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Author Topic: MFJ QRP RADIOS  (Read 1304 times)
K1QQQ
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Posts: 281




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« on: June 25, 2019, 09:31:33 AM »

I ended up with a few MFJ QRP Radios but yet to really try to use any. Although still in their catalog I do not think they make them anymore. Parts problem ?

My broad question is does anybody repair these things ? Are schematics available ? Any MFJ user group message-board  etc ? The circuitry can't be that complex but if certain parts not available....(?)
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KU3X
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« Reply #1 on: June 25, 2019, 10:38:30 AM »

What radios do you have? Can't answer your question if we don't know what radio(s) you are talking about???

Without listing all of your radios, a simple solution is to just call MFJ and ask them a direct question.

Barry
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K5LXP
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« Reply #2 on: June 25, 2019, 07:29:19 PM »

 
How would you know if they're broken and need parts if you haven't used them?

Mark K5LXP
Albuquerque, NM
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K1QQQ
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« Reply #3 on: June 26, 2019, 11:54:47 AM »

ESP.


I have bought things on Ebay and elsewhere and it seems when something develops a problem it is time to sell it. If overloaded with things to take care of sometimes purchases go into the 'take care of' pile. Often that pile becomes a problem pile.

Anyway... I just bought a 6 meter SSB QRP radio on Ebay USED. I tried to buy one new but still on the waiting list and months have gone by and still nothing from  MFJ... (this unit also does CW with another additive if still available)

So looking ahead I thought about keeping these QRP radios (also have other band units) running forever. Thinking of the future and perhaps delusional...... Who fixes something that the cost was low to begin with ? Assume nobody.

MFJ has taken these off their catalog listing. The circuit info in the manual is very limited. How to align, etc. No schematic.
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KX4OM
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« Reply #4 on: July 01, 2019, 04:26:18 PM »

What are the model numbers of those QRP transceivers? Well-known designer Rick Littlfield, K1BQT designed the Cub series. One of those was a companion to a book the ARRL published. A lot of information is available.

Look here:

http://www.g4ilo.com/mfjcub.html

The current QRP Cub series in the catalog is surface - mount construction.

All of those transceivers are pretty much dead simple: NE602 mixers and LM386 audio amp, if I recall correctly. Some similar designs used an opamp for the audio stage. Same basic design as many others, such as the Small Wonder Labs SW-XX rigs.

Ted, KX4OM
« Last Edit: July 01, 2019, 04:34:49 PM by KX4OM » Logged
K1QQQ
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Posts: 281




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« Reply #5 on: July 01, 2019, 07:12:53 PM »

Thanks for the input. I think I am just thinking about money for USED things and my purchase track record is a disaster. I just bought a 6 meter SSB that has not arrived yet. Odds is it has some problem. I bought a USED ICOM 551 a few months ago I am still trying to figure out. NO PROBLEMS ! I ask where is the CW and the answer is..who does cw ?? Buy it used and #1 who services ?

I have collected these MFJ QRP things with just about very band. No CUB series.

The new replacement are YOU-KITS and XIEGU with no schematic and new..they might work !!!!

If one can get the parts run them forever ? Hardware issues but....


https://www.ebay.com/itm/MFJ-9406X-MFJ-9406-6-meter-10W-SSB-transceiver-with-MFJ-259-microphone/183859918641?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
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K1QQQ
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« Reply #6 on: July 01, 2019, 07:45:59 PM »

As said all I sit on are non-CUB.  The 9000 series.

It seems the other ones with SSB are discontinued. I'm getting all mixed up now but I think I have various ones with bands but they had a SSB line and a CW one.

Have to dig into my stuff at another address.

I see now they are just making the 20/17/15 ones.(if they are doing that)

The recent 6 meter one I mentioned can also do CW with an optional board. I am trying to locate that add-on.
« Last Edit: July 01, 2019, 07:51:49 PM by K1QQQ » Logged
KX4OM
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Posts: 357




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« Reply #7 on: July 02, 2019, 09:17:58 AM »

The 90xx are CW only. The 94xx are SSB. Pages 50 and 51 respectively in the current 2019 catalog. I had a 9420 for a few years, and it performed pretty well. I used it portable with  a homebrew 8 foot vertical with a coil in the middle to resonate the antenna on 20m. Looking back, I should have kept it.

For the 94xx series, the schematics are no longer provided with the manuals, but they once were. I still have one for the 9420. They, like the QRP Cub series CW rigs, are single conversion superhet employing common NE602 (SA612) ICs for the mixers. No exotic parts, and in the case of the  90xx and 94xx rigs, no surface mount components. The SSB rigs use a reduction-drive variable capacitor for the VFO. The 90xx 5 watt CW rigs do as well. The Cub series use variable - capacitance diodes for a simpler and much less expensive VFO circuit.

Ted, KX4OM
« Last Edit: July 02, 2019, 09:21:07 AM by KX4OM » Logged
W4FID
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Posts: 229




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« Reply #8 on: July 03, 2019, 04:11:08 AM »

I had both the 9440 and 9420 15 years ago. Both were fun on SSB. Both had the CW board and CW with them was OK but not in a league with the QRP CW rigs of today. More like 60s era novice CW QSOs. Still fun. With simple hamstick dipoles at 15 feet (painter's pole bungie cored to the deck railing) under big trees I worked lots of fun QSOs. Both worked as advertised and had no problems at all. Not sure if they are still available new but I wouldn't hesitate to buy a used one after I see it work a few QSOs.
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KX4OM
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« Reply #9 on: July 03, 2019, 06:55:38 AM »

I had both the 9440 and 9420 15 years ago. Both were fun on SSB. Both had the CW board and CW with them was OK but not in a league with the QRP CW rigs of today. More like 60s era novice CW QSOs. Still fun. With simple hamstick dipoles at 15 feet (painter's pole bungie cored to the deck railing) under big trees I worked lots of fun QSOs. Both worked as advertised and had no problems at all. Not sure if they are still available new but I wouldn't hesitate to buy a used one after I see it work a few QSOs.

I would buy a 9440 or 9420 used, even non-working at the right price. Those rigs are so simple I could rebuild one from scratch. Of course, I have all of the test equipment to be able do that.

Ted, KX4OM
« Last Edit: July 03, 2019, 06:58:56 AM by KX4OM » Logged
K1QQQ
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Posts: 281




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« Reply #10 on: July 03, 2019, 11:17:10 AM »

Been busy and still need to digest the posts here.

I ended up with a small set of MFJ QRP units and just wondering about the difficulty of keeping them running and repairing, etc. I don't think anybody is going to pay a normal service person to rehab a unit. (what is it now..$200 an hour ?)

I am not a repair wiz and even circuit boards sort of left me behind nevertheless SMT stuff. Once there were wires and _________ and connect the dots and it worked.

I once thought about investing in test equipment, etc. and the price exceeded anything you would pay for somebody else to repair on an infrequent basis. Yes...everybody should have some collection of test stuff...

Soooo  It seems the verdict is one can keep these things running without the impossible.  Some IC that was last made in Russia 10 years ago, etc.

https://1drv.ms/u/s!AmZu7wUq4-5h7n4zbjxWMAcp3EnQ


Link might work. I see I have 20/40  ssb. I think I bought the cw board..one of them... The rest are cw only. I have another stored elsewhere (forget what) and a 6 SSB coming from Ebay if not ripped.
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KX4OM
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Posts: 357




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« Reply #11 on: July 03, 2019, 01:21:11 PM »

One 9420 and two 9440 SSB units is what are in the photo. Too bad somebody marked the dial on one of the 9440s.

You don't need the CW module to test the power output on the SSB units. Pushing the Tune button generates a carrier for adjusting an antenna matching unit. Or, whistle into a mic with the mic button PTT pressed. Either way, you should see deflection on a power meter or SWR meter. Do this into a dummy load capable of handling 10 to 12 watts carrier output from the transceiver. If you are going to do QRP with them, you need a dummy load and power meter. Or, make a simple RF probe, which measures RF voltage, and do the math. Go to qrpguys.com , click on test equipment, and click on the dummy load and the simple RF probe kits. The dummy land kit has a built-in detector for RF voltage. Use either probe with a Harbor Freight free (sometimes) DMM. Those DMMs are not 11 Meg ohm input, more like 4 or 5, which I have actually measured for those units. As an indicator rather than a precision tool, close enough. That input spec reflects how lightly the measurement is loaded down by the meter. 11 Meg is pretty much a standard.

One other thing. The older typewritten  manual includes "Field alignment instructions" along with a schematic and parts list.

Ted, KX4OM
« Last Edit: July 03, 2019, 01:39:11 PM by KX4OM » Logged
K1QQQ
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Posts: 281




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« Reply #12 on: July 10, 2019, 03:37:49 PM »

I think I gathered together most the schematics except saw none for the 12 meter unit. I know not when over time the circuits changed.

12 meters ? I am not sure anybody has one. I thought for QRP there are numerous CB 10 METER EXPORT radios and several at least claim to cover 12. I don't know if CW works with them but ---- (they claim to have CW option)

I never chased down the MFJ 75 meter unit. (big antennas)

My thoughts evolved with the Condo type living where everything is impossible and radios that use little current at least let somebody do something. Never been a big QRP fan but liked the QRP contests and working all the weak signals that would come and go.

There is a popular Chinese amp to help so-called QRP rigs to increase power to 20 watts or more. I don't know about signal purity.

Where o Where is an amp to take 1 watt and turn it into 100 ? (say for the MFJ CUB radios) Anybody try one of these amps with 1 watt to drive ?

Money-money-money...these solid state amps can get expensive...

These new Xiegu Chinese radios ? It seems you buy one new and the endless bug list begins. What about after usage ?

Don't know how active CW is as to these MFJ things but it is a better weak signal mode than SSB. I never liked to yap my mouth and sometimes I think is it not strange in order to be a HAM you have to use a microphone ?? !!!!

I just added a MFJ SSB 6 METER unit to the list (bought used) but still looking for that CW adapter board.

Enough !!!!!!

LINK. (if it works) LINK https://1drv.ms/u/s!AmZu7wUq4-5h7xQolwrWuhsKz4S6?e=lgW6hY   LINK   ----------------

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N8AUC
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Posts: 585




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« Reply #13 on: July 11, 2019, 06:33:46 AM »

QQQ - I don't know what you're paying for these radios off of ebay.
But the MFJ web site shows the 9420 available new for $279.95.
For the sake of this exercise, let's say you can get them used for $150, which is purely a SWAG.
Unless there is some emotional desire to have the MFJ units, I don't think the economics are very sound.

Here's why.

Let's say you wanted to be able to operate on all bands. 80-40-30-20-15-10-6, that's 7 bands.
At $150 each for a used unit, that's $1,050 for the set. And they're SSB only unless you pay extra for the CW board.

A quick Google search shows that you could pick up a brand new FT-818ND for $599.95 at Gigaparts, and get
all the bands and all the modes in a single unit, PLUS 2M, and 70 cm all modes, PLUS general coverage receive.
And you'd get a warranty to go with it.

I managed to find a clean used FT-817 (pre-ND so no 60 meters) for $350, and it has worked just fine.
Picked it up at Dayton a few years ago, and have had loads of fun with it. Had to send it back to Yaesu once
to get the DC power input jack replaced. That was a fairly inexpensive repair.

Not sure the economics of the MFJ units passes muster in this case.

Of course, your mileage may vary. And this is merely food for thought.

73 de N8AUC
Eric


« Last Edit: July 11, 2019, 06:47:14 AM by N8AUC » Logged
K1QQQ
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Posts: 281




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« Reply #14 on: July 15, 2019, 05:00:35 PM »

I think it is mostly the like of various radios for a persons inventory. Allot of people end up with extra radios and sit on them. Economic sense ? An old-fashioned shortwave listener might end of sitting on endless different radios.

I bought most of them over time. A couple new. I don't get too excited about the latest trend of Chinese QRP Xiegu..You Kits... No schematic. No nothing expect throw it away when it has a problem. This Xiegu seems to have a huge growing bug list before it is even used. Then if you get one you have luck with the model vanishes with some new beta something.

I know it makes no sense money wise vs. all bands like the Yaesu 817/818.  Just sort of a nostalgia of using/playing with the ole MFJ 15 meter unit, etc.etc.

I think MFJ is finished with this QRP line discussed. Try to buy one. Even the CUB series seems nothing but forever back-order.
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