[Yaesu] Mark V w/Linear Amp Problems

Mike Schatzberg cherokeehillfarm at earthlink.net
Sun Dec 28 19:36:52 EST 2003

Hello Javier:

I would assume that the input impedance of the amplifier is not properly
matched by the automatic antenna tuner of the Mark V.

With the Mark V in the CW, and the amplifier on and with the antenna tuner
off, transmit a series of dits, at low input power, say about 20 watts, at
about 30 wpm.  While sending the dits, push and hold the antenna tuner
button in, and allow the Mark V tuner to attempt to match the input
impedance of the linear.  I personally prefer this manner of adjustment,
rather than the Yaesu method in the manual.  You should see the Mark V tuner
attempt to make the adjustment.

It should easily retune itself to a 1:1 state.  You should be able to see
this in CW mode, while monitoring the SWR meter in the Mark V.  If it does
not accomplish a 1:1 match, reset the Mark V memories, and try again.  If
the tuner is starting too far outside of the impedance match for the
amplifier, the tuner may not be able to tune down to 1:1, and you need to
perform the reset.

You should be able to use the tuner to match both your antenna, your
amplifier, and also match into the bypass position of your amplifier when
not in use.  Each of these three conditions requires different capacitance
settings to handle the different reactance of each operating condition.  I
have added some additional capacitance to my amplifier bypass circuitry, to
provide lower SWR at higher frequencies, like on 10 meters.

If a memory reset does not solve the match problem, you have another issue
at play.

Good Luck and Happy DXing,

----- Original Message ----- 
From: "James C. Hall, MD" <nwtcc at earthlink.net>
To: <jlopez at plasticosomega.com>
Cc: <yaesu at contesting.com>
Sent: Sunday, December 28, 2003 6:52 PM
Subject: Re: [Yaesu] Mark V w/Linear Amp Problems

> Hi Javier:
> I see this all the time with my Mark V to a Alpha 87A to Ten-Tec tuner
> and out to the antenna via Array Solutions RatPak antenna switch.  The
> only thing I can figure is that there is some reactance in between the
> amp and the Mark V that is not tuned out.  Now, I don't use the tuner
> in the Mark V to tune this out - Alpha advises against using any tuner
> in front of it - but, boy, am I tempted !
> 73, Jamie
> On Dec 28, 2003, at 5:31 PM, jlopez at plasticosomega.com wrote:
> > Hi,
> > I just had been using my new Mark V for few hours and I found the
> > behavior shown below, wich I dont know if its normal.
> > The rig is feeding a Ten-Tec Centurion Amp after wich there is a
> > Ten-Tec antenna tuner between the amp and the antenna.
> > My antenna has 1.4 swr so the tuner is bypassed and with the amp in
> > standby mode there is no problem but if I operate the amp the swr
> > shown at the Mark V goes to 3 or 4 but the swr meter at the antenna
> > tuner in by-pass mode shows 1.4.
> > What could be happening???
> > Advice welcome,
> > 73's de Javier
> > yv5mbx
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