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Author Topic: Ham Radio Broadcasts on Computer Speakers  (Read 1121 times)
KC2PHJ
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Posts: 21




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« on: August 05, 2007, 04:36:50 PM »

Every time I broadcast on my radio (20m, 10m, 6m), I can hear it on several speakers of the various computers in the house.  Would a low pass filter take care of this? I'm a new ham.

Thanks,

KC2PHJ
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KE3WD
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Posts: 5694




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« Reply #1 on: August 05, 2007, 06:01:25 PM »

Lopass filter would likely not help here.  

Because it is not the fault of the radio, it is the fault of the cheap computer speakers.  

Read the FCC part 15 notice on that stuff, the part where it says the junk "must accept any interference" just after where it says that it musn't make any interference even though it likely does.  

But take heart, there is an easy enough solution that usually works:

Ferrite suppression beads on each speaker wire in question, the open kind of bead where you can wrap several turns of the speaker wire through, or even a toroid donut made of ferrite designed for the purpose.  

Cheaper method that *may* work:  twist the speaker wires to make twisted pair out of them.  This may make them self cancelling to any RF interference.  

How to make twisted pair out of cheap speaker wire fast?  

Chuck the connector into the end of a speed controlled electric drill and slowly spin until you have a nice even twist the length of the wire.  If you can't chuck the connector, fashion a paper clip around the connector and chuck the clip.  

Twisted wires doesn't always work, but is certainly worth the shot.  This may work on some of the speakers around your house and not on others.  Put ferrite on those.  


.
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W3LK
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Posts: 5644




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« Reply #2 on: August 06, 2007, 07:30:54 PM »

Hams do not "broadcast", they communicate. Radio and TV stations broadcast. Smiley

That said, what are you using for an antenna. Most RFI in the house problems are cause by poor antenna installations (end fed wires with no counterpoise, for example), antennas inside the house and outside antennas too close to the house.

The fact that most computer speakers are really trash, and very succeptable to interference, just compounds the problem.

All the filters and ferrite cores on the wires won't do a whole lot if the primary problem is RF in the house from a poor antenna installation.

73,

Lon - W3LK
Naugatuck, Connecticut
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KE3WD
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Posts: 5694




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« Reply #3 on: August 06, 2007, 08:13:56 PM »

Listen to Lon, what him say ring truth.  
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KC2PHJ
Member

Posts: 21




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« Reply #4 on: August 07, 2007, 04:18:39 PM »

1/2 G5RV between two trees. I live in a small lot. That is the only I can install it.
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KE3WD
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Posts: 5694




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« Reply #5 on: August 07, 2007, 08:37:14 PM »

>>1/2 G5RV between two trees<<

Did you construct the neat coil of coax at the connection point to the balanced line to yield a 1:1 balun there to stop RF from radiating back down the coax shield?  

If not, do so.  It may greatly reduce your RFI/TVI at the QTH.  

The air wound balun required for this antenna can be constructed by winding the coaxial feed line cable in a single layer solenoid coil with at least 10 turns of 4 to 6 inch diameter. The turns can be taped or secured by nylon cable ties.

The balun can also be wound on PVC pipe or any other non-metallic form. But is not mandatory to do so, the free hanging air coil, if made in neat concentric turns using wireties or tape, will do the job.  

Place the balun immediately at the feed point connection. The feed line shield should not
be grounded on the antenna side of the balun.

Also, disregard the many posts and such that you will find on the internet regarding "do not use balun with this antenna!" if you want to reduce your RFI problems.  There ain't nothin' worse than RF in the shack.  Many of those 'do nots' are likely the result of trying to use other than air coil balun methods in my opinion.  


.

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VK6AV
Member

Posts: 32




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« Reply #6 on: August 22, 2007, 09:28:58 AM »

After you have run each speaker wire through a ferrite, wrap the AC line around a ferrite rod. Solved my problem (neighbour across the street).
Harris VK6AV
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