[hpsdr] Munin works finally

[Tony Hagen]

Hi Berndt,

Yes, I overlooked the NTC resistor incorporation for bias stabilization.
Though I have not done this addition but my NTC was bad as it never gave 
linear results but then sure I will try.

To reduce heat if we do not use the predriver probably we can save another 1 
amps of current during idle condition.
Further, the kind of heat is generated the 1000mf/25V caps should be 
replaced with 50 volt type or else it will derate.

Please provide me the results after you feed RF. Take care of C25,26,27 with 
the suggested part # by kjell.
I do not have the CGO NPO type yet.

73s
Tony
-----Original Message----- 
From: Berndt Josef Wulf
Sent: Wednesday, December 18, 2013 5:35 PM
To: Tony Hagen
Cc: hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Munin works finally

G'day Tony,

I've just completed building my amplifier and can confirm your
observation regarding the instability of the bias current. The circuitry
for Munin2 implements temperature compensation using a NTC resistor and
my plan is to modify my amplifier using this circuit.

The heatsink supplied with the kit gets fairly warm when in idle mode,
e.g. PTT enabled with input and output terminated into 50 Ohms, which
makes me think that it may require a cooling fan for normal operation.

This raises the question about Munin's capability of being operated at
100% duty cycle, e.g. PSK31, RTTY etc. for prolonged time? Is anyone
operating Munin in these modes and what is your experience?

I've yet to test my amplifier with RF applied, so I can't comment on
this.

73, Berndt
VK5ABN

[...]
>
> Further, what I experienced the bias voltage shifts with the
> temperature rise that might result in instability of the power output
> so something temperature compensated bias circuitry if incorporated
> will enhance the efficiency of the circuit.
>
> Of course, my present worry is C25,C26,C27
>
>
> 73s
> Tony


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