Instructables

Stub Tuning a CB Big Stick Antenna for 10 Meters - Ham Radio

Picture of Stub Tuning a CB Big Stick Antenna for 10 Meters - Ham Radio
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Many long years ago, when I was just a pup, I purchased a Shakespeare 'Big Stick' CB antenna. You've seen them – they look like an eighteen foot long, white fiberglass fishing rod. Because of its long, skinny design, the antenna would fit anywhere, on the chimney, up a mast, or shoved among the branches of a tree. Eventually, I got tired of looking at it up my tree, so I took it down and stowed it in the garage, for over twenty years.

 
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Step 1: First step - just try it out

Picture of First step - just try it out

I had always heard that a Big Stick was wide banded, so I tried it on the10 meter Ham band – just a gnat's whisker from the 11 meter Citizens' Band. Not that wide banded, it turned out.

Nevertheless, with the help of a small antenna matcher I had, I was able to get my rig to work with the antenna. I didn't like the setup, though; I was using a single band, 25 watt amateur band mobile rig and wanted to run the coax straight to the antenna without a lot of hoopla. So I thought and thought and tried something else.

Step 2: Idea

Picture of Idea

Without going into a lot of technical talk, I knew that either an open or shorted section of coax cable could be used to match an antenna to a transmitter. That seemed a good way to do it. That way, the rig would be connected to the antenna with nothing to tune between the two.

Anybody up to speed on an amp instructable?
Indrid_Cold5 months ago

Good day RangerJ

I did a slightly modified version of your stub tune on a mobile CB/10 Meter transceiver. Being a mobile station I could not run a lot of stub at the splitter. One foot of coaxial cable was not enough and I did not want to run more so I put an old fashion terminating resistor for networks at the end of the one foot coaxial cable. The antenna is a Wilson Silverload tunable antenna with the extra ground plane cable at the threaded end of the antenna. Grounding the ground plane cable made the CB band near perfect for Standing Wave. 10 meter was terrible though. The standing wave ratio was 5 to 1 with or without the ground plane cable grounded. I had to place the splitter at the radio end of the coaxial cable. So it is directly on the back of the radio. The standing wave ratio is very close to 1 to 1 in all CB channels. The 10 meter band never gets a standing wave ratio higher than 1.8 to 1. All the way to just under 30 Megahertz the standing wave never gets above 1.8 now. I am not sure how much power I am losing through this configuration yet but the radio has absolutely no danger to it at all. I know the 50 Ohm terminating resistor on the 1 foot coaxial may be acting like a dummy load. My effective transmitted power may be very low. I am not sure yet because the salvaged watt meter does not work. Heck the radio is a dumpster dive I repaired myself too. Your thoughts on the 50 ohm terminating resistor at the end of the 1 foot coaxial at the radio end is very welcome. Thank you for your idea and for your future advice on my modified configuration of your idea.

RangerJ (author)  Indrid_Cold4 months ago

I think the terminating resistor is
soaking up some of the power, for sure. But that's the same case with
the stub or even a transmatch. The point is to trick the radio into
thinking the feedline/antenna combination is a perfect match. I used to
have an old transmitter with a big swamping resistor inside - some
signal went into the antenna and the rest into the resistor, more or
less depending on the antenna.

I guess the real test is how well it works.

Thanks for the comment.

Back in the 70's I put a 7ft FireStik on this, instead of the 102in Whip. Now your Talking! It will also give you a perfect match!!
camogreen1 year ago
Why not just cut the top section? Trial and error but maybe start with 5 or 6" and work from there. Should be able to dial it in.
RangerJ (author)  camogreen1 year ago
The bottom half of the antenna is part of the dipole - if you cut off the top, it gets more and more unbalanced. You can't get much easier than my method of experimenting with different length coax jumpers.
Ok. So the big stick is a coaxial dipole. I use an A-99 for 10 meters which is not that type so cutting the top a few inches dials it right in for 10.
RangerJ (author)  camogreen1 year ago
That's correct. The Big Stick is supposed to be broad banded but it isn't that broad. Also, there are a few different varieties. Mine is 30-some years old, if I count correctly.
dsandds20032 years ago
Great instructable. The key is the matching transformer. Wish i could find the info for making that universal balm transformer that automatically matched your antenns to your reciever.
RangerJ (author)  dsandds20032 years ago
Thanks -
If you find that universal balun schematic, I would love to see it. Hook that to some lossless coax and you would be uptown!