|Customer Reviews for the MFJ-9475X.|
|From: Michael Polia AB1AW|
|I bought this little rig because of its simplicity. I wanted a simple SSB transceiver with no bells or whistles, no microprocessors, etc. ; that is, something that I could power-up and immediately use without the need for lengthy programming or requiring assistance from an IT department. Another reason that I bought this rig was that I desired something that I could easily tinker with using readily available tools and equipment. I consider the MFJ 9475 as essentially a kit that some professional technician assembled for me, and then left for me to make the final adjustments. This is exactly what I was looking for.|
In some circles, MFJ has a reputation for “Mighty Fine Junk”. However, that is clearly not the case for the MFJ-9475. The quality of construction is evident, with a well manufactured and assembled PCB and case. There is a mix of both surface-mounted and through-hole parts on the PCB. All field adjustable components are readily accessible.
Do not expect this rig to work perfectly right out of the box. I found both transmitter and receiver performance lacking when I first powered it on and tried to use it, without first going through the easy-to-follow field adjustments.
The MFJ-9475 is rated for 10 watts output. However, don’t expect this output level across the entire tuning range (which itself is a subset of the 80/75 band). Certainly, the rig puts out a solid 10 watts at the adjustment frequency. However, the power drops off to about 4 watts at about 150 KHz above and below the adjustment frequency.
The field adjustment instructions state to make the adjustments “at the band center”, which was specified as 3900 KHz. I followed these instructions, but then found the power output dropped noticeably at 3944 KHz, which is the frequency of a weekly net that I participate in. So, I readjusted for a maximum output at 3950 KHz. The bottom line here is that if you are going to wander across the full tuning range of this rig, do not expect maximum power output at the band edges. Make the power adjustment at your favorite frequency.
The sensitivity of this rig is quite good. I did not have the equipment to make an accurate, quantitative measurement of receiver sensitivity. The selectivity appears to be sharp enough to prevent interference from adjacent signals during net operations in the crowed upper portion of the 75 meter band. There is some VFO drift for the first 5 to 10 minutes after power-up, but then the rig settles down. This drifting is not unexpected as this is a pure analog transceiver. A slight touch on the fine tuning knob is all that’s needed to compensate and makes it feel like I’m operating a radio and not a computer. Based on my use in various band conditions, I am pleased with the receiver performance.
The field adjustment instructions include a PA Bias Adjustment using the uA function on a voltmeter. These instructions require connecting the meter across the PA-BIAS test points located at RFC6 on the PCB. However, on my version of the MFJ-9475, I could not locate these test points, nor could I find RFC6 on the PCB (even though the schematic indicated it). I did find a different (possibly newer?) version of the instructions on the web. Using these alternate instructions, I made the PA BIAS adjustment by measuring the voltage drop across the base-to-emitter junction of the PA transistor (Q11, 2SC313) and setting it to 0.6 volts using the PA Bias adjustment R66 on the PCB.
I also found two different versions of instructions for adjusting the speech processor. The instructions included with my rig directed me to speak into the microphone and adjust R61 for mid-scale meter readings. The alternate instructions had me use a watt meter and dummy load, adjust L5 and L6 for peak output, then turn R61 CCW until the RF power output dropped by 10%. I chose to follow the second (alternate) instructions and was pleased with the resultant audio quality signal reports.
My experience with this rig has been all positive so far. I can check-in to my local net with S7 signal reports using only an Emtech ZM-2 tuner and a 30 foot doublet in my attic.
Bottom line: If you want a simple, easy to use, QRP rig that you also want to tinker with, the MFJ-9475 fits the bill.
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