[SADXA] First Demonstration of Radio by Marconi Dec. 12th, 1896
Ron Jones
K7RJ at COMCAST.NET
Wed Dec 14 14:36:37 EST 2016
I stumbled on a web page describing a homebrew coherer. I only scanned the
page, but it looks like a really cool project that falls into the "just
because you can" category, and what better reason do we need?
http://www.sparkbangbuzz.com/els/coherer-el.htm
Ron K7RJ
-----Original Message-----
From: SADXA [mailto:sadxa-bounces at mailman.qth.net] On Behalf Of W7EXG (Bill)
Sent: Wednesday, December 14, 2016 10:27 AM
To: 'Southern AZ DX Association E-Mail Reflector'
Subject: Re: [SADXA] First Demonstration of Radio by Marconi Dec. 12th, 1896
Hi Ted,
I did a quick search regarding any type of recreation of the Marconi
transmissions with a Coherer receiver and did not find anything, although I
find that difficult to believe.
Yes, your suggestions of Recreating a Marconi Communication with his basic
apparatus as a Club Project might be fun ... for some of us anyway! Hi Hi.
I was thinking of building the Coherer, and taking some electrical/resistive
data on it, since I have all the equipment for testing. I am guessing O will
go through several iterations. If I can show Coherer would respond to 1mV,
then I think recreation might be plausible.
With a very high Q and highly filtered front end, and tuned for a specific
frequency (including the step up transformer), I could hook Coherer Receiver
to my antenna. After observing a strong signal at the specific frequency on
my FT2000D, I would hope to observe the Coherer detecting the signal, when
switched to antenna. I might use a local ham's signal at night on 10m for
this test.
I am also thinking that the spark gap transmitter could be built and used,
if it was highly filtered, to allow ONLY a specific frequency and bandwidth
to actually be transmitted by the antenna.
If we get all this working in town, then we will talk DXing with the setup.
So, there you go ... ... with framework in place.
It might be doable. I'll mark Dec. 12, 2017 on my Calendar.
Thanks again Ted,
Bill W7EXG
-----Original Message-----
From: SADXA [mailto:sadxa-bounces at mailman.qth.net] On Behalf Of Theodore
DOWNING
Sent: Tuesday, December 13, 2016 11:03 PM
To: Southern AZ DX Association E-Mail Reflector
Subject: Re: [SADXA] First Demonstration of Radio by Marconi Dec. 12th, 1896
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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