[600MRG] Modifying a MFJ259C

[Edward R Cole]

The webpage I had was hacked a year ago and I have not rebuilt the 
page but here is the schematic showing detail of the mod:
http://www.kl7uw.com/MFJVFO.jpg

As in Johns well described version of the mod:
http://njdtechnologies.net/modifying-an-mfj-259b-antenna-analyzer-to-operate-on-630-meters/
you cut the trace on L1 and run two fine wires to a mini-toggle 
switch and place the coil across the contacts of the switch as well 
as the two wires.  The switch merely shorts the coil to restore the 
meter in the lowest freq band to original freq range.  I arrived at 
11 turns on two cores stacked by trial.  The frequency meter in the 
analyzer will indicate the operating frequency.  Mine tunes 450-950 
KHz.  The cores are FT 37-77 which are 3/8-inch toroids.  The MFJ259 
may be different than the MFJ269B that I have.  L1 in my analyzer is 
66uH.  I have no idea what is the inductance of the stacked cores I used.

73, Ed - KL7UW
Used MFJ analyzers can be picked up on ebay.

At 03:57 PM 6/1/2015, Kenneth G. Gordon wrote:
>On 1 Jun 2015 at 16:04, Dick Bingham wrote:
>
> > Hello folks
> >
> > I have been tempted to buy one of the MFJ259C Impedance Analyzers and have
> > heard some folks have a 'mod' to get it to work at 630-meters.
> >
> > Is this true that there IS a modification to extend the 
> low-frequency range a
> > bit. If so, I'll buy one and get busy working on some antennas . . .
>
>Yes. "Our own" John Langridge and Ed Cole have published an article on
>modifying the MFJ-259B to cover MF.
>
>Here is a link to it:
>
>http://njdtechnologies.net/modifying-an-mfj-259b-antenna-analyzer-to-operat
>e-on-630-meters/
>
>The latest version of the MFJ antenna analyzer, for an additional $100,
>covers VLF too, down to, as I remember it, 135 KHz.
>
>Ken W7EKB
>
>_______________________________________________
>600MRG mailing list
>600MRG at w7ekb.com
>http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     dubususa at gmail.com