Technical Topics > The RF Workbench
thinking of making the leap from FM to SW
jackson_r:
Thanks for the additional tips, zazzle! I didn't mean to sound flippant in how easy it would be to create/operate the solar system. I was speaking more to how easy it would be to wire it up. You're right, making sure I got enough insolation would be critical. A 200 watt panel bolted to a tree with a wire running to a mysterious padlocked box is going to draw some attention (if not the feds, some punks looking to cause mischief). If I went with setup like this I'd likely wire in a 12 volt timer between the regulator and the rig. I currently use one for my solar landscaping setup. This is the unit I use:
http://www.amazon.com/Neewer%C2%AE-Digital-Power-Programmable-Switch/dp/B00AJGX0JS/ref=sr_1_2?ie=UTF8&qid=1442489415&sr=8-2&keywords=12+volt+timer
Awesome level of control. I could program numerous ways to not only vary broadcasting schedule, but to also make sure I wasn't broadcasting for more than say 1-2 hours a day.
ff:
Unless you live in an area where Winter is almost nonexistent and cloud cover is nil - you have a lot more figuring to do. I am in the Northeast U.S. east of the Great Lakes - in other words, about the worst place in the U.S. for solar power except for parts of Washington State.
Also, car batteries die quick deaths in this type of usage. They are designed to deliver a huge wallop of current, and then be charged back with another hard wallop of current. Car batts suffer when taken on drawdowns of more than 20%. You will be discharging far more than that.
SLAs are a better choice if not subjected to below freezing temps. Deep cycle batts are what you should be looking for. I generally use marine batts from Wal-Mart but my usage these days is intermittent. For a regular operation golf cart batts are reasonable. They usually come as 6V units which you'll need to use 2 in series for your 12V. If you can find some used Nickel-Iron batteries retired from locomotive duty you will have about the hardiest option out there.
You will need a charge controller. Reflexive types are the cheapest. PWM controllers are best - however - you'll probably go insane trying to filter out the RFI in your system. I ended up using a reflexive controller when operating. The problem with that is they waste more of that precious power coming off the panels.
Lots to think about for a full-time operation Jackson. And let me say from experience, any place you factor in an "optimal" assumption in your calculations is exactly the place that will come back to bite you in the you-know-where. As I said before, I LIVED with one of these systems for more than a decade. Lots to think about... If you limit your operations to an hour or two per day you will have a FAR easier time with this. Have fun.
ff:
--- Quote from: jackson_r on September 16, 2015, 1514 UTC ---I currently use a 100 W panel, regulator, and marine battery, to power an array of outdoor landscaping lights and fountains. It'd be an even easier system to make for powering a radio like this.
--- End quote ---
Okay Jackson, here I go blabbering again. I keep getting hit in the brain with other things you should be considering. This situation is much harder than your fountain and lights setup. Please understand, your present loads are "stupid" loads that can run on just about any raw power supplied at the approximate voltage. Your radio is a "smart" load that is very sensitive to EVERYTHING. Although the textbook will say that your battery will "buffer" the incoming panel voltage, I'd be leery about running it with no protection. Depending on the cell count in your panel(s), the output at full sun will be anywhere from 16-20V. Even a very brief intermittent "quirk" will fry the X1M. At the very least, you should consider a protective zener diode. And you'll need some stiff voltage regulation too. You could sidestep all this by NOT operating the radio during charging hours.
Also if you desire to operate during charging hours you MUST MUST MUST filter that power - clean the crap out of it. A PWM charge controller will be throwing enormous amounts of RFI and will be very difficult to clean up. As I said earlier I ended up using a reflexive charger while operating radios. You will still need some filtering to clean the switching artifacts out of your power although a decent amount of capacitance and an in-line choke would probably be enough. Again, you can sidestep all this by NOT operating during charging hours.
Zazzle makes a lot of great points in his post and you should study it carefully. But remember, Zazzle's setup is powering a crystal-controlled beacon transmitter whose PA is turned on and off at a Morse Code rate. Your setup takes everything to a much more complex level. The X1M has PLL frequency generation and microprocessor control - highly sensitive to RFI and voltage changes. Also, your PA will run continuously and you will be overlaying modulation atop that carrier. Your audio will also be greatly affected by dirty power.
Let me end by saying that I'm not trying to dissuade you, but only to give you an idea of what you're up against should you decide to spend $$$. There's a lot to consider and to plan for. We haven't even mentioned charge / discharge rates, battery and panel sizing, battery maintenance, etc. It's a fascinating project should you decide to do it. But easy? No. It WILL be much easier if you curtail your operating times to a few hours a week... 73
jackson_r:
Thanks for the additional information, ff. I may not have been completely clear in how I use my current solar setup. All power from the 100 W panels runs through the following controller:
http://www.amazon.com/WindyNation-Regulator-Controller-Adjustable-Settings/dp/B00JMLPP12/ref=sr_1_5?s=lawn-garden&ie=UTF8&qid=1442602049&sr=1-5&keywords=solar+charge+controller
From the load output of the controller, the wires are run through the 12v timer so I can precisely control when the lights/fountains go on and off. There's no "raw" power so to speak, and there are no power fluctuations. The only fluctuation that can happen is if the charge on my 100 amp hour marine deep cycle battery drops below a certain voltage. At that point it actually doesn't fluctuate...it simply kills the power to the controller load. So my idea is to build a nearly identical setup with the transmitter connected as the controller load. When the power is "on," I'm transmitting. When the timer shuts off based on my programmed schedule, the transmitter shuts off. If I only ran the transmitter an hour a day, for example, I believe a deep cycle marine battery could hold up quite well. And if I'm only doing that 1 hour of transmitting at night, the battery has the entire next day to build back up its charge. Now, if I don't have enough sun I could certainly still run a deficiency that could leave my battery drained after a week or two. This also says nothing to the mentioned need for filters so the power from the controller doesn't screw with the radio. I'll definitely have to do some more research on that.
All in all, good things to think about and I appreciate all the info. I'm sure that I'll be testing this unit out indoors first before trying out my remote solar solution. :)
jackson_r:
ff - If you don't mind, a question for you (or anyone else who wants to jump in) about this project. I've been casually surfing a bit looking for QRP linear amps that I could use if I wanted to occasionally boost transmit power higher than the 5 watts this unit is capable of. Let's assume we're not talking about the complexity of working it in to the solar system I've been talking about. Let's just say I want to run it inside the house hooked up to AC. Most of the HAM related QRP amps out there are only user selectable to working on the main HAM bands. I'd likely be transmitting in the 43 m band, but the closest any of the consumer amps out there I've seen can get is 40 m. Is an amp designed for 40 m capable of being used on a 43 m transmission? What's going to happen if I tried to transmit on 43 m using a 40 m linear amp? This could very well be a dumb question, so forgive me. If the answer is, "you're going to have some very pissed off HAMs knocking on your door because of the filthy signal you'd be transmitting," feel free to tell me. ;D
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