Editing Tuned radio frequency receiver (section)

== Advantages and disadvantages ==
Terman characterizes the TRF's disadvantages as "poor selectivity and low sensitivity in proportion to the number of tubes employed. They are accordingly practically obsolete."<ref>{{harvnb|Terman|1943|p=658}}</ref>  Selectivity requires narrow bandwidth, but the bandwidth of a filter with a given [[Q factor]] increases with frequency. So to achieve a narrow bandwidth at a high radio frequency required high-Q filters or many filter sections.  Achieving constant sensitivity and bandwidth across an entire broadcast band was rarely achieved. In contrast, a superheterodyne receiver translates the incoming high radio frequency to a lower intermediate frequency which does not change.  The problem of achieving constant sensitivity and bandwidth over a range of frequencies arises only in one circuit (the first stage) and is therefore considerably simplified.

The major problem with the TRF receiver, particularly as a consumer product, was its complicated tuning.  All the tuned circuits need to track to keep the narrow bandwidth tuning.  Keeping multiple tuned circuits aligned while tuning over a wide frequency range is difficult.  In the early TRF sets the operator had to perform that task, as described above.  A superheterodyne receiver only needs to track the RF and LO stages; the onerous selectivity requirements are confined to the IF amplifier which is fixed-tuned.

During the 1920s, an advantage of the TRF receiver over the [[regenerative receiver]] was that, when properly adjusted, it did not radiate [[electromagnetic interference|interference]].<ref name="Glasgow">{{cite journal
  | last = Glasgow
  | first = R. S.
  | title = Radiating Receivers
  | journal = Radio in the Home
  | volume = 3
  | issue = 1
  | pages = 16, 28
  | publisher = Henry M. Neely Publishing Co.
  | location = Philadelphia, PA
  | date = June 1924
  | url = http://www.americanradiohistory.com/Archive-Radio-in-the-Home/20s/RitH-1924-Jun.pdf <!-- page 28 is missing -->
  |quote=But the interference due to regenerative receivers when in the oscillating condition cannot be eliminated by anything the receiving operator can do. ... All types of regenerative sets will cause the connected aerial to radiate energy if allowed to oscillate.
  | issn = 
  | doi = 
  | id = 
  | accessdate = March 14, 2014}}</ref><ref name="Ringel">{{cite journal
  | last = Ringel
  | first = Abraham
  | title = The Receiver Radiation Problem and Some Solutions
  | journal = The Radio Age
  | volume = 10
  | issue = 2
  | pages = 67–69
  |date=November 1922 
  | url = https://books.google.com/books?id=vd7mAAAAMAAJ&pg=RA1-PA67
  | issn = 
  | doi = 
  | id = 
  | accessdate = August 22, 2014}}</ref>   The popular regenerative receiver, in particular, used a tube with [[positive feedback]] operated very close to its oscillation point, so it often acted as a transmitter, emitting a signal at a frequency near the frequency of the station it was tuned to.<ref name="Glasgow" /><ref name="Ringel" />  This produced audible [[heterodyne]]s, shrieks and howls, in other nearby receivers tuned to the same frequency, bringing criticism from neighbors.<ref name="Glasgow" /><ref name="Ringel" />   In an urban setting, when several regenerative sets in the same block or apartment house were tuned to a popular station, it could be virtually impossible to hear.<ref name="Glasgow" /><ref name="Ringel" />  Britain,<ref name="MotorPatrol">{{cite journal
  | last = 
  | first =  
  | title = How the Motor Patrol Wars with Bloopers
  | journal = Radio News
  | volume = 9
  | issue = 1
  | pages = 37
  | publisher = Experimenter Publishing Co. 
  | location = New York
  |date=July 1927 
  | url = http://www.americanradiohistory.com/Archive-Radio-News/20s/Radio-News-1927-07-R.pdf
  | issn = 
  | doi = 
  | id = 
  | accessdate = August 23, 2014}}</ref> and eventually the US, passed regulations that prohibited receivers from radiating spurious signals, which favored the TRF.