[600MRG] [Lowfer] question abt MFJ259b mod

Sat Jun 7 19:52:00 CDT 2014

JL said, " hopefully Neil's issue is isolated to a small freq range that
does not impact his 630m measurements." One of my earlier inductors seemed
to work fairly good whenever the Z was near 50 ohms so I think I will go
back to the minimum L necessary to get down to about 465-470 kHz, and also
persue the bypass cap idea. The latter idea sound like it may solve the
problem since the unit was designed for 1.8 MHz and up. It makes a lot of
sense that larger bypass caps should be used for LMF.

Neil

*"I use the original form of social networking: Amateur Radio." *
 *(my ham radio sites are at 'w0yse.webs.com <http://w0yse.webs.com>'  and
'wg2xsv.webs.com <http://wg2xsv.webs.com>' )*

On Sat, Jun 7, 2014 at 6:37 PM, John Langridge <jlangridge at sbcglobal.net>
wrote:

> good info mike.  Fortunately I don't see this problem very often and its
> only intermittent over a small freq range as I am scanning across.  Neil's
> experience might be different.
>
> I have seen those MFJ filters as well as Tom' Rauch's discussions about
> it.  Its never been an impediment for my operation so I've never pursued it
> further.
>
> I am looking forward to hamcom this coming weekend as I want to talk to
> the VP of sales at MFJ face to face and ask him to tell me exactly what the
> capabilities of the new "no gaps" analyzer are.  In an email some months
> back, he suggested that the board was already prepped for an additional
> coil for get down to 472.  I want to see if he changes his story face to
> face...
>
> I've had the chance to play with and use a PowerAim before and its highly
> resistant to AM BC band.  In fact, one test done near 50 kw WBAP yielded no
> sign of BAP on the analyzer.. the thing is amazing, but you get what you
> pay for HI!
>
> 73 and hopefully Neil's issue is isolated to a small freq range that does
> not impact his 630m measurements.
>
> John
>
>   ------------------------------
>  *From:* Michael Sapp <wa3tts at verizon.net>
> *To:* John Langridge <jlangridge at sbcglobal.net>
> *Cc:* Neil Klagge <w0yse.7 at gmail.com>
> *Sent:* Saturday, June 7, 2014 7:14 PM
>
> *Subject:* Re: [Lowfer] [600MRG] question abt MFJ259b mod
>
> John& Neil: MFJ sells an accessory filter kit for HF overload issues.
> Divining a similar solution for MF/LF would be an elegant solution. It's
> it's been a long while since I have had my head
> into that particular issue.  If you had a low loss MF LPF with a known
> return high loss in the >40 dB range appropriate for the LF frequency of
> interest,  then perhaps you could get some reasonable test information
> from
> a modified 2598B unit where a BC intereference situation existed. Any
> significant insertion loss or poor return loss in such a filter would
> generate inaccurate results. The filter return loss could be an issue at
> 600M with local AM BCs on the low 540~750 end, as the return loss curve
> may
> not be all that great at 475 kHz if it is just 50kHz or so below the LPF
> cutoff.  That AADE filter program may offer some possible solutions.
>
> W8JI's site (or one of Tom's numerous relector postings) may have some
> info
> on the subject for HF that may be transferable to an MF/LF application.
>
> Another thought could be using one of those QRP directional coupler kits
> that Elecraft sells.  Replace the HF ferrites the kit uses with 75 or 77
> cores and calibrate. Non-inductive resistive loads for calibration are not
> an expense issue at 500 kHz and down.  An advantage with that route is one
> can use higher RF generator levels than what the 259 uses (8 mw range) to
> overcome the BCI....depends what you have for monitoring the directional
> coupler output. Dual trace scope is quite handy for that.....
>
> 73  Mike wa3tts
>
>
>
>
>
>
> ----- Original Message -----
> From: "John Langridge" <jlangridge at sbcglobal.net>
> To: "Neil Klagge" <w0yse.7 at gmail.com>; <600mrg at w7ekb.com>; "lowfer group"
> <lowfer at mailman.qth.net>
> Sent: Saturday, June 07, 2014 7:27 PM
> Subject: Re: [Lowfer] [600MRG] question abt MFJ259b mod
>
>
> Neil, there have been a few times that I have observed odd frequency
> behavior when using mine on 630m and depending on what antenna I am using.
> I
> can't say that it was exactly double the freq, however, it might have been.
>
> I have suspected overload from mixing due to local AM BC stations.. We are
> quite saturated here in north texas and there are a number of transmitter
> sites within 15-20 miles of my QTH
>
>
> That might not be the cause but its what I have been blaming when it does
> happen. Seems to impact my lower Q rx antennas more than the TX antenna
> which is really its own BP filter.
>
>
> 73 and I look forward to hearing what others think the cause might be!
>
> John XIQ
>
>
>
> ________________________________
> From: Neil Klagge <w0yse.7 at gmail.com>
> To: 600mrg at w7ekb.com; lowfer group <lowfer at mailman.qth.net>
> Sent: Saturday, June 7, 2014 6:21 PM
> Subject: [600MRG] question abt MFJ259b mod
>
>
> I got an MFJ 259B not too long ago and modified it for LMF (630 meters). I
> have tried several different amounts of extra inductance (inserted into the
> traditional spot on the PCB) but all of them have given me false frequency
> readings in some parts of the range, i.e. the freq reading is exactly twice
> the actual oscillator frequency.
>
> My question is: Has anyone else modified the 259b (not the 269) and
> experienced anything like this???
>
> If you did the mod on a 259 or 259b and it worked just fine, I would also
> like to know about that.
>
> Thanks for any/all reports about this.
> Neil Klagge
> wg2xsv, w0yse
>
> *"I use the original form of social networking: Amateur Radio." *
> *(my ham radio sites are at 'w0yse.webs.com <http://w0yse.webs.com>' and
> 'wg2xsv.webs.com <http://wg2xsv.webs.com>' )*
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