HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: AntiRecoveryUnit on March 31, 2016, 1714 UTC
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I'm not native English speaker, so sorry that Undecided
So, I started to plan little beacon, maybe around 10.240 or 9.990.
The biggest problem is power, on winter, the sun is below the horizon about 2 months which makes solar panels useless.
I have only one place, where I'm having an access to a grid power, but there is possibility to get noticed.
I would not run it from my home qth, too many hams near.
That place has a mast, and it's like 190m ASL on top of ski slope, near of little city.
There is also some abandoned houses and farms, but i have not checked to they still have mains connected.
I had a wild idea to wire an Neontube transformer backwards to a mains pole.
Normal grid is 20kV on rural areas, so 20kV 200mA trafo would give some power for TX.
(I'm electrician, so I know what I'm doing there! I have tested that idea, simply feeding one trafo with second one)
Second issue is temperature changes, on winter it's easily -35 degrees of Celcius for weeks and on summer between +25 to +30 degrees of Celsius.
I have built a transmitter, only have to get on attiny13 for keying.
It's simple 7400 chip, two gates as oscillator and two gates running as buffer, simple lpf and two 2n2222 transistors as final stage before main lpf.
5V on pa, and it outputs about 350mW and on 13.8V about 1.1Watts.
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Wind perhaps? Any off-grid system is going to need batteries, and they don't usually like it that cold. Any flowing hydro nearby?
+-RH
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Some of the recent low loss high capacity capacitors may work better than batteries in the Fin environment.
https://www.youtube.com/watch?v=GPJao1xLe7w
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Hi there!
so, 1,1W @ 13,8V. I Assume you need something like 150mA. That's 3,6Ah/day. Which is quite a bit. And yes, with -35°C, most Batteries start to cause problems. Usually, it's just that it's not possible do draw huge current from them any longer. So 150mA shouldn't be a problem. But with ongoing discharge most electrolytes change and may freeze up.
I need to check literature (abut electrolytes and freezing points) myself before, but the best idea would likely to go with NiCd batteries.
In case you have the option to change the Battery every - say - 2 days, you could go with a starter Battery and change it before it reached a certain level of discharge. Also, you could wrapp the battery up in a LOT of thermal insulation and spend some watts on heating the Bettery itself. But with that much activity you gonna leave a trail on the ground sooner ot later. :D
PV isn't an option. How about wind? Expensive and an eyecatcher. But I wanted to mention it.
Electrician. OK. With experience when it come sto voltages above teh 1KV level? I just ask because with 20+kV even "dry wood" conducts enough to cause deady shocks and... one mistake and you're fried. Also, such "self made" installations may cause danger to other people. Insulation breakdown, whatever.
Kind regards,
~Zazzle
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Going to take it on to the nearby forrest with old 120Ah truck battery, lets see how long it runs :D
Some problems still with keyer code. Maybe I remove whole temperature sensor and code for it.
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Hey,
Eh-hehehehe-he. That made me chuckle. I had intentions to send the Battery state (before I found an opportunity to use the local power grid) and temperature as well.
In the end I kicked those parts out because I happen to never listen to my own beacon just to know the local temperature. Also, since it's not likely that it'll be heard on a regular schedule (there are a few exceptions), it doesn't make much sense anyway. And I've to admit that I didn't want tp spend that much H/W / Construction time / software engineering time on such a feature when it's likely that the unit will be stolen/damaged/busted. I started with the basic setup and gew comfortable with it. But yes, it's a nice cool-to-have feature for sure! :)
And - oh - 120Ah Starter Battery. Your back will love you. :D
Kind regards,
~Zazzle
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Hello!
First prototype is running from solarpanel, QRG is 10,007Mhz and its drifts littlebit.
It's about located about 180m ASL, running 20mW to 200mW to an dipole.
Keyer seems to go crazy when voltage drops, it's transmitting simply FINLAND, about 5wpm.
Now 12.50UTC, it seems to transmit carrier and FI with some nonsense because clouds are blocking sun.
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Someone might be interested about schema.
It's something like this, almost all parts are from old motherboard.
Hams are cheap, pirates are cheaper....
If it wont oscillate, C1, C2 and C5 aren't right.
I build it in small airgunpellet box, easy to solder deadbug directly inside it.
(http://i.imgur.com/IrmFKKj.png)
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Still don't know why anyone would use class AB when class E has been around for 40 odd years!
See;
http://www.k3pgp.org/Notebook/Wd5cvg/Classetx/classetx.htm
http://www.ka7oei.com/mpm_class_e.html
Somewhat more efficient and isn't that what you're trying to achieve if running from batteries?
Far simpler circuit also.
You should get close to 95% eff.
Str.
p.s. if I see anymore Class A, A/B or even C circuits I'm gonna cry! :'(
Please lets move on! :)
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Yeh, I know, but thats what happens when You take couple beers and "Hey, lets build beacon!" ;D
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I'd just build the simplest and most efficient transmitter I could no matter how :P pissed :P I got!
Why complicate things?
;D
Having an L/C oscillator for the frequency you are using is rather silly especially when (if you're using 10.240) Xtals are very cheap for some frequencies and very stable too.
This design;
http://www.uploadarchief.net/files/download/74hc240-48meter(rev.A).gif
And variations of.....
http://new-ham-radio.blogspot.co.uk/2010/07/is-it-possible-to-create-qrp.html
is still the ultimate in simplicity and efficiency.
I see no reason to build anything that's more complicated and not as efficient.
Don't need 10W, don't fit the FET, you'll get a couple of 500mW out of the 74HC240.
They're less than $1 ea.
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Yeh, I know, and I have two unopened tubes of 74hc240 and some (10 to 20) MIL specs russian clones in stock.
But yeh, I let that transmitter run long as sun goes under the horizon, and then I go get it back.
I have only old (made in 80's) solarpanell on that hill where this tx is, and it's only about 4 to 6V and around 400mA.
So i have to upgrade it too.
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That's Plenty of power!
Just invert to get the volts you want!
LTC3105/6 look a good starting point.
You could make the next gen of 'Souper Beacons'!
Good luck Bud.
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Yeh, but have to get new location for winter, with mains!
Couple fets and mains feeding, maybe arduino controlling DDS -> Multi qrg beacon
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If one goes arduino one might consider adding telemetry capability also. Such as temp, weather data, input voltage and current draw, power output etc etc. Much more interesting listening after the novelty of iding it has worn off.
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I have an bigger transmitter waiting on my desk, still some work to do with it.
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Any updates? (after all this time has passed)