Folks,
I just spoke with Kenwood customer service. They understand the problem and
don't believe they are responsible to resolve the issue.
In particular the Ford truck's 12vdc circuits are RF and Audio freq. rich
and I have to agree with him. We have ten of these radios dispersed at each
of our county fire stations and not one of them has exhibited the same
problem, no doubt because they are on 'clean' 12vdc.
I'm off to build the audio freq. choke and will report back with results.
73,
Dave
Wa3gin
-----Original Message-----
From: dgsvetan@rockwellcollins.com [mailto:dgsvetan@rockwellcollins.com]
Sent: Wednesday, October 29, 2008 12:39 PM
To: David Jordan
Cc: rfi@contesting.com
Subject: Re: [RFI] Kenwood TM-D700
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
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|