Recommend Ground Plane Kit For Imax 2000?

[Wire Weasel]

good to hear you had positive results on both TX and RX .
can you tell any difference in your noise floor/static levels ?

Yes absolutely Booty I forgot to mention. Imax is much quieter I noticed that right off the bat. Is a quiet day anyway but meter lays slap on zero and is noticeably quieter noise floor. Nice!

 

[BOOTY MONSTER]

getting a stronger recieve level and a lower noise floor is a double shot in the arm for your ears .

 

[loosecannon]

wire weasel,

did you end up using the choke balun?
if you posted whether you did or not, i mustve missed it.

if not, you might try it.

i have heard from a few different sources that four radials are not enough to decouple all of the currents on the coax shield.

whether or not this applies to your particular situation i dont know.
LC

 

[Marconi]

wire weasel,

did you end up using the choke balun?
if you posted whether you did or not, i mustve missed it.

if not, you might try it.

i have heard from a few different sources that four radials are not enough to decouple all of the currents on the coax shield.

whether or not this applies to your particular situation i dont know.
LC

LC, how do we tell if our choke is working as you suggest? I have heard many claims on the issue, but nothing has ever been suggested that is provable and duplicatable to be obvious and convincing without a doubt. I'm reluctant to take anything I hear on the Internet without being able to duplicate the process and realize some or the same results. Otherwise I have to depend on blind faith, which is so often based on a whole lot of CB BS. I know what efforts I make on testing and it is not easy work. There are exceptions I'm sure, but I suspect that most of the claims we hear are just so much writing on the rest-room walls. Most guys are just not going to put forth the effort necessary. That's alright though, it takes a lot of work, but I say, "...don't give me your ideas and dreams as though they are facts without producing some tangable results."

I am convinced, however, you're correct in your comment about adding extra radials, but I want to try and duplicate my findings on that subject several more times to make sure. I have experimented with such ideas in 2003, 2006, and my recent work on adding radials did not prove to be successful in duplicating my previous efforts, so I must re-think what I am trying to do in each step, plus I do not even try to report my work from memory and this is where even my notes sometimes fail me.

W8JI is a much written author on such matters and in this case says, somewhere on the Internet, that just touching or moving your coax or your radio is not a good enough test for the presence of Common Mode Currents. He says a suitable clamp on amp meter is required to definitively tell if CMC are on the feed line. 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?

I think I recall that freecell once told us that the Sigma 4 responded exceptionally well to the addition of a choke at the feed point. I recently added a choke, 7' section of RG8/U coiled on a 4.5" non-conductive form, and so far I can't tell anything except that my bandwidth curve shows me that my adding the 7' feet of coax dropped my SWR from an average of 1.21 @27.605 down to 1.16 @27.305. At this point this only shows me I have a bit of feed line transformation in my system due to a bit of reactance at resonance and frankly I am not one that thinks that is the least bit important to operastions.

I also may be realizing a bit of reduction to noise from the radio due to the choke, but it is really hard to tell with conditions as they are and because I cannot test the system for noise differences instantly---using a line switch. I am just taking the facts of my choke on faith and that it is working as it should---making some positive difference.

So, you see what I'm saying about following the ideas and claims of others on the Internet. To be fair though, I was not scanning at the feed point so my figures will likely be skewed a bit due to reactance and the approximate 82' feet of feed line I have installed, but I have nothing more to go on than some easy to say words, right?

LC, if you know of a test or comparison procedure to be sure in this case please let me know and I will check it out even if you are just brainstorming and idea.

How say you?

 

[Wire Weasel]

Hey guys,

No I haven't tried the balun but that may be the next step.

Mr. Marconi I believe the point of a balun is use on if you need one. If station is experiencing TVI or other stray RF in the shack or around the house, then taking steps to remove stray RF from the feedline can be one cure and/or one thing to try anyway. These baluns are easily done/undone.

TNX!!

 

[freecell]

"....the current will flow into the properly placed resonant radials without insulating anything."

no it doesn't. if this was the case then everyone who simply added a radial system would report improvements in performance. this forum is replete with posts reporting exactly the opposite scenario. simple rf current measurements comparing the total current in all radials to the current in the radiator will bear this out. until total radial current equals radiator current the system is operating out of balance. furthermore, a 1:1 current balun is (required) not an option as long as unbalanced feedline is being used to feed a balanced antenna design.

the best materials i have found for isolating the support structure from the antenna are teflon and delrin because of their high (k) dielectric properties. the objective is to insure that all common mode current flows ONLY in the radiator and the radial system, thereby insuring that maximum current in the e-plane is transferred to the initial primary electric field. this condition is defined as "perfect elevated ground".

reference:
http://www.worldwidedx.com/cb-antennas/19996-e-plane-h-plane.html#post30424

as was previously posted, a reduction in overall average noise in the system is the result of the suppression of common mode current present on both the support structure and the outer shield of the feedline.

signal strength increases on the order of 1.0 - 2.5 S-Units are not actually occurring as the common s-meter (asynchronous) reads much less than 6 dB. per S-Unit below S-9 but improvement in signal strength does occur nonetheless. my measurements indicate that actual figures are more on the order of 1.5 - 3.75 dB..

