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Autek Research QF-1 analog active audio filter designed for amateur radio CW/SSB reception

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MPN:
QF-1
Condition:
Used
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  • Autek Research QF-1 analog active audio filter designed for amateur radio CW/SSB reception
  • Autek Research QF-1 analog active audio filter designed for amateur radio CW/SSB reception
  • Autek Research QF-1 analog active audio filter designed for amateur radio CW/SSB reception
$24.99
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Description

Autek Research QF-1 analog active audio filter designed for amateur radio CW/SSB reception

 This filter works great for older Analog Transceivers and receivers. 

 They work great, are easy to use, and last forever. This one was tested on the air and it works great!

 I have a manual I will include for a QF-1A which is very much the same as the QF-1.

The Autek Research QF-1 is a vintage (circa mid-to-late 1970s) analog active audio filter designed for amateur radio CW/SSB reception. It was one of the first commercial IC-based audio filters from Autek Research (the originator of such devices for shortwave comms starting in 1972). The unit is a compact 4-pole active filter in a small metal table-top enclosure (approx. 4.5" W × 3.5" H × 5.5" D, ~0.9 lbs). It plugs into a receiver’s headphone or speaker output (high input impedance, any speaker impedance OK) and provides filtered audio out to headphones or a speaker. Power is 115 VAC (two-wire cord; modern users often upgrade to 3-wire for safety/hum reduction). It does not bypass when switched off (audio output is muted).
 
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Key Features & Operation (QF-1)
  • Controls: Separate Frequency (tunes the filter center ~250–2500 Hz range) and Selectivity (adjusts bandwidth/Q) knobs, plus a multi-position Function switch for Peak (bandpass/narrow CW peak), Notch (rejects narrow interference like heterodynes or whistles), Low-Pass (cuts high-frequency hiss/splatter), and Off.
  • Performance: Excellent for pulling weak CW out of the noise/mud and cleaning up SSB. Users report it still competes with some modern DSP filters for analog “natural” sound with no latency or artifacts. It’s particularly valued by vintage rig owners and low-band CW DXers.
  • Notes: Simple “bare-bones” design compared to later models. No auxiliary notch or high-pass mode. Early units can develop hum (fixable with grounding/capacitor upgrades) or need contact cleaner on the pots/switches after decades of storage. Extremely reliable when working; parts are mostly standard except for the dual pots.
It was originally sold new for ~$75–80 and was popular in the 1970s–early 1980s
 
 

 

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Autek Research QF1A Manual Copy

$5.00
This Manual was Re-produced using a State of the Art, Sharp Laser Printer with the High Resolution Scanning option. Each Manual is digitally scanned and all pictures and images are reproduced in the...