| |
LW1DSE > TUBES 20.09.20 17:19l 189 Lines 9922 Bytes #999 (0) @ WW
BID : 1101-LW1DSE
Read: GUEST
Subj: Regenerative Receivers (2 of 4)
Path: IZ3LSV<IQ5KG<I0OJJ<EA2RCF<LU9DCE<LW3DBH<LU7DQP
Sent: 200919/1504Z @:LU7DQP.#LAN.BA.ARG.SOAM #:38686 [Lanus Oeste] FBB7.00i
From: LW1DSE@LU7DQP.#LAN.BA.ARG.SOAM
To : TUBES@WW
[¯¯¯ TST HOST 1.43c, UTC diff:5, Local time: Sat Sep 12 13:41:41 2020 ®®®]
Regenerative circuit.
ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ
For CP437 !
ÄÄÄÄÄÄÄÄÄÄÄ
Part #2 of 4
6.- History:
ÄÄÄÄÄÄÄÄÄÄÄ
The inventor of FM radio, Edwin Armstrong, invented and patented the
regenerative circuit while he was a junior in college, in 1914. He patented
the super-regenerative circuit in 1922, and the superheterodyne receiver in
1918. Lee De Forest filed a patent in 1916 that became the cause of a
contentious lawsuit with the prolific inventor Armstrong, whose patent for
the regenerative circuit had been issued in 1914. The lawsuit lasted twelve
years, winding its way through the appeals process and ending up at the
Supreme Court. Every court up to the Supreme Court had ruled in favor of
Armstrong. However, the Supreme Court ruled in favor of De Forest.
At the time the regenerative receiver was introduced, vacuum tubes were
expensive and consumed lots of power, with the added expense and encumbrance
of heavy batteries. So this design, getting most gain out of one tube, filled
the needs of the growing radio community and immediately thrived. Although
the superheterodyne receiver is the most common receiver in use today, the
regenerative radio made the most out of very few parts.
In World War II the regenerative circuit was used in some military
equipment. An example is the German field radio "Torn.E.b". Regenerative
receivers needed far fewer tubes and less power consumption for nearly
equivalent performance.
A related circuit, the super-regenerative detector, found several
highly-important military uses in World War II in Friend or Foe identification
equipment and in the top-secret proximity fuse. In the 1930s, the
superheterodyne design began to gradually supplant the regenerative receiver,
as tubes became far less expensive. In Germany the design was still used in
the millions of mass-produced German "peoples receivers" (Volksempfänger) and
"German small receivers" (DKE, Deutscher Kleinempfänger). Even after WWII,
the regenerative design was still present in early after-war German minimal
designs along the lines of the "peoples receivers" and "small receivers",
dictated by lack of materials. Frequently German military tubes like the
"RV12P2000" were employed in such designs. There were even superheterodyne
designs, which used the regenerative receiver as a combined IF and
demodulator with fixed regeneration. The superregenerative design was also
present in early FM broadcast receivers around 1950. Later it was almost
completely phased out of mass production, remaining only in hobby kits.
7.- Operating limits:
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
Quality of a receiver is defined by its sensitivity and selectivity.
For a single-tank TRF (tuned radio frequency) receiver without regenerative
feedback,
Bandwidth = frequency / Q
where Q is tank "quality" defined as
Q = Z / R
Z is reactive impedance, R is resistive loss. Signal voltage at tank is
antenna voltage multiplied by Q. Positive feedback compensates the energy
loss caused by R, so we may express it as bringing in some negative R.
Quality with feedback is:
Qreg = Z / (R - Rneg)
Regeneration rate is:
M = Qreg / Q = R / (R - Rneg)
M depends on stability of amplification and feedback coefficient, because if
R - Rneg is set less than Rneg fluctuation, it will easily overstep the
oscillation margin. This problem can be partly solved by "grid leak" or any
kind of automatic gain control, but the downside of this is surrendering
control over receiver to noises and fadings of input signal, which is
undesirable. Modern semiconductors may offer more stability than vacuum tubes
of the 1920s, depending on other circuit parameters as well. Actual numbers:
To have 3 kHz bandwidth at 12 MHz (short waves travelling all around Earth)
we need:
Q = F / f = 4000
A two-inch coil of thick silvered wire wound on a ceramic core may have
Q up to 400, but let's suppose Q = 100. We need M = 40, which is attainable
with good stable amplifier even without power stabilizing.
8.- Super-regenerative receiver:
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³
Û ³
Û ³ Figure 2.
Û ³
(AERIAL) ÛÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ(ÄÄÄÄÄÄÄÄÄ¿ Single Tube (TRIODE)
ANTENNA Û ³ ³ Super-regenerative
Û ßßß ³| Receiver Schematic.
\|/ Û CG ÚÄ----- Û|
³ Û ³ ÕÍÍ͸ Û| CHRF
³ ³³/ ³ ³³ ³ ³ Û| RG and CG returned
ÀÄ´ÃÄÄÄÄÄÁÄÄÄÂÄÄÄÄÄÂÄÄ´ÃÄÄ´ ³ Û| to +B allow the tube
/³³ ³ ³ ³³ ³ ³ Û| to oscillate at the
³ ³ ³ ³ ³| quenching frequency.
COUPLING ³ ³ ³ ³ ³³ ³
³ Àı±±±ÄÙ ÃÄÄÄ´ÃÄÄ´
³ ³ ³³ ³
³/ RG ÄÁÄ CBPR ³
ÄÁÄ /// O
ÄÂÄ ) HEADPHONES
/³ O
³ MAIN CBPB ³
³ TUNNING ³
³ ³³ ³
³ ÚÄÄ´ÃÄ´
ÄÁÄ ÄÁÄ ³³ ³
/// /// ³
+B o
The super-regenerative receiver uses a second lower frequency
oscillation (within the same stage or by using a second oscillator stage) to
provide single-device circuit gains of around one million. This second
oscillation periodically interrupts or "quenches" the main RF oscillation.
Ultrasonic quench rates between 30 and 100 kHz are typical. After each
quenching, RF oscillation grows exponentially, starting from the tiny energy
picked-up by the antenna plus circuit noise. The amplitude reached at the end
of the quench cycle (linear mode) or the time taken to reach limiting
amplitude (log mode) depends on the strength of the received signal from
which exponential growth started. A low-pass filter in the audio amplifier
filters the quench and RF frequencies from the output, leaving the AM
modulation. This provides a crude but very effective AGC (Automatic Gain
Control).
9.- Regens vs. Super-Regenerative (super-regen or superregen) Detectors:
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
Super-Regenerative Detectors work well for wide-band signals such as FM,
where it performs "slope detection". Regenerative Detectors work well for
narrow-band signals, especially for CW and SSB which need a heterodyne
oscillator or BFO. A super-regenerative detector doesn't have a usable
heterodyne oscillator - even though the super-regen always self-oscillates,
so CW (Morse Code)and SSB (Single side band) signals can't be received
properly.
Super-regeneration is most valuable above 27 MHz, and for signals where
broad tuning is desirable. The super-regen uses far fewer components for
nearly the same sensitivity as more complex designs. It is easily possible to
build super-regen receivers which operate at microwatt power levels, in the
30 to 6,000 MHz range. These are ideal for remote-sensing applications or
where long battery life is important. For many years, super regenerative
circuits have been used for commercial products such as garage-door openers,
radar detectors, microwatt RF data links, and very low cost walkie-talkies.
Because the super-regenerative detectors tend to receive the strongest
signal and ignore other signals in the nearby spectrum, the super-regen works
best with bands that are relatively free of interfering signals. Due to
Nyquist's theorem its quenching frequency must be at least twice the signal
bandwidth. But quenching with overtones acts further as a heterodyne receiver
mixing additional unneeded signals from those bands into the working
frequency. Thus the overall bandwidth of super-regenerator cannot be less
than 4 times that of the quench frequency, assuming the quenching oscillator
produces an ideal sinewave.
Continue at part #3.
ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
º Compilled from Wikipedia.com and "Regenerative and Reflex Receivers" by º
º Kim Smith and The Radio Electronique. Translatted and drawings in ASCII º
º by LW1DSE Osvaldo F. Zappacosta. Barrio Garay, Almirante Brown, º
º Buenos Aires, Argentina. º
º Made with MSDOS 7.10's Text Editor (edit.com) in my AMD's 80486. º
º April 15, 2012 º
º Updated July 17, 2020 º
ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ
ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
º Osvaldo F. Zappacosta. Barrio Garay (GF05tg) Alte. Brown, Bs As, Argentina.º
º Mother UMC æPC:AMD486@120MHz 32MbRAM HD SCSI 8.4Gb MSDOS 7.10 TSTHOST1.43C º
º 6 celdas 2V 150AH. 24 paneles solares 10W. º
º lw1dse@yahoo.com ; lw1dse@gmail.com º
ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ
Read previous mail | Read next mail
| |
