[hpsdr] MUNIN III boards

Fri Jan 5 03:54:17 PST 2018

I will be attempting this soon with a Hermes.  My boards should be here 
any time.

73

Glen K4KV

On 1/5/2018 05:10, Kjell Karlsen wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> 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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