This is an original AMSAT Mode J Desense Filter, it was handcrafted by Joe D’Arcy, W7TYN, to the specifications described on the web page http://www.amsat.org/amsat/articles/w6shp/jfilter.html
This type of filter can be used in a Mode J satellite station (uplink on 2m, downlink on 70cm) to reduce the problem of the uplink signal desensing the receiver. The filter has low insertion loss (typically less than 0.5 dB) in the 70cm band and good rejection (typically over 50dB) in the 2m band. Ideally, the filter should be inserted between the 70cm antenna and the 70cm preamp. It is not recommended to be transmitted through.
Crafted from 3” copper pipe, Joe added silver and teflon trim coax fittings to the input and output connections, this piece of AMSAT history could either be a functional addition to your station or a wonderful conversation piece up on the shack shelf!
Cost $20.00 plus USPS flat rate shipping of $13.50.
Can send a photo upon request.
73, Nick, KB1RVT