Recommend Ground Plane Kit For Imax 2000?

[W5LZ]

Marconi,
"...so induced currents will tend to be mainly on the shield. That leads to an unbalanced condition with radiation from the feedline ocurring as a consequence."

I'm afraid a balun is no 'sure cure' for that CMC, and I think you know that.
---

"Since the voltage at ground should be constant..."

Right, it -should- be, but very seldom is.
---

Using a balun can be profitable in some circumstances, and just not worth the effort in others. When the 'cost' of using a typical balun with a groundplane, or dipole is weighed against it's benefits, I don't think it's worth the 'cost'. That 'cost' isn't just $$, but the potential problems also found with the typical balun.
One of the 'benefits' of using a balun is symetricity of the antenna's radiation pattern (or maybe the most quoted benefit with maintaining balance). Except for directional antennas, that's just not worth worrying about at HF.
As far as balanced/unbalanced and RFI is concerned, that's another one of those associations that just doesn't hold water. RFI, or unwanted radiation can be a product of any feed line and antenna combination you can think of. The most you can hope to do is minimize it, you can't stop it. That minimizing is certainly something that's good to do, just don't expect miracles, and keep things practical. A balun on every coax fed antenna is just not very practical, and in my opinion isn't reasonable.
- 'Doc

 

[delta]

Hi there guys, im in the UK just inside the M25 north side and have been running a Imax 2000 for about 10 years or so and had good results on my lattice tower thats 57ft to the base of the antenna. I was thinking about changing it for something else just for the change, something like the sirio 827 or the sigma moantova turbo 8 or the intercepter 10k. I'm not sure wich way to go to be honest, i have thought about the GPK for the imax and reading this thread has got me re-thinking. The money side of things doesn't bother me, i just want the best antenna i can get my hands on for rx and tx.

 

[Marconi]

Marconi,
"...so induced currents will tend to be mainly on the shield. That leads to an unbalanced condition with radiation from the feedline ocurring as a consequence."

I'm afraid a balun is no 'sure cure' for that CMC, and I think you know that.
---

"Since the voltage at ground should be constant..."

Right, it -should- be, but very seldom is.
---

Using a balun can be profitable in some circumstances, and just not worth the effort in others. When the 'cost' of using a typical balun with a groundplane, or dipole is weighed against it's benefits, I don't think it's worth the 'cost'. That 'cost' isn't just $$, but the potential problems also found with the typical balun.
One of the 'benefits' of using a balun is symetricity of the antenna's radiation pattern (or maybe the most quoted benefit with maintaining balance). Except for directional antennas, that's just not worth worrying about at HF.
As far as balanced/unbalanced and RFI is concerned, that's another one of those associations that just doesn't hold water. RFI, or unwanted radiation can be a product of any feed line and antenna combination you can think of. The most you can hope to do is minimize it, you can't stop it. That minimizing is certainly something that's good to do, just don't expect miracles, and keep things practical. A balun on every coax fed antenna is just not very practical, and in my opinion isn't reasonable.
- 'Doc

Yep 'Doc, I can't argue the negatives, but if all I see is an improvement in RX when adding a coax choke to my old Sigma IV, then that's good enough for me. If I don't read a perfect zero on the scale of my CMC meter---then I'm satisfied. Like I said earlier:

That said though, I suspect that CMC are present as a matter of degree, and if that degree is small---is that important enough to be concerned about?

 

[freecell]

"I'm afraid a balun is no 'sure cure' for that CMC, and I think you know that."
"Since the voltage at ground should be constant..."
Right, it -should- be, but very seldom is.

the only BalUn that doesn't suppress or eliminate common mode current on a feedline is a BalUn that doesn't impose high enough levels of impedance upon the outside of the feedline shield. furthermore, any condition that exists that prevents the ground voltage from remaining constant IS the presence of common mode current on the outer shield and/or a poor ground connection as the voltage there is always ZERO with reference to ground potential. the only fluctuating voltages existing in the feedline should be in the center conductor and on the two poles of the antenna itself. it's no mystery why the voltage at ground with reference to ground potential is constantly fluctuating since the absence of the BalUn and improper antenna design is a predisposition to this condition. in any situation where a BALANCED ANTENNA IS FED WITH UNBALANCED FEEDLINE THERE WILL BE UNWANTED RADIATION FROM THE FEEDLINE ITSELF.

common mode current is the portion of conductor currents not matched by exactly opposite and equal magnitude currents. This is the portion of total current responsible for a feedline behaving like a single wire line. common mode current is most commonly caused by improper feedline installation or antenna design. The feedline, in effect, behaves like two very different transmission lines connected to the antenna and equipment at the same time.

a properly designed choke or current balun inserts a large amount of common mode impedance in series with the feedline without causing unwanted changes to differential mode operation. when common mode impedance substantially increases, common mode current on feedline will be greatly decreased. the combination of proper grounding and high common mode balun impedance can reduce unwanted currents to immeasurable or unnoticeable values, restore symmetry of expected radiation patterns, eliminate unwanted feedline radiation and correct imbalances between the current that exists in the opposing elements of a wide range of antenna designs, guaranteeing maximum and equally opposing electric and magnetic fields required for absolute efficiency in the radiation of the generated electromagnetic field.

transmitter power radiated from the feedline doesn't get radiated from the antenna. transmitter power radiated from the feedline destroys the symmetry of the expected radiation pattern. the use of BalUns may be impractical and unreasonable to you but if you don't mind terribly the rest of us would like the opportunity to be the judge of that for ourselves.

