Author Topic: Do I have a dead channel  (Read 1047 times)

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Offline va3mw

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Do I have a dead channel
« on: May 24, 2015, 07:18:19 PM »
Since I have only been running for 24 hours or so, I am starting to work on interpret what I am seeing. 

My 1B channel seems way too quiet.  Being this is a new build I could have something wrong in the amplifier chain if this is not normal.  As I don't have anything to compare it to, I will assume that to be the case.

Not a big deal as I can scope it out once I get back to the site if my assumption is correct.

Mike
http://www.walkerphotography.ca/Weather

BTW, I gather there is no easy way to imbed an image in the body without actually hosting the image somewhere else.

Offline Cutty Sark Sailor

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Re: Do I have a dead channel
« Reply #1 on: May 24, 2015, 07:36:38 PM »
Yes, you are 'flatlined' channel B H field.
 

Offline corwyyn

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Re: Do I have a dead channel
« Reply #2 on: May 24, 2015, 07:48:37 PM »
Mike I had a similar problem with my station when I first got it set up, the culprit turned out to be missing solder on a pin of one of the op-amps; once I added some solder it was like I flipped a switch on that channel.  Best advice is to give everything a fresh look and see what turns up. 
Kevin
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Offline va3mw

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Re: Do I have a dead channel
« Reply #3 on: May 24, 2015, 08:40:11 PM »
Odds is it is a bad crimp on my cat 5 cable. That is the first thing I'll look at.

After that, I'll just work my way up and down. It's a good thing we have a schematic.

Thanks all

Offline miraculon

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Re: Do I have a dead channel
« Reply #4 on: May 25, 2015, 09:49:48 AM »
Nice thing about the two channels, it is much like troubleshooting a stereo amplifier. You have a good channel for comparison all the way down the signal chain. You could even substitute a generator for the antennas and run them in parallel (or set a stereo audio generator to be equal on both channels).

There are two possible problem areas. One is the signal path itself, but the other is that one (or more) PGAs could have a bad SPI connection and not receiving the gain commands.

Greg H.


Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline Cutty Sark Sailor

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Re: Do I have a dead channel
« Reply #5 on: May 25, 2015, 09:57:17 AM »
Nice thing about the two channels, it is much like troubleshooting a stereo amplifier. You have a good channel for comparison all the way down the signal chain. You could even substitute a generator for the antennas and run them in parallel (or set a stereo audio generator to be equal on both channels).

There are two possible problem areas. One is the signal path itself, but the other is that one (or more) PGAs could have a bad SPI connection and not receiving the gain commands.

Greg H.

Wait!  Did he say 'stereo amplifier'??? hmmm... that's not thinking 'RF"... hemmm... :twisted:
 

Offline dfroula

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Re: Do I have a dead channel
« Reply #6 on: May 25, 2015, 10:41:29 AM »
Reminds me of an old wireless headphone project I saw in Radio Electronics back in the mid-60s. There was a project where a long length of wire was routed around a room in  a loop and connected to the speaker terminals of an audio amp. The receiver was a simple battery-powered audio amp and earpiece connected to an old telephone recording pickup coil (the kind with a suction cup that connected to a telephone handset). One could hear the audio loudly as long as one was "in the loop" - literally!

That's an example of a purely inductive reception of an audio signal. The system in the magazine creates a very large audio transformer - no RF involved, strictly near-field induction.

The lightning signal we receive is a true EM RF signal which behaves very differently in terms of propagation, antenna behavior, etc. I didn't understand the difference between that system and an RF receiver until I studied field theory much later in my career. I remember it confusing me at the time, until I actually wrote the author of the article. He tried to explain the difference, but my 12-year old brain couldn't quite grasp it!

Don
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Offline va3mw

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Re: Do I have a dead channel
« Reply #7 on: May 25, 2015, 02:19:50 PM »
All fixed and the performance is greatly improved.   It was 'fun' set up on top of a step ladder with the scope.  It is a good thing those test point pins are very handy to get to.

It turned out to be cold solder joint on I5 pin 5. 

You can see the 2 scope shots with only 1 channel functional and the next one with both channels functional. 

It gave me a chance to play with the new Siglent scope I bought at the Dayton Hamvention for $246.  Not bad for a 50Mhz 2 channel scope.  It even does FFT, but I didn't have a chance to play with it as I will killing mosquitoes at the same time.

Mike

« Last Edit: May 25, 2015, 02:21:22 PM by va3mw »

Offline miraculon

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Re: Do I have a dead channel
« Reply #8 on: May 25, 2015, 04:47:20 PM »
Wow, nice scope. I see it on Amazon for $279.
Hmmm.....
Glad you found the problem.

Greg H.



Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline Cutty Sark Sailor

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Re: Do I have a dead channel
« Reply #9 on: May 30, 2015, 06:42:20 AM »
I've got an 1102CNL Siglent... great device... Brand New, unopened, estate sale... $20, I think it was... .  :D
Good job nailing that issue!
 

 

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