{"type_number":"UX199","canonical_url":"https://tubeofile.com/tubes/UX199","manufacturer":"RCA","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"UX4","description":"Directly heated triode with thoriated tungsten filament designed for dry battery-operated receivers. General-purpose detector and audio-frequency amplifier with very low filament current (60 mA at 3.3V). One of the earliest mass-produced radio tubes, introduced by GE for RCA in 1922 as UV199, redesignated UX199 in 1925 with the change to UX4 base pins.","is_directly_heated":true,"completeness":"medium","notes":["Originally issued as UV199 (UV prefix = bayonet base variant), redesignated UX199 in August 1925 when the UX4 pin base became standard. UV199 and UX199 are electrically identical but have different pin lengths.","Cunningham marketed the same tube as CX-299 (bayonet) and later C-299 (UX pins).","Thoriated tungsten filament — requires careful filament voltage regulation. Rated for 3.3V DC from dry cells; do not exceed rated voltage or filament life will be drastically shortened.","Designed for portability: the extremely low filament drain (60 mA) enabled receivers to run from small dry cells, making portable radios practical for the first time.","Production by RCA continued until 1931; after 1927 few new receivers were designed around this tube as newer types offered better performance.","Historical significance: one of the first tubes to enable truly portable battery-powered radio receivers, helping bring radio to rural areas without electricity."],"references":["https://www.radiomuseum.org/tubes/tube_ux199.html","https://vinylsavor.blogspot.com/2019/04/tube-of-month-ux199.html","http://www.r-type.org/exhib/abz0025.htm"],"source_urls":{"r_type":"http://www.r-type.org/exhib/abz0025.htm","tdsl":null,"radiomuseum":"https://www.radiomuseum.org/tubes/tube_ux199.html"},"raw_equivalents":["UV199","CX299","99","X99","X199","UX99","SX199"],"equivalents":[],"similar":[{"type_number":"01A","reason":"Similar-era DHT triode on UX4 base but with 5V/0.25A filament — not a drop-in due to different filament requirements","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Filament (f+)","function_code":"h","notes":null},{"pin_number":"2","function":"Plate","function_code":"a","notes":null},{"pin_number":"3","function":"Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Filament (f-)","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"3.3","numeric_value":"3.3","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.06","numeric_value":"0.06","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"90","numeric_value":"90","unit":"V","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"90","numeric_value":"90","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-4.5","numeric_value":"-4.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"1.7","numeric_value":"1.7","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"15500","numeric_value":"15500","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"0.425","numeric_value":"0.425","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"6.6","numeric_value":"6.6","unit":"—","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:53:01.317Z"}