 

[mackmobile43]

Why bother wondering if what you read here is true? why not build your very own rf sensing current mode meter? and see what's really what>? Clip-on RF Current Meter

 

[BOOTY MONSTER]

ive seen folks say ring magnets are good for combating CMC's . is there any truth to that ? if it is how would they compare to a balun or coax choke/coiled up ?

if so this seems to be pretty high quality magnets at a decent price . but itll only fit 8x or smaller coax .
NSN0814 - Rare Earth Magnet - Ring - D0.500 x d0.250 x T0.125 - Package of 12 - Detail
12 for 9 bucks + S&H

these wil fit the .405 stuff
NSN0616 - Rare Earth Magnet - Ring - D1.000 x d0.500 x T0.125 - Package of 4 - Detail
4 for 9 bucks + S&H

 

[freecell]

optimum results can be had using either teflon or delrin. pvc and "rubber" will work but the dielectric coefficient of these materials is compromised due to the presence of carbon black and other conductive trace elements.

 

[W5LZ]

BOOTY MONSTER,
Those ring/donut magnets can work, but not because of the magnetism. They would work because they are iron, which would be less effective than ferrite mixes, but still usable. The magnetism might come in handy to keep them all together, or stuck to a pole, but that's it.
How effective are ferrite cores as compared to a coax choke? Not very. One or two won't be enough. Usually takes at least a foot or two of them, if not more.
And just by chance, if you happen to have an old TV laying in your backyard, look for a large ferrite core under that gob of wire wound on the picture tube (deflection coil). Not very pretty, but you can thread coax through it and it does work just dandy. Don't loose the metal clips that hold that core together, you'll need them. Forget the flatsceeens or plasma TVs, they don't have any useful parts in'em.
- 'Doc


That's not exactly true about no usable parts in a flatscreen TV. If you take that flat screen apart, remove all the wire, etc., then grind the remaining flat parts up really fine, spread it over the yard under your antenna. Does absolutely nothing, but it'll keep you off the streets for a while.

 

[HiDef]

And just by chance, if you happen to have an old TV laying in your backyard, look for a large ferrite core under that gob of wire wound on the picture tube (deflection coil). Not very pretty, but you can thread coax through it and it does work just dandy. Don't loose the metal clips that hold that core together, you'll need them. Forget the flatsceeens or plasma TVs, they don't have any useful parts in'em.
- 'Doc

Are you serious or is this some sort of yoke?

 

[W5LZ]

HiDef,
That's not a joke. It also means more than just one time through that core, wind a few turns on it.
- 'Doc

 

[HiDef]

HiDef,
That's not a joke. It also means more than just one time through that core, wind a few turns on it.
- 'Doc

I can't believe that one went over your head.

Yoke not joke.

Ya know.....deflection yoke.

It was a play on words.

 

[W5LZ]

... @#$. I can't believe I missed that either. Oh well, some days are better than others. That's what my 'nurse' keeps saying. And considering what my 'nurse' looks like, I don't mind having those days at all!
- 'Doc

 

[BOOTY MONSTER]

BUSTED !!! hahahaha

i herd/read a good one today . dude on another forum told me God showed him that theres perceptable difference by human ears in different metals on antennas .

LMAO !!
http://www.sparkyscbshack.com/board/board_topic/3935213/481319.htm

 

[loosecannon]

booty,

WOW!!!!!!!!!!!!!
i almost made it all the way through that thread, but my head was swimming with all the different ways i wanted to yell "moron!". LOL

there is just so much wrong with those guys i wouldnt know where to begin to try and explain things to them.

the guy with the God quote obviously didnt understand the idea of velocity factor. LOL

i dont know how you can stand to hang out there. you are a patient man indeed.
LC

 

[Marconi]

BUSTED !!! hahahaha

i herd/read a good one today . dude on another forum told me God showed him that theres perceptable difference by human ears in different metals on antennas .

LMAO !!
http://www.sparkyscbshack.com/board/board_topic/3935213/481319.htm

BM, was Old Grandpa posting on that thread? I think he was trying to tell me about that one too. Wrong Website but maybe the same players. Never mind.