Li-Ion Battery Pack

Here’s a little battery pack I put together for use as an external, portable power source for my YouKits HB-1B.  I wanted something relatively lightweight and inexpensive that would put out at least 13 volts.  This solution has fit the bill, so far.

There isn’t too much to it.  I already had some Li-Ion cells on hand, so I wanted to make use of them.  They are 18650 cells with a 6000 maH rating.  I haven’t actually verified the claimed capacity but most cells tend to be somewhat over-rated. These particular cells are the “protected” type; each cell contains some circuitry that prevents overcharge and over-discharge.  There are much cheaper unprotected cells but I’d rather be safe than sorry.

Battery pack with cable stowed
Battery pack with cable stowed

To put it together, I bought a 4-cell battery holder for 18650-size cells.  With 4 fully charged cells, the voltage can exceed 16 volts.  To keep the voltage below 14 volts (the maximum for my HB-1B), I put 3 silicon diodes in series with the output.  This brings the voltage down to about 13.7 volts with fully charged cells.  I also added a 2-amp fuse and an Anderson Powerpole connector.

Li-Ion battery pack layout
Li-Ion battery pack layout

To package it, I had a sandwich-sized Rubbermaid container that wasn’t being used.  It turned out to be the perfect size to hold everything snugly.  When not in use, everything is neatly tucked inside the container.  In use, I lift one corner of the lid to bring out the connector.

Battery pack as I normally use it
Battery pack as I normally use it

For charging, I remove the cells from the holder and charge them with a Nitecore D4 charger.  This is a 4-bay smart charger.  It automatically detects the type of battery inserted and applies the proper charging method.  Each bay works independently, so balanced charging is not an issue.  The D4 works with a variety of battery types (Ni-Cad, NiMH, Li-Ion, etc.) so it is a handy accessory in the shack.

Nitecore D4 smart charger. Each cell is charged independently.
Nitecore D4 smart charger. Each cell is charged independently.

I haven’t done any formal testing of this battery arrangement, but it has provided adequate power for an afternoon of portable operating.  For extended operating sessions, I throw 4 extra cells in my backpack that I can swap in if needed.

It’s not the most elegant solution but it works fine.

72, Craig WB3GCK

AlexLoop Mounting

In my 40+ years in Amateur Radio, the AlexLoop Walkham was the first commercially-made HF antenna I ever bought.  I wanted something for those spur-of-the-moment QRP outings when I want to get on the air quickly and not have to deal with putting wires into trees.  The AlexLoop fit the bill nicely.  There’s probably nothing novel or new here but here’s how I mount the AlexLoop for operation.

Tripod Mounting.  While I was waiting for the AlexLoop to arrive from Brazil, I ordered a Vivitar VPT-1250 tripod from a vendor on eBay for less than $20.  The VPT-1250 is super lightweight and stores nicely in the AlexLoop’s carrying bag.  It’s a decent tripod for casual use but for something like a SOTA activation under windy conditions, you’d be better off with something more robust.

vivitar_tripod_2
Vivitar VPT-1250 Tripod with PVC pipe installed.

To use the VPT-1250, I removed the pan/tilt head.  I cut a 4-inch piece of 1/2-inch PVC pipe, which I slide over the center post of the tripod.  I added a bit of electrical tape to both the tripod post and the PVC pipe to give a slight friction fit.  The base of the AlexLoop slides onto the PVC pipe.

Picnic Table Mounting.  This is an idea I got from AK4LP’s QRZ page. For mounting to a table, I take the same piece of PVC pipe and insert it into a 1/2-inch PVC elbow fitting.  I sanded the end of the PVC pipe so it was easier to remove from the elbow fitting.

table_mount_1
Table mount attached

I just use a 2-inch C-clamp to secure the pipe and elbow fitting to the side of the table.  Again, the base of the AlexLoop just slides over the pipe.  I store the PVC parts and the C-clamp in the tripod’s nylon carrying bag.  When a picnic table is available, this mount goes to together faster than setting up the tripod.

table_mount_2
AlexLoop base mounted to table

If anyone knows the ham who came up with the picnic table mounting idea, let me know in the comments and I’ll make sure he gets credit for it.

