Higher noise floor with external speaker connected?

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  • Updated 2 months ago
What would cause a higher noise floor on the waterfall when a speaker is connected to PWR SPKR? When I am using PC Audio I have a dramatic improvement. When I switch my speaker from my PC to the radio, the waterfall turns bright green and eventually adjusts to blue again, but signals are not as strong. I have tried using other cables, and I have tried putting snap-on ferrites on the audio cable.
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Posted 2 months ago

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Photo of Al K0VM

Al K0VM, Elmer

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1) Does the same thing happen if there is no antenna connected ?
2) Does a different powered external speaker produce the same results?
3) What radio are you using ? What version of software ?
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Stan - VA7NF

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Please remember the rf signal processed can be either:
Antenna signal vs ground or
Chassis signal vs quiet antenna lead, or a combination.

Your speaker probably has a high noise figure and your chassis connection is missing or long. 
Photo of David-N5PSM


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Where can I find what you are saying in greater detail please?
73 de N5PSM
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Stan - VA7NF

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I do not have a citation but have experimented.

All receive input circuits are the difference voltage between the antenna lead and the chassis and one good reason to pull the chassis down to ground.  This does not include the safety ground unless the power supply case is connected to the radio chassis.
Photo of KD0RC


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Things to consider:
1. grounding of the rig and station accessories. does grounding or un-grounding anything help?
2. noise from switching power supplies (does your powered speaker have a switcher or linear supply?) what happens if you leave the speaker plugged in to the radio, but disconnected from power?
3. are you using a physically small antenna (like a mag loop) in close proximity of the radio and speakers?  if so, what happens if the ant is moved?
4. how long are the speaker leads?  are they stretched out or coiled up (perhaps around ferrites)? does coiling or un-coiling them help?  do ferrites help?

You want to start eliminating potential issues to home in on the actual problem.  Try changing some things to see what has an effect, good or bad.  Let us know what you find and we may, as a group, be able to see a pattern that will lead to solution.  You have already provided a huge clue - the PC vs powered speakers.

Len, KD0RC
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Tim - W4TME, Customer Experience Manager

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I suspect a ground loop