Using MFJ-941C Antenna Tuner With CB

[jopcobra89]

Hi all,

I have a few "makeshift" antennas and use an antenna tuner to lower SWRs. The low power tuner made for CBs that I've been using works great, but I just bought a MFJ-941C tuner / meter combo unit for cheap that's rated to handle 5 to 300 watts. Unfortunately my 4 watt stock radios don't put out enough for it to be of much use.

I had one of these tuners way back in my "ham" days and loved it... but of course my HF rig was putting out 100+ watts.

Just wondering if anyone has experience with this tuner and can it be modified somehow to handle low power tuning below its rating?

Thanks!

[231]

According to what I read on that, the maximum power it can handle is 300w. It doesn't say anything about minimum. Guys use antenna analyzers to set their tuners up all the time. That only puts out a fraction of a watt. I see no reason why 4w is too little. Nor do I see in the instructions that it can't be used for QRP (lower power).

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Best of luck.

[303_in_il]

I had a 949E tuner, I could tune both my a99 and my 40 meter dipole with just 300mw from my hf rig, it should work fine. Hope you have good luck with the tuner, the inductor switch burned up on mine at 100w and I had a fire in the shack. Running a Palstar now and I LOVE IT!!!

[North Texas Mudduck]

ok did you know the "antenna tuner " does not tune your antenna

heres a test no more trying to explain but just do the test

radio coax swr meter coax "antenna tuner" coax swr coax antenna

you can twist and turn that tuners knobs left and right and watch the swr go swinging but the swr meter out the antenna side of the tuner remains the same

what ever your swr is with just radio meter and antenna that is your swr

if you want to tune anything then tune the antenna for lower swr

['Doc]

The idea for using a 'tuner' is to match the antenna system's impedance to the transmitter's impedance. It doesn't change anything about the antenna system except the impedance presented to the transmitter. It allows that transmitter to put out full power to the antenna system, no matter what the antenna system's impedance happens to be. Ideally, adjusting the antenna's impedance to match the feed line's and the transmitter's is the way to do it.
But what if you can't adjust that antenna for some reason? Maybe it's not a CB antenna? In that sort of case, a 'tuner' comes in real handy. I know I've done that with some pretty 'odd' antennas, it works. Probably won't mean a very 'good' signal, but it works. You've heard about using bed-springs I'll bet. How about window screens? Or maybe a wire fence? They can all be made to work if the 'tuner' has the range of adjustment required. Sometimes those 'odd' things can work amazingly well. I wouldn't count on it, but it's certainly possible. It certainly beats not having an antenna too.
Tuners aren't miracle workers but sometime a little 'skootch' here and there comes in handy.
- 'Doc

[North Texas Mudduck]

You have to learn how to hook them up to your tranceiver properly and tune them correctly to make your radio think that it is feeding it's signal into a "perfect or near perfect 50 ohm load called your antenna.
An antenna tuner, (transmatch), doesn't really TUNE your antenna OR ANY PART OF IT!

What an antenna tuner or transmatch does do, however, is transform the impedance at the antenna feed output at the radio to a value that your transceiver can handle, (typically 50 Ohms).
When thinking about antenna tuners and SWR, it's important to remember that
the tuner has no effect whatsoever on the SWR between itself and the antenna.
It's the SWR between the transmitter and the tuner that is changed with the tuner controls.

In layman's terms, all a tuner does is act as a kind of adjustable impedance transformer between the radio and the antenna. It takes whatever impedance the antenna system presents, up to the design limits of the tuner, and attempts to convert it back to 50 Ohms--or something reasonably close to that value for the transceiver. When the transceiver "sees" a 50 Ohm impedance, it is able to load or produce it's maximum designed RF output into the system because it is designed to operate into a 50 ohm load.
Your rig "thinks" it's seeing a 50 ohm antenna on it's output!
That power is transferred through the antenna tuner, to the feed line and, ultimately, to the antenna--minus any losses incurred along the way.
If you have high loses and a poor excuse for an antenna, you will have a poor excuse for a good signal no matter how well your tuner "tricks" your radio.
Most of the power will be lost as heat in the tuner and very little will get to the other station!

['Doc]

You were really doing good till you got to that last sentence. I'm afraid the losses in tuners is greatly exaggerated, they really aren't that bad unless the antenna and feed line are totally unreasonable. There are losses with any antenna and feed line, all of them. The typical losses in a tuner are not all that great if the antenna is harmonically related to the transmit frequency. There will be losses, but not as much "loss" as not having an antenna at all. Staying within the tuners abilities is also a very good idea.
- 'Doc

[Double D]

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[jwalker48]

You were really doing good till you got to that last sentence. I'm afraid the losses in tuners is greatly exaggerated, they really aren't that bad unless the antenna and feed line are totally unreasonable. There are losses with any antenna and feed line, all of them. The typical losses in a tuner are not all that great if the antenna is harmonically related to the transmit frequency. There will be losses, but not as much "loss" as not having an antenna at all. Staying within the tuners abilities is also a very good idea.
- 'Doc

Yup! Spot on! NOTHING beats a resonant antenna for each frequency you are working. BUT sometimes that isn't possible. For me, I have to work frequencies from 1.8 thru 30 MHZ on HF. I'd have to have a plethora of antennas across the yard to cover all I do! This includes amateur and some military frequencies. My LDG tuner, while not doin' the absolutely the greatest signal in the world, gives some surprising results and really good reports. WIth the tuner and One "folded" dipole, I can go anywhere on HF I need to.


jwalker

[Night Crawler]

WIth the tuner and One "folded" dipole, I can go anywhere on HF I need to.

Just curious what do you use for feedline?