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Base A-99 and Neighbors?
- Thread starter 338_MtRushmore
- Start date
Just had a nice roundtable with the local tech and the vice president of the local radio club. Life is good
I have been researching new antenna's to go w/ my Sirio 27-4 I currently use an A-99 and thinking of an I Max an a forum I read on Copper Electronics they did on the GP Kit more or less stated if the kit does nothing at all it helps Electronics interference the way it changes the wave .It was quite a lengthy and informative article .
http://www.copperelectronics.com/discus4/messages/7750/20506.html?1023340740 I found the link they mention the A-99 same design as Imax only 1/2 wave . Good Luck .
I am working on a grounding plan, but I need to move my station to the other end of the camper and I'm short on coax. Is 45 feet of Rg8x too lossy, or would that be ok? I've only done short runs in mobiles before, so I have never researched longer runs and I'd like to get some coax shipped today. Thanks
It just dawned on me to find a calculator, and it said a .6dB loss with 8x compared to 400. Seems like a lot to me, but I'm not sure of the real world difference
It just dawned on me to find a calculator, and it said a .6dB loss with 8x compared to 400. Seems like a lot to me, but I'm not sure of the real world difference
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You just need a simple 1:1 RF Choke to choke off common mode currents on the feedline. WTF is a voltage choke?
I do have a 12t on 3" choke up there now, and it actually did help with rf in my stereo. I have no idea if it is causing any other issues though.
I also got a ground rod sunk at the mast, but I haven't actually grounded anything yet. I'm not sure what I want to use for equipment grounds yet. I should probably figure that out and get on that.
I also got a ground rod sunk at the mast, but I haven't actually grounded anything yet. I'm not sure what I want to use for equipment grounds yet. I should probably figure that out and get on that.
just a few things to add to the thread, hope im not too late. (as in, i hope you havent gone to too much trouble and expense yet)
first, driving ground rods into the ground isn't going to help you one bit, unless you get struck by lightning, and even then, they are not going to stop your RV's electronics from being destroyed.
your problem stems from the way the A99 works.
Ever seen the old ads for it where they say it's a "half over a quarter wave, mutual transductance tuned antenna" or something like that?
well what they don't tell you in the ads is that the "quarter wave" part is made up of the first 8.5 feet of coax coming out the bottom of the antenna.
so if you put a choke right at the feedpoint you are changing the characteristics of the antenna design and probably upsetting the pattern. on an A99, the choke should be placed 8.5 feet down from the feedpoint.
with an antron, you need to get the antenna up 10 feet or more above the roof line, and put ferrite on the coax 8.5 feet down from the feedpoint.
which brings me to my next point. wrapping coax into a coil is not the way to make a choke. there is a diagram with lots of colors on it that has been floating around the internet confusing people for a decade now.
the purpose of the chart was to show people how much worse coax wrapping was than using actual ferrite over the coax, but everyone misinterpreted it to be a chart showing you how much coax to wrap.
you can buy kits on ebay that include 5 or 6 snap on chokes, and this is the right way to make a common mode choke.
after that, since it's an RV, you might want to make sure that the metal case of your stereo is actually grounded to the vehicle body/frame.
also make sure your radio is not a splatterbox.
hope this helps.
LC
first, driving ground rods into the ground isn't going to help you one bit, unless you get struck by lightning, and even then, they are not going to stop your RV's electronics from being destroyed.
your problem stems from the way the A99 works.
Ever seen the old ads for it where they say it's a "half over a quarter wave, mutual transductance tuned antenna" or something like that?
well what they don't tell you in the ads is that the "quarter wave" part is made up of the first 8.5 feet of coax coming out the bottom of the antenna.
so if you put a choke right at the feedpoint you are changing the characteristics of the antenna design and probably upsetting the pattern. on an A99, the choke should be placed 8.5 feet down from the feedpoint.
with an antron, you need to get the antenna up 10 feet or more above the roof line, and put ferrite on the coax 8.5 feet down from the feedpoint.
which brings me to my next point. wrapping coax into a coil is not the way to make a choke. there is a diagram with lots of colors on it that has been floating around the internet confusing people for a decade now.
the purpose of the chart was to show people how much worse coax wrapping was than using actual ferrite over the coax, but everyone misinterpreted it to be a chart showing you how much coax to wrap.
you can buy kits on ebay that include 5 or 6 snap on chokes, and this is the right way to make a common mode choke.
after that, since it's an RV, you might want to make sure that the metal case of your stereo is actually grounded to the vehicle body/frame.
also make sure your radio is not a splatterbox.
hope this helps.
LC
I appreciate the help. I am going to ground the mast for lightning protection. I couldn't find a ground rod at the utility box to use. I figured that being insulated with rubber and wood that I should probably give lightning a safe path home.
What ferrite mix is the proper one to use?
I just don't understand the antenna needing the coax. Why wouldn't it use the metal mast? Is the wound choke completely ineffective, to the point that 8.5' of coax is still part of the antenna? If so, and I put ferrite chokes at the feed point, the vswr would be off the chart. Maybe I will try ferrite at 8.5', then insulate the antenna from the mast and snap some ferrite at the feed point.
I second that question
I have an A-99 where I used an extra piece of wire/metal to ensure continuity between coax shield and mast pipe (done at the so-239/pl-259 feedline attachment point) and I have a "choke coil" (several wraps of coax in a circle about 3 or 4 inches down from the threaded connectors).
SWR on a simple meter, almost looks like a dummy load, I'm not thrilled about that and thought something was wrong at first. But it is still working that way, any suggestions or tips please?
Thank You, Best Regards
PS: Having a direct connection to earth soil must have some affect on the antenna characteristics, I don't have any citation or reference or anything for that, it's just my "half-baked" interpretation.
Question: the home made ground plane on this A-99 would be {electrically} before the "choke coil" in this setup, no?
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Mix 31 is best for HF, you could get by with mix 43 since CB is near the top of the HF band. Mix 31 covers 1-300 MHz while mix 43 starts at 25 MHz up to 300 MHz.
Interesting, why wouldn't the whole coax radiate not just 8.5 ft?
If so, then a choke definitely needs to be placed at that point.
Maybe that's why I've read where people call these antennas "bleed sticks" because the coax is radiating as much as the antenna.