[SADXA] First Demonstration of Radio by Marconi Dec. 12th, 1896
Theodore DOWNING
w7key at mac.com
Wed Dec 14 01:02:31 EST 2016
Bill,
This is great information. If you told Captain Kirk to ask Scotty to activate the Coherer
detector - no fan would blink an eye!
But you might suggest a great club project - if it has not already been done - to recreate (within reason) , the original transmission and reception. The club members could all wear period-clothing. That would be a Time-Travel DX-Pedition and hopefully make the cover of QST.
Ted
> On Dec 13, 2016, at 9:24 PM, W7EXG (Bill) <W7EXG at q.com> wrote:
>
> Thanks Mike and Ted.
>
> Here are some more interesting aspects on Marconi's Transatlantic Radio
> Propagation.
>
> As an Electrical Engineer, I find it interesting, if not amazing, that the
> 1901 receiver was created prior to the Fleming valve - tube invention and
> thus there was NO electronic diode element - everything in receiver was
> passive.
>
> The RF detector used a mechanical element called the COHERER Detector. It
> consisted of a metal tube, filled with loose metallic particles with a
> metallic plug on each end. The end-to-end resistance is high due to loosely
> packed particles. However, when a voltage is applied, the metal particles
> cling to each other between the ends, and create a low resistance path. By
> noting the change in current flow, or resistance, the voltage can be
> detected. Marconi used a RF step up voltage transformer in his receiver, to
> increase the sensitivity of the Coherer detector.
>
> One drawback of the Coherer detector was that once the metallic particles
> cohered, the tube needed to be tapped, to return the filings back to their
> loose and high resistance state. So, Marconi built a mechanical tapper, to
> tap the tube automatically after signal detection.
>
> Apparently, there was no 30WPM with the repeated letter S.
>
> To think about the sensitivity of the RF detector, we know an S9 Signal is
> referenced as a 50uV signal into 50 ohms at receiver. This IS a strong
> Signal. So my guess is Coherer might have been responsive to 100uV, or 0.1
> mV. The Transformer might have stepped this voltage to 1mV.
>
> The Spark Gap Transmitter was developed by later-to-be tube Inventor
> Fleming, and run by a 30kW alternator. Thus powerful gap energy was coupled
> to the transmitting antenna. Maybe received signal was 40/9??
>
> There are some doubts about Marconi's timing and wavelength used. It is
> documented that the time of transmissions was 11:30am to 2:30pm Newfoundland
> time. If true, then it is unlikely the reported 850kHz signal (AM band)
> would travel 2000 miles. If the times are correct, it is more likely higher
> frequencies propagated from the spark gap, and were the frequencies being
> detected?
>
> I have also seen some recent articles of people constructing Coherer
> detectors. It might be fun to play with them, and see what their actual
> sensitivity might be. They are truly just metal filings in a tube with metal
> plugs on each end.
>
> As we all know, everyone is trying to push the envelope in Amateur Radio.
>
> Perhaps a WAS with ONLY passive detector receivers, [such as the Coherer
> Detector] should be an ARRL Award? This may stimulate better inventive
> passive element detectors. There is some value in this, since electronic
> detectors are at risk during high levels of radiation.
>
> I suspect the FCC won't let us build a 30kW Spark Gap generator for our
> Transmitters.
>
> Thanks again for your comments.
>
> Best 73s,
>
> Bill W7EXG
>
> -----Original Message-----
> From: SADXA [mailto:sadxa-bounces at mailman.qth.net] On Behalf Of W0LTL - Mike
> Zonnefeld via SADXA
> Sent: Monday, December 12, 2016 11:55 PM
> To: sadxa at mailman.qth.net
> Cc: MikeZW0LTL at aol.com
> Subject: Re: [SADXA] First Demonstration of Radio by Marconi Dec. 12th, 1896
>
> Nice!
