M
marconi390
Guest
A similar topic is being discussed in the thread below entitled "Imax 2000."
If you want to check out the ground plane affect on an antenna, a check that is pretty easy and revealing, then consider this experiment. Instead of using a more complicated system like an end fed 1/2 wave element, or a coiled antenna, which requires matching, then just use a 1/4 wave whip. Considering the problems you hear about with many mobile setups, you will see from this example just how important the ground side of your antenna really is to its operation. Maybe this will help you understand why so many guys have trouble getting mobile antennas to work, antennas which for the most part are simple plug and play type antennas.
You to can probably make this simple setup to experiment. I took a mirrow mount and mounted it to a metal mast 10' or so just to get the AT off of the ground. I used a 20' pushup mast. I screwed a 1/4 SS whip into the top, hooked a line to it and hooked a radio to it with a good meter in line. A very quick check tells you that you have no workable match to work with.
Ask your self if an A99 uses the coax or the mast as a part of the matching for the antenna, then maybe it works the same way with a 1/4 wave antenna and antenna we know does not need a matching device. WRONG!
Why didn't the 1/4 wave use the coax shield, the mast, or both to complete the system network to allow the natural match we know the 1/4 wave has to work? Was it simply because we left the ground plane system off? If that is so, then why dosen't it act just like the A99, which is determined by many to do just that?
Now, attach another 1/4 wave whip to the base, the mount, close to the feed point using some vice grips and check it again. Wow, what a big difference you will see. I also use a spacer with threads in both ends so I could attach two elements, one on each side. I find that one is quite enough and that two is just too much. Does that surprise anyone? Try it yourself and then try a different length element or several longer or shorter elements, and see what happens. Experiment around a little, I think you will be surprised.
Why didn't this setup do like they say the 1/2 wave end fed antennas do, use the shield, mast, or both to complete the circuit? Is there something else at play in this scenario, maybe so and maybe another time.
I will try to attach some picture here so that you can see exactally what I did. It is pretty simple and it may be revealing to you too, just how important the ground side of these antennas, in particular mobile antennas, really are. Then realizing how delicate the ground side of these antennas are, think what it is that is going on when we install them on a vehicle that has all kinds of shapes, angles, and mass to present.
Marconi himself
Hang loose,
Marconi CDX 39ZERO
27.365 >
No amps, no more!</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=marconi390>marconi390</A> at: 6/1/04 8:00 am
If you want to check out the ground plane affect on an antenna, a check that is pretty easy and revealing, then consider this experiment. Instead of using a more complicated system like an end fed 1/2 wave element, or a coiled antenna, which requires matching, then just use a 1/4 wave whip. Considering the problems you hear about with many mobile setups, you will see from this example just how important the ground side of your antenna really is to its operation. Maybe this will help you understand why so many guys have trouble getting mobile antennas to work, antennas which for the most part are simple plug and play type antennas.
You to can probably make this simple setup to experiment. I took a mirrow mount and mounted it to a metal mast 10' or so just to get the AT off of the ground. I used a 20' pushup mast. I screwed a 1/4 SS whip into the top, hooked a line to it and hooked a radio to it with a good meter in line. A very quick check tells you that you have no workable match to work with.
Ask your self if an A99 uses the coax or the mast as a part of the matching for the antenna, then maybe it works the same way with a 1/4 wave antenna and antenna we know does not need a matching device. WRONG!
Why didn't the 1/4 wave use the coax shield, the mast, or both to complete the system network to allow the natural match we know the 1/4 wave has to work? Was it simply because we left the ground plane system off? If that is so, then why dosen't it act just like the A99, which is determined by many to do just that?
Now, attach another 1/4 wave whip to the base, the mount, close to the feed point using some vice grips and check it again. Wow, what a big difference you will see. I also use a spacer with threads in both ends so I could attach two elements, one on each side. I find that one is quite enough and that two is just too much. Does that surprise anyone? Try it yourself and then try a different length element or several longer or shorter elements, and see what happens. Experiment around a little, I think you will be surprised.
Why didn't this setup do like they say the 1/2 wave end fed antennas do, use the shield, mast, or both to complete the circuit? Is there something else at play in this scenario, maybe so and maybe another time.
I will try to attach some picture here so that you can see exactally what I did. It is pretty simple and it may be revealing to you too, just how important the ground side of these antennas, in particular mobile antennas, really are. Then realizing how delicate the ground side of these antennas are, think what it is that is going on when we install them on a vehicle that has all kinds of shapes, angles, and mass to present.
Marconi himself
Hang loose,
Marconi CDX 39ZERO
27.365 >
No amps, no more!</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=marconi390>marconi390</A> at: 6/1/04 8:00 am