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<font size="-1"><font face="Courier New, Courier, monospace">Hi
Kjell,<br>
<br>
That's good to hear that there are so many Munin implementations
out there - mine has been in pretty much constant use for the
last few years - although it's all packaged up now along with
the rest of my kit for eventual unpacking somewhere in
Scotland! Good also to hear about the excellent results of your
experimentation. You mentioned that you can get 100W with less
than 1W of drive - have you tried using Penelope as the source
of the drive - and if so what input/output power levels did you
see?<br>
<br>
73, Pete, N3EVL/Future MM0???<br>
<br>
</font></font><br>
<div class="moz-cite-prefix">On 8/3/2017 9:41 AM, Kjell Karlsen
wrote:<br>
</div>
<blockquote type="cite" cite="mid:op.y4edm0q9nknqug@kjellkarlsen-pc">*****
High Performance Software Defined Radio Discussion List *****
<br>
<br>
Hi all.
<br>
<br>
Some years ago I did a layout for a 100W PA using a pair of
RD100HHF1 MOSFET transistors and called it Munin and an updated
version, Munin II. As far as I know more than 250 of them were
built around the world.
<br>
<br>
Munin was more or less a copy of the 100W PA´s used by ICOM,
Kenwood and Yaesu. Apache Labs also have used a variant of this PA
in all the 100W units sold until now. It is extremely robust and I
have only managed to destroy 1 pair of them when I forgot to
install the heat sink and used them for a long time at 100W out.
<br>
<br>
In the ANAN-7000, Apache Labs has removed the Push Pull Driver
stage that uses 2 pcs. RD16HHF1 and drive the RD100HHF1 directly
from the Orion MKII board that can deliver maximum 3W out.
<br>
<br>
I was very surprised when I saw this so I decided to test with one
of my Munin boards. Using the same values as in the -7000 for the
input circuit and a 1:1 transformer, I got 100W OUT with <3W IN
on all bands except 6 meter. I measured the input Return Loss and
found that by removing a 200 pF capacitor across the secondary of
the transformer, the output on 6 meter could be reach with 2,5W
IN.
<br>
<br>
Then I tried to reduce the feedback in the PA. The feedback
resistors were 2 pc. 22 Ohm in parallel on each transistor and by
increasing them to 39 OHM each, I can get 100W out with <1W
drive on all bands! That means that the gain is >20 dB! And the
linearity is not worse using less feedback.
<br>
<br>
According to the data from Mitsubishi, the gain on 30 MHz is 11,5
dB for one devise so for 2 in Push Pull the gain is 3 dB higher,
14,5 dB. So were does all this extra gain come from?
<br>
<br>
The gates are purely capacitive (Ciss=260 pF for each gate) so no
power is lost in the input. So by just using a 1:1 transformer and
load it with 50 Ohm on the secondary, the driving voltage is 20V
P-P. There is a mismatch on the highest frequencies so one should
expect that the gain should drop a lot of dB but still the gain is
above 20 dB. It might be possible to optimize the input RL but I
see no point in that as we have the Gain By Band adjustments in
PSDR and PiHPSDR.
<br>
<br>
Another positive observation I did was that the efficiency is
better when using this solution.
<br>
<br>
When using the original Munin, the current draw at 100W OUT was
between 18 and 20A on all bands up to 10 meter and 22A on 6 meter.
But now the current is <15A up to 10 meter and just a bit
higher on 6 meter. I have no explanation for this!
<br>
<br>
May be it is time to do a new layout for a MUNIN III? It can be
really small.
<br>
<br>
73, Kjell
<br>
<br>
</blockquote>
<br>
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