Introduction: UHF Ham Radio on the Ultra Cheap
I've written about ham radio on the cheap. Now it's ham radio on the ULTRA cheap! How cheap? Hows about being able to get on the air from home or in the car with a usable signal while spending less the $10 on a radio?
What was long ago a hobby for those with deep pockets or strong electronics skills has gradually come down in price to were anyone can jump on board. Chinese radios have changed the face of the hobby making it affordable for all. At the time of writing, a Baofeng VHF/UHF can be had for under $25 shipped.
You may be asking... So if you can get a useful VHF/UHF radio for $25, why bother with what I'm doing?
The Baofeng radios and their brethren while being amazing deals for the money, have very poor receive selectivity. In other words, the receivers will quickly saturate when near strong signals regardless of their frequency. This makes the radio annoying to use in dense urban areas for example due to all the squawks and buzzes it's going to pickup. Radios from the pro companies intended for commercial users, even the basic construction site type radios, will have much more selective receivers.
Also, as DIY'ers we often have junk boxes loaded with miscellaneous carcasses of expired whatnots. A good scrounger can put this together for free or darn near it. Need a ham radio that's not worth stealing to use in a beater car in a bad neighborhood? Want a ham radio for some crazy harebrained idea that might result in it getting ruined? Hows about just doing it so you can go against the grain and sound just as good on the air as those guys spending a grand on a "Look Important Feel Important" Motorola radio? Well here's your project!
What you'll need...
1) Basic electronics skills and tools
2) a usable radio that will cover the VHF or UHF ham band
3) a good electronics junk pile to raid or a few bucks to spend online
4) a way to program the radio (there's always someone in the ham radio community that can do this)
Step 1: Sourcing and Programming the Radio
The FCC has mandated that commercial and public safety radio users switch to what is called narrow band if they haven't already done so. This has caused a flood of cheap 2nd hand gear to show up on the surplus markets. You can get some amazing deals on some really fancy 2 way radios! The not so fancy ones are practically going for dirt if you look in the right places.
Most cities have surplus stores were retired government stuff is sold off. Most will also host events called "hamfests" were ham radio guys go to buy and sell radio gear and electronics. These two places can yield sweet deals on 2nd hand radios. Anywhere that uses 2 way radios may just have some retired stuff laying around for the asking. Get asking!
You are looking for radios that will cover the 144-148mhz range or the 440-450mhz range. These will cover the 2 meter and 70 cm (VHF and UHF) ham bands. Looking up the radio model number on Google should yield enough data to tell you what band it's on and it's power output. A great many handhelds are in the 2w-5w range. If you have a choice, go for the higher powered ones. It seems to be easier to find UHF ham band capable radios than it is VHF. Those are the breaks in budget ham land.
What about programming frequencies into it?
CHIRP software (free download) covers a great many Chinese radios and a few from the more well known brands. Check the CHIRP website for a full list of what it can program. Radios not covered by CHIRP will need to be programmed with the manufacturers software, once again, something you may be able to get done at the ham radio club. Every ham radio club has at least one guy that knows how to program radios. Getting your radio programmed may be the biggest stumbling block here and access to the local ham radio club is a HUGE help in doing this.
If it looks like you'll be messing with radio hacking, get an "octopus cable" from the web. It's a USB cable with multiple connectors to fit a multitude of radio brands. It doesn't work on all but covers many. Those are under $10 typically.
The radio in the pic is a house branded Uniform Warehouse radio. It's Chinese made but I couldn't figure out who actually made it for them. I did find the programming software free online and my octopus cable programmed it.
Step 2: A Word About the Radio's Antenna Connector
The antenna connectors on handheld 2 way radios basically fall into two categories, a stud type or a coaxial type. The stud type is just a hole that looks like a bolt would screw into. The coaxial will be a hole with some kind of insulating insert inside and a male or female connection in the center.
The coaxial type is superior if you are going to connect the radio to a remote mounted antenna. The stud type is much more rugged but is not really intended for a remote mount antenna. Adapters are available but yield poor results.
The one pictured is male SMA connector. It's very common on Chinese radios.
Step 3: Powering Your Radio
Part of the deal with finding cheap radios is you'll likely find just the radio. No charger, no battery, maybe no antenna. The main reason behind this instructable is to give you two cheap options to power these discarded radios and give them a new life.
In the pic you'll see the back of a Kenwood worksite radio with battery removed. You'll see the battery connections and ID plate. The ID plate will list radio manufacturer, model number, and if you're lucky, the operating voltage.
The battery connections can vary from radio to radio. On this model, it's easy to figure out which is the - (negative) side. It's the connection tab that's bolted right to the radios metal frame. Not all are this easy so you may need a little radio geek help to figure out which is + and which is -.
The manufacturer info and model number will tell you what frequency range, power output, and number of channels the radio supports. It can also be used to figure out what the radio's operating voltage is. If you can't find the radio's operating voltage anywhere, just look for a replacement battery online. Most battery vendors will tell you what the voltage and capacity of the battery is.
Long ago handheld radios were powered from NICAD or NIMH batteries. This means the operating voltage will be some multiple of 1.2vdc. If the radio was made after about the late 1990's, there's a good chance it used lithium batteries meaning it's operating voltage is likely to be a multiple of 3.7vdc. Small low powered radios tending to run on 3.7vdc and stuff like construction site or security guard radios often running on 7.4vdc to achieve higher output.
Since battery voltage varies as it runs down, the radio will be tolerant of a bit of voltage variation. Some digging online for the manufacturer's manual will give you the operating range. A few volts higher than battery voltage is generally not an issue but try to match the factory pack voltage as best as possible. Some radios will incessantly beep if voltage is too low to warn the user it's time to charge the battery.
Step 4: Option 1, Setting Up Your Ultra Cheap Ham Radio for Home or Car Use
In the pic you will see a circuit board strapped to the back of the radio. That's a voltage regulator board. These are easy to find on ebay and amazon for under $5 shipped. I've scored them as low as a couple of bucks shipped. This board will take the input voltage of your car or power supply and step it down to what the radio operates on.
There's plenty of ways to do this but these boards have a built in LED voltmeter that can be switched to display input and output voltage. Adjustment of the output voltage is via a small trim pot on the board you turn with a jewelers screwdriver. For a couple of bucks each, you can't beat it!
First set the board up by feeding it 12vdc with your power supply. Input and output terminals are clearly marked on the board. Monitor the output voltage either via onboard meter or an external multimeter. Turn the pot to adjust voltage up or down. When new they require maybe 8-10 turns before you start to see the output voltage move. Set it to match the battery voltage your radio would normally use. Once setup, cut off the power, solder leads from the output of the board to the power tabs on the back of the radio.
You'll need to mount the board to the back of the radio without any of its connections shorting out or touching the metal frame of the radio. I've been doing this successfully for years using RTV silicone glue. Find a good placement for the board, squirt some RTV silicone on the back side of the board, use a zip tie or rubber band to hold it in place while it dries overnight. Make sure you have enough tension holding the board to keep it in place while it dries but not enough to squeeze out all the glue and short it against the metal frame of the radio. Let it dry overnight and snip off the zip tie. Cheap, quick, and it works.
If all went well, the radio should power up off 12v. If you care to use it as part of an ultra cheap ham radio in the car just find a junked something with a cigarette lighter cord you can repurpose. Be sure to check for proper polarity before plugging it in. The board will burn out if wired incorrectly. In case you've never done this, the center pin on the cigarette lighter cord is positive and one of the outer side tabs is negative.
Step 5: Option 2 - Setting Up Your Ultra Cheap Ham Radio for 18650 Rechargeable Battery Use
In the first pic you see the back of the radio with two 18650 cell holders zip tied in place while the glue dries. In the second pic you see a single 18650 cell holder.
