Dudley Edmondson wrote:
> In recent months I have experience a strange thing with my HHB portad=
sic
> recorder and parabolic stereo DAT mic.
>
> When I am recording bird audio near a resident or near city limits I can
> hear a low frequency hum or buzz with music or voices in the background.
> What I am picking up is no doubt a local radio station. In fact once I
> heard the station say it call letters.....OLDIES 107 FM....... It is not
> super loud or anything it just at a sound level that gets picked up in an=
y
> recording you make BUT not loud enough to overshadow the subject source.
> But Just loud enough to be heard during moments of silence during a
> recording
>
> What the heck would make my recording set pick up radio stations?? Has
> anyone else had this problem. This sounds crazy to me and NO there are no
> voices in my head........
I had a hydrophone that would always do this when used in shallow
freshwater, anywhere, even many miles from towns or radio towers. I
tried all kinds of shielding, chokes etc to no avail and finally gave up
and bought a new hydrophone, which never does that. So, strange things
do happen.
The combo of the HHb Portadisc and the Telinga Pro V with Stereo DAT mic
has never done this to me. And I have recorded right next to radio
towers for some pretty high powered stations. I can get some 60 cycle
hum if recording under high voltage electrical lines. But, then, under
those conditions I'm usually also picking up the discharge crackle from
the wires, which is real audio.
What model Telinga are you using, Stereo Miniplug or XLR? If using the
miniplug version did you interconnect signal cold to shield ground in
your adapter? Whichever way you have try it opposite. I do not intertie
signal cold and shield currently, but have done so in the past with
little problem. Of course it's important to make sure all connectors are
working properly, maybe try some contact cleaner on them to make sure.
Damage to the cable shielding or conductors can do this sort of thing too.
Of course changing to a different mic negates the advantages of the DAT
Stereo Telinga, but have you tried other mics to see if you can
reproduce the problem? If it reproduces with other mics then the suspect
has to be a problem with the Portadisc. But the reverse probably does
not prove the Telinga defective. Most likely culpret is the connection
between the two.
As Klas has noted, the circuit board inside the handle is not shielded,
the handle is plastic. So it can pick up interference in strong enough
electrical fields. If this is just occurring in a limited area that's
probably the explanation. Though you seem to be saying it's more
widespread. Maybe you are picking up the cable TV system in the town
that was not properly installed? Those usually carry FM stations as
well. If that's the case, the FCC will be interested. Those cable
systems are not supposed to be radiating like that.
Walt
________________________________________________________________________
________________________________________________________________________
|