[hpsdr] Munin2 Update

[Kjell Karlsen]

Hi Berndt.

Thanks for publishing your  findings. I believe the results you have  
achieved are very near what I got.

The main reason I included the stabilization circuit was the problems I  
got when using Munin on 24V. The rise in bias current was much higher due  
to the higher power dissipation at 24V.

The measured input return loss can be improved just by changing R9 to 56  
Ohm. This will lower the gain and probably also remove the resonance you  
see in your recording. The gain is still high enough for use on all bands.  
This is one of the modifications I was planning to publish soon.

I am very glad to get inputs from people like you and if you can help me  
to improve the construction, I´ll be very glad.

I have also found that Munin is not working good with Pre Distortion. I  
have worked with Warren to try to find the reason but so far no solutions.  
As Munin is very like the PA in ANAN-100/100D it is strange. The only main  
difference is that in Munin I use a bifilar wound transformer(L3) to feed  
the Vdd and in ANAN-100, the output transformer feeds the Vdd. I have  
tested Munin by modifying the output but I see absolutely no difference.  
So if you have any ideas to solve this puzzle, I´ll be glad!

In my Hermes/ Apollo TRX, the PS works very good. The improvements in PD  
are from -35dBc IMD without PS to -60 dBc with PD.

73, Kjell


På Mon, 10 Mar 2014 03:16:31 +0100, skrev Berndt Josef Wulf  
<wulf at ping.net.au>:

> ***** High Performance Software Defined Radio Discussion List *****
>
> G'day Rod,
>
> I've now included the circuit diagram showing the modifications. Its
> basically the same as Kjells original circuit except I'm using two NTC
> thermistors, one mounted onto the casing of each final transistor.
>
> 73, Berndt
> VK5ABN
>
>> On Sun, 2014-03-09 at 18:00 -0700, Rod Brink wrote:
>> > Hi Berndt -
>> >
>> > I've noted the same un-compensated bias drift characteristic on my  
>> Munin and
>> > have been a bit worried about it, notwithstanding the comment from  
>> K2UE.
>> > I'm puzzled by your assertion that the compensation you achieved was  
>> not
>> > good enough - it looks damn good to me.  Kjell has come up with two
>> > different compensation circuits and each has employed a single NTC  
>> resistor.
>> > You have used two and it appears you are also using a pot.  Can you  
>> publish
>> > your latest circuit, please - I'd like to try it.
>> >
>> > 73 de Rod KQ6F
>>
>
>
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