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Reviews For: MFJ 93X0 Cub QRP xcvr

Category: QRP Radios (5 watts or less)

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Review Summary For : MFJ 93X0 Cub QRP xcvr
Reviews: 40MSRP: 79.95
Single band CW QRP tcvr.
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
KE0SBX Rating: 2023-01-02
Great Kit for a Tight Budget Time Owned: 3 to 6 months.
The MFJ Cub is an excellent kit for any ham to have. Whether you are new to the hobby or experienced, I think you'll appreciate having this kit on your desk or in your Field Day bag.

I'm not quite sure if MFJ still makes these despite eHam saying that they are still in production. It seems that they are made upon request because almost all outlets that sell these label them as out of stock or on backorder. I waited for almost 2 or 3 months just to get mine from Ham Radio Outlet, but I won't complain about that too much. In the end, I got my kit, an MFJ-9320K. As of 2022, the price is about $150 - not too bad for someone on a budget.

Building the kit is pretty straightforward - a solder job here and a solder job there. Then comes the fun part: alignment and tune-up. I had a troubling time when it came to tuning and I ultimately ended up setting it aside for a while. Needless to say, I was somewhat disappointed and frustrated.

After consulting with other hams for help and tips, I was able to tune up the Cub recently for 20m with great success. It puts out 1.5W easily, but I have noticed that it drifts quite a bit, both on transmit and receive. I've heard other reviews say that after about 10 or so minutes, the Cub's oscillator normalizes without drifting and there are plenty of mods out there to fix or improve this condition. For now, I can live with it. I was able to test it out and can say that the receiver pulls in signals with ease. The transmitter also produces a nice, soft, and clean tone.

In conclusion, I would recommend this to any ham, but for newer hams, consider asking for help. The instruction manual lists several ways to tune this, but there is always more than one way to do something right. A seasoned ham who has lots of experience putting together kits will offer you a wealth of assistance and information. I just wish that there was a video or two online showing you how to properly tune up one of these, but as of now, there aren't any.

Summary: The MFJ Cub is an excellent kit for someone who wants to get into the world of QRP. Once you get past tuning it up, you'll have hours of fun on the air. It will beat a Pixie any day, especially with a crystal filter, a strong and well-performing receiver, and more than a mere 500mW of output.
KM7Q Rating: 2021-01-27
Wonderful Fun QRP Radios Time Owned: more than 12 months.

I have an article, published in the “Hints & Kinks” section of October 2016 edition of QST, about putting ten turn tuning pots on MFJ Cubs. The mod improved tuning by a huge margin.

Having completed this project on 40, 20, and 15 meter Cubs, I continued my quest to work all states and a bit of DX, using a fan dipole at 30 feet in Portland, Oregon. I had started in September of 2012.

I had all but Maine by the middle of 2017, finally getting that state in Sept 2020. It is ironic that I finally got Maine at the low end of the solar cycle. I had worked all states surrounding it many times.

I’ve worked the fifty states, 46 of them two or more times. I have twelve QSOs with Japan, spread across all three bands. I have Mexico and the Virgin Islands as my other DX.

Be you be a beginner, or an old ham like myself, you will find this little radio great fun. Its amazing that two watts and a dipole can make so many contacts. I give this rig high marks.

73 Bob Crispin KM7Q
UA1CEX Rating: 2016-08-23
Very nice qrp rig! Time Owned: 6 to 12 months.
Hi, friends. I have to say, very nice rig. I am very happy. I noticed some drift 9320k and changed caps C6 and C7 to NPO. Now, I forget about drift, but for the first time, if you replace caps to NPO, leave your rig for one hour to train caps.
AF7EC Rating: 2016-07-11
MFJ 9340K - Fun little kit! Time Owned: 0 to 3 months.
This review is for the MFJ-9340K 'Cub' 40-meter QRP CW transceiver kit.

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As mentioned elsewhere, all of the surface-mount (SMT) components are already soldered onto the circuit board when you receive the Cub kit. The kit I received was fine *except* for one SMT capacitor (C1) being soldered vertically to the circuit board instead of the normal horizontal mounting. Either the pick-place machine that populated the board with SMT components was having an issue, or the adhesive failed on that particular part during wave soldering. I ended up soldering a wire jumper between the empty pad on the circuit board to the disconnected leg of the SMT capacitor.

