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Reviews For: MFJ-260C 300 Watt Dry Dummy Load, up to 650Mhz

Category: SWR & Wattmeters & Dummy Loads

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Review Summary For : MFJ-260C 300 Watt Dry Dummy Load, up to 650Mhz
Reviews: 14MSRP: 34.95
Description:
The MFJ-260C is an air cooled, non-inductive resistor in a perforated metal housing. It has SO-239 connectors. You can handle a full load for 30 seconds. Silk-screened derating curve to 5 minutes. Handles 300 Watts. SWR below 1.1:1 to 30 MHz, 1.5:1 from 30 to 650Mhz. It measures a super compact 2 1/4x2 1/4x7 inches.

Specifications
IMPEDANCE: 50 Ohms, ± 10 %
VSWR: Max: 1.3:1, 0-650 MHz
POWER: 300 Watts for 30 seconds
DISSIPATION: (2 min cooldown) 25 Watts continuous
DIMENSIONS: 2½" x 2½" x 7"
Product is in production
More Info: http://www.mfjenterprises.com/products.php?prodid=MFJ-260C
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00143.9
VE7EFF Rating: 2023-11-09
It Works - After I Had To Completely Rebuild It Time Owned: 0 to 3 months.
Sorry for the extremely negative review, but this is no exaggeration.
This is the worst ham radio product I have ever purchased, by a long shot.
I'm a retired electronics RF technician/technologist, so I have some idea of what I'm doing.
I should have returned it immediately to DX Engineering when I first tested it and noticed the dc resistance check was out of spec and erratic, but I thought it would probably be an easy fix - after all, MFJ is well known for their poor quality workmanship and many hams have to do minor repairs to fix the poor workmanship - it's almost expected. This was is the first MFJ product I have ever purchased, so I expected to maybe have to do some minor repairs.

This was no minor repair. I had to completely rebuild the dummy load - twice, because of intermittent shorts, and intermittent conductivity to ground.

I thought it would just be a simple open the dummy load, fix a loose contact/connection and all would be fine........no such luck.

The grounding bracket holding the dummy load resistor was intermittently open. Turns out that none of the grounds in the case had good ground, including the SO-239 VHF connector mounting did not have ground contact. Why? As it turns out, the whole unpainted inside of the aluminum housing had some kind of clear coating preventing electrical contact anywhere. I had to completely disassemble and remove ALL the components inside the dummy load so that I could sand down the aluminum surfaces everywhere that was needed to make RF ground. Around all screw holes, all mounting brackets, and even the So-239 connector.

Now that everything was reassembled and I had good grounding at all metal to metal contact points, I retested it with an ohmmeter again. Now I was reading a dead short between the SO-239 center contact and ground.

I found 2 places causing the shorts. The mounting bracket holding the top end of the 50 ohm dummy load had a screw with only about 1mm or less clearance touching the aluminum chassis after I reassembled. Because of this design flaw, I had to file down the bracket screw and put some insulating plastic sheet under the screw to keep it from touch chassis and thus preventing shorting.

Next problem was when I went to put the RF shield back over the 50 ohm dummy load resistor. Now the shield had no clearance and was also shorting to the top end of the 50 ohm resistor. I had to install extra washers under the RF shield to increase its height so that it would not make further contact with the top end (rf input side) of the resistor. I also added some insulating material to prevent contact between the two as a safety measure.

Also, all screw contact points between the case cover and chassis were heavily painted over. Looks great..... problem is RF shields doesn't like paint on their contact points. So, I sanded off the paint around all 8 screw mounting points so that the case could now provide proper RF shielding.

My mind is blown away at how poorly designed such a simple device like a dummy load could be manufactured. But MFJ seems to have it down to a science. Their mechanical and manufacturing engineers should be fired for producing such a poorly manufactured product.

Once I did all these fixes noted above, the dummy load now reads 48 ohms at the SO-239 connector. I then connected my Rig Expert Antenna Analyzer up to the dummy load and got < 1.1:1 across the HF bands. And, 1.4:1 on 2M band. 1.18:1 on 6M, and 2.5:1 on the 70cm band.
WA2CLP Rating: 2023-01-13
Ground connection needed repair Time Owned: more than 12 months.
I recently noticed that it wasn't working. The SWR was just over 3:1 on 160m thru say 20m. Above that it started to drop to more normal levels up to 10 meters.

It did not act like this when it was new so I opened it up to snoop around with my ohm meter. I noticed that the feed point impedance was over 100 ohms. A check of the resistor from end to end however, showed exactly 50 ohms.

