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Re: [RFI] Kenwood TM-D700

To: "David Jordan" <wa3gin@comcast.net>
Subject: Re: [RFI] Kenwood TM-D700
From: dgsvetan@rockwellcollins.com
Date: Wed, 29 Oct 2008 11:39:20 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
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
>
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi 


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