[Lowfer] DGPS

[Jim Davey]

Hi Garry:

Most houses now are hotbeds of digital crud that might be mistaken for
IMD.  Routers, ethernet cable, appliances with digital displays (even
those that are not in use; still energized and ready), dimmers or other
low voltage lighting, laptop power supplies, etc.  The house wiring just
radiates this stuff all over the place.  On the BCB with a portable radio
I can hear the din drop off with distance like Neil suggests below.  You
might try putting the Clifton Labs e-probe on a temporary ground stake as
far away as you can manage for comparison, or try various distances and
measure the noise floor at each distance.  You might also try less whip
antenna at the rooftop height.

Jim K8RZ
Jasper, GA






On 7/15/13 3:56 PM, "Neil" <lowfer.nklagge at gmail.com> wrote:

>Garry, I had to move my E probe about 45 or 50 feet away from the house
>and away from the shed in order to get better IMD performance. When I
>moved it toward the shed which has AC wired to it my IMD got worse. I
>decided to keep it as far away from the house and the shed as possible
>and still be on my property. Apparently all AC lines create a problem. My
>E probe is only 15 feet above ground and I get pretty good reception from
>it there.
>
>So, is your E probe 30 feet above the house or just 30 feet above the
>ground? Just curious.
>
>Sent from Neil's iPhone
>
>On Jul 15, 2013, at 13:01, Garry Hess <k3siw at sbcglobal.net> wrote:
>
>> Neil, thanks for the kind words but I don't think my receive setup is
>>anything special. The people with really good reception have room for
>>REALLY long wires (like AA7U).
>> 
>> My QTH is reasonably quiet, but certainly could be better (I have quite
>>the picket fence of 60 Hz harmonics at VLF that can't be tamed with
>>common-mode chokes). I use a Clifford Labs e-probe at about 30' on the
>>house roof because it has better IM performance than the homebrew ones
>>I've built. Recently I increased my VE7SL shielded loop size from 3' to
>>10' and that's what I was using for most of the DGPS decodes. It's
>>noticeably more sensitive than the e-probe, can be placed at ground
>>level, and has nulls, but of course it occupies a lot of space and needs
>>a rotator. For some time now my "receiver" has been an SDR-IQ, with an
>>external 66.666 MHz clock locked to GPS. Originally I used an IC706MkIIG
>>and that's fine at HF but below 1 MHz it's really deaf so a lot of
>>preamp gain is needed.
>> -- 
>> 73, Garry, K3SIW, EN52ta, Elgin, IL
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