[CW] I don't get it?

[David J. Ring, Jr.]

Regarding the power used on the 600 meter band, at sea it was not
uncommon to run a quarter kW on 500 kHz.  Our emergency battery
transmitters ran about 40 watts output but they were about 80% modulated
with about 400 Hz audio double side band - and that type of signal had
many advantages - it was broad and if you couldn't copy it on 500 kHz,
you could still copy it on 499 or 501 kHz as it was a nominal 800 Hz
wide.

Most coastal stations ran about 1 kW but many ran about the same as a
ship about a quarter kW.  The notable exceptions were Land End's Radio
in near Sennen Cove in the Duchy of Cornwall which is the most westward
part of the United Kingdom (technically Cornwall isn't part of England,
but is part of the UK).  It was said by the "ancients" to be the
Bolerium - the "End of the Land", and for us sparky sailors was a fading
beacon was we left Europe, and a welcoming one when going to Europe.
I've never bothered to look on a globe to see if this is true, but I
know on a regular mercator projection northern Scotland looks more
westerly - and of course, they didn't include Ireland.  I guess the
inhabitants from Cork didn't sail that far.

Typical ship antennas were 40 to 60 foot high, and 100 to 200 foot long,
sometimes more.

The efficiency of 600 meters over water is fantastic - Terman's Radio
Engineering Handbook (c. 1950) has the distance over water for 1 kW as
1500 statute miles - so if you think that a ship had a circle of
communication with a 1500 mile radius, you can see how desirable it was.

But when you started sailing up a river, the distances just got quite
small - communications with New Orleans from Baton Rouge, LA was
difficult, and sometimes RCA Chatham, MA radio WCC could not hear me
from Albany, NY when I had sailed up the Hudson River to upstate NY from
NYC.

I haven't found many groundwave studies of 600 meters over soil - but
Fritz Raab and the ARRL Experimental group (of which I am a member) are
starting to document it.  Your reports will help us do this, and we
invite you to participate in the research  http://www.500kc.com/

Our best DX is about 6,600 miles reception - WD2XSH/6 was received in
the Marshall Islands.

You can read archived messages and look at some articles.
http://www.500kc.com/news_archive/index.htm

Most receivers are terrible on 500 kHz - but there are a few exceptions.
The old Debeg, Marconi, ITT/Mackay, receivers were equipped with a tuned
preselector which tuned the very low impedance of the antenna - very
very low real part radiation resistance when you consider that a full
size 1/2 wave wire on 500 kHz is 936 feet.  With a preselector that
tunes these antennas, you start to hear stuff coming out of the noise.

73

David Ring, N1EA, WD2XSH/18
Member ARRL 600 Meter Research Group
-30-



On Tue, 2008-11-25 at 17:04 -0500, wealsowalk at aol.com wrote:
> Don, I am on the periphery of our experimental groups on 500 Kc.  there 
> are several groups in the US and yes, the use of the band is old, but 
> most of the 3/4 century of work is for communication over water where 
> ships were heard all over the world.  Over land, the situation is 
> different and most of the communication appears to be by groundwave, 
> although there have been a number of contacts over several thousand 
> miles.  Furthermore, the work is done at fairly low power, not QRP by 
> any means, but low compared to previous work and the antennae in use 
> are all electrically short, so the radiation resistance is low and the 
> effective power out bare hundreths of what a 1/4 wave would put out.  
> Further, the technology that there is a great deal of experience with 
> is also all old and one of the positive goals is to learn what newer 
> technology can do.  Some, of course, are just implementing older 
> equipment.  For example I know that at least one of the group members 
> was just this week attempting to purchase a TAJ-19 which is a WWII 
> transimitter that naval aviation used, but it is not necessarily the 
> transmitter that is the experiment.  Receivers also are in the 
> experiment as well as receive antennaes.  If you tune your yeacomwood 
> to 505-515 kHz (where the original group is at), you probably will not 
> hear anything and for several reasons.  First your antenna is wrong.  
> Some people are using s
> hort electric probes with wideband preamps to 
> hear with.  Also, your radio desensitizes between 500 Khz and about 
> 1800 Khz because the broadcast band is so strong that the manufacturers 
> deliberately desensitize the receivers for that region.  But even if 
> you have a proper receiver/antenna, depending upon where you are, you 
> still might not hear anything, even with very narrow CW filters, 
> because the signals you are looking for are well under the noise.  Some 
> are attempting to use PSK31 because that is a low signal approach.  
> Another is QRSS CW.  QRSS means very slow.  So slow that a computer can 
> scan the region of the signal hundreds of times or more during a single 
> dit.  Doing that averages the random noise out, but leaves any peak 
> that was a signal.  There are many other new technologies that will be 
> applied to the experiment.  Of course, there is also now a toe in the 
> door that may result in additional band spectra for HAMs everywhere 
> depending upon another part of the experiment:  Can just anybody do 
> this?  What happens when I live in an apartment and try to send a 
> signal out on this band?  Do I get into the neighbors telephones?  
> Sure, out on the farm you can put up a big signal and have a big 
> antenna, but at your house, with a short antenna that is loosing most 
> of its signal, how badly do we get into our neighbors AM radio?  Where 
> does the signal go?  There are litera
> lly hundreds of questions that 
> need to be answered before the FCC will allocate a band down there to 
> the HAMs.  Thus it is an experiment to find out.  WARC has given a 500 
> KHz allocation, but the FCC has not, except in the case of the 
> experimental licenses.
> I hope this is a help to your understanding.
> Bill Isakson
> AC6QV
> California
> 
> -----Original Message-----
> From: D. Chester <k4kyv at charter.net>
> To: cw at mailman.qth.net
> Sent: Mon, 24 Nov 2008 10:35 pm
> Subject: Re: [CW] I don't get it?
> 
> 
> > What is "experimental" about the 500kHz neighborhood? It's not like 
> this > is some newly discovered spectrum, never used before. Yet the 
> FCC issues > "experimental" licenses to operate there, and now I see 
> the Canadians are > doing the same. What are hams going to learn that 
> isn't already well > known from the nearly-100-years or so of previous 
> use? 
> > 
> > 73, de Hans, K0HB 
>  
> The previous users for the most part didn't have the kind of antenna 
> and financial limitations most amateurs have, and amateur communication 
> is different in many ways from commercial. The "experimental" aspect is 
> to discover what amateurs can actually do in that frequency range under 
> the circumstances with what we have available. 
>  
> Don k4kyv  
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