New High Isolation Relay Board Schematic (PDF) 22-DEC-2008
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12V activated relays with 50Ohm termination for unused antennas to reduce reradiation and unwanted internal coupling.
Impossible for one radio to transmit directly into another.
NEW: I measured worst case port to port isolation to be 61.2dB! This is a whopping 24dB improvement over the previous version, while keeping the same features and size with a lower parts count!
Jeff, AC0C, has done a thorough analysis of the switch and posted the results on his web site. Read the charts carefully. The "both antennas selected" cases are the typical use. There are several other interesting configurations as well. GREAT STUFF! |
New High Isolation Relay PC Board Layout (PDF) 22-DEC-2008
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High quality FR4 double sided 2oz copper, masked, and silk screened both sides.
Dimensions: 10.1875" x 6.5".
Available for purchase. Email for availability.
Construction instructions
Performance Analysis
Bandpass Filter Switching Ideas
Chassis Dimensional Drawing
!!Please use caution with the templates. Verifiy that the resulting printed file matches the board!!
Chassis Drill Template - mirrored
Chassis Drill Template - standard
Mouser Project File:
Please note: All electronic parts are included in the project files. Any unneeded part can easily be removed from the Mouser order. There are "optional" parts included in the list and most are noted in the comments for the part.
Relay Board Parts
Relays are sometimes in scarce supply. This link will show all compatible relays from Mouser. You can choose whichever has the best price/availability/delivery!
Compatible Relays from Mouser
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