My Imax 2k...

[Heavy Metal]

How's it changed?

 

[Heavy Metal]

I run 9913f7

 

[Oatmeal]

Had plans on running a big amp, but lost interested in the 11m stuff...

 

[Heavy Metal]

Had plans on running a big amp, but lost interested in the 11m stuff...

Ah, so what did you go to now and how are over all swr's over all

 

[fourstringburn]

I would think stranded be better all around to a point, reasonis it's usually just slightly thicker than solid yet 10ga solid / 10ga stranded hmmm. But is not stranded better to manage if making bends and wrapping around something to make a choke than solid is and also stranded so says some lasts longer not as susceptible to braakage ect?

That's primarily why stranded is more widely used. However solid coax has practical uses to for needing a stiff rigid cable to run up thru walls and around corners and such.

You don't want to keep making repeated bends with it because yes you could break the center conductor. You could wrap a choke with it and it will hold in place better but you would have to be careful winding it.

 

[fourstringburn]

Just a note, weather an antenna is near 50 ohms has nothing to do with weather or not it is resonant. It is possible to have an antenna that has zero reactance and be resonant, and yet has an R, or "ohms" of either hundreds or even thousands. That near 50 ohms number just happens to make the antenna at resonance naturally compatible with 50 ohm coax, and thus possible to directly wire.

What did they do before the existence of coax where 450 and 600 ohm feedline was commonplace?


The DB

Your right generally speaking. I was referring to this antenna because it has it's own matching network that is 50 ohms at the feed point. I should have pointed that out.

When the impedance and resistance value is at or near 50 ohms for this antenna, then the reactance value will be around 0.

Here is a screen shot of my analyzer which is the Rigmaster AA54 which is far better than the MFJ259B. Even MFJ came out with a new style analyzer to compete with these ones so the 259B to me is now antiquated.

You can see below that the impedance (Z) at 52 ohms is equal to the R value making for less than 0 reactance as shown by the X value. This is as perfect as you can get but not always achievable. This is the true resonant point of the antenna. As you tune away either direction, you may still have a ideal SWR, but you are no longer be at the true resonant point of the antenna.

 

[The DB]

Your right generally speaking. I was referring to this antenna because it has it's own matching network that is 50 ohms at the feed point. I should have pointed that out.

When the impedance and resistance value is at or near 50 ohms for this antenna, then the reactance value will be around 0.

Fair enough as many antennas are designed this way, although not all. Many that use a loading coil for shortening purposes have nothing to account for the lowering of R aside from the crappy ground plane that is the vehicle body...

Here is a screen shot of my analyzer which is the Rigmaster AA54 which is far better than the MFJ259B. Even MFJ came out with a new style analyzer to compete with these ones so the 259B to me is now antiquated.

You can see below that the impedance (Z) at 52 ohms is equal to the R value making for less than 0 reactance as shown by the X value. This is as perfect as you can get but not always achievable. This is the true resonant point of the antenna. As you tune away either direction, you may still have a ideal SWR, but you are no longer be at the true resonant point of the antenna.

I agree, the analyzers from MFJ are all a bit low end. For not much more you can get a far better antenna analyzer. I count your Rig Expert as a step above the MFJ offerings.

Ohh show and tell? My turn...

The DB

 

[fourstringburn]

That's truly an in depth analysis, is that from your equipment and what did you use?

Also if you are not too familiar with the RiG Expert series, they have USB ports so you can view on your PC and print graph charts including Smith charts.

 

[The DB]

That's truly an in depth analysis, is that from your equipment and what did you use?

Also if you are not too familiar with the RiG Expert series, they have USB ports so you can view on your PC and print graph charts including Smith charts.

Its from my AIM4170c VNA. It can do more than I know what to do with, but I am still learning, even after using it every chance I get for over two years... As a matter of fact, I have seen many things that it can do, then had to do some research to figure out what it was telling me. There are still other aspects I an figuring out as well...

In the end I've learned from using it, and still am... Its a bit pricey compared to most others I have seen, but it has been well worth the investment...


The DB

 

[fourstringburn]

That's a real nice analyzer. It doesn't seem to be the most ergonomical device for portable use. That's also nice that you can interface it to a tablet for field use.

 

[222DBFL]

I need to hook up my anritsu S331E and take some good readings. It shows, return loss, distance to fault, vswr, cable loss, distance to fault vswr, has built in smith chart, and will do a bunch of other stuff. Have never used it for 11m. But it will sweep from 0 to 4GHz. Neat tool. I use it for sweeping coax jumpers and hard lines for cell sites. It only has the RF out port and not RF IN, but it does what I need it to do. Maybe breaking out a piece of equipment that cost more than all the radio equipment I own is why I don't use it lol. But seriously, I have used the mfj on my antenna and it's close enough for what I am using it for.

 

[222DBFL]

 

[Oatmeal]

Heavy Metal, haven't had much time to play on the radio much due to working, but for time been I'm going to take the Imax 2k down and retune it for the other bands....for now all I'm legal to talk on is the 10m band as you all no....

For the Imax to work on the other bands, what part of the band do you all recommend me tuning it for ?..

Way it is now I tuned it for 11m use and the swr is flat to a 1.1 on 28.325.00 to 28.500.00.....have checked it on 12m and best I recall the swr wouldn't calibrate on the radio....

Guess only way I can check the swr on the other bands is by using the 450d now in my car, I don't have anything else but a external swr meter....this still work tho won't it?


I have a beam but don't no when I'll get it up...

 

[fourstringburn]

With the Imax 2000 antenna, it has harmonic frequencies aligned with other bands. At 24 ft. factory length, the antenna is just a little over 5/8 wavelength for 11 meters as the antenna is marketed as a 5/8 antenna.

At 24.6 ft. the antenna now becomes 1/2 wavelength on 15 meters (21.000) and covers the band well and 11 meters without a tuner.

Remember the formula, wavelength speed divided by frequency equals wavelength in meters.

300.000.000 simplified to 300 into 21.000 =14.285 meters (15 meters)

convert 15 meters to feet = 49.2 for a full wavelength

now divide in 2 and you have 24.6 ft equaling a 1/ 2 wavelength on 15 meters.

For 12 meters is you do the math it is a too long for a 1/2 wave. Needs to be 19.6 ft.
For 12 meters at 5/8 wavelength the antenna is short needing to be 25.6 ft.

You can do the math yourself for 10 meters to see where this antenna could line up on this band. The shortcut method for 5/8 wavelength is easier by dividing 615 by the frequency.

It isn't possible to get this antenna truly resonant on all bands from 10 thru 15 meters. If you trim the antenna for 10 meters, you will lose the resonant point for other bands. The bandwidth of the antenna will determine how far you can go either direction before using a tuner or re-adjusting the antenna.

However, with an antenna tuner, you could operate all those bands since the antenna is in range of most tuners. When I used this antenna, I had it setup to run at 11 meters 5/8 wave and 1/2 wave on 15 meters and used a tuner on the other bands and had very good success.

Remember also, an antenna tuner is a contradiction in terms. You never really tune the antenna, you are only matching your radio to a mismatched antenna. Since this antenna is close to those bands, your effective radiated power (ERP) will still be good enough to work with.

 

[Heavy Metal]

But using what it does in base and with running rings, cannot get as good eliminating that and using an external coil instead?