Identify this for me

[JDWilbourn]

I found this on eBay and I have seen them on some trucks but what is it and does it help?
http://cgi.ebay.com/GROUND-PLANE-KI...hZ001QQcategoryZ48692QQtcZphotoQQcmdZViewItem

 

[Seminoles]

They call it a ground plane kit but I think it acts like a capacitance hat just at the bottom. I used the 3 element version don't remember who made it years ago on dual 4ft mirror mounts on the big truck seamed to help didn't run any scientific test but could hear better and talk to Cal from Fl parking lot maybe they brought the take off angel down since a 1/4 wave has a high angel.

 

[Master Chief]

:shock: :shock: :shock:

Its not on the "ground" side of the antenna system. If anything, its nothing more than a LOAD at the base of the antenna.

(now where is that cool icon for "snake oil"?)

 

[Highlander_821]

It's called a "separator."

It separates you from your money, and that's about it.

 

[W5LZ]

A "separator", best description I've heard yet - lol. You gotta admit though, it isn't one of those cheap imitations!
- 'Doc

 

[C W Morse]

Capacity hat that, if used, should be at the TOP of the whip. The REAL use for it is to reduce the number of turns in a loading coil. ANY coil produces resistance. But coils sometimes have to be used to reduce length, height, to permit a mobile antenna to be used at a very low frequency--or for a few other reasons. So, if you can reduce the resistance, and/or reduce the height to fit a given applications, it is usually done with this capacity hat (increases the capacity of the load). There is a benefit in increased signal tho the actual amount of the increase is subject to various factors. For physical reasons (should be obvious), the capacity hat is often located farther down the whip, but should not be right over the top of the coil.

In a nutshell, it really doesn't help in CB radio other than to make people think they are really doing something more and cause people to spend $$ in the search of the ever more big signal! It has NOTHING to do with "ground"! The whatcha-ma-call-it is an active part of the radiating element so it can't BE part of the ground; if it were, the antenna would be SHORTED out.

I put this on another website,and it was promptly deleted as, I suppose, the truth about CB "gadgets" was not wanted!

73

Gadfly

 

[Switch Kit]

I've seen and had a few of those myself , did I ever see them do anything ? Yes I did . Weather or not it's rose colored glasses or not ? I've seen them slighty raise swr readings and I have have also seen then bring them down a few notches as well , yes ! but for the most part , not much , Especially if the guy already has a decent match to begin with. I once used a air conditioning unit for a ground plane on a wilson 1000 with 40 some odd feet of coax , the match was best at 1.8 ,one of those little ground planes brought it down to 1.4 , weather or not they were false readings , the antenna had good clearance and got out very well. I've seen many of those on peoples rides over the years , and I personally didn't have anything to say about it. Weather or not it's a placibo or not ? if a guys conscience is better at ease with one of those and he can live with it , that's all that really matters. It's not like they cost an arm and a leg to begin with. And even if they don't do a damned thing , I can see where a guy would think they looked pretty cool all the same. 8)

 

[W5LZ]

They are definitely not a 'cure-all' for anything. But, they can make some differences. If they make connections with the radiating element rather than ground, at the very least, they will make the 'whip' portion slightly longer. Effectively changing the length of the antenna, so retuning it, sort of. If that's what happens then you could do the same thing by just adjusting the whip, probably. That doesn't say anything about it being a capacitive hat, but it would act that way too.
If it makes connection to the ground side of the antenna, then it would act sort of like the opposite of a capacitive hat by making 'ground' appear closer to the whip. About the same as shortening the whip, so it ~could~ make an SWR change to the better, or worse too. Same sort of change you'd get from readjusting the length of the whip.
Now. It the price of this thingy worth it? Uh... not to me cuz I'm cheap and would rather just change whip length (if possible). I don't think it's particularly 'good looking' so that part of it isn't much use to me. And then there's the fact that there's always more than one way of doing things. This 'way' just doesn't suit me (cheap again)...
- 'Doc

 

[C W Morse]

CWM

 

[W5LZ]

karo,
That 'stretcher' may change take off angle but not much, if at all. The thing that determines take off angle is the length of the antenna, and it's environment (what's close to it, where it is). A length difference of about an inch (if that's the thickness of the thingy?) just isn't gonna do much. Certainly not a $15 difference - lol.
- 'Doc

 

[C W Morse]

They are definitely not a 'cure-all' for anything. But, they can make some differences. If they make connections with the radiating element rather than ground, at the very least, they will make the 'whip' portion slightly longer. Effectively changing the length of the antenna, so retuning it, sort of. If that's what happens then you could do the same thing by just adjusting the whip, probably. That doesn't say anything about it being a capacitive hat, but it would act that way too.
If it makes connection to the ground side of the antenna, then it would act sort of like the opposite of a capacitive hat by making 'ground' appear closer to the whip. About the same as shortening the whip, so it ~could~ make an SWR change to the better, or worse too. Same sort of change you'd get from readjusting the length of the whip.
Now. It the price of this thingy worth it? Uh... not to me cuz I'm cheap and would rather just change whip length (if possible). I don't think it's particularly 'good looking' so that part of it isn't much use to me. And then there's the fact that there's always more than one way of doing things. This 'way' just doesn't suit me (cheap again)...
- 'Doc

Doc,

I agree except on one point (minor) Top hats will make the physical whip shorter because it has the same affect of adding turns to a coil IF the coil was too short too short to start with. SO you can add a "hat" to the coil to make the whip effectively longer. We may be saying the same thing, different words. *IF* we could get away with it, we---well, most of us, perhaps---- would do like you: just use the longer (or shorter) whip as needed and forgo the funky-looking radials or discs. For the lower HF bands, I can understand using capacity hats (for 160 mobile, about no way to do without one!). For 27 MHZ it is mostly a placebo that makes people think it does something for them! It is a useless appendage! It does absolute nothing and is one of those CB myths and legends!!

For the others who believe it does "something"------YES! It WILL change the SWR of the antenna and cause you to have to adjust the length of the whip or reduce the number of turns in the loading coil (if any). Remember the word "CAPACITY"!

It does NOTHING TO, FOR, OR AGAINST GROUND!
Stop and think a minute. This thingy is attached to the WHIP itself. IT IS PART OF THE RADIATING ELEMENT OF THE ANTENNA. Now take a wire and attach it to nearby ground. Your antenna will be SHORTED down with the VOM reading "INFINITY" (dead short)!!!!!!

Doc (and the others) are right! Save your money unless, of course, you want to send it to me! I'll put it to good use!

73

Gadfly

 

[W5LZ]

I think we're saying the same thing, just different view points.
- 'Doc

 

[C W Morse]

73 Doc!

 

[bob85]

i have a local that uses a similar device and swears it gives him a lower vswr and better signals,
i played with one years ago and it did nothing usefull for my antenna,
the difference betwen our antennas is the mounting position,
i always mount my antennas roof center while he has his mounted at the rear corner of his roof,
these things are part of the radiator which i imagine would give extra distributed capacitance to ground, if that is the case could they also be compensating for the lack of ground mirror around his mobile antenna when the antenna is mounted in a less than ideal position :?:

 

[W5LZ]

Bob,
What lack of 'mirror' ground? The capacitance is all that it's really going to contribute. The 'ground' is there, it just may not be as symetrical as you may want it (then again, it may be just where you want it?). The 'shape' of the radiation pattern doesn't say much about resonance, but the 'size' of the pattern does. 'Size' relates to power, 'shape' relates to the characteristics of what/where the antenna is.
- 'Doc