UPDATE (11/16/2015):  I remember now where I got the idea for the picnic table mount and have updated the post accordingly.  Many thanks to Bob AK4LP for coming up with this simple and novel idea!  Be sure to check out his page on QRZ.com for pictures of his picnic table portable setup.  I had the pleasure of working him at that Smith Mountain Lake location back in 2013 while I was camping in Maryland.

73, Craig WB3GCK

Line Isolator

One of my favorite portable antennas is a 30-ft wire fed through a 9:1 unun.  This type of antenna generally the uses coax feeder as a counterpoise, since the 9:1 unun configuration provides no line isolation.  Most of the time, this has worked well for me with no issues with stray RF getting back into the equipment.

On a couple of occasions, my Elecraft T1 auto tuner began to act up, refusing to load up on one or more bands. (Running through the T1’s diagnostic mode always seems to restore operation to normal.)  I’ve also had one of my keyers behave erratically once or twice.  Since this has only happened when using the 9:1 unun, my suspicion is that common-mode RF currents on the coax shield are the culprit.

My proposed solution for this is to use a line isolator between the tuner and the coax feeder.  (Note:  Using a line isolator at the antenna end of the coax would defeat the purpose in using the coax as a counterpoise.)  A quick survey of my junk box stash of parts showed I had everything I need to build a line isolator from scratch.

Parts List

  • RG-174/U coax (approximately 24 inches)
  • FT-140-43 ferrite core
  • (2) BNC-F chassis mount connectors
  • Hammond Manufacturing 1591MSBK Enclosure (2.2 x 3.3 x 0.8 inches)

Construction

This is a very simple project.  You can build one in well under an hour.

  • The RG-174 coax is wound on the FT-140-43 core for a total of 10 turns.  Take note of how the 5th turn goes across the core.  This makes installation in the case a little easier.  I used a couple of small nylon tie-wraps to hold the windings in place.
  • Drill the holes for each of the BNC connectors and wired up the choke, as shown.  I used a 5/64-inch drill bit and had to use a reamer to get the holes to the right size for the BNC connectors I used.
  • Solder the coax to the BNC connectors.
  • To mechanically secure the core, I used a piece of two-sided foam mounting tape to mount the choke to the bottom of the case.  As an additional precaution, I put a piece of packing foam on top of the choke before attaching the lid.  This foam provides a slight downward pressure on the choke to prevent it from shaking loose in the case during handling.
line_isolator_core
Core winding
isolator_core_installed
Core installed in case

Testing

I don’t have access to the equipment necessary to do any type of exhaustive testing of the line isolator.  In lieu of that, I hooked it up to a 50-ohm dummy load and checked the SWR.  It was basically flat from 160M through 6M.  While that tells me nothing about how effective it is in reducing common-mode currents, I at least know I didn’t make any serious screw-ups in building it.

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Completed line isolator

In Operation

Well, this part will have to wait until I have a chance to get out for some portable operating.  I want to make sure that the line isolator doesn’t affect the T1’s ability to tune my antenna.  Since the initial problems were very intermittent, only time will tell if I solved those problems or not.  I’ll be sure to update this post with any new insights I gain.

Update 5/16/2017:

Since this article seems to get a lot of traffic, I figured it was time for a long-overdue update.  Not long after this post was published, I tested this 1:1 unun in line with the coax to my 30-foot wire and 9:1 unun.  As I suspected it might, it affected the tuning of the antenna.  One or two bands wouldn’t load up properly.  This made sense to me, since this antenna configuration relies on the shield of the coax for the counterpoise.  So, there’s some RF on the coax shield by design.  This device obviously is blocking some RF, as it should.  I haven’t pursued it further and I still have done any measurements to determine its effectiveness.  With a change of connectors on the output side, it could definitely be useful as a 1:1 balun, I suppose.

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Tilt Stand for the YouKits HB-1B

This is another one of those projects that took longer to write up than to build.

The top facing controls on “trail-friendly” radios like the YouKits HB-1B and others are very convenient when you’re sitting on the ground out in the middle of nowhere. When operating “picnic-table-portable,” however, the display can sometimes be a little hard to read. For those situations, I came up with a little tilt stand using some stuff I had on hand.

tiltstand-1
Magnet applied to the corner brace.

