I’ve had a very busy weekend that kept me away from working on my portable design much. I was able to stop by HRO and Frys and get the rest of the parts I needed.
My next entry will dig into selecting a case to haul this gear around and some quick and dirty mounting of the circuit shown. I’ll likely build something out of wood and 3D printed parts initially and think about a more permanent solution if that attempt doesn’t turn out to be good enough.
Not sure when that will happen, since next weekend will be keep me even busier then the last. Hopefully, I’ll have it all done by the end of the month and I can take it with me to the Belton hamfest.
This post is the 6th in a series – Especially since this month is national preparedness month, investigating off-the-grid power is my next stage of going portable. I’d like to have something light, rugged, safe, cheap and that can run my ICOM 7100 for at nearly a day (but not at full power). There are clearly going to be some compromises involved in this choice.
I settled on 35 Ah battery as my benchmark to cost against. An amp-hour is the ability to pull one amp for one hour, or 10 amps for 1/10 of an hour… It’s not quite that simple, since you can’t pull too much power from certain kinds of devices reliably. If you have a device that pulls 20 amps, and you use it for 20 minutes, then the amp-hours used would be 20 (amps) x .333 (hours), or 6.67 AH. Therefore, if you plan to transmit 20% time on HF: 20 amps x 0.333 hours = 6.67 amp hours and on receive the radio pulls 1.5 amps x 0.66 hours = 1.0 amp hours that means the radio will consume almost 8 amps in an hour. My ‘back of the napkin’ calculations say: I should be able to operate for about 4 hours at higher power levels. Sounds like I better plan on having an amp meter in my circuit if I want to have predictable usage.
For batteries, there are a number of possibilities in the marketplace:
This table is based on some quantitative analysis but I’d call it primarily a qualitative perspective. Feel free to comment with better info if you find have it.
Since I don’t know how often I will use this portable solution yet, I didn’t want to invest in higher cost batteries or solar recharging… They’ll be time for that later, if I become addicted to being in the field. Right now I just wanted something ‘good enough’ to be usable and get started, so I went with the AGM solution.
Once you go with a battery based solution, you need to think about charging. Do I want to have a solution where I can switch over to battery if there is a power outage or will I depend on remembering to charge the battery before I need it? Although the switching option is appealing, I think I’ll hold off on that as well since it should be easy enough to add later.
How about connecting to the various devices? I want something flexible, standard and commonly available. I convinced myself that Anderson Powerpoles from Powerwerx are the way to go. Besides there is an HRO in Plano (near my house and they have a huge selection of options).
Next time, I will cover the circuit and configuration I ended up putting in place, as well as what Powerpole based options I purchased to get started.
Humor you may get a charge out of:
Did you hear the one about the radio operator arrested for battery? The charges were dropped because he only resisted a little.
The first field test of the radio and antenna went off successfully. Though the VHF contest was a bit of a bust, I did make one contact on 6 meters that was 138 miles away. I looked on line at 6 meter band propagation and didn’t see much going on – so I gave up and reconfigured for 17 meters.
It was fairly active and I talked with a number of people including one in Belize and on in Canada north of Washington state. He was also portable and had been trying the VHF contest but also gave up – that made me feel a bit better.
Empty milk jug or similar – this is great ballast to keep the antenna from falling over (see above).
Below is a picture of the setup I was working from. It was 92°F but not too bad in the shade. As you can see, I am operating using a 1970s era power supply, so power is my next dimension to tackle. Closely followed by my solution for carting all this around effectively.
The antenna is easily the second most important component of a portable station and unfortunately it is also the area that is most easy to compromise on. I wanted to have one that would support multiple bands and yet still be small and flexible enough to carry with me and set up in minutes (by myself).
There are a number of types of antennas that may fit that bill:
A multiband wire antenna (like a G5RV) – These have some of the same issues as the long wire although they shouldn’t require an antenna tuner.
Mobile antennas – Little verticals are easy to switch out. Carrying around the various antenna resonators to support the bands would be a bit unwieldy. Verticals can be set up quickly but the costs can quickly add up if you want to work on multiple bands. Small verticals like this are always a compromise on performance as well. An alternative is a screwdriver antenna that adjusts to support multiple bands.
Buddipole – I’ve known a number of hams over the years who have purchase these. They are not cheap but they do work on everything from 40M up through 2M with the default configuration. They are light (9.5 lbs.) and easy to carry. If you get the deluxe package, you get a tripod to mount the antenna on and pretty much everything you need. The antenna can be set up in minutes and it seems like the ideal solution for my needs.
I am sure there are others that I’ve missed but those are the alternatives I investigated.
I eventually ended up getting the Buddipole and hope to put it through its paces on the September VHF contest this weekend – more on that later.
Just to round out this post about antennas I’ll add: I heard the other day about two antennas getting married. The wedding was nothing to call home about, but the reception was amazing.
Probably the most important decision when pulling together a mobile station is the radio. You need to understand what you want to do with it and the radios capabilities.. I was looking for one that could handle HF, VHF and be all mode.
For about the last decade the only radios I’ve had were ICOM radios. The most versatile ICOM radio I could find that aligned to what I want to do is the IC-7100.
This radio is fairly small with a separate control head that can be mounted in a range of positions, away from the box that does the heavy lifting. It can transmit across a wide range of ham bands and modes (CW, SSB, digital and FM), that I am interested. At home, I operate mostly digital but I think single sideband will be more common when operating portable. That’s also the mode most of the mobile stations I hear run on 17M. Hopefully the bands will behave well enough to keep 17M open for a while, since it is a great band that balances antenna size and propagation.
One thing intimidating thing about this radio is the instruction manual. It probably weighs in more than the radio, if you print it out. The 7100 is complex and wonderful, where all the buttons have multiple functions and it has a touch screen as well. It is definitely going to take a while to get comfortable operating this thing.
I was able to load in all the DSTAR repeaters in the world on the SD card and program numerous repeaters across north, central and southern Texas as well as a few of my favorite HF frequencies. I did end up buying some software to help load up the frequencies though.
I’ll have to go into the details a bit more in future posts but this is enough to get started.
Over the weekend I was thinking about the elements of an HF “Go Kit”. At a high level the main components would be:
Antenna and coax
Power source (battery source would be ideal)
Computer (though not really necessary very useful)
Tools and documentation (Antenna analyzer, Manuals, flash light, actual tools …)
A rugged case that can hold all these stuff safely.
I am sure I am forgetting some things that will make it more usable but this is a good start. Now I just need to researching and buying stuff to test it out. Fortunately, there are numerous guides on the Internet concerning what others have done with Go Kits.
I have been a ham radio operator (AD5EN) since the early 70s and have only worked portable on field day (like most folks).
Now I have an issue that will probably require me to be remote for most weekends. So I thought: “Why not take my radio with me?” I want to see what it will take to get set up quickly, remotely and hopefully without a connection to “the grid“.
I hope to put out a series of posts about what I take with me and how things go. We’ll see if I have the discipline to get this done. I plan to post about once a week on taking amateur radio on the road.