[hpsdr] Munin revisited.

Warren C. Pratt warren at wpratt.com
Fri Aug 4 20:14:02 PDT 2017 

Hi Jim,

I am the author of PureSignal.  Please see below for answers and comments.

73,

Warren  NR0V


On 8/4/2017 1:41 PM, Jim Sanford wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Since Helmut brought it up, I'd like to weigh in again.
>
> I think Pure Signal is a profound contribution to the state of the art 
> and stand admiration of its developers.
>
> I would like to see Pure Signal for the Atlas-based systems, since I 
> have two.  I have spent some time thinking about the mutual 
> interference problems at multi-operator contesting and agree with an 
> author on here who posited that commercial manufacturers have improved 
> their receivers over the years, but not done much for the 
> transmitters.  Pure Signal changes that.
>
>
> I acknowledge that Pure Signal for Atlas-based systems is not high on 
> the developer's priorities.
>
> I acknowledge that Pure Signal for Atlas-based systems may not even be 
> possible due to bandwidth limits on the Atlas bus.
I believe it is possible; however, the required implementation is 
somewhat different than for the other systems.  We need someone who can 
work on Verilog FPGA code to support that implementation. (That's not me 
... I write software but not Verilog.)  Also, results may not be quite 
as good as for other systems.  However, without trying it, we don't know 
exactly where we'd end up.
>
> Helmut's use of the word, "yet" gives me hope.
>
>
> Tinkering with the new audio chain gave rise to the following thought:
>
> How dynamic is the Pure Signal correction data, once the correction 
> transfer function is determined?  If not very dynamic, would it be 
> possible to start with a default transfer function, and then stations 
> suitably equipped to measure distortion or linearity could "tweak" 
> constants to reduce IMD?  Presumably the correction function would be 
> several segments in a piecewise linear approximation.  This would 
> probably have to be a set of constatnts per band.
>
> Would this be at all possible?  Or am I totally out to lunch?
It is possible to do this; however, it is perhaps not very practical to 
use.  Any change in Drive level or in antenna/tuner load impedance 
changes the shape of the curves and requires some re-adjustment.  At one 
point I did a "manual adjust" version, using polynomials, for another 
person who was interested in this approach.  After experimentation, I 
believe that it was abandoned.
>
>
> Again, thanks & congratulations to the Pure Signal developers.
>
> Very 73,
>
> Jim
>
> wb4gcs at amsat.org
>
>
>
> On 8/4/2017 5:05 AM, Helmut wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hi Kjell,
>>
>> Nice improvements. Congratulations!
>>
>> Maybe you can spend time to investigate IM3 vs. quiescent current. 
>> 24dBc (30dB PEP) without linearization seems to bad for me. Don't 
>> forget folks, who are using Atlas-based HPSDR stuff, not capable for 
>> PS yet. What's the actual supply voltage?
>>
>> 73, Helmut, DC6NY
>>
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von 
>> Kjell Karlsen
>> Gesendet: Freitag, 4. August 2017 10:15
>> An: hpsdr at lists.openhpsdr.org
>> Betreff: [hpsdr] Munin revisited.
>>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hi.
>>
>> Some more tests with the modified Munin board shows that if the 
>> feedback resistors are increased to 100 Ohm each, the gain is 
>> increased to >23 dB in the output stage. That means that it is 
>> possible to drive the PA to
>>> 100W by using Munin or Angelia on all bands except on 6 meter. But on 6
>> meter the output is >80W PEP.
>>
>> I also tested without any feedback and the stage seems to be stable 
>> and the output on 50 MHz is >100W with a setting of 38.8. I can not 
>> see any increased IMD without feedback, it is at -30 dBc(ref PEP).
>>
>> So from this, I conclude that it is possible to use the Push Pull PA 
>> with
>> RD100HHF1 directly connected to Hermes, Angelia and Orion I to get 
>> 100W out.
>>
>> I also find that the PA handles Pure Signal much better than the 
>> original Munin. The IM3 is >50 dBc on all bands. When using the 
>> original Munin it was difficult to get >40 dBc IM3.
>>
>> 73, Kjell
>>
>>
>>
>>
>> Hi all.
>>
>> 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.
>>
>> 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.
>>
>> 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.
>>
>> 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.
>>
>> 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.
>>
>> 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?
>>
>> 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.
>>
>> Another positive observation I did was that the efficiency is better 
>> when using this solution.
>>
>> 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!
>>
>> May be it is time to do a new layout for a MUNIN III? It can be 
>> really small.
>>
>> 73, Kjell
>>
>> -- 
>> Sendt med Operas e-postklient: http://www.opera.com/mail/ 
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