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Message |
    
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 321
Registered: 9-2004
| | Posted on Sunday, March 27, 2005 - 12:29 am: | 
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im planning on using some of those ferrite beads that clamp around your coax on my next antenna install.
my question involves using one or two of them right near the coax connector on a TOP ONE antenna. i have read in the patent sheet that this antenna needs to have the coax running down the mast to work correctly. i would like to know if using the ferrite beads at the connector would somehow interfere with whatever effect that running the coax down the mast has. in other words; "will using ferrite beads near the coax connector have any negative effects on the performance of the TOP ONE antenna?"
thanks for any help and/or input
matt |
Marconi
Intermediate Member
Username: Marconi
Post Number: 414
Registered: 11-2001
| | Posted on Sunday, March 27, 2005 - 7:09 am: |
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Kid I can't answer your question for sure, but I can pose something to think about.
First off the type of beads you are referring to may not be sufficient to do what is need in that situation if your idea is to prevent common mode currents that might be on the feed line. Next is, if they did work and a metal mast was attached at the hub, then this mast would serve the same function as the coax and allow common mode currents to go to ground. If you used the beads and they worked to prevent current from riding the shield down to the ground and if you used an insulated mast, I'm not sure what would happen to the operations of the antenna.
I have tried this on an Imax 2000. I used a non conductive mast and used my analyzer at the feed point and the match of the Imax went away. I added various lengths of coax, 3' to 30', and as the coax got longer the match got better. I even made a coax choke at the feed point and that did not make one bit of difference to the match, but I'm not sure that it was working either. My guess is that nothing you do at the feed point of these two antennas is going to stop what mother nature is going to do and still work. I guess another option to try with the Imax would to install a GPK and then to the non conductive mast thing and see what happens then.
Are you showing a lot of RF at the station using the Top One, or was it just an idea that crossed your mind? I was stimulated to do the test noted above after reading an article located at
W8JI on Verticals and Baluns
Take a look.
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Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 325
Registered: 9-2004
| | Posted on Sunday, March 27, 2005 - 7:42 pm: |
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thanks for the link marc!
yeah, this was just a precautionary measure that crossed my mind as i was trying to take any and all possibilities into consideration before installing my top one.
yes, this is the same project ive been blabbering about for the past month or longer. ive just been planning and aquiring parts like a madman.
im just about ready. im still planning on posting the details when im finished, but here's a few just to get you thinking. aluminum oxidization was taken into consideration.
the hardware was upgraded to stainless steel.
the ring is now a "perfect" circle, and will be secured to the mast.
the coax is LMR400.
the tip of the antenna will be at 54 feet.
and last, im going to incorporate "rhinoliner" into the equation.
chew on that for awhile and look for a post titled "top one at 54 feet". and i think im going to add the beads on the notin that they cant hurt. thanks for the input. the way you laid it out for me makes it much simpler to see.
look for the post!!!!!!!!!!!!!
matt |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 427
Registered: 7-2004
| | Posted on Tuesday, March 29, 2005 - 7:03 pm: |
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Kid,
Do a search for Radio Works (Line Isolators
I use this system, combined with a LM-TVX2
TVI filter from Coppers.
Also,an interesting book to buy is:
The ARRL RFI BOOK, excellent imformation
on all types of RFI problems & on how
your grounds should be set up.
JIM/ PA/ CEF 375 |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 335
Registered: 9-2004
| | Posted on Tuesday, March 29, 2005 - 10:48 pm: |
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thanks jim, yeah, that ARRL RFI book is quite helpful. i bought one years ago while trying to track down a TVI problem. (i ended up finding that all the townhouses in my section were grounded to eachother and nothing else. (i moved)
my reason for asking this question isnt because i am interfering with the neighbors; im just adding the ferrite in an attempt towards the "perfect" antenna installation. my reasoning is that common mode currents are bad, and ferrite beads reduce them, so i thought i should have some on there since they're cheap and easy to put on.
i just didnt know how this would affect the performance of the antenna, being that it is a somewhat unique design. i think marconi laid it out for me pretty well, and im planning on adding a couple. my goal is to not need a low pass filter, although i have a DRAKE here that i can use if need be.
thanks for the link. i will check them out.
matt |
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