[hpsdr] Munin problem

[Helmut Oeller]

Hi John,

Munin is well designed, but a lot can happen during assembling, soldering
etc. with the components. Some things you mentioned would concern me: 
You talk about strange behavior of bias current. Without drive power the
bias or quiescent current of the finals and driver stages should be stable
on all bands, otherwise it can be clue for self oscillation.
Be careful with stressing the amp when see high input and unusual little
output. Power must be dissipated somewhere.
You mentioned that Hermes VNA probably together with a measuring bridge is
available. It's always a got idea to control transmission or at least
reflection of the transformers and compensation capacitors before placing
the semiconductors.

In the current situation look for the 'power traps' first before applying to
much drive power .

Good luck.

73, Helmut, DC6NY

-----Ursprüngliche Nachricht-----
Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von John
Gesendet: Sonntag, 18. Mai 2014 13:12
An: hpsdr at lists.openhpsdr.org
Betreff: [hpsdr] Munin problem

***** High Performance Software Defined Radio Discussion List *****



I'm trying to get my Munin working with Alex and Hermes, now using 
PowerHPSDR v 3.2.10 (4/10/14) and Windows 7 Pro 64 bit.

I did not notice any problem when running Munin without Alex into a 
50 Ohm load using a signal generator for a signal source.  The output 
power was a little low on the higher bands and on some bands the bias 
current readings were strange to me.

I calibrated my 30 dB power attenuator and cables for the ham bands 
to 54 mHz using Hermes VNA and calculated the correct Voltmeter 
readings to be used to set up the gain and Wattmeter settings in 
PowerHPSDR.  My Voltmeter is not fully  calibrated, but it agrees 
with each of my two signal generators.  I used this setup to set the 
gain in PowerHPSDR on all bands.  At 12m I could not get 100W and the 
supply current was lower than expected.  The output was also low on 
6m, but the supply current was very high.  The PowerHPSDR wattmeter 
was calibrated at 1.8 mHz using the same test setup.

However, when connected to an antenna having a low SWR and running 
reduced power, PowerHPSDR indicated very high SWR and reflected power.

I then ran power from my TS-440 rig through Alex at 3.5mHZ (no PA, 
Hermes on a dummy load with no drive and keyed in CW) and checked the 
PowerHPSDR readings:
     Forward Power  82 Watts
     Reflected Power 1.0 Watts
     SWR  1.3:1

This seems to indicated my problem(s) is not caused by Alex.

I also used an external SWR bridge and found very low SWR when using 
a 50 Ohm load and very high SWR using an antenna.

The only explanation I can come up with is that my Hermes/Munin/Alex 
system has very high spurious output and the antenna system is 
reflecting the spurious output.  I don't have access to a spectrum analyzer.

Is there another explanation for the above results?

73,  John  WoGN


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