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Messages - AA7EE

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22 Meter Band / Solar-Powered BRS On-Air on 13556.9 From SF East Bay
« on: January 06, 2019, 1936 UTC »
I built this little beacon back in May of last year, but only just got around to mounting it permanently outside. It is powered by a small solar panel, with no battery. As a result, it operates during daylight hours only, coming on 30 minutes to an hour after sunrise, and going off-air 30-45 mins before local sunset. It works on bright and moderately bright cloudy days, but does struggle a bit when the clouds are particularly thick and dark. I've thought about adding another panel or even a battery but, for the time being, am considering the slightly quirkiness of it's operating hours as part of it's charm.

It sends the letter "BRS" at 10wpm, in honor of my neighbor's cat Boris. Power is a stunning 1mW to a half-wave dipole in a slightly bent configuration on a second floor balcony. With such low power and a compromise antenna, I'll be amazed if anyone hears it. The plan is to run it at 10wpm for a few months then, if it has not been heard, to change to QRSS.

The frequency is a nominal 13556.9 KHz, which varies up and down by a few 10's of Hz, depending on the ambient outside temperature.

I hope it's OK to post this link. There's some more info, and pics, here -

https://aa7ee.wordpress.com/2019/01/03/putting-the-hifer-brs-boris-beacon-on-the-air-finally/

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Thanks for the info and encouragement Ed. Space for antennas is limited here, due to my living situation, but this beacon project has already taught me a few things. A couple of good lessons have already been learned, and I am currently leaning towards not putting it on the air. It will most likely be the subject of a blog post though. I will provide a link to it in this thread if and when that happens.

The two things I have learned so far are -

1) I am hopelessly behind the times in continuing to use 78L05 regulators. I had a small stash of them, so was blindly using them, without considering alternatives. However, the 4mA quiescent current and ~2V dropout voltage was a needless drain on a little beacon that only draws ~3mA on key-down and is intended to run solely from a small solar panel with no battery. I have finally put in an order for some more modern LP2950 regulators, which have a quiescent current of <0.1mA and much smaller voltage overhead of ~0.1V.

2) The ATtiny 85 which keys the oscillator was not starting up properly in the mornings when the sun came up. I think this was because I had the BOD (brown-out detection) set to 1.8V. At that low voltage level, the small panel wasn't supplying enough current to power the beacon properly. The remedy was to burn the fuses on the chip again and increase the BOD to 2.7V, which seems to have cured that problem. Another cure would be to simply include a battery in the circuit that is powered from the panel.

Anyway, I'll link to my blog post when this particular learning experience is over. Thank you for your help and comments.

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Thanks for the input, Σ and Dag - and thanks for the kind words on my blog, Σ. This little beacon will probably get a write-up. I also built a little temperature beacon, which will get written up first. It's a neat little device that outputs the current temperature as Morse code on the HiFER band. I liked the circuit, and got to wondering if I could build it as a simple beacon. Dag - using QRSS speeds for both your FSK and CW is a good choice. Even at the maximum radiated field strength allowed on this band, we're still talking about very low power levels. I use 4.6mW into a dipole as my standard, as calculated by W1TAG.

I ran it into a 50 ohm resistor this afternoon and put it on the scope. Peak-peak voltage into 50 ohms is only around 0.6 - 0.7V, so it looks as if the RF power out is only about 1mW. This could turn out be more challenging than I had thought.

I think I'll start out using ~5wpm and go from there. It sure will be great when the sunspots return. Perhaps I should say "if", but I want to be optimistic about this. The thought of spending the rest of my life in a repeat of the Maunder Minimum isn't very inspiring!

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22 Meter Band / Question About Morse Code Speed for Beacon "BRS"
« on: April 15, 2018, 1835 UTC »
Hello there, fellow HiFERs. I'm very happy to see a dedicated HiFER section on these forums.

I am scratch-building a little beacon that will put out about 2mW into a horizontal dipole on top of my property fence, at about 7 feet above ground. It will be a bit of a cloud-warmer, I think, but I'm interested to see how it will get out. It will be powered by a single small solar panel with no batteries, so will be operational during daylight hours only. I hope I won't be missing the valuable grey-line propagation time with this approach, but we'll see how it goes. It should be on the air sometime this week. As it sits on the bench, it is coming up on around 13556.91 or thereabouts.

My question to the group is what you think an ideal code speed is? I want it to be fast enough to be copyable to the ear, so no QRSS. I have a personal preference for something around 10 - 12wpm, as anything slower bores me somewhat. However, I want the decision to be driven by what is most likely to be copyable to listeners struggling with what will almost certainly be a very weak signal. The beacon's callsign will be BRS, in honor of my neighbor's cat Boris.

I'm thinking that a relatively high speed would maximize the chance of copying the entire callsign before any fading takes the signal out, so I'm veering towards around 10wpm. What do you guys think?

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