Antenna tuning question for CB radio

Thread Starter

Darkstar

Joined Sep 3, 2010
139
I was wondering if it is okay to use 2 antenna matchers in series to help match a radio & cable to an antenna? The component placement would be radio- long coax - SWR meter - ant matcher - ant matcher - antenna.
Thanks
 

SamR

Joined Mar 19, 2019
2,590
No... The word superfluous comes to mind. The sequence should be radio, coax jumper, SWR meter (if radio doesn't have one), coax jumper, tuner, coax, antenna. The antenna should also be tuned first. Anything introduced into the "line" between radio and antenna introduces inherent signal loss. So does the quality of the coax and its connectors. My preference is a wattmeter that has dual needles to display both forward and reflected signals whose crossing gives me SWR.
 
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Thread Starter

Darkstar

Joined Sep 3, 2010
139
I used to do it just the way you described but I recently saw something that said the SWR meter and tuner should be at the antenna end of the coax because the radio and coax are already made for 50 ohm impedance and it's the antenna that usually has to be matched to the rest of the system. I've found that in some cases with poor antenna placement or design, my tuner is incapable of fully matching the system. Putting another tuner in line has seemed to give me extra tuning capability. With the 2 tuners, I can sometimes get SWR as low as 1.0:1 when I can't even get close with only 1 tuner.
 

nsaspook

Joined Aug 27, 2009
7,594
Using two inserts more losses and hides problems that need to be fixed. Use one more capable tuner and/or design and place the antenna correctly. While it might be perfectly match to the transmission line the actual radiation resistance losses at the physical antenna increase to make it a net loss.
 

SamR

Joined Mar 19, 2019
2,590
I only use a SWR meter at the antenna when tuning the antenna. There are available very expensive waterproof external automatic antenna tuners but you have to run power out to them. Not a typical installation. CBs have very limited legal power available. Long ago I learned that radio power is useless without an antenna to radiate it. The better the antenna the better it radiates that power and money spent on antennas gives a better return of value than spending it on better radios. Simple things like elevation, wavelength, coax losses pay great dividends. If you have to use 2 tuners to get a better signal then you need a better tuner. In fact, you shouldn't even need a tuner for CB if your antenna is tuned.
 

Thread Starter

Darkstar

Joined Sep 3, 2010
139
This seems to be the best I can do with the parts available and my condo rules about antenna placement and radio operation. It's not a long term set-up, just something to fill my time. I just wanted to be sure I wasn't way off base. I can receive and transmit but I don't know how my range. I threw together a mobile antenna on a tripod with 102'' ground planes in my living room. I can't even put it on my balcony. I don't detect any interference on any TV or radio in my home but I would get shut down if I bothered neighbors so I just listen now and then. This is mostly to check that a CB and some antennas I have are working all right because I'm selling them. Thanks.
 

nsaspook

Joined Aug 27, 2009
7,594
Just remember, you can make a antenna from just about anything conductive with the right tuner. It might not be the best antenna but that's rarely needed in most conditions.

 

Thread Starter

Darkstar

Joined Sep 3, 2010
139
I only use a SWR meter at the antenna when tuning the antenna. There are available very expensive waterproof external automatic antenna tuners but you have to run power out to them. Not a typical installation. CBs have very limited legal power available. Long ago I learned that radio power is useless without an antenna to radiate it. The better the antenna the better it radiates that power and money spent on antennas gives a better return of value than spending it on better radios. Simple things like elevation, wavelength, coax losses pay great dividends. If you have to use 2 tuners to get a better signal then you need a better tuner. In fact, you shouldn't even need a tuner for CB if your antenna is tuned.
Long ago I had a half wave antenna on my roof and one tuner. I have the same Radio Shack radio & tuner now but I have to cobble antennas together to hide them from my condo association. I can't use the 1/2 or 1/4 wave base antennas and I only have a mobil bumper mount antenna to use. I definitely do not have the good set up I had 50 yrs ago.
 

Thread Starter

Darkstar

Joined Sep 3, 2010
139
Just remember, you can make a antenna from just about anything conductive with the right tuner. It might not be the best antenna but that's rarely needed in most conditions.

That's what I'm trying to do. I've tried to figure out how the Radio Shack tuners work but it's hard to make sense of them. They work but when I check continuity, half of the unit seems shorted out. It's not one bad tuner, both are identical. If I understood that part more I might experiment with new or modified tuners. As it is, it's not worth the effort at this time in my life.
 

Thread Starter

Darkstar

Joined Sep 3, 2010
139
Attached is a photo of a 4 foot fluorescent bulb being lighted my my indoor mobil antenna on a tripod. With better tuning I can get almost the whole tube to light up.CB Lighting 4 foot Fluorescent.jpg
 

SamR

Joined Mar 19, 2019
2,590
Condos and HOAs... Arghhh... Tuners are typically used for bad antennas. In fact, recently saw an article about a ham operator using an aluminum lawn chair on his balcony for a "camouflaged" antenna. When antenna tuners started to become popular around 50 years ago there were several articles about tuning up the good ole lawn chair just to prove it could be done as a novelty and telling whoever you made contact with that you were using a lawn chair antenna. Attic antennas to thwart HOAs have been popular but the living room not too good an idea performance wise. CBs operate ~11 meters so dropping a half or quarter wave antenna out of the window would work better. Legal CB is 4 watts so the wire can be very very small in diameter and almost impossible to see from a distance. You would end up with a much more effective Vertical antenna that way. Check out some of the FREE PDF ARRL antenna books that can be found online.
 

SamR

Joined Mar 19, 2019
2,590
The antenna tuner is basically a large adjustable PI filter. A large inductor coil in the transmit line with an adjustable capacitor to ground both before and after the coil. Cheap ones use a fixed, sometimes tapped, coil and better ones (for wide bandwidth) use a roller inductor. Most that I have come across that were marketed for the CB craze in the 70s were pretty much junk. Check out MFJ Enterprises. They started out with just a couple of specialty Ham Radio items long ago but now have quite a large selection of antenna adjuncts to improve performance. I have one of their MFJ-1040C tuners that I use on a long wire antenna for my ICOM R-75 all band receiver that not only tunes but also has some pre-amp and filtering capabilities. It has a fixed and tapped coil with a band (wavelength) rotary selector switch and knobs for the variable caps. No meter but for receive only it is a simple matter of twist the knobs until it sounds better. I don't pay a whole lot of attention to the small meters found on a lot of radios. If I remember correctly, it can also be used with a low power (<100W) transceiver. My 100W ham transceiver has its own built-in tuner.
 
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