Inexperienced instrument rated private pilot descended early on an ILS approach when he flew the glideslope out procedure in lieu of the ILS because he felt the glideslope display was malfunctioning.

Narrative

Weather forecast was clear below at least 9000 FT along entire route. Approximately 40 miles west of HYA noticed developing low cloud layer; checked ATIS at HYA and heard 1600 BKN; 2000 OVC. Asked for and received a pop-up IFR clearance for the ILS Runway 24 into HYA; received vectors to the ILS. After establishing on the localizer; did not receive glideslope and decided to convert the approach into a localizer approach in-place. Bad decision; got confused and descended too early. Tower called low altitude alert and I stopped descent. By this time I was below the cloud deck; which was at 1000 FT; not 1600 as on the ATIS; and completed approach visually. Possibly I misinterpreted the instruments and confused being below the glideslope (normal for the localizer intercept) with not receiving it at all. Observations: 'Real' IFR is not the same as under the hood. I need to spend more time doing real IFR. Or at least do a lot more practice approaches; and ones where things don't go exactly as planned. Possibly; as a casual pilot (less than 100 hours per year) I should do an instrument proficiency check every six months whether I need to or not.