Power Systems – Introduction
We can think of a functioning amateur radio ‘station’ as a tripod – the three legs are Power, Transceiver, and Antenna. If any of these are missing or out of whack, the tripod falls over, and the ‘station’ is inoperable or very inefficient.
In this blog, we will focus on the Power System portion of the tripod, what it does, how does it do it, and how can it go wrong. In some ways the Power System is unique. The Transceiver and Antenna components are under your control – you can build or buy whatever antenna you want, and mount it in what ever manner you choose (okay, subject to local ordinances and covenants); you can buy or build whatever radio system you want (subject to federal regulations, and your bank account). But often your power system will depend on an amazingly complex infrastructure – one that you have little or no control over. With that in mind – let’s get started!
What does a Power System do anyway?
The function of a power system is to deliver usable energy to the transceiver. This energy is then modulated to contain a signal on a specific radio frequency, and delivered to the feed line and the antenna. On the receive side, it provides the power to enable the radio to demodulate a received signal, and present the result as audio to the operator. Since it is the starting point for the radio’s function it is a key component of the Radio Station tripod.
So what can go wrong?
Well, of course the simplest thing that can go wrong is that the power simply isn’t there. Let’s begin by looking at three common ways of delivering power to the station, and examine their strengths and weaknesses. The three we will examine are: ‘shore’ power provided by the electrical grid, generator supplied power, and battery power (and its recharging components).
Power provided by the grid is both the most convenient and the riskiest source of power for your radio station. It is convenient because all you have to do is plug your power supply into the wall socket – everything else is taken care of by other people. It is the riskiest because everything else is taken care of by other people; and there is a lot of other stuff to take care of.
Lets take a look at what is needed to deliver the power to the socket in your wall.
- The power supply that converts the AC from the wall into the correct DC voltage for your radio needs to be operational – this may be built into your radio, or it may be a separate component;
- The house wiring needs to be correct and intact;
- The line from your house to the street needs to be functional;
- The transmission lines and transformers from the substation need to be intact;
- The substation needs to be operational;
- The distribution lines from the power plant to the substation need to be intact;
- The generators in the power plant need to be operational;
- The power plant needs to have fuel (coal, natural gas, nuclear, wind, solar); and
- The surrounding power networks need to be ‘in sync’
All of these have to be working in concert to enable you to power up your rig. Since ARES focuses on emergency communications, we need to look at what can go wrong.
You could have a local problem: your power supply goes bad, taking out #1, or a tree is blown down in your yard taking out #2 or #3.
A neighborhood problem: A truck plows into a power pole, a transformer blows during severe weather, or your local sub-station blows up taking out #4 or #5.
A regional problem: An earthquake, hurricane, or ice storm results in damage to the distribution lines (#6) or the power station (#7)
A national / global problem: Disasters, labor unrest or transportation problems block fuel delivery, or a nearby power grid becomes unstable forcing a shutdown in adjacent grids, taking out #8 or #9.
Wow, when you look at it this way – it’s amazing that we have reliable electrical power at all! So, what’s your backup plan?
Probably the most common solution is to have a standby generator. This approach is used by most critical facilities such as hospitals, commercial radio and TV stations, emergency operations centers, etc., and by many home owners. Whole house generators are available as are smaller limited use generators feeding a subset of the home perhaps only providing power to the furnace and the refrigerator, and some lights. Of course for radio operators that limited use will include the ham shack 🙂 So with this solution we cut away a lot of the complexity of the power distribution system:
1) The power supply that converts the AC from the wall into the correct DC voltage for your radio needs to be operational (this may be built into your radio, or it may be a separate component)
2) The house wiring needs to be correct and intact;
7) The generators in the (your) power plant need to be operational;
8) The power plant (generator) needs to have fuel (gasoline, natural gas, propane)
Clearly a lot simpler, so less can go wrong. Assuming you can disconnect your home from the power lines in the back yard, you can eliminate #9, and you can almost ignore any neighborhood, regional, or national problems (for a while). You can get around the tree falling down issue by running dedicated lines (extension cords) directly to the equipment you want to run – if you planned ahead.
But this has costs. First there is the cost of the generator and installation – a whole house generator can run into the tens of thousands of dollars – and even a small standalone generator can run you several hundred bucks, and that’s just the monetary costs. You also need to maintain the generator and test it regularly, if it fails you are out of luck (#7). You are still dependent on fuel (#8). This can become problematic in the case of regional disasters where the gas stations may be unable to pump gas (if it is available) and refilling propane tanks may be impossible.
Let’s see if we can reduce this even more. Let’s start with a battery – one that supplies the DC voltage needed by the transceiver. That eliminates #1. Since we aren’t using the house wiring at all, #2 is covered. There is no generator so #7 is gone. That leaves only #8 – since a battery is only a storage system, how are we going to recharge it? What fuel can we use?
We can recharge it with a generator or a car (that brings #7 back into the list) but then we will need to ‘recharge’ the generator with some fuel source. Alternatively, we go green. Solar panels and / or wind generators can easily provide the ‘fuel’ for the battery. Because even a small home wind generator requires some form of tower – which could be damaged by that pesky tree that keeps falling over, let’s settle on a simple, portable solar panel set. Pull it out, set it up, plug it in, and wait for dawn. Hopefully you sized your battery to handle the radio traffic overnight, and sized your solar panels to both recharge the battery and provide power for radio operations during the day. Factor in that not every day is a beautiful sunny experience, so add some extra watt-hours for cloudy days. Not a bad solution for the delivery of power, but there is more that just the quantity of energy to think about.
