

[Marconi]

The same is going on here in CB. The only thing I hear is if DX is working and that is spotty too.

 

[w9cll]

Where are you trying to use this antenna? It's only going to be efficient on 10/11 meters.

 

[Justme]

The Imax 2000 with GPK radials or your own homemade radials will work fine on 15/12/11/10.
With tuner on 17 but there the efficiency is already lacking forget about getting lower... there it's a leaky dummy load.

I'll replace the Imax this summer with a homemade 25 foot vertical with 1:4 un at the base followed by a 1:1 to keep the R.F. from the coax, both are made from FT 240 - 43 Cores and Teflon wire for the windings, all homemade.
This set up already running at the end of my garden and works from 40 - 10 meters.
Just needs to be put on the roof.....

 

[Oatmeal]

W9CLL, I've heard guys talking about using there Imax on different bands, and thought I'd ask about it...if you dont have a mif 259b antenna analizier how else can you tune it on the other meter bands?..

I've listened in the 12-17m bands and never have heard anything..
But I do listen on 40-80m bands sometimes to people talking there...

I was just curious, I no I have a lot to learn...

 

[KD2GOE]

I fined it works good on 10/11/15 meters i have no way of comparing 12 & 17 meters
and i am impressed with its operation on 15m. on 15 it is more like a 1/2 wave and SWR is LOW at 1.3:1 when propagation is up there is no difference or 1 s-unit grater then my horizontal 15 meter dipole in some cases. i have tested it 30 miles with a local ham on 15 then switched to 10 meters single strength was the same...
operations for people will vary as every one sets them off different..

20 and lower freq are useless. and i have no GPK just on a steel 25' tower with every thing ground strapped

 

[The DB]

W9CLL, I've heard guys talking about using there Imax on different bands, and thought I'd ask about it...if you dont have a mif 259b antenna analizier how else can you tune it on the other meter bands?

And from another thread...

How do you tune the swr on one of those dipoles without owning a 259B ant analizer ?

The Imax2000 has a ton of bandwidth built in, and it is often made even wider simply by how it is installed. Get a low SWR on the CB band and it isn't uncommon for people to have a useable SWR as far away as the 15 meters ham band. No need for an antenna analyzer to tune. Mind you it is questionable how well this antenna works in the first place, but some people still swear by it.

When it comes to dipoles, you simply need to get the SWR below a certain point and they will perform reasonably well. No magic to it, its just their nature.

You don't need an antenna analyzer to tune either of these antennas, or in fact most commercially made antennas and well known simple antenna designs like a center fed dipole, to be functional. Mind you using an antenna analyzer definitely won't hurt either.


The DB

 

[wavrider]

http://www.k3dav.com/solarconimax2000antenna.htm

good read

 

[Justme]

Not adding radials will put most of the R.F. in higher elevation not good for DX.
SWR might suffer a little, but you keep the R.F. from the coax, lower the angle of radiation back to the horizon and maximize low angle radiation.

SWR doesn't mean all is well, I'd rather have a bit higher swr that I can tune and low angle radiation as a good swr with lobes going up at 45 degrees, bad for DX.

The fact you need a coil at the antenna without radials already shows the antenna needs a ground plane.
And yes 17 metrs already the antenna gain drops as does the gain of the antenna, it will work, but there another dipole or better vertical will work better.

One reason I replace the Imax 2000 ( yes that old is mine) with a homemade 25 foot vertical fed with a 1:4 unun on the FT 240 - 43 core, already build it and test situated at the back of the garden running 800 watts in it from 40 - 10.
That one also has 4 ground plane wires connected to it.

 

[The DB]

Not adding radials will put most of the R.F. in higher elevation not good for DX.
SWR might suffer a little, but you keep the R.F. from the coax, lower the angle of radiation back to the horizon and maximize low angle radiation.

If you install a proper RF choke on the feedline at the feedpoint of the antenna, and isolate the antenna from the mast, adding or removing horizontal radials will make no difference when it comes to the angle of radiation. In this case, the downward pointed kit radials that Solarcon sells will actually hurt performance.

If you don't have the mast isolation and coax choke installed, then adding Solarcon's kit radials will make virtually no difference, however a set of 1/4 wavelength horizontal radials will make a world of difference...

SWR doesn't mean all is well, I'd rather have a bit higher swr that I can tune and low angle radiation as a good swr with lobes going up at 45 degrees, bad for DX.

As your not actually changing the physical length of this antenna, making adjustments to the matching system won't actually change the angle of radiation. Unless you are changing the actual physical length of the antenna while tuning, as you do with some of the aluminum antennas, however, not the Imax, you have nothing to worry about when it comes to angle of radiation when adjusting the Imax for lower SWR.

The fact you need a coil at the antenna without radials already shows the antenna needs a ground plane.
And yes 17 metrs already the antenna gain drops as does the gain of the antenna, it will work, but there another dipole or better vertical will work better.

The matching system with the Imax is more than just a coil. Will it benefit from having radials? That depends actually. Generally, yes, a proper set of radials will generally benefit this antenna, at least to a small degree. However, depending on how your antenna is set up some radial configurations can be detrimental, driving the pattern high, which as you have been saying is undesirable.

