[Lowfer] Antenna Analyser Mod?

[John Langridge]

Ive added a 2nd switched mod to get down to 137.. I think I bottomed out
around 110 kHz.  I dont trust R or X at all down there as it shows 1:1
around 40 ohms into a known 50 ohm load and known good diodes in the
detector but SWR on the analog meter seems consistent with what I see with
other tests here on 137.  The 472 mod is generally pretty good as long as
you don't get too hung up on the numbers, although they seem to be more
accurate than lower down... the further away from 50 ohms resistive you get
the less accurate the numbers seem to be...Its a descent instrument that
most hams already have and will get you in the ball park if you trying to
get a system going.  But don't mistake it for an accurate, high-performance
system.

On the 472 mod, I did one for someone recently using the Mouser inductor
specified at the top of the article, mounting the inductor directly to the
board where the trace is cut with short leads to the switch.  this actually
worked better than the mess that I outline in pics in the article.  I've
since gone back and added the "improved" mod to my instrument and it doesnt
seem worse for it.

As to how low will the existing slug will go, I dont know.  I didnt want to
lose 160m so I didnt try but the new 259 "C" (I think that's the model)
apparently comes with enough slug to get down to 460, or so say the MFJ
people...

73 and good luck!

John KB5NJD / WG2XIQ...

On Mon, Nov 23, 2015 at 6:01 PM, KD7JYK DM09 <kd7jyk at earthlink.net> wrote:

> I checked out the followin gmod for the 259b:
>
>
> http://njdtechnologies.net/modifying-an-mfj-259b-antenna-analyzer-to-operate-on-630-meters/
>
> Very straight forward.  Anyone just tweaked the existing L1 inductor to see
> how low the unit can go without a mod?
>
> Hoping this will apply to my 249, haven't opened it up yet, but looking
> forward to checking it out.
>
> Anyone found out how low the 259b can go- overall?
>
> Kurt
>
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