ATC: 121.5 Aviation Emergency, Snohomish County airports, Air2Air

Located at 600ft elevation near the King/Snohomish, WA county border, this feed is dedicated to high-responsiveness monitoring of the 121.5 Emergency Guard frequency comms in a range over 160 nmi and local North Sound general aviation, Snohomish's Harvey Field and Air2Air comms and KPAE Clearance Delivery (CLNC).

Note: High-altitude traffic is mostly covered on my Stratosphere feed to preserve local channel purity. That feed pairs well with my larger KSEA/Seattle commercial aircraft feed. 

Active Frequencies Covered:

• 121.500 – EMERGENCY GUARD (VHF Distress)

• 123.000 – Harvey CTAF (Snohomish County)

• 122.750 – Air-to-Air Operations

Prioritization Hierarchy:

• Tier 1 (Priority 10): 121.5 GUARD. Primary emergency monitoring.

• Tier 3 (Priority 2): Harvey CTAF - Local recreational and training traffic.

• Tier 4 (Priority 1): Air-to-Air. Secondary pilot communications.

Technical Specs: Powered by an Airspy Mini SDR and Raspberry Pi 5 with a DPD Productions Airband antenna at 50ft AGL.