[CW] SAQ Live Stream

Wed Jul 8 01:19:58 EDT 2020

    Once upon a time fire engines were pulled by horses. The 
horses lived in the station with the fire wagons behind them When 
an alarm came in the harnesses were dropped over the horses and 
hooked up by the firemen who got into their own rigs. They would 
then take off galloping to the fire. Retired fire horses would 
often begin to run when they heard the bells of a fire wagon or 
if they  smelled smoke. So someone with a fire horse complex get 
excited by something that they have had experience with or even 
just are very interested in.
    If the receiver was a regenerator it might have been on a 
verge of oscillating or actually oscillating. When adjusted for 
minimum bandwidth the gain is maximum and very slightly more 
makes the receiver oscillate. Works very well for CW. The famous 
old Navy receivers were regenerators mostly with a tuned RF stage 
ahead. The purpose being to increase sensitivity but also to 
provide some isolation so that the oscillating detector did not 
radiate out the antenna.
    Many early broadcast receivers were regenerators. For AM they 
were supposed to adjusted to some point before oscillation but 
often the users didn't know how to work them so the early 
broadcast band was filled with howls and whistles from 
misadjusted receivers. For a couple of 1930s Navy receivers, used 
through WW-2   There are earlier Navy receivers on the same site.
<http://www.navy-radio.com/rcvrs/rak-ral.htm>
    If I can find the link again I will see if I can read the 
labels on the dials.

