In a recent article we did a deep dive into assembling a portable off grid radio station that was light and minimalist enough to be carried a fairly long distance by one person, but still had enough functionality to be an effective communications tool. That goal necessarily required using QRP to keep the weight and size within a manageable limit. But what about radio amateurs who want or need portability with standard 100 watt transmit power? Portable QRO is certainly possible if we plan carefully
Setting expectations.
In our last “challenge” we focused carefully on weight and calculated everything down to the last ounce. This time weight will still matter, up to a point, but it’s not productive to fuss over ounces on a project that could potentially go as high as 200 pounds.
We also will not be going into detail about radios, antennas, and other accessories, and instead focus mostly on the power source because for most amateurs that is the hardest problem to solve.
As before we need to define what attributes we want our portable QRO power source to have. I came up with a list of qualifications that offers features and performance without losing the original mission of the project:
- The power source will support 100 watt transmit power with a realistic duty cycle on HF, and 25 watts VHF/UHF.
- Power from a vehicle or generator permanently mounted on a vehicle/RV/trailer does not count.
- This project assumes two eight hour operating sessions over a 48 hour period.
- The system will be transported, set up, and operated by one person.
- The power source and fuel may be transported to the operating site in/on nothing larger than an average sized personal vehicle.
- The power source must be manually portable by one person for a short distance, such as from a parking lot. Wheeled carts/wagons are permitted as long as they also fit into the same vehicle that brought the rest of the equipment.
The HF radio.
If you already have a 100 watt radio for your home station and do not have resources for a second rig to devote exclusively to portable QRO operation, then the decision is made for you. You’ll have to incorporate your existing radio into your portable QRO plans even if it’s not an ideal rig for portable use.
If you do not have an HF rig but are considering getting one, then you have the advantage of being able to plan for dual base/portable QRO operation. Although we are not obsessing on weight this time around, it’s still a factor. I did a little research and it seems that 100 watt HF rigs weigh from around 4.5 pounds all the way up to 22 pounds, with the average being around 13 pounds.
Of special note is the Yaesu FT-857D. This extremely popular and respected radio was born for QRO portable. It weighs less than five pounds and includes VHF/UHF coverage so you would not need a separate VHF radio. I have some misgivings about the 857, namely the menus are deep and tedious and there is a lot going on in one box, but the stuff I don’t like about it is the stuff that makes it such a great portable.
The power source.
Having enough solar and battery capacity to push a 100 watt radio with any kind of reasonable duty cycle is possible within our stated portability criteria, but wow, it’s going to be close!
A 100 watt solar panel weighs 16 pounds and measures 47.3 x 21.3 x 1.4 inches. Since we know that solar panels do not produce full power all the time, we will need at least two panels and preferably three to compensate.
Then we’ll need a battery. How much battery do you need? We went over that a few articles ago. It’s all about duty cycle. We will go with a base power capacity of two 100 amp-hour batteries. Connected to two 100 watt solar panels, with decent sun and a reasonable duty cycle you should be able to operate all day and still stay ahead of your battery. An acceptable compromise would be two solar panels but only one battery. In strong sun, the panels will do most of the work.
The main theme to keep in mind is that the less sun you have, the more battery you’ll need. As I’ve alluded to many times on this blog, off grid ham radio is a form of gambling.
So now have two solar panels (32 pounds), plus two batteries (120-140 lbs). That’s a total of 150-170 pounds just for a power source. Can you fit this stuff in/on an average personal car, keeping in mind you’ll also need to have room for the rest of your gear? Maybe. We haven’t broken our own rules yet, but it’s getting close.
The purpose of this analysis is to show that portable QRO with renewable energy is possible, but it’s quite a reach. On top of all this, you’re still not going to have a lot of power to work with. That’s a lot of weight to lug around for a modest energy payoff.
The generator may be your savior. Or will it?
