[600MRG] How Much Better Today?

[Brian, WA1ZMS]

Frank-

No "cerebral incident" required. :- )

Real easy to tally this up between then and now with rough numbers.

1) Keep mode the same, human copy CW. Net change: 0dB
2) Channel medium is the same; trans-atlantic sky wave at 600m. Mother nature has nothing different now than she did 100 years ago. Net change: 0dB.
3) Assume 100kW spark TX power in 1915, assume 100W CW TX power in 2015. Net change: 30dB worse.
4) Assume RX MDS (min. decernable sig) was -90dBm in 1915. (I MAYBE WRONG.) Assume MDS is -120 in 2015. AGAIN MAYBE WRONG with today's local EMI/RFI noise floors. Net change: 30dB better.

So far an equal game....

5) Antenna gain......this is where I think it gets VERY different.... Antenna size in 1915: 10 acers of land near "The Hamptons on Long Island" vs. 0.66ac lot of mine in central VA with houses all around.  I would call that Net change: 20dB worse, likely much more.

Thus.....I either need to buy land I cannot afford or switch to a DSP based digital mode to get processing gain.  So maybe I need to find a way to modulate my own MOPA with JT-9. 

See: http://w4dex.com/500khz/wd2xsh31.htm

Fact is, I'll have it either way. Wireless is just plain fun!

Good topic you bring up.


-Brian, WA1ZMS/4 & WD2XSH/31 & WG2XFQ in Va.
iPhone

> On Jul 3, 2015, at 9:06 AM, Frank Lotito <k3dz at live.com> wrote:
> 
> 
> I would like to propose an academic exercise that is beyond my present capabilities, unless I want to risk a cerebral incident.  Maybe one or more of the readers can "quantitatively" demonstrate that indeed in the last 90 to 100 years significant progress has been made in "2-way communication" at wavelengths "greater than 600 meters."  The exercise: Can long path (greater than 500 miles) communications be reliably accomplished between today's "amateurs and Part 5 licensees, with their ERP and typical antenna constraints" in comparison to long path communications from 90 to 100 years ago as practiced by radio services of that era, be they amateur, government, military and commercial radio-telegraph?  This could be done by constructing a "model" of all the key factors (blocks) in the transmit / receive communications path with each block in the model characterized with a quantitatively determined range of of its transfer function, S sub 21.
> 
> I would suggest that initially the analysis exclude QRSs, JT-9 and WSPR modes. After the "communications path model" is developed, we can then insert the more advanced communications modes to demonstrate how a poor to marginal current era station might be elevated to an effective (but painfully slow w.r.t baud rate) communications station.  The model could be used by present and future 600 / 630 and 220 meter participants to determine which updates to their present / proposed station  would get them the best bang for the buck.
> 
> Using a similar approach around some 9 years ago, WB8YYY and WN3F (now W2VDX) co-authored a 2-part article that appeared in the Antique Wireless Association's "The AWA Journal", January 2006, pages 26-28, and April 2006, pages 40-42.  They tried to "quantitatively" demonstrate trans-Atlantic communications of the initial Marconi transmissions between the (now) Canadian Maritime provinces and Ireland.  The co-authors attempted to put performance numbers to items such as antenna efficiency, path loss, detector sensitivity, information band-width, transmitter power, etc.  Using an on-line Excel Spread Sheet, the reader could use the authors' performance numbers, or change one or more performance numbers to see what would happen.  I would assume that the EME amateurs have done similar analysis (plural) over the years.
> 
> For this particular exercise, I would submit we do know with reasonable reliability reliably the "black box" S-Factor transfer function S sub 21 of each block of each block (stage) of a modern transmit and receiving 2-way path.  For 90-100 year old equipment educated guesses may be the best than can be done for the "communications path model."
> 
> Last, you may ask why spend the time modeling a 90-100 year old transmit / receive station.  The old vs new comparison reaffirming the advantages of using technology to overcome obstacles that could only be breached in the past with brute force.  The old vs new modeling may also attract to the ranks of Lowfers the amateur who's interests lie with the historical aspects of communication, including the plethora of rather simple "hollow-stage designs," alla pre-WW2 designs.  This past winter we saw an example of a historical 630 meter CW transmitter built by NO3M / WG2XJM.
> 
> 73 Frank K3DZ / WH2XHA
> 
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