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
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.
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!