MFJ-841 2 Meter SWR and Power Meter

Shows the selection switch, connections, and sensitivity pot

Rear view of the MFJ-841 SWR/power meter

With my first purchase of ham equipment, I decided that I couldn’t live without a simple SWR meter. I did some shopping and made my purchase based on price alone. For the last couple of weeks I was not sure if I made a good purchase, but I decided to email MFJ with a question, and now I know that I did a good thing.

I paid about $50.00 for the MFJ-841 from hamradio.com. I had already built my 2 meter vertical dipole and I assumed that it would have a good SWR so I raised it on it’s 20 foot pole and secured the guy wires. This was all done a few weeks before my call sign came in so I couldn’t legally test the antenna’s SWR by transmitting.

It was when I could legally test the antenna that I became confused. I followed the directions that came with the meter, but I did not understand what “setting the switch to
SEN (sensitivity), keying up and adjusting the meter for maximum needle
deflection” meant. Did it mean setting the needle to the end of the printed scale, or did it mean setting the needle to bend against the meter case? I assumed that it meant setting the needle to the end of the printed scale, but when I did that I had a 1:1 SWR on my antenna at 146MHz. I doubted that it was that good! I was hoping for the best and preparing for the worst, which would mean bringing the antenna down and cutting the caps off to trim the copper for the best SWR.

After emailing MFJ, they confirmed that the needle should be set to the end of the printed scale and not bending the needle at ‘max’ deflection. If I wrote the directions, I would have put a picture as an example since I believe that max deflection sounds like the needle needs to go as far as it can. Their definition of ‘max’ means the maximum that the printed scale shown extends. I learned something valuable today, and with this information I am going to test all kinds of antennas for 2 meters!

I want to finish with photos that I took using my new knowledge, but I want to say that MFJ has quick customer service. I also want to thank them for providing downloadable user manuals and for including the schematic for this device in that manual.

Five watts

FT-60 Xmit power shown on the MFJ-841

This 2 meter dipole has a great SWR across the whole 2 meter band

Graph of SWR using data from MFJ-841 SWR/power meter

This is bending the needle!

Wrong setting for sensitivity

This shows the correct setting. The meter needle is at the end of the scale.

Correct setting for sensitivity

My 2 meter vertical dipole's swr @ 147.960MHz

My 2 meter vertical dipole's swr @ 147.960MHz

My 2 meter vertical dipole's swr @ 146.190MHz

My 2 meter vertical dipole's swr @ 146.190MHz

My 2 meter vertical dipole's swr @ 144.830MHz

My 2 meter vertical dipole's swr @ 144.830MHz

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