B737-700
Flight Crew Last 90 Days 177
Aircraft Equipment Problem Less Severe
General Declared Emergency; General Maintenance Action
Aircraft
We were descending via the HHOOD 2 RNAV Arrival into PDX. ATC asked us to try and call an aircraft on 121.50 that was having an emergency. I tried to contact them but got no response.  Captain called Center to tell them we were unable to contact [the aircraft] but had a hard time contacting [Center]. After some more effort; he was able to contact [Center] and [Center] switched us to Approach; I believe. We were never able to contact ATC again on that frequency or any other that we tried. We both tried on both radios with no success. We checked our intercom switches and handheld microphones for stuck mic also. We were coming up on the end of the arrival at SHAFR. I told him we need to execute the lost communication procedure on the arrival; which stated for a west operation for Runway 28 to proceed from SHAFR to NACIY and execute the ILS to 28R. The Captain squawked 7600 and we did exactly that and landed on 28R. We tried Tower; Ground; Approach; etc. all the way in on both radios with no success. After landing and clearing the runway; we taxied to the gate but were never able to contact anyone on either radio.  I don't know what Maintenance was able to find wrong; but I have read some things about the aftermarket yolk switches failing or having communication problems. I'm not sure if it was a failure of a switch or radio etc.; but if it is something that is happening frequently it needs to be looked at.
B737-700 First Officer reports lost communication with ATC during the HHOOD 2 RNAV arrival to PDX. The HHOOD 2 lost communication procedure is complied with and the crew lands at PDX and taxis to the gate without communication.