All the correct parts were included with my kit ('packed by Carrie' -- thank you Carrie!) and the physical condition of the case, knobs and components was good. There were no visible gouges or scratches anywhere.

The kit took between three to four hours to solder and assemble because I was taking my time and had a few small breaks. I wanted to enjoy the experience but also wanted to finish so I could try out my new transceiver!

The only very small snags I hit were trying to smoothly insert the RF transformers. Because they have so many pins and two tabs, I had to be patient and carefully wiggle them into place. Sometimes I can be heavy-handed, so I tried not to bend or break any of the pins. Thankfully I was able to get them all in without breakage.

The kit requires the builder to wind two small toroidal inductors. For the 9340K, it was eighteen turns on each toroid. Some folks make winding toroids sound like an impossible feat, but it's really not hard at all. The hardest part about it is keeping track of how many turns you've wound and to make sure you wind the wire tight.

When I completed the kit, it was time to align the transceiver. Unfortunately I did not have non-metallic tools for this so I really was not able to dial everything in properly. Some other circuits can tolerate metallic tools, but the Cub is not one of them. I ended up purchasing a non-metallic alignment tool set off of eBay, and *then* I was able to get everything aligned and adjusted the way it should be.

The Cub kit currently does not come with an internal speaker (although it's listed on the schematic). If you'd like to add an internal speaker, the circuit board does have two solder pads available for one. Based on the schematic, the speaker will disconnect when something is plugged into the headphone jack.

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As mentioned in other reviews, the Cub has some drift when powering up. In my case, the frequency drifts downward until it settles after about ten to fifteen minutes. The drift is pretty drastic, so something I do is to turn on the Cub (when not on battery) and let it sit for a good long time until I'm ready to use it.

You can choose which segment of the band you want by adjusting an RF transformer during alignment. The span on my particular kit is about 70 KHz. I have the top end at 7.070 MHz and the lower end just above 7.000 MHz. Tuning is by a potentiometer and varicap diode setup (not a variable capacitor). The tuning, at least on my unit, is not linear. Everything from 7.070 MHz to about 7.040 MHz is fairly scrunched together while the lower part of the band segment starts to space out a bit. While MFJ provides a medium-sized knob for the tuning control, it really needs to be a bit larger in diameter so tuning isn't so sensitive. You really need a feather touch when trying to tune some of the higher frequencies, and the medium-sized knob is less than ideal.

The sidetone is pleasant to listen to and is derived from your transmitted signal. I wish there was a way to adjust the volume of the sidetone -- maybe MFJ could tweak that a little? The transmitted CW note sounds good, even with my cheesy MFJ straight key.

The receiver performance is adequate. If you are using the Cub for receive-only and are using a short antenna indoors, it's not very sensitive. Using a better exterior antenna or resonant antenna indoors will yield better receiver results. I guess my Heathkit SB-303 has spoiled me as it is a much hotter receiver than what the Cub has.

The specifications state that the Cub puts out about 2 watts. Unfortunately, I do not have a power meter so I can't verify this. I do know that the signal is leaving the confines of my little town as I've seen my signal (intermittently) 310 miles away on a WebSDR server. I am currently using a random wire antenna fed by a homebrew 9:1 UnUn and antenna tuner. My antenna is definitely a 'compromise' antenna, so better transmitting results will be seen when I upgrade my antenna system.

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I am definitely on a very very tight budget. I had purchased a sub-$5.00 Pixie 2 'toy' QRP CW transceiver for 40 meters but never made any contacts with it. I *was* wanting a Heathkit HW-8 but they are currently running a bit too expensive for my budget. The open box deal I got on my Cub was just the right price for me. The 9340K is definitely not a fantastic transceiver, but it's fun to build and fun to operate. It's a good compromise rig when you don't have much of an amateur radio budget. The Cub is very good for portable QRP use because it sips power. I use it on my small 12 volt lead-acid battery with great results and it doesn't drain my battery to zero after a session.

If you're looking for a relatively simple and fun one-day QRP project, definitely give the Cub a go!
VA3YG Rating: 2016-01-13
Lots of fun! Time Owned: 0 to 3 months.
I had a little difficulty with the alignment process for my MFJ-9320. This was my first time building a transceiver. Had previously built a couple keyers and an OHR WM-2 QRP wattmeter.