What else can be a problem?
There are two other aspects that arise when you are your own power company – you become responsible for both the quality of the power and you are responsible for keeping things running.
Your transceiver is a very sensitive piece of equipment, and it can be thrown off by a number of things – including your choice of power system. The problems generally come down to two aspects: line noise and radio frequency interference (RFI).
Starting at the simplest side, a battery provides high quality energy. While it lasts, it delivers pure DC voltage with no ripples, pops, or noise.
We need to recharge it and the recharge system can be noisy. Note: if you are using ‘smart batteries’ they add electronics to control the discharge voltage and so they can be noisy even when discharging. Some of the noise can be on the line – as the charge controller adjusts charging rates and voltages. These can impact the transmission side of your radio, potentially causing drop outs and adding noise to your outgoing transmission. These controllers can also cause RFI – pops, sizzles, and hums on the radio frequencies. This won’t impact your transmissions, but it can cause havoc on the receive side of things.
If you add a generator into the mix, the same problems are increased. Generators can be incredibly noisy on the RF side – so keep it as far away from your antenna as is practical. They can also provide ‘dirty’ AC line power.
The power companies, bless their hearts, spend literally hundreds of million of dollars to provide as close to pure sinusoidal AC to your house as possible. And your radio power supply depends on that beautifully smooth wave to provide clean DC to your radio.
The backyard generator from the local big box store may not do the same. It often provides clunky square-wave like profiles, with hums, spikes and drop-outs. This doesn’t matter to your refrigerator, but is not good for your radio or your radio power supply. In addition, with all those moving parts (stator rings, whirling magnets, and so forth) they can actually generate more RF noise than your transmitter. So, if you go the generator path – check reviews by radio operators before you sink cash into a noise farm.
Moving up to shore power – things get better and worse. As I said above, the power companies want to deliver clean power to your house, and they generally do. But there are a lot of parts to the delivery chain. Substations and transformers can inject noise into the line – and even more into the RF spectrum. There are lots of stories and techniques for hunting down RFI in the power grid, and, once it is brought to their attention, the companies are pretty good about fixing the problems. But if we are talking about an emergency situation – all bets are off. Not only can damaged grid components generate tons of noise, but during the recovery the focus is on getting any kind of power to the customers, they will worry about clean later. Again, the more complex the system, the more parts are out of your control, but you do get a lot of convenience from just walking into the radio shack and pressing the power button on your rig.
Safety and Maintenance
You are your own safety officer! When you are delivering power you have to wear a lot of hats.
Generator Safety and Maintenance
If you are delivering 120V AC from a generator – you might be in for a shock – literally. Shock hazards, whether from a ratty old extension cord of questionable integrity, or due to badly engineered connections are a real risk. Emergency generator power during storms adds in the risk of water shorting out your system. And remember – generators get hot, and they emit potentially poisonous gasses. So make sure that you place the generator on a level, non-flammable surface that is clear from any nearby fuel sources (gasoline, dried grass, piles of newspaper, you get the idea) and do not operate a generator inside, neither your house or the garage. For generators, maintenance items include making sure you have fresh fuel (either gas or propane on site), the oil has been changed according to the manufacturer’s schedule, the generator has been tested, you know how long it will run under what conditions, etc. And test it on a regular schedule – the last thing you want is to confidently run out to fire up the genny and have it not start.
First, remember that a battery is an energy storage device. There is a lot of chemical energy in there. Remember all those stories of batteries exploding? So these things also take care and feeding. Storing them appropriately is important for safety.
They can emit explosive gasses when charging so think through when and where you plan to charge them, the back of the closet in the kid’s room may not be a good choice, neither is next to the water heater. You will need to make sure there is a good charge on the batteries – notice, I did not say keep them full.
Batteries have a lifespan – ranging from a few hundred charge / discharge cycles to a lifespan measured in years. But eventually they die – you don’t want that to happen on the day you need the battery.
Many batteries have a maximum lifespan when they are kept around 80% full, not continually topped off. Depending on the battery type, they will have an effective lower discharge limit as well. Factor this in when sizing your battery. A 1000 W-Hr battery may only give you an effective 500 W-Hrs for normal use, or 750 if you are willing to damage the battery. Many batteries prefer to be discharged before they are recharged – follow the manufacturer’s guideline’s and build a maintenance schedule for you emergency power. Then remember to follow your schedule. Plan your work, then work your plan.
So that wraps up our tour of the Power System leg of the radio station tripod. We looked at sources of power, we looked at the delivery paths. We looked at what is needed to get AC to your ham shack, and some of the many, many things that can interrupt that flow. We did a quick dive into simplifying the needed infrastructure going from generators to renewable energy sources to pure battery power. Then we did a quick look at the quality of the power, since that also contributes to the operation of your radio station. Next we looked at some of the causes of both line noise and RFI, and made some suggestions about what can be done to reduce that noise. Finally, emergency power requires that you take on the job of the power company in many ways – importantly you are responsible for safety and maintenance of your emergency power system.
Remember to check out the other two legs of your Ham radio station tripod:
For some additional info on Power systems for Amateur Radio – check out this video by Dave Casler: