I have had in the past RFI when
Emergency vehicles are in the neighborhood
transmitting possibly in the 450Mhz or 800Mhz
arenas. These transmitters are quite strong.
They have possibly 25 watts fed into the transmitters.
With 7Db or so of antenna gain, possibly an
effective power of 25 watts is being transmitted too
vertically polarized within the horizontal
360 degree omni directional plane.

It will typically show up on my amplifier as a
one way excursion of the signal plus or minus.
Possibly depending upon the frequency transmitted.

The only other thing is possibly the jamming of the GPS
which results in a loss of lock and i simply will
reset the GPS when such a thing happens.

There are also people occasionally using very powerful linear amplifiers 
on their CB radio and you can tell this because
their signal will reverberate against the ionosphere making
an echo sound in the receiver.

I recommend a 100% metallic shield around all your electronics.
Except possibly the computer doing the recording.

Regards,
geoff

On 9/12/2011 10:01 PM, Robert Thomasson wrote:
> I have had some trouble keeping my WinSDR up and running.  It frequently
> shows just a blank screen, with all helicord traces gone.  Just as if I'd
> just opened the software without a seismometer connected to the computer.
> The computer is an older Dell with a 2 GHz processor and 512 Mb RAM, running
> WinXP with I think service pack 3.
>
> What is interesting about this phenomenon is that there is a wireless router
> in the house (the seismo server has no wireless capability and is not
> connected to the network) and WinSDR will work fine until someone sits down
> at another computer and the wireless network starts exchanging traffic.
> Then the WinSDR screen loses the displayed data and goes blank.
>
> Is it possible that somehow the USB cable from the seismometer to the seismo
> server computer  is acting as an antenna and picking up enough interference
> from the 2++GHz wireless LAN system to crash WinSDR?  WinSDR does not
> actually crash, it just loses the data traces, which disappear.  My next
> step is to dig out some old books and see if I can figure out what length
> the seismo cable would have to be to resonate at the wireless LAN
> frequency.   But I think it would have to be very short?
>
> This is another unexpected educational aspect of this hobby!   Just
> wondering if anyone else has experienced this issue?
>
> Thanks,
>
> Bob
>

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