Why 18650 cells? These cells have become extremely popular being used in vaping devices, high powered LED flashlights, as part of laptop batteries, and even used in Tesla products. While you can buy them new, you can also scrounge them out of old laptop batteries and from vaping buddies who also seem to be upgrading.
18650's are rechargeable 3.7v lithium cells. They require special chargers but even those can be had for a couple of bucks. Here's were your scrounging skills really come into play. Find a buddy that's really into vaping. The ones that are really into it are quite likely to own the fancy chargers that check cell capacity. You want access to that charger and hopefully some "old" cells they aren't happy with. The demands these folks place on their cells are huge compared to what your radio will pull. Their trash is your treasure. The cells that wont keep up with their high current heaters are just fine for our needs here. They may even have a basic charger laying around not being used. The basic charger wont check capacity but once you have known good and matched cells, it will give you a way to charge them.
If you can't score any free cells but can get access to the fancy charger all is not lost. 18650 lithium cells are found in many different consumer products like laptop batteries and cordless tools. When a pack fails, not all the batteries are bad. Carefully opening a discarded battery pack may yield a few usable cells. They will have tabs and be welded together. Using needle nose pliers one can carefully pull the tabs off and "liberate" the cells. For more info on this, google search "reclaiming 18650 batteries from used packs" for countless articles on how to do it.
Once you have some used cells to test, take them to your buddy with the fancy charger and ask them to perform a capacity test on them. This is an automated process that the better quality chargers will do in which it charges the cell fully, runs it down, measures it's capacity, and then charges it back up. It typically takes a few hours to run. You may be pleasantly surprised to see how many good cells can be recovered from junked packs.
One more caveat about using reclaimed 18650 cells. Some of these will be protected cells, some won't. This means the cell has a protection mechanism to protect it in case of a catastrophic failure like a short circuit. Once again, google is your friend here. Educate yourself about how to identify them based on a few key outward appearance differences.
Back to wiring your radio...
I bought my battery holders from ebay at a ridiculous price of under $3 for 10 of them shipped. Hunt around and look for deals! My radio originally took a 7.5v pack so (2) 18650's in series gave me the voltage I needed. I wired the holders in series. I soldered the negative lead from one holder to the negative tab on the radio, soldered the positive lead from the other holder to the positive tab on the radio, and soldered the remaining two leads together. Since the batteries are in series, you want to use two batteries that are closely matched in capacity.
The holders were fixed in place using RTV silicone and zip tied overnight to dry. The loose wires were then carefully tucked down and glued in place with crazy glue. This is low budget remember? Stop laughing.
Step 6: The Finished Product and Some Cautions
This instructable is geared towards doing the most, with the least. It's meant for the frugal hobbyist. With frugality come some added risks. The battery compartment and wiring are somewhat exposed. In order to be able to pop the batteries out and charge them, they need to be accessible. Be careful with tossing your radio in a bag with metal objects. For added peace of mind a final dabbing of RTV silicon on any exposed connections would be a good idea. Just dont get it inside the battery holders as it will act as an insulator and you'll have no electrical flow.
While even the cheapest 18650 charger will charge up these cells, you must used balanced cells if using more than one. This guarantees equal discharge from both cells.
As an added safety feature, a 2A fuse in series with the battery leads is a good idea. Your friendly neighborhood electronics geek may just have what you need laying in their "junk" box.
now the good stuff..
I just tested my radio (pictured) on 2 of the local UHF ham repeaters. I got good signal reports and nobody was the wiser I was on a radio I paid about $1 for using reclaimed cells and $3 worth of new parts. The antenna I used was from one of my other Chinese radios but one of the factory antennas that came with my cheap radio lot worked almost as well and I'm on the fringes of coverage.
My cells came from a local vape "dragon" who said they were junk and couldn't keep up with his personal furnace. They worked great in my application and tested out at just under manufacturers rated capacity.
As an added bonus popping in another set of charged cells takes under a minute but these should last me at least 2 days worth of constant use before the radio starts to give me low battery warnings.
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Trash to Treasure