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Author Topic: MFJ-9440X - what power supply?  (Read 4606 times)
NO4L
Member

Posts: 14




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« on: November 23, 2009, 03:00:17 PM »

Hi,

Just acquired a MFJ9440X.  I would like to hear some
power supply ideas.  Guy I bought it from suggested a
7AH/12V battery -- I'm thinking of going this route.

However, for AC - would any small to mid size PS work okay.  I know a 3-4 amp would prob be perfect.  But would
the amp output of a bigger supply say, 11-14 amps hurt the radio.

Any suggestions welcome, I need to get something asap.
Dying to try it :-).

Regards,
Rob - k4ixe
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VE3WMB
Member

Posts: 290




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« Reply #1 on: November 24, 2009, 06:04:58 AM »

A 5 to 7Ah Sealed Lead Acid Battery (i.e. GEL cell ) would work well and is still reasonably light so you could use it portable. Check out the 12v battery booster packs that places like WalMart sell. (I have an 18Ah one). The smaller ones make great power sources for QRP radios and they can be pretty cheap.

The 9440 only draws a maximum of about 2 amps on TX so you could also use something like :

http://www.mtechnologies.com/cup/

But, I am not absolutely certain that the plug is the correct size.

Also Radio Shack sells a 3 Amp P/S

http://www.radioshack.com/product/index.jsp?productId=2103959

Best of luck ...

Michael VE3WMB
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VE3WMB
Member

Posts: 290




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« Reply #2 on: November 24, 2009, 06:09:40 AM »

Whoops forgot to answer you question about using an 11 - 14 amp power supply. No problem, the radio will only draw 2 amps. You just need to ensure that the Power Supply can supply a minimum of 2 Amps.
A higher capacity supply will not damage the radio. Just make sure that you use a regulated supply (not a cheap wall-wart) that is rated for something in the range of 12 to 13.8v.

Michael VE3WMB
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NO4L
Member

Posts: 14




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« Reply #3 on: November 24, 2009, 07:27:37 AM »

Excellent Michael, thanks so much for the info.
First thing I will do is head to Wal-Mart today
to look for one of the "battery booster packs".
If I cannot locate one, I'll go to the local
Batteries Plus store and price the 5ah & 7ah batts,
and charger.

Regards,
Rob, K4IXE
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AA4PB
Member

Posts: 13032




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« Reply #4 on: November 24, 2009, 08:19:50 AM »

MFJ-4103. I've used it with several QRP setups and not experienced any switching noise.
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NO4L
Member

Posts: 14




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« Reply #5 on: November 24, 2009, 07:28:11 PM »

Thanks for the replies so far, I'm still open to
suggestions.  I have, however, decided to go with a 7ah
12v battery.  I found a Hangar9 battery with charger
online for 29.95 + $5 shipping, local battery store
wanted that much for the battery alone and another $27
for the charger.  Since I have no battery chargers I
figured I'd go with this combo for starts.

I'll most likely pick up a 3amp PS for home use.

Happy Thanksgiving & God Bless!
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KF4HPY
Member

Posts: 17




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« Reply #6 on: November 28, 2009, 04:37:47 PM »

Oh me, are you ever going to have fun with the 9440x!  Any small regulated PS will suit you at 2A and above.The plug for the 9440 is a 5.5 mm od, 2.1 mm id or the "M" adaptaplug at RadioShack.  The RS 270-1533  lighter cable will fit for those lighter socket PS's as it is rated for 2A. The battery will be handy also. All you need now is a 40m dipole and away you go.  My radio is set to 5W and still reaches out.  I think I'll just leave it at 5W.  I normally work the midwestern states like OH, IN, IL and VA from a mtn. valley in N. GA with a dipole at 16 ft. off the ground.  I may try MFJ's 10m radio, the 9410; but I do have a Yaesu FT-817 also.  Have fun!!!  73, Ed
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NO4L
Member

Posts: 14




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« Reply #7 on: November 28, 2009, 05:03:08 PM »

Hi Ed,

Thanks for your reply and all the valuable info.
I'm actually in Athens, GA now -- so not too far away
from your location.  I've been to Gainesville for a graduation ceremony a few years back.
I'm living in a condo right now, and have a ProComm (or Workman...not sure) 40M ham stick type vertical -- I'm thinking about grabbing another stick and the dipole center and trying that combo.  I've got enough 14G wire to make a 40M dipole no problem...I'm just not sure I can hang a 66' antenna off the balcony without raising the neighbors and the association's eyebrows.  Could I have your email address in case I have another question or 2 about this radio?  Mine is rpclark(at)ymail.com

In any event, I'm excited -- I've had the 9440x for nearly a week now with no way to power it.  The 7ah batt is supposed to be here Wednesday, so I'll follow-up after I work 40 some later in the week.  
I'm going to  grab a 3-4 amp PS too.  I bought a pack of those 2.1/5.5 plugs (yep, M's) from Radio Shack.  And I'll grab that
cigarette plug too, RS is about a 1/2 mile away.

Question, how do you change the wattage on this radio.
You're the 2nd person I've heard of running only 5W on this radio.  Is there an internal pot or something that controls this?

73 & Thanks Again,
Rob
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KQ6Q
Member

Posts: 993




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« Reply #8 on: December 01, 2009, 01:25:39 PM »

Running a hamstick dipole, you won't need to worry about reducing the output power of the radio! Make some 5W contacts on the hamstick dipole first!
I use a hamstick dipole with 100W on CW, and can generally work anyone I can hear 559 or better. But with a QRP radio, contacts are much harder to come by - local nets only. The micropower stuff ONLY works if you have lots of metal up in the air!
You'll be much happier running on battery - with a QRP radio on headphones, you'll notice definite hum if you use a wall-wart or transformer Type AC supply. The battery give you picnic/adventure tupe capability. - make a wire dipole to take out with you!

Fred Wagner, KQ6Q
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KB0EPY
Member

Posts: 4




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« Reply #9 on: February 16, 2010, 08:27:00 PM »

I love my 9440!  I use a modified 300 Watt computer Power supply that supplies 12.7v 16a to my radio and works perfectly!.  I consistently get 55 to 57 sometimes 59s.  Since This past Friday I have worked 18 states and my goal is all 50!

73s

Mike
KB0EPY
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NO4L
Member

Posts: 14




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« Reply #10 on: February 22, 2010, 01:11:49 PM »

Thanks for the info Mike. I've often thought about doing
one of those PC PSU mods -- just haven't done it yet.

I ended up going with a 7Ah battery, which is normally
what I use. I also grabbed an older model RS 3A PS with
the cig lighter and +/- terminals.  

I love the 9440x, its small footprint and portability.
Unlike most things, I'll prob keep this one a while :-).

Thanks for all who answered, I appreciate each and every
response.  I will now unsubscribe from this thread.

73,
Rob NO4L
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KG6BRG
Member

Posts: 119




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« Reply #11 on: February 01, 2013, 06:34:01 AM »

Greetings, does anyone know the voltage range of these transceivers?  The manual states 13.8 nominal but no lower and upper limit, such as 13.8 VDC, +/- 10 %.  I suspect that is right.  I want to use it mobile and my alternator charges at about 14.5 volts.  Any idea if this is a safe upper limit, and how low has anyone gone before the rig is unstable.  Thanks for any insight.  cheers.
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