Dave,
The CorCom is not doing you any good. It has no effect in the range of a
few hundred Hz to 2500 Hz, which is roughly the range of the alternator
whine. The required series L needs to insert at least 100 ohms or more of
inductive reactance at a frequency as low as 200 Hz, followed by a big
value electrolytic cap. The problem is that with a radio that draws
around 0 to 15 amps, or more, the inductor gets large and also builds up a
big back-emf when you release the PTT on the mic. You then need a big
power diode connected in reverse across the inductor itself so that you
don't blow out the rig with that back-emf.
73, Dale
"David Jordan" <wa3gin@comcast.net>
Sent by: rfi-bounces@contesting.com
10/29/2008 11:02 AM
To
"'Hardy Landskov'" <n7rt@cox.net>, <rfi@contesting.com>
cc
Subject
Re: [RFI] Kenwood TM-D700
Thanks,
I have as does my friend the radio 12dc cable going directly to the
battery.
I also have a Corcom EMI/RFI filter in line with the 12dc to the radio.
Seems odd that with both deterrents the interference persists.
73,
Dave
Wa3gin
-----Original Message-----
From: Hardy Landskov [mailto:n7rt@cox.net]
Sent: Wednesday, October 29, 2008 11:49 AM
To: David Jordan; rfi@contesting.com
Subject: Re: [RFI] Kenwood TM-D700
Not odd at all. The alternator is varying the 12 VDC and frequency
modulating the transmitter. Look at the 12VDC line with a scope and you
will
see what's happening. I believe a big common mode choke is in order or try
running the TM-D700 power cables directly to the battery as the car
battery
looks like a 1 Farad capacitor. Sounds like the TM-D700 is not decoupled
from the 12 volts very well.
GL N7RT
----- Original Message -----
From: "David Jordan" <wa3gin@comcast.net>
To: <rfi@contesting.com>
Sent: Wednesday, October 29, 2008 8:00 AM
Subject: [RFI] Kenwood TM-D700
> Hi folks,
>
>
>
> This one is a bit odd. My buddy has a Ford F-150 and installed in the
> truck
> is his TM-D700 dual band VHD/UHF radio. We chat during our drive into
work
> in the mornings.
>
> Almost without fail when he is transmitting at least once during the 30
> min.
> drive I will hear what sounds like a siren on his audio Whrrrrrrrrrrr
> starting at a high pitch and slowly going down in audio tone freq. He
has
> grounded the radio, etc., yet the weird noise continues to occur. Last
> week
> I installed a TM-D700 in my Ford Sport Trac and guess what - now he says
I
> have the same odd occurrence of the erratic whine syndrome.
>
>
>
> My radio is also grounded extensively as I run 1KW on 75 and 40m.
>
>
>
> Thoughts and recommendations welcome.
>
>
>
> 73,
>
> Dave
>
> Wa3gin
>
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> RFI@contesting.com
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