Doug, The Sinclair AF-2140 is a VHF harmonic filter that is intended to follow a ferrite isolator. According to my Sinclair catalog, it comes in two versions: 132-150 MHz, and 150-174 MHz. It has a 0.1 dB insertion loss and can attenuate the second harmonic a minimum of 40 dB. It can be tuned easily with a TG-equipped spectrum analyzer; just tune for maximum notch at the second harmonic.
73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Doug Sent: Sunday, March 22, 2009 12:54 PM To: [email protected] Subject: [Repeater-Builder] RE: AF2140 filter I have come across this filter in my junk box and am unable to find much information on it. I think it is a Sinclair unit, but does not appear to be listed in the Sinclair Catalog. I am sure it is a vhf unit but am not sure of the tuning procedures. It follows an Isolator. Is it a LP filter or a 2nd harmonic filter?? It only has one tuning control which is offset from the centre of the small block and appears to be a capacitor similar to those used in Sinclair's notch cavities. Lots of listings on ebay for them, but no tuning instructions or descriptions otherwise. Since I have it, I thought I might as well use it... How do I tune it?? Thanks Doug
