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> Micron-pti 10.7MHZ 35KHZ wide xtal if filters (qty.2)
Micron-pti 10.7MHZ 35KHZ wide xtal if filters (qty.2)
Micron-PTI 10.7MHz 35kHz wideband XTAL IF filters (Qty.2)
Useful for SDR and Meteosat projects
On offer are several lots, each with two 10.7MHz wideband crystal filters by Micron-PTI.
Internally these filters have 4 x 2 pole MCF (Monolithic Crystal Filter) HC49 cans, two matched pairs, in sequence to produce an 8 pole filter with an unusually wide (for a crystal) bandwith of 35kHz centred on 10.7MHz and about 3k ohm (?) impedance. My hastily constructed test jig didn't allow me to test the out of band attenuation (it gave only 50dB isolation and the filter was better than that) but I'd expect 70..90dB based on similar parts I've seen.
Manufactured by PTI - Piezo Technology Inc, who have since merged with Mtron to form MTron PTI.
Outline dimensions are approximately
These filters should work well as roofing filters for a Multi-mode receiver or spectrum analyser. Their bandwidth allows many signal modes, from CW up to wide FM, whilst their out of band attenuation means downstream amplifiers and detectors (which provide the appropriate selectivity) can be designed for high performance.
Particularly, for Software Defined Radio (SDR), most CODECs (like PC soundcards) allow much wider bandwidth than the 7.5khz you'd commonly get from an IF filter; with these you can make a much wider bandwidth available for analysis (listening). Unlike with narrow filters, these give you the capability of receiving wider bandwidth signals, such as from Meteosat, with steeper skirts than simple LC networks.
They should work well in a Weather Satellite receiver, either scratchbuilt or by modifying the IF of an existing receiver (such as one of the scanners commonly available on the surplus market). To quote http:// /luxorion/qsl-satellites-reception2.htm
"APT signals are transmitted on 137 MHz. This band is easily accessible on low cost receivers at the condition to use an IF FM Filter offering a 30 to 50 kHz bandwidth. Indeed, many all-band receivers and scanners come with either a too narrow (15 kHz) or too wide FM filter (230 kHz). "
Crystal filters are rarely cheap, and the price tends to rise with the number of elements. Of the two main European RF suppliers I often quote, one lists 8 pole units like these at 21 and another at 44.92 each.
