[Lowfer] Antenna Analyser Mod?

[Cliff Sojourner]

hi Kurt,

On 2015-12-10 21:18, KD7JYK DM09 wrote:
> : hi John, thanks for the encouragement from your web pages.  Today I
> : modified my '249 with a switch and 940uH inline.  the '249 board gives
> : even easier access to the switch than the '259.
> : Why 940uH?  because 470uH wasn't enough and 470s are all I had here.
>
> Thinking of getting a variable inductor for my mod so I can add another
> "band" from x-KHz to the current low end of 1.8 MHz using the current
> capacitor to tune.  I don't need to go too low right now, just something I'm
> thinking about...

that's a great idea.  I thought about installing a 3 or 4 way switch, 
didn't find any that were small enough.

>
> Some thoughts...  Where do those that have the MFJ-249 think the instability
> is?  The only variable appears to be the tuning capacitor.  What if, for the
> mod, a fixed capacitor was switched in and a variable inductor used?  Any
> chances it would increase stability?

the instability on mine is something like +/- 2kHz.  doesn't matter from 
1.8MHz on up but matters a lot at 474kHz...  472..476..

the high Q of antennas there means we won't be able to make good 
measurements with that kind of "sweep".

have to think this one through, personally I don't think a variable 
inductor would be any different.  as long as it needs to be variable, we 
have no chance to "lock" it to 10MHz or whatever.

>
> Cliff- Can you send me some pics of your mod?

will do - off this list

>
> Kurt
>

Cliff