What I found was that the 90 degree bracket up against the end of the tube resistor was to blame. I loosened the bracket and inserted a 1/4" lock washer against the end of the resistor then re-positioned & tightened the bracket. The feedpoint impedance now returned to exactly 50 ohms.

As far as realiablility on 70 cm I noticed the following once the feedpoint impedance was corrected:
The results all depended on the type of cable I was using to connect to the SWR meter. A 20 ft section of old RG-8 showed just under 2:1. The same length of RG-8X resulted in same. However, with the same length of LMR-400, the SWR was a perfect match using 5 watts or so from my Kenwood TH-F6 into a Diamond SX-400 SWR meter.

As far as I'm concerned the dummy load has been repaired and can now be returned to 'general Amateur use.' I hope that my experience can help anyone out there with the same product.
GM1EXK Rating: 2019-08-06
Unusable on 70cm and not great shielding Time Owned: more than 12 months.
1.1:1 SWR on HF
1.25:1 SWR on 6m
1.5:1 SWR on 2m
2:1 SWR on 70cm

This is not a 50Ohm Dummy load above HF. Above 200MHz it becomes unusable as a test instrument. They shouldn't advertise 650MHz.

Shielding could be better. Noticeable TX radiation and can also RX strong HF signals!
KF5VUD Rating: 2016-10-25
Works well, power curve seems accurate Time Owned: 0 to 3 months.
I have only had my HF rig (a 100 watt Icom 7410) for a short time, but I load tested this for 90 seconds at the full 100 watts and while I felt a little bit of heat dissipation (just passive convection) I would only say it barely got warm. If anything, I would say the power curve printed on the front is conservative.

It works well and was inexpensive (purchased from another ham here).
AD0AR Rating: 2015-02-27
it does radiate a bit if not grounded properly Time Owned: more than 12 months.
I agree with WK2X, it does radiate. Once I was running 100W from my radio on 17M into this while testing some extra fans on my IC-7000 to check out thermal management, when I heard some Canadians discussing band conditions and how I was the only thing they heard?!?! I added some more ground wires from the shield cage to my station ground and no more unwanted radiating.
Initially setting this up I ohmed it out and it was infinite. Upon inspection, the resistor had popped out of it's copper clip and had to be reseated (much like a barrel fuse) and all is good now.
WK2X Rating: 2015-02-27
Not as "dumb" as you'd think Time Owned: 6 to 12 months.
It does, indeed, provide a good load for the specified frequency range, and has not complained about running 100w through it.

However, I've actually been able to make contacts with the thing. One was on 20m from Michigan to Mississippi! So be careful about assuming that because you're running into a dummy load that no one can hear you. This thing seems to radiate a lot more than one would expect. Perhaps MFJ should market it as a "broadband indoor antenna."

I'm thinking about taking the resistor and so-239 out and putting them into a paint can with mineral oil, just to see if that makes for a "dumber" dummy load. We'll see.
KO1C Rating: 2011-05-30
Workmanship? Time Owned: 0 to 3 months.
I got this mainly to connect to my 2nd unused antenna port just in case I hit the wrong button ... cheap insurance indeed!

My only gripe (an I own a lot of MFJ equipment, all fine) is cosmetic. I worked for years for a company that made cabinets, etc for the computer and telecommunication industry. Made stuff for EMC, Cisco, IBM, etc.

I can tell MFJ painted the cabinet wnen it was still flat, then used press brakes or something similar to bend it. Because they painted it first then bent the cabinet it has less than desirable corners where the bends were made. The paint cracked and no longer fully covers the bend area.

C'mon MFJ, you're really not saving that much money!

W2FDH Rating: 2009-05-24
Does its job well Time Owned: more than 12 months.
Does what it is supposed to do with no problems. No shack should be without one.

73 de Frank/KB2VYZ
WV1K Rating: 2007-09-06
Fine so far Time Owned: 3 to 6 months.
This is better than having a Cantenna leak, which used to be The Way.

I own three of the MFJ-260C. A ham who has been around much longer has the KW version and says it's been fine for him.

As always, check the soldering, before you buy if possible. Mine were actually fine.

Also, specs are there for a reason. They mean it !

300w for 30 seconds... 25w continuous with a 2 minute cooldown.

Indeed, after 30 seconds at 200w, it's hot because it dissipates the RF as heat.
W6BP Rating: 2007-09-05
Killed by 40 watts Time Owned: more than 12 months.
I used to think that even MFJ could build a dummy load, but perhaps I was mistaken. Maybe the "C" version is better, but my model 260 died after about a week of intermittent use with my mighty 40-watt PSK31 transmitter.

Now I'm using the 1000-watt-rated model 262, which I figure should be good for an entire month or so.