On 7/7/2020 9:36 PM, D.J.J. Ring, Jr. wrote:
> What's a "firehorse complex?"
>
> The alternator didn't have modulation, but when I heard SAQ the 
> signal sounded like it had a tone on it, maybe the effect of 
> long range propagation, I don't know.
>
> From Wikipedia (see below)
>
> 73
>
> DR
>
> Beginning around 1905 continuous wave 
> <https://en.m.wikipedia.org/wiki/Continuous_wave> (CW) 
> transmitters began to replace spark transmitters for 
> radiotelegraphy because they had much greater range. The first 
> continuous wave transmitters were the Poulsen arc 
> <https://en.m.wikipedia.org/wiki/Poulsen_arc> invented in 1904 
> and the Alexanderson alternator 
> <https://en.m.wikipedia.org/wiki/Alexanderson_alternator> developed 
> 1906-1910, which were replaced by vacuum tube transmitters 
> beginning around 1920.^[21] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Phillips1-21> 
>
>
> The continuous wave radiotelegraphy signals produced by these 
> transmitters required a different method of reception.^[93] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Lauer-93> 
> ^[94] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Phillips9-94> 
>  The radiotelegraphy signals produced by spark gap transmitters 
> consisted of strings of damped waves 
> <https://en.m.wikipedia.org/wiki/Damped_wave> repeating at an 
> audio rate, so the "dots" and "dashes" of Morse code were 
> audible as a tone or buzz in the receivers' earphones. However 
> the new continuous wave radiotelegraph signals simply consisted 
> of pulses of unmodulated carrier 
> <https://en.m.wikipedia.org/wiki/Carrier_signal> (sine waves 
> <https://en.m.wikipedia.org/wiki/Sine_wave>). These were 
> inaudible in the receiver headphones. To receive this new 
> modulation type, the receiver had to produce some kind of tone 
> during the pulses of carrier.
>
> The first crude device that did this was the tikker 
> <https://en.m.wikipedia.org/wiki/Tikker>, invented in 1908 by 
> Valdemar Poulsen 
> <https://en.m.wikipedia.org/wiki/Valdemar_Poulsen>.^[45] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Marriott-45> 
> ^[93] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Lauer-93> 
> ^[95] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-McNicol1-95> 
>  This was a vibrating interrupter with a capacitor 
> <https://en.m.wikipedia.org/wiki/Capacitor> at the tuner output 
> which served as a rudimentary modulator 
> <https://en.m.wikipedia.org/wiki/Modulator>, interrupting the 
> carrier at an audio rate, thus producing a buzz in the earphone 
> when the carrier was present.^[8] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Lee2-8> 
>  A similar device was the "tone wheel" invented by Rudolph 
> Goldschmidt 
> <https://en.m.wikipedia.org/wiki/Rudolph_Goldschmidt>, a wheel 
> spun by a motor with contacts spaced around its circumference, 
> which made contact with a stationary brush.
>
> <https://en.m.wikipedia.org/wiki/File:Heterodyne_radio_receiver_circuit_1920.png> 
>
> Fessenden's heterodyne radio receiver circuit
>
> In 1901 Reginald Fessenden 
> <https://en.m.wikipedia.org/wiki/Reginald_Fessenden> had 
> invented a better means of accomplishing this.^[93] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Lauer-93> 
> ^[95] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-McNicol1-95> 
> ^[96] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Patent1050441-96> 
> ^[97] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Hogan-97> 
>  In his /heterodyne receiver/ an unmodulated sine wave radio 
> signal at a frequency */f/_O * offset from the incoming radio 
> wave carrier */f/_C * was applied to a rectifying detector such 
> as a crystal detector 
> <https://en.m.wikipedia.org/wiki/Crystal_detector> or 
> electrolytic detector 
> <https://en.m.wikipedia.org/wiki/Electrolytic_detector>, along 
> with the radio signal from the antenna. In the detector the two 
> signals mixed, creating two new /heterodyne 
> <https://en.m.wikipedia.org/wiki/Heterodyne>/ (beat 
> <https://en.m.wikipedia.org/wiki/Beat_%28acoustics%29>) 
> frequencies at the sum */f/_C * + */f/_O * and the difference 
> */f/_C * − */f/_O * between these frequencies. By choosing 
> */f/_O * correctly the lower heterodyne */f/_C * − */f/_O * was 
> in the audio frequency 
> <https://en.m.wikipedia.org/wiki/Audio_frequency> range, so it 
> was audible as a tone in the earphone whenever the carrier was 
> present. Thus the "dots" and "dashes" of Morse code were 
> audible as musical "beeps". A major attraction of this method 
> during this pre-amplification period was that the heterodyne 
> receiver actually amplified the signal somewhat, the detector 
> had "mixer gain".^[95] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-McNicol1-95> 
>
>
> The receiver was ahead of its time, because when it was 
> invented there was no oscillator capable of producing the radio 
> frequency sine wave */f/_O * with the required stability.^[98] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Nahin2-98> 
>  Fessenden first used his large radio frequency alternator 
> <https://en.m.wikipedia.org/wiki/Alternator>,^[8] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Lee2-8> 
>  but this wasn't practical for ordinary receivers. The 
> heterodyne receiver remained a laboratory curiosity until a 
> cheap compact source of continuous waves appeared, the vacuum 
> tube electronic oscillator 
> <https://en.m.wikipedia.org/wiki/Electronic_oscillator>^[95] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-McNicol1-95> 
>  invented by Edwin Armstrong 
> <https://en.m.wikipedia.org/wiki/Edwin_Armstrong> and Alexander 
> Meissner 
> <https://en.m.wikipedia.org/wiki/Alexander_Meissner> in 
> 1913.^[45] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Marriott-45> 
> ^[99] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-McNicol16-99> 
>  After this it became the standard method of receiving CW 
> radiotelegraphy. The heterodyne oscillator is the ancestor of 
> the /beat frequency oscillator 
> <https://en.m.wikipedia.org/wiki/Beat_frequency_oscillator>/ (BFO) 
> which is used to receive radiotelegraphy in communications 
> receivers 
> <https://en.m.wikipedia.org/wiki/Communications_receiver> today. 
> The heterodyne oscillator had to be retuned each time the 
> receiver was tuned to a new station, but in modern 
> superheterodyne 
> <https://en.m.wikipedia.org/wiki/Superheterodyne> receivers the 
> BFO signal beats with the fixed intermediate frequency 
> <https://en.m.wikipedia.org/wiki/Intermediate_frequency>, so 
> the beat frequency oscillator can be a fixed frequency.
>
> Armstrong later used Fessenden's heterodyne principle in his 
> superheterodyne receiver /(below)/.^[95] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-McNicol1-95> 
> ^[8] 
> <https://en.m.wikipedia.org/wiki/Radio_receiver#cite_note-Lee2-8>
>
>
>
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> =30=

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL