WOLF Test results from DF0WD]

Mon, 16 Apr 2001 08:13:24 -0400

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DL4YHF@aol.com wrote:

> Hello Jim, Markus, and group,
>
> Some on-air testing of Stewart's implementation of WOLF took place on
> sunday
> evening, which was partly successful (tnx Markus, DF6NM and Jim, M0BMU
> for
> their patience and to Stewart, KK7KA for the new software).
>
> Here is the new setup used at DF0WD:
> - An LF-transverter which was once intended to be a linear transverter
>
>   (until I blew the first set of matched MOSFETS a few months ago).
>   Transverter mixes 10.136MHz down to 136kHz and vice versa.
> - An oven-controlled 10MHz XO which feeds the transverter
>    and synchronizes the 30MHz 'master' oscillator inside the IC706
> - An old IC706 shortwave TRX, slightly modified
>  (30MHz clock 'voltage controlled').
> - WOLF signal taken from soundcard, fed to IC706 in USB mode
>  (to test amplitude shaping of new WOLF software by KK7KA).
> - TX output power about 10 Watts (a little more later with "rough
> keying")
> - Antenna 200m horizontal wire (no straight line), end fed,
>   about 8..10 meters above ground.
>   EIRP once estimated by PA0SE about 80mW with max. drive,
>   depending on WX (see www.qsl.net/dl4yhf/lf_index.html).
>
> I received the WOLF signal with the IC706 in "CW" at (10MHz+)137.500,
> using a
> the narrow CW filter.
> To transmit, the IC706 runs in "USB" at (10MHz+)135.500. The audio
> frequency
> should have been 2000.000 Hz, so the transmitted WOLF carrier should
> have
> been on 137.500 kHz (but it wasn't, see below). The soundcard's A/D
> conversion rate was once measured as 7938.086, this value was passed
> to WOLF
> as command line argument (because this is quite 'far off', I will
> verify it
> later with the 10MHz-ref divided down to audio freq. Thanks Markus for
> the
> point).
>
> To Jim, M0BMU: The "test carrier" was transmitted "CW", so it was not
> generated the same way as the WOLF signal. This may explain the
> problem.. I
> don't know how you generated the "leading carrier" before your WOLF
> transmissions a few weeks ago.
>
> One intention for the test was to compare the new 'amplitude shaped'
> WOLF
> signal. I found that with the amplifier currently use here, I can not
> generate such a 'crystal clean' WOLF spectrum like the one shown on
> Stewart's
> updated WOLF page (http://www.scgroup.com/ham/wolf.html).
>
> It seems that each MOSFET (IRF540) in the PA needs an indivudual
> carefully
> adjusted bias point, and a little more source resistance (as negative
> feedback) to make the small PA work linear. Each FET carries a
> different
> current, especially when the driving power is very low. Result: the
> damn
> thing looks like a linear when the power is 10%...70% of the output,
> but it
> does not behave linear when drive is less than 10% (because of
> different FET
> behaviour) or more than 70% (compression point).  The low-power
> linearity ot
> the PA was better, when I used the 4 "best-matched" FETS which I
> selected
> from a bundle of 50 low-cost FETS.  I blew two of these 4 FETS a few
> months
> ago when was experimenting with a slowed-down variant of PSK31 (which
> produced the sample modulation spectrum as WOLF with the option 't
> 1').
>
> The best way to drive a high-power BPSK transmitter is the way M0BMU
> described (do the phase reversal by "XOR-gating", and do the envelope
> shaping
> by "modulating the PA supply voltage" or similar).  On the other hand,
> a
> 'completely linear' concept will allow low-power experiments with
> QPSK, MT
> HELL etc. As long as I am still resctricted to the crazy power limit
> in DL, I
> don't have to care for a highly efficient TX design (there's enough
> "spare
> power" to compensate the losses in the ATU and in the cable which I
> consider
> as part of my transmitter hi).
>
>
> Hope I'll have better luck next time, and thanks to everyone involved.
>
> Also thanks to all stations active in fast CW, which will remain my
> favorite
> mode. Nice to meet you again; no matter if in CW, any kind of BPSK or
> whatever.
>
> 73's Wolf (DL4YHF).
>

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&nbsp;
DL4YHF@aol.com wrote:
<blockquote TYPE=CITE>Hello
Jim, Markus, and group,
Some on-air testing of Stewart's
implementation of WOLF took place on sunday
 evening, which was partly
successful (tnx Markus, DF6NM and Jim, M0BMU for
 their patience and to Stewart,
KK7KA for the new software).
Here is the new setup used
at DF0WD:
 - An LF-transverter which
was once intended to be a linear transverter
 &nbsp; (until I blew the
first set of matched MOSFETS a few months ago).
 &nbsp; Transverter mixes
10.136MHz down to 136kHz and vice versa.
 - An oven-controlled 10MHz
XO which feeds the transverter
 &nbsp;&nbsp; and synchronizes
the 30MHz 'master' oscillator inside the IC706
 - An old IC706 shortwave
TRX, slightly modified
 &nbsp;(30MHz clock 'voltage
controlled').
 - WOLF signal taken from
soundcard, fed to IC706 in USB mode
 &nbsp;(to test amplitude
shaping of new WOLF software by KK7KA).
 - TX output power about
10 Watts (a little more later with "rough keying")
 - Antenna 200m horizontal
wire (no straight line), end fed,
 &nbsp; about 8..10 meters
above ground.
 &nbsp; EIRP once estimated
by PA0SE about 80mW with max. drive,
 &nbsp; depending on WX (see
www.qsl.net/dl4yhf/lf_index.html).
I received the WOLF signal
with the IC706 in "CW" at (10MHz+)137.500, using a
 the narrow CW filter.
 To transmit, the IC706 runs
in "USB" at (10MHz+)135.500. The audio frequency
 should have been 2000.000
Hz, so the transmitted WOLF carrier should have
 been on 137.500 kHz (but
it wasn't, see below). The soundcard's A/D
 conversion rate was once
measured as 7938.086, this value was passed to WOLF
 as command line argument
(because this is quite 'far off', I will verify it
 later with the 10MHz-ref
divided down to audio freq. Thanks Markus for the
 point).
To Jim, M0BMU: The "test
carrier" was transmitted "CW", so it was not
 generated the same way as
the WOLF signal. This may explain the problem.. I
 don't know how you generated
the "leading carrier" before your WOLF
 transmissions a few weeks
ago.
One intention for the test
was to compare the new 'amplitude shaped' WOLF
 signal. I found that with
the amplifier currently use here, I can not
 generate such a 'crystal
clean' WOLF spectrum like the one shown on Stewart's
 updated WOLF page (<A HREF="http://www.scgroup.com/ham/wolf.html">http://www.scgroup.com/ham/wolf.html</A>).
It seems that each MOSFET
(IRF540) in the PA needs an indivudual carefully
 adjusted bias point, and
a little more source resistance (as negative
 feedback) to make the small
PA work linear. Each FET carries a different
 current, especially when
the driving power is very low. Result: the damn
 thing looks like a linear
when the power is 10%...70% of the output, but it
 does not behave linear when
drive is less than 10% (because of different FET
 behaviour) or more than
70% (compression point).&nbsp; The low-power linearity ot
 the PA was better, when
I used the 4 "best-matched" FETS which I selected
 from a bundle of 50 low-cost
FETS.&nbsp; I blew two of these 4 FETS a few months
 ago when was experimenting
with a slowed-down variant of PSK31 (which
 produced the sample modulation
spectrum as WOLF with the option 't 1').
The best way to drive a high-power
BPSK transmitter is the way M0BMU
 described (do the phase
reversal by "XOR-gating", and do the envelope shaping
 by "modulating the PA supply
voltage" or similar).&nbsp; On the other hand, a
 'completely linear' concept
will allow low-power experiments with QPSK, MT
 HELL etc. As long as I am
still resctricted to the crazy power limit in DL, I
 don't have to care for a
highly efficient TX design (there's enough "spare
 power" to compensate the
losses in the ATU and in the cable which I consider
 as part of my transmitter
hi).
 &nbsp;
Hope I'll have better luck
next time, and thanks to everyone involved.
 Also thanks to all stations
active in fast CW, which will remain my favorite
 mode. Nice to meet you again;
no matter if in CW, any kind of BPSK or
 whatever.
73's Wolf (DL4YHF).
 &nbsp;</blockquote>
</html>

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