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CB Radio Forum - Discussions regarding Citizens Band Radio (CB)

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  #21 (permalink)  
Old 02-06-2018, 3:41 PM
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I forgot to mention if you want to use sky wave propagation "shoot skip" get a couple of 102" whips and mount that one horizontally.
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Old 02-06-2018, 7:20 PM
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Cutting your coax based on wavelength and velocity factor for the type of antenna you have is a huge waste of a calculator and wire cutters. It sounds like your dipole is a bit too long if the SWR is better on channel 1 than 40 and you should be able to get a better match if its not too close to large metal objects. You can also improve the match to 50 ohm coax by making it an inverted V instead of a horizontal flat top.

An RF choke made of coiled up coax on PVS pipe is also a wast of good coax. For a cheap and really effective RF choke at CB frequencies wrap 8 turns of coax around an FT-240-61 ferrite core which will give you close to 30dB of choking impedance.
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Quote:
Originally Posted by Bryan_G View Post
I have the regular dipole up, 1/2 wave horizontal, and it seems to get out. So far I've only talked to one person about 2 miles away and he said I sounded good. Also, he was on the end side, not the direction I'm broadcasting. My dipole is east west and he's east, so I'm somewhat encouraged.

I don't have a good SWR, it was 3:1 on ch 40, same on ch. 1, and about 2:5 on ch. 19. That was with 100' of coax. I can't go below 70', that's where it comes out of the wall. I used the full 100' because that was the length I bought and it came with connectors on both ends, so I thought I would just run it and use it.

Last night I did some calculating on signal velocity and wavelengths and came up with 15.29' as lengths I should use ( 492 x vf frequency), my nearest length over 70' was 75.95' so I cut it there (I read many posts saying length isn't important, and just as many saying it is) .SWR stayed at 3:1 on 40 but dropped to 2:1 on ch 1. I wish it would have gone the other way as everyone I know is on the higher channels. After that I read later in the same post that you should just go by 11' lengths, but it's too late as I'm already under 77'...

Reading other stuff on the web, someone put together a page on making a choke/balun by winding the coax around a piece of PVC, I'm going to try that and see if I can get the SWR down. Optimum Coax Coiled Turns Choke Baluns for Antennas

I'm hoping that adding that balum and adding a ground at the antenna end, I can get the SWR down...

The firestick dipole:
I still haven't put this one up yet, I was waiting on one part. After reading on this post that I want the coax leaving the dipole at 90 degrees, I ordered a 90 degree connector, and it just came here yesterday, Sunday. I'm planning on going to the attic tomorrow and installing it.

I was worried about all of this being a waste of time and money, then I thought, if all this fails, an antenna tuner and small boot will fix it all, but I'd rather not have to go that route.
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  #23 (permalink)  
Old 02-06-2018, 11:39 PM
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Originally Posted by w2rea View Post
This is all you need. I have this setup in my attic and it works great.
That's what I was talking about when I mentioned my firestick dipole. I just installed it this afternoon. I have the cable run, I just need to drop it down the wall in my office and put the end on. I'm hoping this does better than my wire dipole as far as SWR.
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Old 02-07-2018, 1:32 AM
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One 9 foot whip and a few 9 foot wire radials, will make a nice ground plane antenna!
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Old 02-07-2018, 4:59 PM
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Originally Posted by w2rea View Post
This is all you need. I have this setup in my attic and it works great.
Well, I tried this and it did not work, 5:1 SWR across all channels. The one you posted, he cut the antenna down to get a match, I can't, I have the firestick firefly's, they have the screws on the end, I can only make them longer...

Quote:
Originally Posted by prcguy View Post
You can also improve the match to 50 ohm coax by making it an inverted V instead of a horizontal flat top.
I don't have the room for a 90 degree angle, does it have to be 90? Where I located it, the center would be 4' higher than the ends, would that make a difference or just screw things up worse?
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Originally Posted by prcguy View Post
An RF choke made of coiled up coax on PVS pipe is also a wast of good coax.
prcguy
From what I read, I only need to wrap my coax around a 4" piece of PVC and only need 4 windings, I can do that without haveing to add any coax, I can just use the slack in the attic. Would that work?
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Old 02-26-2018, 12:12 PM
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this would work https://durhamradio.com/t225-mini-ba...io-canada.html
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  #27 (permalink)  
Old 07-01-2018, 10:20 AM
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I ended up making a ground plane from a 4' firestick and some #14 wire. My SWR is 1:1 on ch. 1 and 1:1.3 on ch. 40. I can't get the SWR down any further on 40 because the screw used to adjust the antenna is all the way down already, but this is good enough.

I bought a versa tuner 2 for the dipole so that is now matched.

I have all the info on a web page I made. I have pictures of my antenna systems here 2112/1673 - Milwaukee
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Old 07-01-2018, 4:30 PM
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1:1 or 1:1.3 no one could complain about that. I like the 'groundplane' nice work.
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Old 07-03-2018, 5:44 PM
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Good picture worth 1000 words this should help lots of people with questions.
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Old 07-03-2018, 5:45 PM
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Quote:
Originally Posted by w2rea View Post
This is all you need. I have this setup in my attic and it works great.
Nice set up
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