[1000mp] Low Output on the Mark V

Mon, 4 Mar 2002 17:34:25 -0600

hi Mike:

Very interesting !  I have also noticed this same phenomenon and have called
it 'normal'.  You're right that the antenna tuner isn't perfect.  My guess
is that what we are seeing is imperfect linearity of the amplifier. In my
amplifier manual there is a line about increasing the load a notch after
tuning 'to improve linearity on SSB.' This is only done once and after
everything else is tuned.

I, too, am extremely cautious about tuning the amp with the Mark V - it just
seems very sensitive - compared to my ol' Drake T4XB hi hi.

Jamie
WB4YDL

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Mike Schatzberg
Sent: Monday, March 04, 2002 11:38 AM
To: [email protected]
Subject: Re: [1000mp] Low Output on the Mark V

Hello Jamie and All Yaesu Fans.....

Thank you for your reply....Although I have written to Yaesu twice now, I
have received no reply from them....I did try to obtain the latest service
manual on the radio, but it is back ordered.....you can obtain an earlier
edition, but since we have new radios, I'm going to wait for the latest
book.....

I have continued to work on this problem, and I have some observations to
share, which might be helpful to others, or may merely represent a work
around for my particular radio.....

The issue with low output on the higher frequencies, appears totally related
to the automatic antenna tuner.....naturally, the higher perceived SWR, the
lower the output.....I didn't realize exactly what this means on the higher
frequencies....but apparently, even a modest SWR will limit the output
somewhat, especially on ten meters.....

The procedure I have come up with is rather simple, yet interesting....you
will notice that on SSB, while observing the SWR meter in the Mark V, that
there will always be an upscale indication during modulation....regardless
of the match through the tuner....it is actually impossible to ascertain the
SWR in this manner....

If the match is truly 1:1, the indication in the CW mode will be that the
indicator will not flicker, and only one bar will be displayed, unlike in
the SSB transmit position...So, I do the following.....

  a.. Select the desired band of operation
  b.. Lower the RF output control to a minimum setting, perhaps ten watts or
so
  c.. Preset my amplifier tuning, (band selection, tuning, loading)
  d.. Select the CW mode of operation
  e.. Select the keyer option to send dits at about 50 words per minute
  f.. Engage the transmitter and keyer, and quickly tune the amplifier at
this low level of input with continuous dits (50% duty cycle)
  g.. Operate the Tuner Button several times,  while sending the dits, until
the SWR indication stops flickering, and only one bar appears, indicating a
1:1 SWR has been achieved
  h.. Retune the Linear for maximum output
  i.. Increase the RF output from the Mark V to achieve full linear output
(perhaps in one or two steps), which in my case requires about 110 watts
drive for 1.5 KW output with a pair of 3-500ZG's from China.  You will
notice that at full drive, the SWR meter will still not flicker, and only
one bar should be displayed.....
  j.. Switch to SSB, and observe power output, and monitor to not exceed 1.5
KW, by adjusting the RF output control....You will notice that the SWR meter
is again flickering upward several bars....this is normal.....
Whether you are driving your amplifier, or loading up your antenna, the same
procedure is required....I force the tuner to operate until it matches the
load, 1:1, which then guarantees full output....I did not seem to be able to
achieve the match in SSB, for some reason...perhaps your Mark V will work
differently, but mine works well in this way, now that I have figured out
what was happening....

If you can not achieve the 1:1 tuning in CW, reset your tuner's memories,
and try again...You should be able to achieve a 1:1 match over quite a large
range of SWR conditions...

I guess afterall, the automatic antenna tuner, is not so completely
automatic afterall....at least in the case of my personal Mark V.....I now
achieve at least 170 watts on all frequencies, and the Power Output Meter
matches my Autek Research WM-1 readings.....this output is similar to other
Mark V radios from what I have been able to discover.....

Sorry for the length of this posting....let me know how your Mark V tuner
handles the SWR adjustments.....

Happy DXing and 73,

Mike Schatzberg
WB2AJI
http://www.qsl.net/vu2wap/wb2aji/