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Re: [RFI] Kenwood TM-D700

To: rfi@contesting.com
Subject: Re: [RFI] Kenwood TM-D700
From: W2RU - Bud Hippisley <W2RU@frontiernet.net>
Date: Wed, 29 Oct 2008 21:21:20 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
It's clear from the original description of the TM-D700 problem that  
it's *not* alternator whine.

However, with respect to alternator whine:

I agree with the earlier comment that most of the easily available  
filters and chokes (such as from Radio Shack) are not going to do the  
job -- especially with the high current drains when a 50-watt rig is  
transmitting.  What I've found really simple to implement for my  
various (Kenwood) 2-meter mobile rigs over the years has been to use  
the inductance of the filament winding of an ordinary 10- or 20-amp  
6.3-volt filament transformer in series with the positive lead from  
the engine compartment.  I then shunt the rig side of the filament  
transformer winding with an old-fashioned 100uf 50VDC paper  
electrolytic to the negative lead.  Of course, the leads for the  
primary winding of the transformer go nowhere -- they just get taped  
up.  The whole assembly has fit very neatly up under the heat ducts of  
my dashboard in every car I've installed a 2-meter rig in.  And it's  
all been from junque-box parts -- I didn't spend a penny!

Bud, W2RU
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