On Sat, May 26, 2012 at 9:53 AM, Brian Lloyd <brian-wb6...@lloyd.com> wrote:
> On Sat, May 26, 2012 at 9:02 AM, Gerald Youngblood <ger...@flexradio.com > >wrote: > > <snip> > So the solution is to do one of two things: > > 1. Keep adding all kinds of switching to the radio itself, e.g. more > processing loops; > 2. move all the switching to an external box or patch panel. > > <snip> > > So, here is hoping for a sensible external crossbar switch that will allow > any combination of switching under software control (Ethernet/IP > connection, please), with high (70+ dB) isolation. That is going to be much > more flexible than any sort of switching one is going to put on the box > itself. > > -- > Brian Lloyd, WB6RQN/J79BPL > 3191 Western Dr. > Cameron Park, CA 95682 > br...@lloyd.com > +1.767.617.1365 (Dominica) > +1.916.877.5067 (USA) > _______________________________________________ > Many of the high-end RF switch companies sell some very nice blocking RF switch matrices that meet these requirements. They'll set you back quite a few $$$$$, though ;-) For a less pricey alternative, take a look here: http://www.microwavejournal.com/articles/1615-matrix-switches-blocking-versus-non-blocking then acquire the appropriate surplus multi-port mechanical coaxial switches off of eBay, etc., and homebrew the beast. Let's say you wanted a 4x8 matrix. You would need: 4 8-port switches (RX-side) ...can't find any 8-port? Use 2x 4-ports and a Transfer switch configured as a self-terminating SPDT (corner common and a termination on the opposite corner) 8 4-port switches (Antenna-side) 32 short low-loss coaxial cables w/ connectors to match the switches (you might want to have these made new - or DIY) 1 control mechanism of your choice N appropriate DC power supplies (go linear here to keep the RF noise down) Ta-Daaa ... you have a matrix that can connect any one of the 4 RX-side ports to any one of the 8 antenna-side ports simultaneously, with the sole exception being that a single Antenna-side port can only feed one RX-side port at a time, and vice-versa. Insertion loss at HF/VHF will be very low in the switches, with the dominating factor being the interconnecting cables. Isolation will be 80 dB or better (I've measured in excess of 100 dB at HF/VHF). If you want more ports on either side, just follow the general example above accordingly. If you plan on running TX power through the matrix, then look up the power handling capability for the particular switch model numbers you have. I've been able to find data online for switches just by doing Google searches with the exact part number - even when they haven't been made for several years. I've used this sort of matrix in complex engineering characterization test systems for years and they can be quite versatile for routing signals in both directions to where you need them. Oh... and if you decide to try this with solid-state switches, the insertion losses will be greater and the power handling capability will generally be much lower. 73 Dan KB5MY/6 DM13nc _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