Say what you want about MFJ, but Richard at MFJ went the extra mile and helped me get a 20m Cub on the air.

I have had a ball with this little QRP rig. If you enjoy QRP and have the patience that QRP requires, you should love this little rig. I've worked all over North America on 20 meters with a small LifePO4 battery, a resonant antenna, an iambic paddle connected to a keyer and a small amplified speaker in place of headphones. 1.5 watts output with 13.2 volts.

The assembly went great for me. Soldering the board was no problem and the instructions were pretty good. Things fell apart at the alignment steps due to my inexperience. I got the rig to receive 100% but no output on tx. Went back over everything two and three times and re-melted as many connections as I could but all to no avail. In retrospect, I would have put the rig aside for a couple weeks and re-visited it later.

After a couple emails, Richard at MFJ came to the rescue and now I use this little rig a couple times a week. The audio with the little speaker I use fills my shack.

I won't hesitate buying another MFJ Cub kit for another frequency. This is not an Elecraft by any means but instead a fun little kit, a learning experience and a QRP rig that you can have lots of fun with.

N8YA Rating: 2015-11-01
Great Fun for the $$. Time Owned: more than 12 months.
Great Fun in a little package! There is no excuse not to have a radio with you on vacation, camping or whatever!
W3FIS Rating: 2015-08-31
Excellent buy + fun Time Owned: more than 12 months.
I now own four of the Cubs. 40, 30, 20, and 15 meter version. About 3-4 hours assembly, and another hour testing and alignment. The alignment requires a hex insulated tool. It would be great if MFJ included one, otherwise the instructions are quite complete. Excellent receivers, considering the complexity. The drift issue is there, but just let them run for a while, and they settle down nicely. Good for main QTH, portable, and field use with a tuner/antenna combination of your choice. MFJ also makes a nice amplified speaker (MFJ-382) that is a handy companion piece, if you don't want to use headphone. DO put the optional BNC fitting in place, and as one other poster noted, replace the small tuning knob with a larger one (Radio Shack has one that is a good style match). Use some "marker dots" to show the approximate frequency of the QRP "watering holes," and you are ready to go! Fun to build, and fun to use!

Earlier 5-star review posted by W3FIS on 2014-07-31

I have two of these - 20 and 30 meter versions. Quite sensitive, easy to assemble, and fun to work with. Tuning is a little "touchy," but a larger knob solves that. Drift issue is minimal, IMHO.

73 /paul W3FIS
I5EFO Rating: 2015-05-31
MFJ cub 9315 WPX Contest 2015 Time Owned: 0 to 3 months.
Today I used on WPX Contest my new MFJ cub 9315 with my old Hygain 18AVT/WB GP antenna and on about three hours only I made QSO with 15 DXCC countries.
Beautifull QRP rig !
KF7ATL Rating: 2014-10-20
Fun little radio Time Owned: 6 to 12 months.
I built the 20 meter version and use it for portable ops outdoors. The kit went together easily without major problems, and worked first time. The only minor problem was during alignment--I didn't have a non-magnetic tool and had to make one. Overall a fun radio to operate. The first time I used it portable, I got a QSO in NJ from UT with decent signal report using a half-wave end-fed wire. I give it a 4 because overall it's a great little rig. Drawbacks include touchy tuning, and warm up time needed to eliminate frequency drift. I was pleasantly surprised at the receiver. It's pretty good for the price.
NG9D Rating: 2014-10-18
Easy Does It Time Owned: 0 to 3 months.
I got the 40m version from ARRL in a package with an informative book on Low Power Communications. The kit came with more than half of the work already done - all of the SMD were factory installed. The relatively few thru-hole parts, adjustment and mechanical work was done today. I answered W8HOG CQ and he reported the Cub's signal was good. By the way, ARRL shipped within a few days, all part were included and the quality of the kit and instructions (included in the book) were superb. Current kit was supplied with NP0 capacitors and the manual indicated special component selection had been made in the VFO circuit for stability. The highlights of the assembly and that first QSO are on a YouTube video at:

73. Lynn/NG9D