[aprssig] Kenwood D700/D710 RF Problems

J. Gary Bender, WS5N ws5n at wildblue.net
Wed Jul 21 18:25:19 CDT 2010

This may be the same problem in a more simple configuration.
I run a D700 as a mobile APRS (A side) and VHF (mostly) scanner (B side).  The rig is sitting under the passenger seat, not properly installed and grounded.  Power comes from inside the trunk, so it is a long line for a mobile.  If I run APRS on HIGH power, the B-side will occasionally pop over to one of the WX channels I have programmed in to the high memory channels.  I have not noticed if it is always the same channel.  Seems to happen at random but only when running high power on the A-side.  I just run medium power for APRS and the problem is avoided.
  --  73  --
  J. Gary Bender, WS5N
  Fence Lake, New Mexico USA

On Wed, 21 Jul 2010 15:42:44 -0700, Herb Gerhardt wrote:
> Since we are discussing noise issues, this might be a good time to bring up
> my problem with a D700 radio.  I am also changing the title to Kenwood
> D700/D710 RF Problems.
> I am using a Kenwood D700 up on a mountain top as an APRS digipeater.  Here
> in the Pacific Northwest we are experimenting with 9600 baud APRS on several
> bands.  Well I am supporting both the traditional APRS on 144.390 at 1200
> baud on the right side of the radio using a KPC3+ TNC (Vers 9.1) and on the
> left side of the radio I am running 9600 baud APRS on 144.350 using the
> internal TNC.  The beauty of this set up is that one Kenwood radio and only
> one antenna, can operate both digipeaters.
> Yes, we are experimenting with this set up at a number of locations around
> Western WA using both D700 and D710 radios and have not had any equipment
> problems until now.  As soon as I installed this equipment at our site on
> South Mtn and the radio transmitted on either side on high power, the Astron
> SS-25 switching power supply tripps off the line.  Turning the output power
> down to 5 watts (low), seemed to keep the power supply from tripping.  This
> dual digi worked fine for about a week and then the 9600 baud side
> disappeared off my screen.  I had to wait until I had time to make another
> trip up the mountain about a month later.  The 144.390 digi side continued
> to work fine, so that proved that the power supply had not tripped and the
> radio's right side was still operating fine with its external TNC.
> What I found when I went back up there was that the D700 internal TNC had
> completely reset itself to parade rest but the radio's memory channels were
> still as programmed.  I brought another power supply and D700 with me, so I
> replaced both the power supply with an identical one and a different D700
> radio.  Well, we experienced the same power supply tripping problem as
> before on high power and  also on medium power.  We did lots of head
> scratching and investigating and it appears that the problem is an RF
> problem of when the radio transmits on high or medium power, it trips the
> Astron SS-25 power supply off line.
> I had one torride  core with me and installed it on the head cable with one
> additional wrap through the core.  That helped.  We then moved the D700
> control head around in our enclosure to get it as far away from the power
> supply as possible but that is still less than 6 inches and wrapped the head
> with some aluminum foil that my sandwich was wrapped in.  We also rolled up
> the head cable and put a steel plate over the top of it.  We then set the
> power level to low power on both sides of the radio and so far, so good.
> So the question is:  has anyone ever experienced similar problems with their
> D700 or D710.  If so, how did you resolve the problem?  Keep in mind that
> the mic is not connected to the radio.
> Like I said, so far, so good but being on a mountain top is not the ideal
> place to have equipment which might randomly trip off line especially since
> this site is not accessible during the winter months.  Any help or
> suggestions are welcome.....  BTW, the 9600 baud experimentation on VHF, UHF
> and 220 works great.  In my area with VSOMTN (144.35 APRS @9600 baud) on the
> air, it works better than the traditional SOMTN (144.39 APRS @ 1200 baud),
> so that is what I am running in my trackers......
> Thanks,
> Herb, KB7UVC
> NW APRS Group, West Sound Coordinator
> Our WEB Site:  http://www.nwaprs.info

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