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Old 04-12-2017, 3:13 PM
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Coyote-Frostbyte Coyote-Frostbyte is offline
Join Date: Feb 2016
Posts: 607

This 2200 little experiment will provide me with plenty of entertainment, Majoco. I cut my teeth, so to speak, on E/LF radio in grad school, so I am under no illusions about what I have embarked upon. Thank you for the web site info....

One of the antenna I have consider’d is exactly what you mention’d; the Double T, although I won’t go that direction because of the mechanical issues in maintaining one (where my Colorado home is- this radio’s future site-- we can get over 20 feet of snow in the winter… which has taken down every one of my wire antennas.)
So far, the plan is something vertical, --and sturdy. I have a friend who has been trying to get me to take off his hands a 50 foot section of an old AM broadcast radio tower. What’s attractive is this is the bottom section with the insulator and base…. plus I have some cowboys who owe me a few favors whom I’ll enlist to place it. The bigger task I see, however, is going to be the ground matrix beneath it.
I have attached a picture of Radio NSS, the naval station in Annapolis Maryland, dated just before the demolition of all but the three Eiffel (seen to the right.) The central tower was 1200 feet high, forming the core of a huge Goliath array. What isn’t seen is the massive spider web of copper lines that cover the point of land this array was built on. This winter I got to walk about the old site, beneath the three 600 foot remaining towers. Over the years erosion has exposed lots of that matrix, and I tripped twice over some large gauge copper wires. My feeble ground system will be a mockery of NSS’s, I’m afraid.
The matching circuitry will be mounted directly at the base, and I don’t envision that tower going taller than 50 feet- with a top loading coil and capacitive ’hat.’ This morning, in my enthusiasm for this project, I ran a computer model of several verticals at 136Khz, and confirm’d there isn’t much advantage making it taller than 50 feet unless it goes a lot, lot higher- and with my limitations, it won‘t. At very-best, it will radiate approximately 0.2% of the input RF**… With the 60 watts or so from my transmitter I can expect, maybe, a whopping 120 *milliwatts* ERP. Breath taking, No? (laffs)
What will be breath taking will be the RF voltages generated at antenna matching circuit at the tower base. Tuning will be easy:, just dip the circuit until the thing stops sparking (just kidding.) I can feel Telsa looking over my shoulder, smiling.
But sparking is not something I take lightly. The Q of this array will be so high, and thus the bandwidth so narrow, that +1Khz deviation will likely cause it to arc… hence I plan on a slow speed digital data mode..
I am lucky to have access to several remote receiver sites, so I can listen for my signal. So far I haven’t heard any ham activity on 2200- though I hope to hear myself- lots of hope, any way. I have a friend who says she’ll try it out too, if it can be heard in New Mexico- but neither of us are holding our breaths……
It should prove an interesting summer, however ………

** NSS, at 20Khz was 0.3%
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Last edited by Coyote-Frostbyte; 04-12-2017 at 3:32 PM..
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