My Imax 2k...

[Oatmeal]

I've got one of these up 21ft off the ground at the shack, and have been using it for 11m use the last couple years....coax I'm using 50ft of RG 213 and also a 12ft of LMR 240 coax on it....yea I no I needed to stay with one type of coax but this was something I didn't plan on doing.....( my Imax has just been at the shack for a little over a year now, that's all )......but it works good....

On the 11m band the swr is setup to be lower on the high end of the band, so from channel 10 and below channel one the swr runs a 1.3 to a 1.5....and from 27.2050 up through 27.6550 the swr runs a 1.2 or less, and the swr goes up a little around 27.7050 to 28.200 swr runs around a 1.5 to a 1.7....and at 28.3250 through 28.500 the swr runs a 1.2 to a 1.5....

This is what it was running at the last time I checked it when I was running a 2995dx...and both the rings are in the center of the black together...

I ordered a FT 450d, when I get it I'll check the swr on the 10m bands I do hold a Tech lics here, and do plan on up grading to my General soon as I can...

As far as the antenna goes, nothing has been moved the rings are still in the middle of the black, oh yea all I have done since its been put up here at the shack is added the 12ft of 240 coax, that is because I didn't have enough coax to reach the shack, other than this nothing has changed since I bought it new and set the swr on it......so, the swr all should be good on the 10m band where I set it up at from the first, right ?....

 

[Captain Kilowatt]

I've got one of these up 21ft off the ground at the shack, and have been using it for 11m use the last couple years....coax I'm using 50ft of RG 213 and also a 12ft of LMR 240 coax on it....yea I no I needed to stay with one type of coax but this was something I didn't plan on doing.....( my Imax has just been at the shack for a little over a year now, that's all )......but it works good....

You are 100% wrong about that. At NO time is it necessary to stay with one type of coax cable and whoever told you that doesn't know anything about transmission lines. As long as it is 50 ohm cable everything is fine. I have small RG-8X jumpers in my shack to connect gear followed by heavier pigtails of Belden 8214 (RG-8 type) that goes into the basement and then the main run of Andrew LDF4-50 heliax cable to more Belden 8214 on the other end.It's all 50 ohm cable so it is all fine.

On the 11m band the swr is setup to be lower on the high end of the band, so from channel 10 and below channel one the swr runs a 1.3 to a 1.5....and from 27.2050 up through 27.6550 the swr runs a 1.2 or less, and the swr goes up a little around 27.7050 to 28.200 swr runs around a 1.5 to a 1.7....and at 28.3250 through 28.500 the swr runs a 1.2 to a 1.5....

This is what it was running at the last time I checked it when I was running a 2995dx...and both the rings are in the center of the black together...

I ordered a FT 450d, when I get it I'll check the swr on the 10m bands I do hold a Tech lics here, and do plan on up grading to my General soon as I can...

As far as the antenna goes, nothing has been moved the rings are still in the middle of the black, oh yea all I have done since its been put up here at the shack is added the 12ft of 240 coax, that is because I didn't have enough coax to reach the shack, other than this nothing has changed since I bought it new and set the swr on it......so, the swr all should be good on the 10m band where I set it up at from the first, right ?....

Why would you think the SWR would change if you didn't do anything to it? Other than any effects from damage it should remain the same.

 

[Oatmeal]

CK, just kinda thought maybe it was....haven't had a radio with 10m band in it for around 2 years to check the swr there..

 

[Ham Man]

Just an idea, maybe I am just thinking out loud.
Do a simple little check.
Get a long piece of pipe or 40' of tower and put ground radials under the tower and cut the coax so it is 2 wavelengths long - electrically and then turn the power on your radio - ham or CB down to it's lowest setting and check the SWR again with a real SWR meter or a Bird Meter.

In the world of antenna's there is two kinds of antenna's, the kind that works and the kind that doesn't!
The Q of the antenna determines if the antenna is broadband or if it is a high Q antenna - it will only be resonant on one frequency and not resonant everywhere else.
A high Q antenna is very efficient, while a low Q antenna throws away most of the power put to it, or at least it doesn't transmit your signal as well.

The key is to get a different antenna, put it up at the same height, do a side by side comparison within one half of one hour of each other and see which one transmits the best. My guess is that if it is so broad banded it is either because the coax is lying to you - making a reading that the swr meter likes, or that the antenna is effectively a dummy load.

A Ringo Ranger has a high Q. I once spent two days adding and subtracting aluminum from a Ringo Ranger until I got it to operate on 11m.
It ended up being 1.6 to 1.4 to 1 everywhere from channel 1 to channel 40 @ 16.5 feet long..
That was the best that I could get out of it. If I got it low on channel 19, the SWR would be about 2.5 on channel 1 or channel 40 - just too much disparity in frequency for it to operate well everywhere.

Rule of thumb, just because the SWR meter says it is ok, doesn't mean that it is resonant!!