The biggest advantage of a generator is that you’ll have steady power all the time, even at night. An inexpensive 3500 watt gas generator weighs in around 100 pounds. At 50% load, it will run about sixteen hours on four gallons of gas. Assuming a run of eight hours per day, four gallons should pull you through a weekend. We might get away with less gas because we won’t need even a half load. Gasoline weighs about six pounds per gallon, or 24 pounds for a weekend supply. The weight of the generator plus fuel comes to 124 pounds; less than the solar panels and batteries.
Using a generator for portable QRO still presents the same transportation issues: Can you fit the 3500 watt generator in an average car and still have room for everything else? Probably, but it will be tight. There is also a fire safety concern regarding the gas.
Another possibility is an inverter generator. If you’re unfamiliar with these nifty powerhouses, there just happens to be a previous Off Grid Ham article covering them in detail. The weight of inverter generators is typically less than comparable conventional versions. They use less gas and make a lot less noise. The big downer is that they are expensive. If you have the money to go First Class, the inverter generator is where you should be.
STOCK PHOTO
There is one last option that might be a reasonable compromise of weight, power, and physical size: Harbor Freight has a neat little 900 watt generator that weighs less than 40 pounds and will run at 50% capacity for five hours on a half gallon of gas. Applying our runtime requirements, that comes to less than 1 gallon/6 pounds.
The mini generator and a weekend’s worth of gas weigh less than just one battery in our solar option! And this setup will easily fit in a car. Even better news: The generator retails for $114.00; I’ve seen it under $100 on sale. I know many Off Grid Ham readers have (justifiable) reservations about Harbor Freight products, but I have used this generator myself and it belies Harbor Freight’s reputation and performs well above its price tag. It is a 2-cycle engine, so make sure you use the appropriate oil/gas mix.
Adding it all up.
The solar and conventional generator choices both come it at 125-170 pounds, including fuel. An inverter generator plus fuel will check in around 60 pounds and takes up much less space. Lastly, the mini generator, our lightest, smallest, and least expensive option, comes to about 50 pounds including fuel.
So the power alone for your portable QRO station will be 50-170 pounds depending on what option you choose. All will fit in an average car, but the solar and conventional generator options are pushing the envelope and may not work at all for small cars.
Then we must add the radio, antennas, and associated hardware. Let’s use that thirteen pound average for a radio, and add another fifteen pounds for antennas, feedlines, and other assorted gear. Finally, Add another 8-10 pounds for a VHF radio (if not using a an FT-857). plus antenna and coax.
The bottom line is your complete portable QRO radio is going to top out between 80-200 pounds, with varying space demands.
Getting ahead of the critics.
In the past I’ve received feedback from amateurs who have done off grid portable QRO with much lighter and smaller equipment. Let’s deal with it up front: They are not wrong. It absolutely can be done. The issue I have is that they never talk about duty cycle, and they never talk about how much money it will cost. One amateur used a $1400 ultra light folding solar panel and a $1000 lithium battery. I admire these successful projects; I’m even envious. But I can’t afford to live in a world where it costs $2400.00 just to turn the juice on, and I’m guessing most of my readers can’t either.
I’m not trying to talk anyone into or out of any particular path, nor do I think less of anyone who does not do things my way. My purpose is to point out a few realities and offer options to those whose budget for an entire portable QRO station is less than what others spend on one single solar panel. The lucky few with the means to buy high tech lightweight gear or have corporate sponsors giving them stuff for free have my highest respect. Everyone else, the regular people, follow me!
I can only assume your just feeding the power from the mini generator to a battery charger to keep the battery charged. I have one, its output is electrically dirty, so the battery becomes the filter. One good aspect of the mini generator being 2 cycle is that up here in the arctic where I live they run well at sub zero temperatures. Good article, lots of food for thought.
Hi Lt. Heit, Using the generator to push a battery charger will work, but then in addition to the generator you also have to transport a battery and a charger. I also forgot to mention in my article that if you’re running off a generator, then you’ll need a power supply too. They don’t necessarily add a lot of bulk to the overall package, but it is a consideration.
You also bring up a good point: Most of the non-inverter generators marketed for consumer use do not have very clean outputs. This is not as bad as it sounds. The radio power supply has its own internal filters, and you can always get a “power conditioner” such as those used for computers. Power conditioners are often integrated into power strips so they do not add much extra weight or space to the portable QRO setup.
As for cold weather operations, where I live we get some hellish winters, but not anything like the Arctic, so I’ll defer to you and others’ experience on that one. Cold weather operating is something of a sub-speacialty within ham radio because it requires specific skills to be done successfully.
Arctic ops are a challenge. No matter the time of year it’s a challenge to operate distance. Winter is a while new challeng. I have built my Elecraft KX3 system around batteries and a solar set up for the summer operations, and winter around a generator for recharging the batteries. The northern lights while beautiful, don’t do much to charge batteries.
Shelter is number one priority, followed by heat, then radio ops can begin. One only has to try driving stakes into frozen ground at 50 below and windy to appreciate prior planning for such adventures.
I plan to do a couple of trips above the arctic circle this winter to test my otherwise portable system. Thank you for the reply, 73
Lt. Mike
Mike, if you are ever inclined to document your cold weather operations I would love to use your experiences and observations as the basis for an Off Grid Ham article. I live in the upper midwest USA and here we do indeed know what serious winters are, but nothing compares to Alaska. As you correctly point out, extreme cold operations is much more than just layering on an extra sweater.
Along with the battery perhaps consider the large capacitor sold by MFJ or auto stereo shops for big amps. This will provide power on the peaks needed by a QRO transmitter and perhaps not cause the generator to “sag” when max power is needed.
Hi Don, a large capacitor will give a “boost” but keep in mind that the capacitor charges off the battery. As the battery runs down, it will take longer and longer to charge the capacitor. Also, a capacitor will never charge to a voltage higher than the charging source. These factors limit the effectiveness of the “boost” capacitor. As for using them on a generator, I’d say that if a 100 watt radio causes a generator to “sag” then there is something wrong with either the generator or the radio.
These little gen-sets are a God-send, they are often quite cheap and have way more uses than just portable radio operation.
We survived Hurricane Patricia in Mexico, at one point a frightening CAT 5+ storm with 320kmph winds, the strongest ever measured and the eye passed not 20km south of me. As our casa is brick and mortar, amazingly we survived almost unscathed, although the laminas from my breezeway were in pieces and in the neighbors yard. Patricia was frightening, this brick house just vibrated in the wind, water constantly blew under the door, and I have absolutely no doubt had it been made of wood as most homes are in Canada or the USA are, it would have been gone with me in it, in scattered in splintered pieces.
As the storm eased I fired up a little 900 watt gen set similar to the one depicted, disconnected our power from the ‘grid’ service, (we have an old fashioned knife switch) and using a double male ‘suicide’ extension cord I plugged it into a duplex power outlet. Our house has many lights, all 9 watt LED, and the entire house instantly lit up nice and bright. .. and we had plenty of power to spare for the frig. Stove is LPG gas so no problem. Even out little microwave worked if you timed things right, although that was the limit.
Of course my wire antenna (a 1/2 square) was on the ground, but a quick repair and for $50 pesos I hired the young guy next door who shinnied 60 or 70′ up the palm tree (in his bare feet, they do that well here) and he tied the end of my antenna back up… easy money for him. The band was open and with 50 watts into an efficient gain wire antenna, emergency communications would have been no problema.
For net operations on the HF low bands, if this is your ‘thing’, I strongly recommend building antennas designed to favor NVIS on 3.5 or 7mhz. These antennas are especially designed to take advantage of high angles of radiation, good out to about 350-400 miles. A simple dipole with a reflector wire on the ground, 5% longer is just like a 2 element beam pointed straaight up. .19 of a wavelength spacing is ideal but not essential, this makes most of the energy go up, and is much quieter especially on 80 meters in the summer at night.
