[sdiy] EFM VCF1e thinks it's an FM receiver

[Fahl, Romeo]

Hello,

I tried posting this to the EFM list last weekend, but it didn't go
through... so here it goes again with a cross-post to synth diy:

I built the EFM VCF 1 e.  A schematic of it can be found at this URL:

http://www.spiritone.com/~8brain/schems/vcf1e.gif

It's a basic two-pole state-variable VCF.  It sounds really nice, but if I
turn up the resonance and the input signal goes below a certain level, it
starts emmitting a fairly loud hiss with local FM radio stations mixed in.
Turning the cutoff pot changes the station.  

Any idea as to why this is happening?  Has anyone else who has built this
filter experienced this side-effect? If it were a more interesting section
of the spectrum I might let it stay, but I loathe commercial radio.

Romeo