You probably found this page as a result of a Google search for the Toyocom TQF-456C crystal filter. I seem to collect filters like this…in case they are useful in the future 😉
It seems that an eBay seller known as ‘hifissb’, who breaks down radios and sells their modules, has a large stock of these filters…but no info whatsoever on what they were used in or their termination data. I did try e-mailing him…but got no reply. The TQF-456C sells for just under £10 plus postage, and is advertised as a filter for an ‘upconverter’ receiver; which seems quite reasonable.
The form factor of these filters is identical to that used in many receivers in the past decade or three…most FM filters used by Pye were like this. They are 37mm long by 17mm wide by 14mm high, with the apparently standard pinout.
There is no data (well, almost none) on the internet, so you pretty much hope you can work out the connections and termination requirements. Does anyone have an old TOYOCOM data book with the TQF-456C in it? If so, please let me know and I’ll share the information.
What I do know is that they are 68.545 MHz filters (hifissb tells us that much) and they have a 15 KHz bandwidth and six poles. I’m fairly certain they are of monolithic design too, probably produced in the last 10 or 15 years.
The connecting pins show two insulated ones adjacent to the grounding pin. Commonly, this form factor filter has only one insulated pin, with the other two grounded. This applies to each end of course. There may be a matching transformer at each end.
My filter test rig only covers up to 30 MHz so I will have to set up a manual check using the tracking generator in my spectrum analyser. Once I’ve done this, I’ll share the results here…unless someone else lets me know before I run the tests.