Has anyone tested or had any experience with the Rig Expert AA-54
antenna analyzer? How does it compare to the MJF 259B? I recently
purchased one after deciding on it over the 259? I like the graphical
plot feature and the ability to show up to 5 frequencies
simultaneously. I don't like the frequency limitation of 54 MHz.
On 6/9/2011 7:44 AM, Carl wrote:
> ----- Original Message -----
> From: "Jim Thomson"<firstname.lastname@example.org>
> Sent: Thursday, June 09, 2011 2:05 AM
> Subject: [Amps] Dummy load varying R
>> Date: Wed, 8 Jun 2011 11:22:11 -0400
>> From: Al Kozakiewicz<email@example.com>
>> Subject: [Amps] Dummy load varying R
>> Maybe not quite amps related, but this is the best forum I know of for RF
>> expertise ...
>> Without belaboring irrelevant details, I'm calibrating an LP-100A
>> wattmeter I just built. With a brand new MFJ 300W dummy load I measure
>> 50.1 ohms with my old Fluke DMM. The dummy load is connected to the
>> coupler with about 6 feet of RG-8U. It appears as though the resistance
>> of the dummy load increases with frequency, to the point where it is 65
>> ohms in the 20m band and the LP-100 can no longer compensate.
>> After fiddling with the coupler with no joy I decide to connect my MFJ-259
>> to the cable and verify that the resistance is actually 50 ohms across all
>> the HF bands. Turns out that it's not. In the 20m band the impedance at
>> the end of the RG-8 has risen to 66+6j.
>> ### 66+6j ?? This implies the swr is aprx 1.5:1 What swr did you
>> measure into the dummy load on 20m? What is the swr on 160/80m.... and
>> again on 17-15-12-10-6m ? Sounds to me like it will just get worse
>> as freq goes up....and it's already out to lunch on 20m ! This is typ
>> mfj 'engineering'. Take a simple concept.....then screw it up.
>> ## sure, stray L and stray C will have an impact.... which is why it has
>> to be designed correctly. Any globar is non inductive. Now if mfj used
>> an inductive resistor.. [ I doubt it] then it would really be bad on
>> upper hf. If wide cu strap is used for all internal connections, you
>> will eliminate the stray L.... and probably be away ahead of the game.
>> ## If worse comes to worse, get a real dummy load. Even the old heath
>> dummy load... or the mfj 1 gal dummy load will give u an almost perfect
>> 50 ohms and no reactance up to 10m...and probably higher.
>> This is as simple a setup as I can imagine - a 50 ohm resistor in a metal
>> box and 6 feet of new 50 ohm coax cable. Tonight I will test again
>> without the cable if I can find a M-M UHF adapter. But I'm puzzled as to
>> what the issue could be.
>> ## My hb dummy load has better swr than that mfj unit. Mine consist of
>> 4 x 3" OD thick wall AL tubes welded together. A 200 ohm resistor
>> is inside of each of the 12" long t 7=ubes. The entire mess sits
>> suspended from the lid of a 7 gal paint drum. 7-16 female chassis din
>> sits dead center in the top lid. It's like the heath dummy load..on
>> ## did u read any reviews on the mfj 300w dummy load. I'm guessing
>> either [A] you got a defective unit.....or [B] they are all defective
>> due to a design flaw.
>> ## flash..per e-ham etc. The mfj- 260-C is flat swr to 10m...and only
>> 1.5:1 between 30-650 mhz. Rated for 300w for 2 mins. Rated for 25 w
>> CCS. It's just a 25 w dummy load..in air.
>> Later... Jim VE7RF
>> Any ideas?
> Using a MFJ to test a MFJ just doubles the error (-;
> The early analyzers were poor at reading reactance altho the analog VSWR
> meter is OK.
> Even the later 259B has had many factory revisions and not all can be
> upgraded. So now they have a new model 266 to start the process all over
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