[hpsdr] MUNIN III boards

Fri Jan 5 02:10:59 PST 2018

Hi Chris.

You beat me with one hour! I had just started to find the mail. I also  
found a later mail with comments:

"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."

Today I tested again just to confirm my observations and except for 6  
meter I measured the same. On 6 meter the PEP out was around 80W.

When using the Orion MK II board, it delivers >100W PEP on all bands.

73, Kjell, LA2NI

På Fri, 05 Jan 2018 10:30:18 +0100, skrev Chris Smith <chris at vspl.co.uk>:

> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Jim
>
> Attached below is Kjell Karlsen’s original message to this reflector. In  
> it he explains the design philosophy.
>
> Cheers & 73
>
> Chris G4NUX
>
>> Begin forwarded message:
>>
>> From: Kjell Karlsen <la2ni at online.no>
>> Subject: [hpsdr] Munin revisited.
>> Date: 3 August 2017 at 14:41:14 BST
>> To: "hpsdr at lists.openhpsdr.org" <hpsdr at lists.openhpsdr.org>
>> Resent-From: <chris at vspl.co.uk>
>>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> 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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