Richard VA7AA Punta Perula Mexico
Richard, it sounds like you have the off grid thing down pretty good! I also appreciate your views on NVIS. In fact, I’m such a believer that I did a whole article on the topic some time ago. NVIS is important because in a crisis situation, it’s probably not going to be important or relevant to run DX because are you really going to care about communicating with another continent? Some folks may have a specific and special need for DX, but 95% of the hams out there will be more concerned about their geographic region in the 100-500 mile range that is too far for FM simplex and too far for traditional ionospheric skip. NVIS is the perfect sweet spot. I urge all amateurs to familiarize themselves with it.
I really like those little inverters in the 2KW range. They’re light weight, amazingly quiet, and extremely fuel efficient. But as you said they can be pretty expensive. I think I paid around $800 for the 2 kilowatt Yamaha I have. I also have a 9.5 KW Generac gasoline generator that can just about run the entire house, but it’s so awkward to set up, so heavy and noisy that I don’t like to use it unless I absolutely have to. The last few power outages we had I used the Yamaha, running the sump pumps, some lights and all of my amateur radio gear off it. Oh, and the coffee maker. Can’t forget that! Prices on inverters have been coming down. I’ve seen 2KW ones now going in the $500 range. I have a 9.5KW Generac but that thing is a beast to get set up and moved into position. Even worse, it can be an SOB to get started if it’s in a bad mood. And it isn’t exactly quiet, either.
— a major problem with generators for most people is fuel storage. Gasoline goes, well, I was going to say it “goes bad”, but that’s not really true. What happens is that over time the additives in the fuel degrade and can cause issues in the engines it is used in, like gumming up carburetors, plugging injectors, and altering the burn characteristics of the fuel. The cheap plastic fuel containers most people use doesn’t help things much either. There are products like Sta-bil out there which can help, but in my experience they don’t help very much. Another issue is ethanol blended fuels. It’s almost impossible to avoid the stuff these days, but a lot of small engine manufacturers still recommend avoiding the stuff.
Inverter generators should be something every off grid amateur aspires to have. Unfortunately, they are still a big hit in the wallet. The Gold Standard of inverter generators, the Honda eu2000i, will set you back about $1000. But wow, what a great machine. And with proper care it’s one of the few things made today that can truly be a “lifetime investment”. I have a 1400 watt Honda (non-inverter) that was pulled out of a junk pile and fixed up. I do not know how many hours are on it , but it’s close to 30 years old and whoever had it before me kicked the hell out of it. Yet, it’s still chugging along. As for fuel storage & preservation, that is a complex topic with more opinions than facts. I’m thinking of doing an entire article about it.
The Yamaha’s specifications are identical to the Honda inverter, but I bought the Yamaha because I can get parts and service right at my motorcycle dealer.
I think doing an article about fuel and fuel storage is a great idea. There are problems with storing gasoline for long periods of time. Avoid the plastic storage containers if possible. Avoid using ethanol blended fuels for generators if at all possible. Modern vehicles can handle the stuff but a lot of small engines still have problems with ethanol. I try to keep 10 gallons of fresh fuel on hand, enough to keep both the inverter and the big generator going for 48+ hours. But my main fuel supply is my truck. it has a 40 gallon extended range fuel tank and I have a siphon kit ready to go just in case.
One thing I’ve always wondered is if those fuel stabilizers actually work as advertised. My personal experience is that they don’t seem to make much difference with stored fuel. For years I use the stuff religiously in small engines and even my motorcycles before they went into storage, and every year I still had problems. Then back in, oh, 2010 or so, I forgot to use it in my bike, a BMW, before it went into storage for the winter and, well, no problems at all in the spring. I haven’t used the stuff since in any of my equipment and I actually seem to have less problems with the fuel systems in the equipment than when I did use.
You gave me a great idea Randall, and I’m currently researching for an article about storage/use/rotation of fuel. As always, a lot of what appears on Off Grid Ham is the direct result of reader comments, questions, and suggestions.
