K3WWP's QRP Rigs

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K3WWP - Reviews of QRP Rigs

This review of the MFJ-9040 transceiver was written by Bob, KK5R.

I have owned several Powermites in the past. They were the first little QRP rigs made by Tentec. I later bought an Argonaut and loved it. However, in a famous fit of stupidity, I either sold or traded off the Argonaut. I have to stop going to the flea markets of hamfests, I guess. Haha...

In the process of owning an Argonaut, there came a time where I came to grade other QRP radios against the Argo much like space science fiction movies are graded against Star Wars.

WB9MII found with his radio that it put out something less than 5 Watts. When I got my MFJ 9040, it also only put out about 5 Watts. I read in some reviews where it was designed for 10-12 Watts so I decided to check the alignment of the radio. It was perfectly aligned. However, there was one comment in the Field Alignment Procedures section where I was to set a voltage regulator to 10.2 V. and it was only set to 8 V. or so. When I followed the directions and set it up to 10.2 Volts, suddenly I found the power out was between 10 and 12 Watts.

I wondered why it was set for the lower level and concluded that it was sold as a QRP rig (actually QRPp) and the voltage regulator is MFJ's way of setting it to the accepted QRP level. This does not make much difference on CW since if you can hear 'em, you can work 'em on CW if you're using more than a simple curtain rod antenna. But, on SSB, doubling the output power is a significant power gain.

I also decided to make an addition to the radio. The tuning range for SSB is 7150 KHz to 7300 KHz and this only stops you from using it on the lower 25KHz of 40M SSB segment if you are an Extra, but others have all the 40M SSB band for voice. I bought it with the CW option which means it also has 7000KHz to a little over 7150KHz for CW merely by pushing a small push-button switch on the back top corner of the rig. However, this caused me a few moments of grief, as follows:

One night I was tuning around and most American 40M SSB users had been run off by the SW broadcasters. Suddenly, there was a Brazilian ham calling CQ! I was thrilled since I had lived in Brazil. Therefore, I answered his call. He hesitated and called CQ again. I answered again. Then there was nothing and I knew from some experience with the radio that if I could hear him that well, he could hear me so I began to wonder why he did not come back to my reply to his CQ. Then it dawned on me -- I was in the CW portion of 40M where the Brazilians can operate... I was in some sweat for a while wondering when I'd get a letter from the FCC but I was again very lucky. However, it gave me an idea that I immediately incorporated.

I put a small but bright red LED on the front panel to let me know when I'm in the CW part of the band. Sure, I can use the bottom 25KHz of the SSB band now but have only heard a few American hams there. But now I know when the rig is in the CW portion of the band by the red LED warning indicator. I used the standard LED mounting (super glued it into an appropriate hole) so it looks like something done by MFJ. I grounded it to the front mounting screw of the CW option board which is very close. The "hot" lead I ran through a current limiting resistor (about 1000 Ohms) connected to the switch-on terminal of the CW option power switch which is only abut 3 inches away. The LED is mounted about 1/4-inch to the left of the word "VOLUME" painted on the board and about 1/4-inch from the tuning scale, just 1/4-inch above the "7.15" on the scale.

It is a super rig. I detect no drifting after 5-10 minutes and only then if it starts very hot or cold from the ambient temperature. There is volume in excess. I use it mobile with a popular vertical similar to the one sold by MFJ. I got this one from a friend for about half the MFJ price (plus no shipping). With it I have worked the Caribbean and from coast to coast on SSB and have been told it sounds similar to radios running 100W. This may be due to the very well-designed speech processor in the radio.

Hope this helps others. Oh, just one more thing: I shorted out RFC6 when checking the PA bias setting. RFC6 is a 4.7uH choke. I had an old choke that was 12uH so I mounted it and shorted out half the turns. Works fine... Apparently it is not critical but being closer to 6uH is better than being less than 4.7uH, in my opinion. But to make sure, I called MFJ and asked their tech about it. In about three days I received two replacement chokes in the mail at no cost to me even though I did not buy the radio from MFJ. Good people! Still need to replace my substitute part but the radio works so well with my substitute that....

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