[1000mp] MPV Driving Amp

[Mike Schatzberg]

The tuner in the Mark V memorizes capacitor settings, one for the CW portion
of the band when CW is selected, and one for the SSB portion of the band
when USB or LSB is selected for example.  It remembers these settings each
time you select band and mode.

The tuner can be taught to memorize the settings by pushing and holding in
the tuner button, at which time it will attempt to tune the load to as close
to 1:1 as is possible based upon the tuning algorithms in the rig.

Once you are set on SSB on a particular band  the tuner should not be
hunting for new capacitor settings, it should have selected the memorized
previous solution.  When you engage the tuner, it returns the capacitors to
the previously determined settings, it does not retune itself.

Now of course, this solution may not be the best for the current frequency,
and load combination you are currently using.  Meaning, you may have
previously memorized the tuner capacitor settings into the antenna at some
particular frequency, and this time you are asking the tuner to work into
the amplifier rather than directly into the antenna at some other frequency.
This may not match very well.

Another Mark V issue, is when you do make such a large change in load, that
the tuner can not achieve a 1:1 match when forced to retune.  This may be
due to the algorithms not correctly identifying the starting position of the
capacitors from the previously memorized positions.  In this case, it is
necessary to do a memory clear reset, which will also reset the capacitors
to their default starting positions, and allow the tuner algorithms to reach
a more optimal match.

If the radio is changing in output while you are tuning your amplifier, it
may be due to other factors.  If ALC is being used, the amplifier may be
generating some voltage and be folding back the transceiver output for
example.

In the description of wandering, it was not stated whether the Mark V
indicated a large change or even a small one on the internal SWR meter.
Amplifiers with tuned inputs should not be showing a large change in input
impedance over a range of transceiver output power levels.

The issue in fact may have nothing to do with the tuner, but be due to the
fact the internal SWR protection circuit is adjusting the power slightly
because a perfect match was not achieved.  Some adjustment in the power
foldback calibration maybe necessary.

Personally, I always have made it standard practice to use the Collins
approach with the 1/4 wavelength coax line between the rig and amplifier, to
achieve the best match and stability.  On the higher frequency bands, it may
be well to "prune" the line for optimal SWR into the amplifier, and
eliminate the need altogether for the transceivers tuner.

73 and Happy Dxing,

Mike
W2AJI
----- Original Message ----- 
From: "Steve Fraasch" <sfraasch at earthlink.net>
To: "Scott Manthe" <n9aa at arrl.net>; "FT1000MP Board"
<1000mp at mailman.qth.net>
Sent: Sunday, October 22, 2006 1:56 PM
Subject: Re: [1000mp] MPV Driving Amp


> I just tried it on two bands with my QRO HF2500: absolutely no tuner
"wander" whle tweaking the output settings.  The amplifier output circuit is
isolated by the amplifier gain, hence output tuning changes will make little
difference at the amplifier input.
>
> Did your MP tuners drift into loads other than amps ? If they did the SWR
threshold may be too low, hence an adjustment.
>
> The tuner is not "active" either, I assure you it is quite passive.  I
think you mean it is automatic.
>
> This is getting silly.  I quit.
>
> Steve, K0SF
>
> -----Original Message-----
> >From: Scott Manthe <n9aa at arrl.net>
> >Sent: Oct 22, 2006 12:03 PM
> >To: Steve Fraasch <sfraasch at earthlink.net>, 1000mp at mailman.qth.net
> >Subject: Re: [1000mp] MPV Driving Amp
> >
> >I've had three Fields, all of which "wandered." This is normal, because
> >when you tune-up the amp, the load to the rig changes, causing the tuner
> >to readjust to follow those load changes, hence the wandering.
> >
> >Scott, N9AA
> >
> >Steve Fraasch wrote:
> >> Yours might require an alignment.
> >>
> >> -----Original Message-----
> >>
> >>> From: Scott Manthe <n9aa at arrl.net>
> >>> Sent: Oct 22, 2006 11:40 AM
> >>> To: Steve Fraasch <sfraasch at earthlink.net>, All about Yaesu 1000mp
<1000mp at mailman.qth.net>
> >>> Subject: Re: [1000mp] MPV Driving Amp
> >>>
> >>> I have a Field and it does.
> >>>
> >>> Scott, N9AA
> >>>
> >>> Steve Fraasch wrote:
> >>>
> >>>> Mine doesn't wander.
> >>>>
> >>>> K0SF
> >>>>
> >>>> -----Original Message-----
> >>>>
> >>>>
> >>>>> From: Scott Manthe <n9aa at arrl.net>
> >>>>> Sent: Oct 22, 2006 11:31 AM
> >>>>> To: All about Yaesu 1000mp <1000mp at mailman.qth.net>
> >>>>> Subject: Re: [1000mp] MPV Driving Amp
> >>>>>
> >>>>> The tuner in the Mark V isn't passive. If you use the rig's tuner
while
> >>>>> you are tuning up the amp, you'll find that the tuner will "wander,"
> >>>>> causing the output of the rig to vary and making tune-up more
difficult.
> >>>>>
> >>>>> There are other reasons I'm sure the more technical types on the
list
> >>>>> will come up with, but for me, this is a very good reason not to use
the
> >>>>> rig's tuner. If the amp is already tuned, of course, this is not a
problem.
> >>>>>
> >>>>> 73,
> >>>>> Scott, N9AA
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>
> >>
> >>
> >>
>
> ______________________________________________________________
> 1000mp mailing list
> Home: http://mailman.qth.net/mailman/listinfo/1000mp
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:1000mp at mailman.qth.net