NVIS is very important for local comms and regional training. However when a large storm such as Michael hits it may clean out a wider than 500 mile wide path. That means survivors may need capability to communicate longer distances. I believe after suffering many Hurricanes in Florida over the last 50 years and an Earthquake in Ecuador that it is wise to have both short haul and long distance comms. I have a NVIS antenna nand a vertical end fed so that I can work 80, 40 or 20 meters. I have a Spider 12 meter pole and a home brew PVC 35 foot mast. These would allow me to erect a satisfactory antenna in the aftermath of a big storm.
In addition to several 12 v 7 AH gell cells I also have a larger 12 volt 700 cranking amp Everstart battery. At $49 This is an economical alternate power source when more than QRP is necessary. Plans are to supplement this with a couple solar panels and gas generators.
I have a ham friend living on the Alabama/Florida boarder who has lost all power. He had a 10KW generator which worked for 1 day then died. Fortunately he had the paperwork and was able to get to Lowes to exchange generators. Biggest problem is being handicaped and not supposed to lift more thaan 10 pounds, he has to carry 5 gal jerry cans of gas in a wheel borrow to the generator. So, I suggest keeping your generators in good operating condition with weekly checkouts and provisions for obtaining, storing and moving fuel.
Since the same equipment can be used for both NVIS and DX, it’s easy to do both. I do not want to give readers the impression that one needs “special” gear for each method. This Off Grid Ham article from 2015 discusses NVIS in more detail.
DX is also essential for hams in Hawaii and any other extreme remote location. If contact with the mainland USA was needed and amateur radio was the only option, it obviously will require throwing a signal a lot farther than what NVIS can do.
what I don’t often see is anyone talking about power out VS input voltage.
yaesu is great at having power out at low battery voltage. (why I bout so many of them)
yet sadly if you use a yaesu radio off grid or a few years you find a huge design flaw. They put DC voltage on the ceramic filters… so after living off grid in an unheated home, they fail.
another fail of 857 is that the average power out (not PEP) is very low. so 100W kenwood that only has something like 40W out PEP at 12.5V gets a way better copy at distance than the yaesu at full voltage.
my solution was to use an 817 with a 45W external amplifier. It takes way less power than the 857 I have and has a way higher average power output. (at least on SSB)
in the end of all my testing and trying to find the best radio for off grid. my alinco dx77 is the only thing still running that gets good signal to the other side.
so my point is that off grid not only tests things like low battery voltage, it tests things like storage conditions. and yaesu might seem ideal, but they fail. every one of them failed, from the pocket VX-R3 (have 2 dead ones) to full size mobile radios. They all have the same design flaw.
kenwood is not much better with its huge power fade with anything less than 13.8V, but it at least they can still here others transmit off grid.
meant to try the icom HF radios, but ran out of money…
and this was my final lesson on off grid.
you have whatever you have to start with. You get nothing new once you get there. Errors can’t be fixed past that point. (and that is where I am at now)
Battery voltage is always going to be an issue no matter what radio is being used; radio amateurs should plan accordingly. Spacecase0’s experience illustrates just how hard off grid QRO can be.
The Yaesu 857 is an excellent radio but it does come with some baggage. This reinforces the importance of field testing your equipment and understanding the quirks before you are in a situation that really matters.
100 watt radios will deplete a battery quickly if talk time is long. I usually run the power back to 50 watts unless more is needed. I also talk less and listen more. Trained well by wife there.
I also purchased a boost power module on internet from China, about $6.00- I believe, that will provide 13.8 volts at 15 amps even from a low battery. Yes, I also got a digital volt meter to assure the battery does not drop below 11 volts. So a bit more power can be run, but I don’t expect to need it very often.
The find boost module is not necessary at the 50 watt level on my Yaesu Transceiver.
The real key is to use the best efficient antenna you can make or afford.
Hi Don, talk time as a ratio to receive time, known as duty cycle in ham radio lingo, has been discussed on this blog before and it is an important factor in how long your battery will go. Reducing power to 50 watts is an excellent strategy. It will not make a meaningful difference in signal integrity but will save a lot of battery.
“Battery boosters” and similar devices are effective up to a point, but in the end, the battery has a finite amount of capacity. The laws of physics are absolute so plan accordingly.