Hello. I have a question about tuning an antenna. Is it better to use an air variable capacitor or a roller inductor "18f" with a choke to change impedanc, to Obtain a lower match ? Please share experience and suggestions. Thanks
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Antenna Tuning
- Thread starter MadisonMod
- Start date
Is that the model with the 3/4" tube for the top whip ?
It should tune as is without a matching device at the feed point by adjusting the tube.
How do you have it mounted?
73
Jeff
It depends on the impedance. A series inductor will lower the resonant frequency as well as make the bandwidth narrower. A series capacitor will electrically shorten the antenna and make it resonant higher in frequency. You really need both an inductor and a capacitor because simply adding one component introduces a reactance that must be cancelled out by an equal and opposite value of reactance. Then there is the question of which component to place in series......the cap or the coil........and which to put in as a shunt to ground........again the cap or the coil. One way allows you to match to a higher impedance, while the other way allows you to match to a lower impedance. A single cap or coil MAY be all you need but we cannot tell you based on what you have told us so far. We need to know your intentions (trying to make a multiband antenna?) or simply tweak the bandwidth?
Umm, so why do you need a tuner on that antenna? Never had one, but I thought it was famous for having a low SWR and being fairly broad banded.
Putting a tuner in line with an antenna that's already tuned just fine only wastes power. Probably not enough to matter, but what is the objective here?
73
Putting a tuner in line with an antenna that's already tuned just fine only wastes power. Probably not enough to matter, but what is the objective here?
73
Its Kales heavy duty 10 k with a larger insulator and uses 3\4" tube for the top section in place of a flexible whip.
It should tune around 82" total length for the CB band as long as its mounted properly.
Put some Nolox on all the set screws, that's the only issues I have ever had with his antennas.
After years exposed to the weather they can corrode and seize up.
73
Jeff
It should tune around 82" total length for the CB band as long as its mounted properly.
Put some Nolox on all the set screws, that's the only issues I have ever had with his antennas.
After years exposed to the weather they can corrode and seize up.
73
Jeff
Any single coiled cb antenna mounted on the vehicle roof in the middle will usually tune to around 1.2-1.3 : 1 swr. Antennas without a coil will usually tune to slightly below that to maybe 1.2- 1.1 something. Impedance when measured on an mfj or something will usually be 37-40 ish ohms.
If you use a shunt you can usually get 1.0 50 ohms. Cbers are scared to see a coil going to ground so they dont do it. Any base loaded antenna like a sirio or a wilson has a shunt matching network built into the base. They usually have a connector like a so-239 for mounting to provide the needed ground to the antenna.
The "regular" style of isolated antenna stud, like a 3/8-24 stud, ball, or puck mount does not provide for that. You can however take a trip to the hardware store and make whatever u want.
If you use a shunt you can usually get 1.0 50 ohms. Cbers are scared to see a coil going to ground so they dont do it. Any base loaded antenna like a sirio or a wilson has a shunt matching network built into the base. They usually have a connector like a so-239 for mounting to provide the needed ground to the antenna.
The "regular" style of isolated antenna stud, like a 3/8-24 stud, ball, or puck mount does not provide for that. You can however take a trip to the hardware store and make whatever u want.
Yes. That is the one. I used it on a 3/8inch stud mount on a 2 " bracket. My swr was 1.2 and 1/4 watt reflect
I switched to a 4" mount with a high power puck. Now swr is 1.5 I ran new ground straps and new 217 coax . For some reason it's not happy. I tried changing the angle up and down, swr gets worse.
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Yes. When I used the stud mount previously I had 1.2 and 1/4 watt reflect. I have an mfj-259d antennaanalyzer. I installed new 4" bracket with high power puck and new 217 coax 18ft . Now swr is 1.5 I tried a shunt but it raised swr to 1.8 , maybe it's too long ? Not sure .
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Yes. Makes sense. I'm try to change the Impedance to make the swr lower . So witch would you suggest. Inductor air coil on the positive lead of coax and cap or chock off the back through the ground ? Here's a picture.
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It was working great with 1.5k . I decided to upgrade. I mounted it on a high power puck on a 4" mount. With new 217 coax . Now the swr is 1.5 I did adjust the stinger in and out with mfj-259d attached. Swr only got worse and ohms changed drastically. For some reason it's seeing something it doesn't like, or not seeing. Strange not sure why it got worse with better products
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Predator 30k short shaft. With 18ft of 217 coax on a high power puck mounted on a 4" bracket
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I had it on a 3/8 stud. With 18ft of 217 coax. Swr was 1.2 and a 1/4 watt reflect at 1.5k . It Was easily toonable for any Chanel. I decided to upgrade. It's now on a high power puck mounted on a 4 " bracket with new 217 coax , but it's not happy. Swr now 1.5
I'm trying to get lower match back
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