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Barakuda318
Intermediate Member
Username: Barakuda318
Post Number: 163
Registered: 2-2002
| | Posted on Thursday, February 19, 2009 - 10:27 pm: | 
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I am in the process of building a home brew base antenna, just for the fun of seeing if I can make it work, I've taken some of my design idea from a super penetrator, but wanted to scale it down, if I use a 9ft whip stainless steel, and make a 4 beam ground plane, my question would be would I scale it down the same as the main mast, what I mean by this is the 9ft whip would be exactly 1/3 the length of the super penetrator main mast, if I remember right they were 27ft long, I can't remember for sure how long the ground planes were but it seemed like they were either 6 or 9 ft, if I scaled down the ground planes the same 1/3rd would that work, or is my math all wrong, any help would be appreciated thanks.
73's Barakuda318
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Slugo4449
Intermediate Member
Username: Slugo4449
Post Number: 179
Registered: 7-2004
| | Posted on Friday, February 20, 2009 - 12:38 am: |
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I think the Super Penetrator is a 5/8 wave vertical and the 9ft stainless whip is a 1/4 wave on CB. With a 5/8 wave, you need some sort of matching on the antenna. 1/4 or 1/2, etc. you don't need any type of matching built in.
Do a search for a simple 1/4 wave vertical and you will come up with the specs.
Hint: SWR too high on that 1/4 vertical you build? Just bend down the radials and that is how you get to 50 ohms.
Good luck and have fun.
73,
Marty |
Tech237
Moderator
Username: Tech237
Post Number: 1123
Registered: 4-2004
| | Posted on Friday, February 20, 2009 - 9:26 am: |
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Any groundplane antenna needs radials AT LEAST 1/4 wave long to work properly. If I recall correctly something I tried over 20 years ago, you can get by with a solid metal sheet if it is 3ft or more in diameter, but individual rods need to be close to 9ft to work.
Simon
Tech237
N7AUS
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Barakuda318
Intermediate Member
Username: Barakuda318
Post Number: 164
Registered: 2-2002
| | Posted on Friday, February 20, 2009 - 2:29 pm: |
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ok thanks guys, so I'm lookin at buying 4 or 5 9ft whips then, man it would be easier if I could just get my hands on a super penetrator again, should have never sold mine, lol thanks for the input guys, I'll let ya know what I come up with, might just end up with a cool looking lightning rod, hahaha
73's Barakuda318
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Barakuda318
Intermediate Member
Username: Barakuda318
Post Number: 165
Registered: 2-2002
| | Posted on Friday, February 20, 2009 - 2:35 pm: |
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O yeah I almost forgot, I'm assuming that ground plane means that the ground plane portion needs to be connected to the shield of the coax, not the center positive lead, sorry If I seem stupid to this but I've never built an antenna, and as far as my confusion goes, there is an adapter at most truckstops you can buy that adds a so called (ground plane) to you're mobile antenna, however this one hooks up to you're main mast and has three small maybe 3 or 4" ground plane antenna's coming out the side, I assumed ground plane ment on the ground side, but when I saw this little adapter it got me wondering, I don't remember were it was hooked up on the super penetrator as I owned that thing about 15 years ago lol thanks.
73's Barakuda318
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Tech237
Moderator
Username: Tech237
Post Number: 1124
Registered: 4-2004
| | Posted on Friday, February 20, 2009 - 3:46 pm: |
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Yes, the ground plane does indeed need to connect to the shield on the coax.
Not sure what you are describing, but sound more like a capacity hat than a ground plane device. Guess I'll have to stop next time I am near a Pilot station or similar and take a look..
Simon
Tech237
N7AUS
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Barakuda318
Intermediate Member
Username: Barakuda318
Post Number: 166
Registered: 2-2002
| | Posted on Saturday, February 21, 2009 - 12:27 am: |
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yep you'll find them in a pilot there a round piece of metal that looks like a nut with a threaded hole in the center that you screw you're antenna mast into then you screw this on you're mount were the antenna would go, then there are three holes on the side that you screw the little tiny side type antennas and thats it, I put one on mine and it made my swr's jump all over the place so I took it off, must have thrown it away cause ain't seen it since lol
73's Barakuda318
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Barakuda318
Intermediate Member
Username: Barakuda318
Post Number: 167
Registered: 2-2002
| | Posted on Monday, March 02, 2009 - 4:11 am: |
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Ok guys, here is an update on this antenna that I'm trying to build, Of course you know I'm using a 102" stainless steel whip for the center mast, as for ground plane radials, I have decided to go with three nine foot lengths of 1/4" steel? Alluminum?? not sure yet, however I believe these need to be facing downward at close to a 45 degree angle???? Correct??? not sure asking the pro's....thanks.
73's Barakuda318
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Bootymonster
New member
Username: Bootymonster
Post Number: 5
Registered: 10-2006
| | Posted on Saturday, April 04, 2009 - 9:44 pm: |
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http://home.att.net/~wizardoz/cbmw/antenna_fabri.html#groundp
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Barakuda318
Intermediate Member
Username: Barakuda318
Post Number: 196
Registered: 2-2002
| | Posted on Sunday, April 05, 2009 - 3:37 am: |
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Sweet thanks Bootymonster, and as far as updates, again, havn't gotten to muc further, as I'm having trouble with the mounting procedure, I think I'm gonna have to fabricate my own mounting bracket that will allow the connection of the Ground plane, if and when I get this done I will post pics thanks everyone for your input.
73's Barakuda318
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