Put your antenna up higher 36' off the ground minimum, put a dozen ground radials beneath the antenna - at least 9' long copper wire, throw all the old crappy coax away, buy Belden 9913 or LMR 400, turn your power down to 5 watts or less and then come back and tell us what kind of SWR it has.

 

[Moleculo]

On the Imax, if nothing changed, then it should still be tuned where you left it. But things can change unknowingly. For example, PL-259's that aren't sealed properly can corrode. A squirrel can have a snack on your coax. The point is, that things change that can affect the measurements, so your safest approach is to measure it with a meter to make sure the antenna is right.

 

[Oatmeal]

Well I received the radio and checked the swr on 28.305.00 up to 28.500.00 and the first bar on the left side of the swr meter lights up, this is a 1.1, according to the swr meter in the radio ?.....and as you talk on it the swr peaks up to a 2...this is with the radio set on a 100 watts....

Is this ok to run like this ?

Been so used to running a radio on 11m, and seeing the swr not go above a 1.3....

 

[n8fgb]

Well I received the radio and checked the swr on 28.305.00 up to 28.500.00 and the first bar on the left side of the swr meter lights up, this is a 1.1, according to the swr meter in the radio ?.....and as you talk on it the swr peaks up to a 2...this is with the radio set on a 100 watts....

Is this ok to run like this ?

Been so used to running a radio on 11m, and seeing the swr not go above a 1.3....

As long as the radio is showing good output, you are good.
Rich

 

[Heavy Metal]

What if say it's 1.5: and goes back when transmitting to 1.2:1 and less and power it up their and good.

 

[wavrider]

if you vswr is less than 2.0 you good to go
make some contacts and enjoy the hobby

 

[fourstringburn]

Rule of thumb, just because the SWR meter says it is ok, doesn't mean that it is resonant!!

True, the only way to accurately know is to use a Antenna analyzer. Preferably the Rig master series which is far better than the quirky MFJ-259b.The antenna is resonant when the impedance is at or near 50 ohms and the R and Z values are the same showing a 0 reactance value or as close to it as possible. An antenna analyzer will show you all of this information and you get the inside picture of what your antenna is really doing. Using a SWR meter will not help you find the true resonant point.

cut the coax so it is 2 wavelengths long - electrically and then turn the power on your radio

Antennas are not tuned by adding or subtracting coax lengths unless that antenna system is one that uses the coax as a radiator like a G5RV antenna for example.

put a dozen ground radials beneath the antenna - at least 9' long copper wir

Yes, but put at least 2 each ( or more) ground radials at 1/4 wavelengths of each frequency your vertical antenna can operate on. The Imax 2000 is also a 1/2 wavelength at 15 meters and when I used one, it was near flat across that band. It can do 10 and 12 meters depending where your antenna rings are tuned but may need a tuner to keep your rig happy.

throw the old crappy coax away, buy Belden 9913 or LMR 400,

If your coax is in good shape, you gain hardly anything by replacing it. Don't get hung up on coax spec's like most people do. Belden 9913 and LMR coax was intended for the high losses that occur at VHF and frequencies beyond. Hence the name Times Microwave< microwaves are UHF frequencies and beyond.

RG213 is still the standard for HF frequencies and stands up to high power with the solid dialectic. The spec's between the 2 types of coax are minimal at 100 ft and even less at shorter distances. The DB loss is what you should be looking at which is very minimal of a DB between the 2 at HF frequencies. At VHF and higher, that's where the differences between the 2 really come into play. LMR 600 or Heliax cable is most commonly used for VHF/UHF on towers.

100 ft. lengths of Belden 9913 and LMR 400 at 10 MHz is 0.5 DB loss, and 100ft. of RG213 at 10 MHz, is only a 0.6 DB. Not much loss to cry about!

 

[Heavy Metal]

So even 213 9913 lmr400 are all good period. But what about 9913f7 and lmr400uf aka stranded centers vs solid centers been told solids holds more aka power ect them hear opposite stranded does which is it to solve the myth lol. Am being serious too just to hear opinions on this as well.

 

[fourstringburn]

Well I was referring to stranded centers. It is true hardline ( solid conductor center) is rated a little bit better at DB losses and higher power ratings. You can look up any manufacture spec's to disprove anybody to the contrary.

Spec's direct from Times Microwave webpage.
LMR 400UF (stranded) 2.77 kilowatts at 30 MHz
LMR 400 (solid) 3.33 kilowatts at 30 MHz.


As I noted before, DB losses is so overrated that people are infatuated with it on HF frequencies. Power ratings can be the same ridiculous argument if you aren't even running that much power anyway.

Interesting that Times Microwave doesn't give spec's on DB and power ratings below 30MHz...but give plenty of spec's way up into the GHz region.

Wonder Why?

 

[Heavy Metal]

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?

 

[The DB]

The antenna is resonant when the impedance is at or near 50 ohms and the L and C values are the same showing a 0 reactance value or as close to it as possible.

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

 

[Oatmeal]

I bought the 400UF because it's flexible......at the time I was going to set it all up for 11m use, but that's changed now..