[hpsdr] Munin output low above 20 meters

[Rick Dykstra]

Thanks for the replies, by the way the subject should be above 20
meters...typo.

All my testing has been into a dummy load.  I have three different meters in
line, all show zero reflected, but the forward power varies a little among
them, within 10 watts highest to lowest. All meters are between Munin/Alex
and the dummy load.
There was a suggestion to bypass Alex to see if that was a problem.  I set
the gains to be close to 100 watts out previously. Here's my latest testing,
results are from the meter reading the highest wattage. Current was
approximate reading off power supply analog meter, with Alex in line.

Band	 Gain	Thru Alex	Alex not in line	AMPS
160	51.7	100		82		15
80	55.4	98		70		15
60	54.3	98		68		15
40	50.0	100		100		15
30	51.7	90		80		16
20	48.9	98		100		17
17	38.8	88		130		14.5
15	38.8	80		95		12
12	38.8	70		70		11-12
10	38.8	70		98		14
6	38.8	52		90		18

I'm not sure what is going on. On some bands it  shows more power through
Alex than when it's not in line.
Alex was purchased assembled from TAPR/HPSDR, as was Hermes.
All the parts for Munin were in the parts kit originally shipped back in
2013 ( I think that's when it was). 
I do have a question on the multi-turn pots. I didn't use them, I ordered
the ones on the parts list, that the board was laid out for. Is this causing
a problem?
I did change the caps to four 220pf 500V.
I did not put in the mod for the bias stability.

Any ideas, help, or suggestions?

Thanks
Rick





-----Original Message-----
From: John [mailto:radio at mediacombb.net] 
Sent: Saturday, April 18, 2015 12:11 PM
To: Rick Dykstra
Subject: Re: [hpsdr] Munin output low above 29 meters



Hi Rick,

I built a Munin last year and tested it with Hermes and Alex.

My Munin worked if feeding a 50 Ohm load, although the power was a little
low on some bands (6m was the worst).

However, if I tried to feed a load that was only slightly different than 50
Ohms I had a bad oscillation.  Because I use an end fed wire with a tuner,
this is a problem for me.  I added capacitors in the feedback look as
suggested by LA2NI, but haven't checked it yet.  I am finishing making a
shield around Munin.  That seemed like a good idea electrically and to
physically protect it.

I wonder if you tested Munin with a mismatched load?  Another guy in New
Zealand was having a problem like mine.

My transformer also has small gaps in the shielding, but LA2NI said it
looked good in the photo I sent to him.

I saw a post by LA2NI on the reflector that he has been experimenting with
the transformer design and will post what he finds soon.

Best regards,

John  WoGN



At 08:43 AM 4/18/2015, you wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>I've finished my Munin amplifier, driving it with Hermes, and using 
>Alex, here are my results.
>Band    output  PA Gain
>6m      52w     38.8
>10m     90w     38.8
>12m     70w     38.8
>15m     85w     38.8
>17m     90w     38.8
>20m     100w    49.6
>30m     100w    50.3
>40m     100w    51.0
>60m     100w    54.1
>80m     100w    55.0
>160m    100w    51.7
>
>I put the four 220pf 500V caps in the C25, C26 and C27 positions.  Are 
>there any other modifications or can anyone advise what I need to do to 
>get 100W on the higher bands?
>I did notice the braid on the back of L4 doesn't cover the wires 
>100%..... I can see the wires through openings.  Could this be the problem?
>Any advice will be appreciated.
>
>Thanks,
>Rick
>KR8T
>
>
>
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