One reason I replace the Imax 2000 ( yes that old is mine) with a homemade 25 foot vertical fed with a 1:4 unun on the FT 240 - 43 core, already build it and test situated at the back of the garden running 800 watts in it from 40 - 10.
That one also has 4 ground plane wires connected to it.

I hope your antenna works well for you. I will point out that at 10, 11 and maybe even 12 meters the higher angle lobe will be the dominant lobe. That being said, that doesn't mean the lower angle lobe just disappears, so it will still work. How much of that lower angle lobe is left depends on the overall length of the antenna, as well as other design elements, such as how well you control common mode currents, which at first glance your design seems to do fairly well. Have fun with that antenna, and you should create a thread with construction details...


The DB

 

[Justme]

One reason the 25 foot antenna sprouts a stinger next to the bottom section of the antenna connected to the ground and resonating on 30 MHz.
That stinger brings back the lobes on 10-12 meters gack to the horizon.

With the length of 25 foot the antenna is already working in the backyard fro 40 - 10.
The GPK kit on the Imax is helped by 4 radials on the roof now each 16 feet long or so, 1/4 wave for 20 meters.

The 25 foot antenna is a non resonant antenna that with the 1:4 unun and radials has an swr not worse as 1:2 and most bands under that.
I had the original Imax 2000 on the roof now for better as 12 years, without radials, then added the original GPK radial kit and 7 years back added the 4 wire readials in 45 degree downwards slope of 16 feet.

The 25 foot antenna in the garden is made of Titanex tubing, same as my 77 feet high inverted L.
Starting with 40 mm and 1/10th of an inch wall thickness these tubes can handle some brute force.
http://www.eham.net/articles/29052
That is the article that formed the base of my tinkering with the antenna.
The only thing added to that design was the 1:4 unun which brings down the SWR on the feedline, which on the roof will be the European equivalent of LMR400 and 55 feet long.

 

[Oatmeal]

Good info there guys...

When I bought this Imax 2k new, I tuned it on channel 20 on the 11m band, in which at the time I used the radio I had in my truck, later as time went on I got my Tech ticket, and a year or so after that I bought a new 2995dx and started listing on 10m and this was when I found out the swr was low on the tech portion of the 10m band...and since I haven't touched the swr on the antenna...been running this Imax 2k about 4-5 years now, no ground plane kit on it, but it's just been up here at the shack for close to 2 years now, and don't have a choke on it, all I run is a 100 watt radio, and it's set at 30 watts..have talked to the neighbors and they say all is ok, I do stay in touch with my neighbors...

But I'm surprised how well this Imax has talked, well on the 10m band the last few weeks....worked a guy in Honolulu, Hawaii the other evening which I was running 30 watts, and the Imax is just 21ft off the ground, never was able to work dx like this on 11m....I thought this was a good trip, no more than I'm running since I'm on the the east coast... but I'm just getting into the hobby and so far enjoy it.....still looking forward to working dx in the other countries....

This last week, I have been checking things out on the bands, been listening to alot of rag chewing on the 40-80m bands....found a spot on the 40m band where guys from the Ky, and the mid west states are talking on a daily bases...still haven't heard anyone local to me on the HF bands...

Going to make some changes soon, this is why I was asking about the swr and if a MFJ meter was needed to set the swr...

 

[Justme]

Don't sweat if the SWR isn't exactly 1:1 I consider it a good match if it stays under 1:3 the rest is for the tuner to deal with.

The Heathkit SB-1000 couldn't care less with an swr under 1:5 for that we have plate and load controls.

Most solid state P.A.s do try to reduce the power if the swr is over 1:2 so then you need a tuner to fool the P.A.
A 1 or 2 dB loss in your antenna system will not be noticed on the other side, conditions do a lot more making/breaking the contacts.

My new homebrew vertical of 25 foot offers good swr from 40 - 10, will have no worse swr as 1:2 measured after the 1:4 unun, and with good coax, low loss, will work fine over quite some range.

Will a band specific 5/8 antenna work better on each band? possibly, but that gain might be 1 or 2 dB, and I need a lot of verticals and coax up...
Using the 77foot high inverted L and auto tuner ( MFJ 998) I can use that for 160 - 80 - 40 and use the other vertical from 40 - 10
The horizontal OCF works from 160 - 10 .
For 6 meters there's a 5 element beam up, all frequencies covered including WARC .

Don't worry too much, get on the air with due care and make qso's

 

[vkrules]

Don't obsess about SWR and needing a mfj analyzer.It's just a piece of test equipment and only as good as the person using it.Great bit of kit if you understand what the measurements are showing you. Most use one as a portable rf source and swr meter only anyway..So no you don't have to have the mfj to adjust swr .You really need to hit the books a bit more ! .You might be better off saving your money for now and purchasing an antenna tuner. The imax will work without a tuner on 10' 11'12 and 15 meters .17 and 20 with a tuner but the signal will be down a lot compared to even a simple dipole.And as someone said earlier any frequencies lower, even with a tuner it's little more than a leaky dummyload . Justme is right his 25 ft with the ant tuner would out perform the imax on the lower frequencies.