Using a 102 whip as a base station

[Lil'Yeshua]

I used my tv antenna as a ground plane but when I replaced it with a Solarcon A99 antenna with the GPK-1 ground plane kit,substituting the GPK-1's 6 foot ground radials with four SS 101.5" Radio Shack whips,my TX and RX went up by a good two s-units. The 102" whip is okay for local talking but leaves much to be desired as a base antenna.
By the way,Marconi,those models you've presented on this thread are more than I thought a 102" whip would do.

Note:if you use just one radial/ground plane segment,point it in the general direction you want to talk towards. op:

 

[Robb]

http://www.worldwidedx.com/cb-antennas/31857-dipole-your-cb-base-station.html

 

[Riverman]

Thanks, Robb.

Followed your link and found lots of good info!

Still hoping someone can tell me what makes the "L" antenna in the pics a dipole rather than a GP.

 

[W5LZ]

...easy. It has two 'poles', and 'di' means two. It's an inverted 'V' laying on one side. It takes at least three points, or two -crossing- lines to make a 'plane', as in geometry.
- 'Doc

 

[Riverman]

Thanks, 'Doc.

Here's where I'm confused: I was thinking the difference is this:

If the bottom leg is grounded (in contact with the metal mast) then it is a GP. If it is insulated from the mast, (not grounded) it's a dipole design.

Anything to that?

 

[nosepc]

This is a inverted V antenna at 36'
This is my model.



If someone wants to test with, copy, modify, here I leave to the public the code I did in 4nec2

CE
GW 1 3 0 0 7.25 -0.0707107 0 7.25 1.e-3
GW 2 150 -0.0707107 0 7.25 -1.979899 0 5.34081171 1.e-3
GW 3 150 0 0 7.25 1.90918831 0 5.3408117 1.e-3
GE 0
EK
EX 6 1 2 0 1 0
GN 0 0 0 0 13 0.005
FR 0 1 0 0 27.2 0

 

[W5LZ]

Using the mounting pole as the 'other half' of an antenna isn't exactly too good of an idea. That 'other half' has to have a couple of electrical characteristics that a random length pole/mast just won't have. If you can make that pole/mast the right length then it would work just like any other conductor as the 'other half' of a vertical dipole. But, usually means that pole/mast is too short to get the thing high enough, and also get's complicated to put together, insulators etc. Making the physical characteristics and the electrical characteristics compatible isn't easy. It can be done, but not simple/easily.
I would have to try that idea about one element straight up and the other pointed down at an angle attached to the rain gutter, the gutter also being part of the 'ground' side of the antenna. I honestly can't say how it would work, or how well, but I'd have to try it just to see. Or, just use that gutter as the antenna's 'other half', don't use that second antenna as a radial at all. That'd be like a 'groundplane' antenna with only two radials.
Again, won't be the bestest thingy in the world, but it'd 'work'...
- 'Doc

Do you happen to have a tree near your house that's fairly tall? You can make a 'groundplane' antenna out of wire and an SO-239 connector that will work too (done that one). Hang the thing from a high limb, and adjust the two redials like an inverted 'Y'.

 

[Riverman]

'Doc, using the mast wasn't my intention. Say I use two 1/4 wave radials made from copper wire. The vertical whip is isolated from the steel mounting bracket via a plastic sleeve in the stud mount. The wires, however, are connected directly to the bracket and tied off at the other end with something non-conductive such as rope, keeping them at their chosen length.

Here's my question: Does the bracket have to be isolated from the steel mast with something non-conductive between the bracket and the pole?

If so, are all ground planes (A99, etc.) isolated from their mast with something non-conductive? I just can't get this clear in my mind. Once I do,

Thanks,
Jim

 

[W5LZ]

Are all radials making up a groundplane insulated from the mast/ground? No. Can they be insulated from ground/mast? Yes. Do whichever is easiest for you.
And just to keep things straight, an 'A99' or other antennas like it are not 'groundplane' antennas, there is no 'groundplane' to them, they don't require one. They use the feed line as the other 'pole'/groundplane/counterpoise.
- 'Doc

 

[Lil'Yeshua]

Are all radials making up a groundplane insulated from the mast/ground? No. Can they be insulated from ground/mast? Yes. Do whichever is easiest for you.
And just to keep things straight, an 'A99' or other antennas like it are not 'groundplane' antennas, there is no 'groundplane' to them, they don't require one. They use the feed line as the other 'pole'/groundplane/counterpoise.
- 'Doc

What about my A99 with ground plane ? I plan on making a rf choke and isolating the antenna from the mastpole.

 

[W5LZ]

"What about my A99 with ground plane ?"
No matter if you put a GPK on it or not, it still uses the feed line for more than just getting a signal to the antenna unless you have modified the internal parts of the antenna. That GPK is more of a 'line isolator' than actual 'groundplane'. That's not bad, but certainly not the stated purpose of the thing.
Something else to think about is that just insulating the 'A99' from the mast isn't really enough. The feed line being near the mast will induce some current on to the mast unless you move it away too. (Won't that be fun??)
You know, these antenna worked just fine until people started over analyzing them, finding all these 'faults'. There was unwanted radiation at times but that dealt mainly with RFI matters (either your own or neighbors), and that's always a two-sided thingy...
- 'Doc

 

[Lil'Yeshua]

Thanks for your reply.
As it is at the moment,I have the coax running down the mast from the A99 then takes a 30 degree or so turn away from the mast straight through the air to the my radio. I'm planning on making a rf choke for it. I want to do everything I can to tweak this antenna for best performance outside from replacing it with something better. I'm having my first experience with my first A99. I'm seeing what one will do personally that's set up right. I read all the comments from the naysayers that poo poo on this antenna. Granted,it's not anywhere near the best burro in the stable but I'm gonna make it work according to all the study I've given it.

 

[Riverman]

'Doc,

Thanks for clearing that up for me. It was driving me nuts that I couldn't remember (of course that was 40 years ago!) and I couldn't find the answer anywhere I searched.

Made my day.

Jim

 

[Riverman]

Now here's another question.

Rather than use 102" (or thereabouts) lengths of wire for my radials, can I use 3' Firestik antennas? I know the length is wrong and that they are 5/8 rather than 1/4 wave (although I've been told all helical antennas of this nature pretty much function as 1/4 antennas regardless of claims). Just wondering if they would provide needed "ground plane" (they will be pointed downward at 45 degrees) that the vertical requires and if the inpedance would be in the ballpark.

Any ideas?

 

[Lil'Yeshua]

The 102" Whip CB Base Station Antenna - YouTube
http://youtu.be/j3Wsxzv-Fjw