The tilt stand I came up with has a grand total of two parts. First is a steel inside corner brace. You can find these at any hardware store. The one I used is 3/4-inch on each side and 1.5 inches long. You can use whatever size gives you the amount of tilt you’re looking for. The other item is a small but powerful magnet. The one I used is about the size of a nickel. I secured it to the corner brace using some Goop adhesive. To use the tilt stand, just use the magnet to put it on the bottom of the HB-1B, as shown in the pictures.

tiltstand-2
Tilt stand attached to the radio

This tilt stand works best when you have rubber feet on the bottom of the radio, as I have on mine. In fact, I added those the first time I used the radio, to keep it from sliding around on my desk.

tiltstand-3
Tilt stand in use

This little gizmo will a permanent part of my HB-1B portable station for those “picnic-table-portable” operations.

73, Craig WB3GCK

Clipboard Keyer

I purchased a set of Palm Mini paddles for portable operating a while back. I love the magnet base, which attaches nicely to the side of my little YouKits HB-1B transceiver. However, in some situations — like sitting on the ground or operating from inside my truck — that isn’t always the most convenient arrangement for me. Here’s a little hack I came up with to solve that problem.

clipboard-1
Figure 1. Washers attached to clipboard
clipboard-2
Figure 2. Paddles attached to clipboard

I purchased an inexpensive 6-inch by 9-inch, acrylic clipboard at my local office supply store. I used some GOOP adhesive to attach two steel washers to the clipboard, as shown in Figure 1. I made sure that the washers lined up with the magnets on the base of the paddles. Figure 2 shows the paddles attached to the clipboard. Figure 3 shows the clipboard in use during a recent outing. For transport, the little clipboard fits in the small plastic container I use for the HB-1B and accessories.

clipboard-3
Figure 3. Clipboard & paddles in use

For less than $2.00, this little accessory makes portable operating a bit more convenient.

73, Craig WB3GCK

Guy Ring for a 31-ft Jackite Pole

Here’s a neat idea I “borrowed” from my QRP buddy, Ed Breneiser WA3WSJ. When I need my Jackite pole to be self-supporting and I don’t have to carry stuff very far, I usually opt for my Jackite ground mount stake. It’s quick and effective but too heavy to carry on a hike. Not to mention the need for a hammer (or large rock) to drive it into the ground. So, in situations where the ground mount is impractical, I use a set of guy lines to hold the pole up. Here’s a simple way that Ed came up with for securing the guy lines to a 31-foot Jackite pole.

It’s pretty simple to build one of these…

Pick up a 2-inch, Schedule 40, PVC end-cap at your local hardware store. You’ll also need some nylon line. I used some 1/8-inch braided nylon rope from my local Walmart store.

  • Drill a 1.75-inch hole in the top, using a hole saw attached to your drill. When slid over the Jackite pole, the guy ring should rest on top of the bottom (largest) section of the pole.
  • Drill three evenly spaced holes around the outside of the end cap. Use a drill size just large enough to accept the size of line you are using.
  • Drill a second hole about 0.5 inch to the left of each of the three original holes. So, you should wind up with 3 pairs of holes around the end cap.
  • Cut three pieces of line. I made each of mine about 9 feet long.
    Thread the line through the end cap holes, as shown in the pictures, and secure the end with a knot.
  • For the other end of each line, I tied a taut line hitch. This allows you to adjust the tension on each guy line.
PVC end-cap drilled out
PVC end-cap drilled out

My completed guying kit consists of the guy ring with the lines attached and four small plastic tent stakes. Everything fits nicely in a zip-lock bag. (I sometimes throw a lightweight, plastic mallet/stake puller in my backpack to drive in the stakes.) To use it, I drive in one of the tent stakes where the pole will go and three equally spaced tent stakes around it. Put these three tent stakes about 5 or 6 feet away from the center stake. Take the bottom cap off of your pole and place the pole over the center tent stake. The center tent stake should prevent the bottom of the pole from kicking out. Attach the guy lines to the three outer tent stakes and adjust the taut line hitches for the proper tension. That’s all there is to it.

Attaching the guy lines
Attaching the guy lines
Completed guy ring
Completed guy ring

I also built one of these for my 28-foot Jackite pole. For this pole, I used a 1.5-inch end cap. I used a 1.5-inch hole saw to make the large hole. The hole was a bit too small, so I did some filing on it to get the proper fit. The final hole size is approximately 1.6 inches. Again, the guy ring should rest on top of the bottom section. Everything else is the same as for the 31-foot pole.

Thanks again to WA3WSJ for sharing this idea with me.

73, Craig WB3GCK