> 73
> Mike
> W0LTL
>
>
> In a message dated 12/12/2016 10:29:06 P.M. Pacific Standard Time,
> ted at teddowning.com writes:
>
> A great answer, Bill. Merry 12 December.
>
> Ted w7key
>> On Dec 12, 2016, at 5:29 PM, W7EXG (Bill) <W7EXG at q.com> wrote:
>>
>> Hi Ted,
>>
>> In the spirit of your DX spot questions, here is my response.
>>
>> On another December 12, but in year 1901, Marconi succeeded in sending
> the
>> first radio transmission (estimated at 850kHz) 2000 miles across the
>> Atlantic Ocean, from England to Newfoundland. This disproved detractors
> who
>> told him that the curvature of the earth would limit transmission to 200
>> miles or less.
>>
>> His message was Morse-code signal letter "S"
>>
>> Thus December 12 is actually a GREAT DAY for Amateur Radio, since it was
> on
>> this DAY in 1901, when "some type" of ionospheric reflection was proven,
>> suggesting world wide DX was possible.
>>
>> Fortunately the FCC was not involved yet, so no call Sign was required.
>> However, rumor has it, that Marconi's WANTED TO HAVE the first amateur
> radio
>> call, so his 1 by call was -- S. In that context, Marconi WAS the 1st
>> Amateur Radio Operator, and 1st DXer on Dec. 12, 1901. This is an
> amazing
>> 1st.
>>
>> Since 2000 mi at 850kHz clearly was a nighttime propagation, the
> propagation
>> reflection was off the F layer.
>>
>> However, the transmitting system consisted of a dipole, driven by an
>> induction coil and a spark gap.
>>
>> I am guessing that the spark gap still radiated energy at frequencies way
>> ABOVE the MUF at the time, and some of that high frequency energy escaped
>> into space -- and is still out there.
>>
>> If the universe is curved with a circumference of 115 Light Years to THIS
>> DATE, I suggest listing tonight on 20m or higher frequencies, about
>> midnight, for ... ... ... ...
>>
>> But, be sure your using one of those whiz-bang SDR receivers with a noise
>> floor below absolute temperature.
>>
>> My DX Spot for Dec 12, IS NOT FOR TODAY, BUT mainly FOR TONIGHT, so you
>> still have a chance at this rare DX event!!
>>
>> If you hear radio Station with call sign S, give him a call.
>>
>> Might be hard to get a confirmation, but you might check LOTW anyway. It
>> will take awhile for S to hear your call and get it in the LOTW data
> base,
>> however.
>>
>> Be wary of bogus "S" stations.. who may be pretending to be "S". This is
>> always an issue for us DXers.
>>
>> Pile-ups.. well YES!. Since I just put S on the DX Cluster forecast for
>> tonight, I suspect the pile-ups might be intense.
>>
>> Good luck and good DX! And Mainly ... Have Fun!!
>>
>> 73s,
>>
>> Bill W7EXG
>>
>> -----Original Message-----
>> From: SADXA [mailto:sadxa-bounces at mailman.qth.net] On Behalf Of Theodore
>> DOWNING
>> Sent: Monday, December 12, 2016 8:48 AM
>> To: Southern AZ DX Association E-Mail Reflector
>> Subject: Re: [SADXA] First Demonstration of Radio by Marconi Dec. 12th,
> 1896
>>
>> Now that's a DX spot for sure! Was it today? Darn it, What call sign?
> What
>> frequency? I doubt there will be a pile up. :-)
>>
>> Ted
>> w7key
>>> On Dec 12, 2016, at 8:28 AM, W7EXG (Bill) <W7EXG at q.com> wrote:
>>>
>>> Dec. 12, 1896:
>>>
>>> First demonstration of the radio:
>>> Marconi demonstrates his radio set to the public, today -- on Dec. 12th
>> in
>>> 1896
>>>
>>> 73s,
>>>
>>> Bill W7EXG
>>>
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