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Reviews For: MFJ-8100

Category: Receivers: General Coverage

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Review Summary For : MFJ-8100
Reviews: 25MSRP: 89.00
Description:
Genearal Coverage SW reciever
Product is in production
More Info: http://
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00253.7
KE2GE Rating: 2022-08-12
For such a simple receiver, nice! Time Owned: more than 12 months.
First off, I'm a big fan of regenerative receivers. Over the years, I've built many radio kits, and many regens from scratch too. My all time favorite is the NR5Q Ultimate Regen. I have most of the kits from the 1950's in my radio collection, Ocean Hopper, Span Master, Space Spanner, Explor-Air, and more modern ones, GR-81, TT-1253, etc. About 20 years ago I owned an MFJ-8100, but sold it before a move. I regretted selling it, and recently found a nice factory built model on ebay for a friendly price. It arrived in nice condition, but the regen control was noisy & intermittent, and cleaning didn't help. I had a nice quality 10k pot which fit perfectly.
This simple little radio is more fun than any of my modern digital radios. I just clip a length of wire to the antenna terminal, plug in a pair of comfortable headphones, and I'm in for many hours of fun. When I got it the calibration was off on all bands, so I adjusted the trimmer cap so WWV was exactly at 10mHz. Low & behold, 40 meters was now close, and WWV on 15 mHz was right on!
I can't say enough good things about this radio; it's been available for decades. Don't expect a plug & play radio, it will reward you if you take the time to learn how to use a regen, but once you do, you'll be rewarded with many hours of shortwave listening. Highly recommended.
UPDATE: I now own 3 of these fine receivers; one in my hamshack, one on my nightstand, and another for portable use. I made a rollup wire antenna and take the radio in the back yard after dinner or to the park. I string up my random length wire, and enjoy. It's a blast to tune the ham bands or just tune in shortwave signals from around the world. The MFJ8100 is a pleasure to operate; and I'm hooked. I have a nice collection of classic receivers, but this is the most fun.
K4HYJ Rating: 2022-07-30
Fun little receiver!! Time Owned: 0 to 3 months.
I bought the little radio at a swapmeet - it was labeled for parts only. The seller wanted almost nothing for it! Found out he had bought it as a kit and after construction would not work. So I thought I would try to bring it to life. I took it home and downloaded the manual from MFJ's website.

Well, after fixing some poor solder joints (the original owner did not know how to solder - huge blobs and cold solder joints did abound), adjusting the calibration cap, RF sensitivity cap, and regen trimmer she came to life! On the bench I connected a Buckmasster OCF dipole to the back and clipped a jumper to my station ground, the 30 meter band came to life and was loud!!!

Learning to tune with the regeneration control is tricky but I'm impressed with how sensitive this little radio is. I tuned to WWV on 10Mhz and tweaked the dial calibration. After tuning practice on different signals for several hours, I decided to route the 9 volt battery clip outside the case and install a clip for it on the back.

I am also impressed with the sturdy case and part selection inside the radio - if you have a decent parts bin, you will find most of the replacements parts there if the need arises, or a quick call to MFJ or to Jameco or Mouser - yay no weird proprietary chips!! It should hold up to use in our camper for years to come.
G4EDY Rating: 2021-12-21
A nice retro design that works! Time Owned: 0 to 3 months.
I have always enjoyed using simple receivers and have many years experience of building and using regen TRFs.

First though, my kit arrived well packed with all parts present, building it was straight forward with a good manual - similar to a Heathkit manual - it worked first time.

Using a regen is quite different to any other design - for AM reception first set the volume control to give a moderate level of hiss in the headphones.

Then advance the regen control until the hiss increases but not too far so the set oscillates, as you tune the frequency dial you will need to simultaneously tweek the regen setting, generally as you tune higher in frequency you need to reduce the regen as the dynamic impedance of the tuned circuit increases with increasing frequency and since you are trying to keep the set on the verge of oscillation you have to get used to two handed tuning!!

The AM audio quality is very good and the set is ideal for SW broadcast reception.

For SSB/CW reception you just advance the regen control a little more until the set just oscillates, again as you tune higher in frequency you need to reduce the regen otherwise the set will become desensitised if too much regen is appled - two handed tuning again!

With very strong SSB/CW signals they can phase lock the receiver - increasing the regen helps but if the signal is really strong the only answer is to attenuate the RF input.

Strong LF broadcast signals can cause issues as well so if you use a broadband antenna with good LF performance like an active loop antenna then I recommend fitting a 2MHz high pass filter to the RF input.

My receiver is currently connected to a Bushcomm BBA120 three wire terminated folded dipole that has a gain of around 3dBi from 4MHz to 30MHz and the 8100 is a delight - I am listening to Radio China International on the 49m band as I type this and the audio quality is superb with my Bose earbuds.

It sips power from the internal 9V battery - I suggest not fitting the LED series resistor to save 3mA - I doubt the set consumes more than 10mA which should give 50 hours of use. As the battery voltage drops you do need to increase the regen setting which is a handy battery condition indicator.
N2MDV Rating: 2020-07-17
Neat radio kit, but keep your expectations low. Time Owned: 0 to 3 months.
I've been wanting one of these kits for years and finally bought one. I've missed the boat on the Radio Shack REGEN radio from the late 70's. As-is, I find the kit very drifty and the single turn REGEN POT just too touchy. However, being a kit, one could add improvements, like a 10-Turn 10k-Ohm POT for the REGEN. (Much better control there now.) That Calibration trimmer CAP was also too much of a pain, so I've swapped that out for a better 5pF - 65pF trimmer CAP. Instead of a 9VDC battery, I've tried to build a 9VDC power supply, since there's ample room to do so. An unshielded transformer just messes with the fixed inductors, but kept the LM7809 voltage regulator that I've add, and now have EXT +13.8VDC going into this kit. The results? Much more stable. Certainly, not the most accurate tuning, but the manual itself does state that. Audio quality is nice with a good pair of headphones. So, for about $90.00 now, you can have a simple receiver for AM, SSB, CW, SSTV, RTTY, and maybe receiving other non-voice modes. Takes a bit of work, but it can be done. I do have to admit the FUN value in this kit.
KB1QYH Rating: 2018-08-29
Wish I got one when I was a kid! Time Owned: 0 to 3 months.
I first saw this in Popular communications as a kid. I always wanted one, but never ended up buying it. Instead, I went for the new-fangled Realistic DX-380. Yes, it was digital, and had presets, but it was a rather poor receiver. I would have had much more fun with this MFJ. I just got mine yesterday direct from MFJ, and I spent most of the day playing around with it. I was impressed by the high build quality of the unit I received- you know the MFJ saying- Mighty Fine Junk- this is not the case with the 8100. It's built like a tank! no loose pieces rolling around inside. And did I mention what great fun I had tuning around with this radio yesterday? I have Ham radios that cost thousands of dollars, and I had a better time tuning this thing around and just listening! It's great! And such a simple receiver. Also- I'm not sure why, but signals seem much more stable on this radio than any super-het receiver I've used. Shortwave stations sound like local AM broadcasters-- No fading! How do they do that? My digital receivers fade in and out constantly, even under fantastic band conditions- not the MFJ Regen receiver- Set the regen control, and leave it there for half an hour! no fading at all---- It was rather shocking to me. Sound quality is fantastic as well- As good, if not better than my Kenwood/Icom radios using Sennheiser headphones! Maybe it's time for more radio manufacturers to get back to basics, and make a regen receiver! It's cheaper, simpler, and sounds better than the fancy digital radios of today! If you've ever thought about buying this radio in the past, I say bite the bullet and just do it- it's worth every penny- Tons of fun!!! I'll give a 3, 6, 12 month follow-up as well. Stay tuned--

W6UXB Rating: 2018-08-04
Great for what it is Time Owned: 0 to 3 months.
I bought one used in great condition, but did not seem to work so good I delved into it the soldering was really good but the jumper wires on the circuit board were way too long, rewired those and replaced the trim pots on the board as well then aligned it as much as you can as per the manual, yes the regen control is tricky but they all are when the sun sets the radio comes to life with just a short wire antenna, no it's not a communications receiver it is nostalgic fun, if you are bored with all your expensive toys come back down to earth it's great! the 6:1 tuning dial really helps too
KA4DQJ Rating: 2017-06-08
Not so Good! Time Owned: more than 12 months.
The regeneration control is so touchy that it is almost impossible to find the correct amount of feedback; especially on the higher bands. Even under the best of circumstances the receiver isn't very selective or sensitive, and even slight shifts in dial frequency require another struggle to find the "sweet spot" on the regen control.

That said, it's a very inexpensive kit radio. Don't expect it to perform alongside high-end commercial receivers.
KG4NEL Rating: 2014-03-17
Not a lot of money - a lot of fun Time Owned: 6 to 12 months.
Whether you’re a complete stranger to the world of HF or have a pair of K3s on your desk, sometimes it's a nice break to go back to how things were done before SDRs, IF DSP or even a frequency readout more complicated than a piece of plastic and a potentiometer. The 8100 is hardly the last word in performance, but it does surprisingly well for what it is.

The real value is in building the kit – price-wise, you can buy a modern Grundig or Sangean portable for less, but being able to assemble something that picks up voices from around the world (well, at least until the demise of international SW broadcasting…) is a thrill that hasn’t gotten old for me after a dozen years in the hobby.
BILZIN Rating: 2013-11-07
Potential DXer Time Owned: 0 to 3 months.
Got one of these kits cheap on Fleabay for No1 grandson.WE built it in a very short time, and it fired up perfectly from the start. Some clandestine tuning on my part soon had it pulling in stations that my Yaesus had difficulty tuning, and the look on his face when he first heard it receiving is well worth the price and effort WE put in.
The X box has been relegated to the spare room for the time being, and I think WE might just have another DXer in the making here....hope so !
KO0KY Rating: 2011-08-30
More than I expected Time Owned: 6 to 12 months.
I gave this rig a 5 because of the performance/price ratio, for the money it's hard to get a better rig that is so much fun to put together and use. It really does have a nostalgic feel to it that my higher performance radios just cannot have. Sure, my Grundig 750 is a lot better, but it costs $250. And you can't get it in a kit.

It is quite satisfying to run around the bands, reliving my early SWL days in the 60's, when I used whatever I could get my hands on. I would have killed for a rig like this. Now that I have much better radios, I use this one more than the others because of that remembrance. I can't quite put it into words, but you know it when you see it.

It's also great for travel. When I take my G4000 on a trip, I have to pack it really well so that the TSA folks don't smash it, not to mention it might just come up missing. This one is so tough I'm not worried at all, and it's so ugly I can count on it not being stolen.

Anyway, I highly recommend it.

John

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Earlier 3-star review posted by KO0KY on 2009-09-25

I purchased one of these recently from a chap on eBay for $30. He had added one mod, a spring clip 9V battery holder on the back. I highly recommend this addition to the radio as it saves so much time changing batteries.

I have tuned up SW broadcasters all over HF with this radio quite easily. You really have to get the 'feel' of the regeneration control, however, which is quite tricky. Once you conquer this you've got it made.

I've also picked up quite a few hams on AM (75m nets), SSB & CW, and they are quite understandable. I am impressed with how sensitive this rig is and how good the audio is. I'm going to add an amplified speaker and use this in my shack as an SWL receiver while I build kits and otherwise piddle around.

One little feature that I really like is the double headphone jacks. My XYLis studying for her Tech license, and I can show her directly about shortwave this way.

Overall, for the money, it is a good deal...conditionally at eBay prices. I can't imagine paying full price for this, especially $109 for the wired version. I will say that I have had a lot of fun with this rig and plan on having a lot more. That's a pretty good bottom line.

KO0KY