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Author Topic: Casette car speaker interface  (Read 471 times)
WA2TAK
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Posts: 19




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« on: December 21, 2004, 01:54:40 PM »

Hi all:

Just finished my very first day as a mobile ham.

Very happy with my 706M2G + 20 M hamstick.

However, when I transmit SSB, my 706 shuts down completely when I use the casette interface from the 706 headphone output to employ the car speakers.

Any help is greatly appreciated,
Steve
WA2TAK
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WB2WIK
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Posts: 20672




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« Reply #1 on: December 21, 2004, 03:02:15 PM »

Sounds like the cassette interface or its cabling is picking up RF radiated by your antenna, pumping that back into the headphones jack, and causing your rig to shut down.  

Not such an unusual problem with the 706 family.

You might try wrapping the audio line between the headphone jack of the 706 and the cassette adapter about half a dozen wraps through a ferrite toroid to act as an RF choke, and see if that fixes it.

WB2WIK/6
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K0BG
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« Reply #2 on: December 22, 2004, 06:59:01 AM »

Steve's on the right track, but I doubt it will help. RFI can and does cause the 706 to shut down, especially when using the extension cable. Later model 706's have split beads factory installed on the extension cable. The fact you're adding a little length might just be enough to act like an antenna.

Alan, KØBG
www.k0bg.com
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WA2TAK
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Posts: 19




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« Reply #3 on: December 22, 2004, 08:16:54 AM »

Thanks for the replies.

I am using the extension cable and the rig works fine until I plug in the cassette adapter.

Will try the ferrites and get back with results.

Just read that the screw on the body-side of the extension cable connector should be used...I did not know this.

I should also mention I did not install a separate ground lead anywhere.

((I'm one of those guys not using an RF ground in the shack, too.))

Thank you for understanding my 'perspective'.

And, truly appreciate your generous help.

Steve
WA2TAK

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K0BG
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« Reply #4 on: December 22, 2004, 08:30:27 AM »

If you bead the control cable, use mix 31 (DX Engineering carries them) and make at lease two passes through the cable on both ends.

You should be connecting the ground at the battery. Through the body grounding can cause a ground loop, and they're nearly impossible to find. Further, the voltage drop could be enough to cause the problem as well.

One more comment. The head of the 706 is isolated from ground. If by chance the shell of the adaptor is grounded, and it touches the grounded shell of the pickup in the cassette player, it could exacerbate the problem.

Alan, KØBG
www.k0bg.com
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WA2TAK
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Posts: 19




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« Reply #5 on: December 22, 2004, 12:33:29 PM »

Hi Alan:

Privilege having your attention, thanks.

I should have been clearer.

My only ground is at the battery location.

You suggest the 31 mix...I was thinking the 43 mix since it's touted as a general use formula.

Any particular reason you like the 31?

Regards,
Steve
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AB2MH
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« Reply #6 on: December 29, 2004, 07:31:51 PM »

Might I suggest (if your car is so equipped) that if you want to employ your car's speakers, that you use a CD changer interface adapter instead of the cassette adapter.  This does require that your car has a compatible CD changer input.

The magnetic pickup on the cassette player is sure to cause a problem.
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