 

[Beetle]

".... furthermore, a 1:1 current balun is (required) not an option as long as unbalanced feedline is being used to feed a balanced antenna design...

Not necessarily. You may benefit from using such a balun if you experience RFI, but there are thousands (and maybe hundreds of thousands) of dipoles -- balanced antennas -- being fed with coaxial cables of various types -- unbalanced feedlines -- with excellent results. In fact, I have one up now for 20 meters, fed with RG-213 and no balun. It works just fine.

 

[BOOTY MONSTER]

isnt rg213 a balanced feedline ? isnt all coax balanced ?

 

[freecell]

RFI is only ONE of several shortcomings resulting from feeding balanced antennas with unbalanced feedline. no one is disputing that good results can be had, it's just imperfect and offers plenty of room for improvement. the currents in dipole antennas fed with unbalanced feedline are just as out of balance in the two poles as they are in the antenna type that is the subject of this thread. if you haven't made the rf current measurements for yourself then i'm not debating the issue with you.

the pole connected to the feedline center conductor always has more current present than the pole connected to the shield and this imbalance prevents a dipole fed in this fashion (WITHOUT a BalUn) from ever developing maximum current in the electric field of the e-plane. if maximum electric field is not achieved then the magnetic field in the h-plane never fully develops either. (electro-magnetic field) the current missing from the pole connected to the shield winds up on the outer shield of the feedline and any conductive structure that may be supporting it, period. anyone wanting to argue the point needs no response from me. make the measurements and you will find that i know exactly what i'm talking about because you'll see the same thing too.

if you want OPTIMUM performance from a dipole or an earth ground independent ground plane type of antenna then the BALUN is a NECESSITY. if you disagree then you are unfamiliar with ALL of the shortcomings which are inherent in the design. MAXIMUM RADIATION from either one of these antenna types depends solely on IDENTICAL AMOUNTS OF CURRENT in both "HALVES" of the antenna completely cancelling each other out for the generation of MAXIMUM ENERGY IN BOTH ELECTRIC AND MAGNETIC FIELDS. Any CURRENT imbalance between the two halves DIMINISHES THE MAGNITUDE of the resultant ELECTROMAGNETIC FIELD.

in any event there are thousands (and maybe hundreds of thousands) of dipoles that could be performing far better than they presently are.

BM. all single "coaxial" feedline types are by their very definition "unbalanced." on the other hand all twin lead and ladder line type feedlines utilizing identical parallel conductors are "balanced."

hope that clears it up for you.

 

[BOOTY MONSTER]

thanks jack . i guess this info is wrong then .
Antenna Notes

 

[freecell]

read it again....

paragraph 7, sentence 6.
"parallel line is often refered to as balanced line."

paragraph 8, sentence 5
"coaxial cable is often refered to as unbalanced line."

same thing i just told you....thanks for the link.
Walt's got some good information there.

 

[BOOTY MONSTER]

im an idiot , not that yall didnt know that already .

thanks again freecell .
its good to know Jack .

 

[W5LZ]

...odd. In a two conductor system, how can you have more current flowing in one of those conductors than in the other? If there is a difference in current flow, where does that 'extra' current come from?
That's not some more of that 'NPC' stuff, is it?
- 'Doc

 

[HiDef]

How many angels can dance on the head of a pin?

 

[Marconi]

...odd. In a two conductor system, how can you have more current flowing in one of those conductors than in the other? If there is a difference in current flow, where does that 'extra' current come from?
That's not some more of that 'NPC' stuff, is it?
- 'Doc

'Doc, freecell is right and IMO Walter Fair address the issue you raise in the following statement. The problems of an unbalanced condition are valid and it is no way more of that "NPC" stuff:

"On the other hand, coaxial line has the center conductor shielded, 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. In addition, most of the time the coax shield is connected to ground, either at the antenna or the transmitter. Since the voltage at ground should be constant, the full voltage differential occurs on the center conductor, which leads to an unbalanced condition. For this reason, coaxial cable is often refered to as unbalanced line. Other measures must be taken to minimize the transmission line imbalance.

That's not too hard to understand---is it?