September 2016 – K7OJL Ham Radio Blog

Letting Out the “Magic Smoke”

An effective QRP station needs a stable, regulated power source to provide power to the transmitter, the receiver (or a transceiver), an antenna tuner, as well as keep a battery topped off for use while off the power grid.

I felt like this would be a good first kit to solder together and ordered a Tuna Power System Kit from Rex (W1REX at QRPME.com). The kit arrived and the build instructions on the web looked very straight forward. However, the diode included with the kit would only work with small batteries. An option was to put in a diode with a higher power rating rather than the supplied 1N4004. So, I decided to order a small quantity of 1N4001 diodes. I found a set of ten diodes at Adafruit.com for $5.75 including shipping. Turn around on the order was very fast and I received the diodes three days later.

The instructions, as I said, seemed to be pretty straight forward, so I began building. It took me about four hours over two days to do the build, which included unsoldering several resistors and moving them to the right spot after making a pretty significant error.

I had a lot of problem reading the color codes on the resistors, even with the help of a 3x magnifying glass. Further, my inexpensive volt-ohm-meter (VOM) wasn’t accurate enough to figure out the exact resistance (even when shorted, the VOM would read a resistance of 2.5 ohms). There were some missing components and a couple of components in the kit that weren’t needed (several zero ohm resistors). Rex provides outstanding customer service and the situation was corrected literally over night.

The power supply takes an input voltage from 15 to 20 volts DC and provides constant 12v out to five RCA jacks and to the battery connection. It also provides a 5v output to a USB connector and 5 volts and 12 volts to a molex connector. The suggested input device was a 20v power supply to an old printer. At the local thrift shop I found a 20v out power supply to an HP printer, cut off the plug at the end so that it would connect to the input jack.

Tuna Power System With the Smoke Let Out

After soldering everything up, I did some testing with my VOM and felt I was ready to plug it in. Within seconds the IC chip caught fire between pins 13 and 14. Obviously, something was not right.

So, I’ve ordered another Tuna Power System Kit … plus several other items.

First, I ordered a 10x / 20x magnifying glass from Amazon. This glass has two LED lights which provide very nice illumination. The resistors are now much easier to read and it’s much easier to inspect the solder connections on the board.

Secondly, I needed a bench power supply … one where I could set the voltage and the current with shorts prevention. The problem with the first unit was probably a short circuit. A short circuit means that the device will pull as much current as the source will give, and in this case the 20v old printer supply would ship up to 20 amps on demand, more than enough to burn up the integrated circuit and surrounding components. A bench supply that would detect a short and shut down before something is damaged or catches fire was now a requirement for my kit building activities. After some research, I ordered one from Amazon.

Thirdly, I needed a much more accurate VOM that also included the ability to test and read capacitors. I ordered that from Amazon.

Finally, I needed a much finer point on the soldering iron to better prevent shorts between components. I found these also on Amazon.

All of that has arrived. The new power supply is now on the bench and ready for assembly. Nopefully no “magic smoke” this time.

Boy Scouts

Another of the ham radio operators here in the area is Paul Crookston, KB7ZIH. He’s been directly involved in getting the new BYU-Hawaii repeater up and operational. Tonight he worked with a group of boy scouts on their radio merit badge. He took his radio over and had the boys talk with several others of us who were standing by. A couple of the boys expressed some interest and hopefully there’ll be a way for them to act on that interest. The Boy Scouts of America operates an excellent website, K2BSA.net, and has been activating a number of locations using the K2BSA portable call sign. In October the scouts will be holding their Jamboree On The Air event. We’ll need to figure out how to get some of the local troops involved in JOTA.

So, now that the J-Pole is up and operational, my Yaesu FT-8900 easily gets into the BYU-H repeater. In fact, both of my HT’s easily get into the repeater at 5 watts output into a better-than-a-rubber-duck antenna. Monitoring the repeater this evening shows some activity on the machine. However, there’s a LOT of QRM here. I’m going to ask him to put a tone on the output side of the repeater which should go a long way towards squelching the QRM.

2 Meter / 70 CM J-Pole Antenna Back Up

This antenna is a J-Pole antenna I purchased on the Internet in April, 2015 from Arrow Antennas after I arrived in Hawaii. I have a similar antenna in storage back on the mainland. I’ll leave this antenna here with someone who needs one when I leave in February, 2017.

I decided to put this antenna on top of a 16′ painter pole I was going to use for my HF dipole antenna. The dipole mount wouldn’t be in the way of attaching the J-Pole above it.

The aluminum bracket to to attach the J-Pole fit nicely onto the painter pole. However, the bolts supplied by the manufacturer weren’t threaded the entire length and I ran out of thread before the bracket could be firmly attached. Another (!) trip to Ace Hardware to buy two more fully threaded bolts ($1.07 including tax) solved that problem.

I wanted the installation to be removable when I leave next February with literally no trace left behind. I decided to put a post in the ground, a PVC pipe on the post, and then insert the pianter pole into the PVC pipe. I could then attach the pole to the roof at the 10′ level and use two guy ropes at the 16′ level to help stabilize the pole. I bought a four foot dowel 1 1/2″ in diameter, cut a point into one end, and then pounded it into the ground about 18 inches. That would provide the bottom support. The house has a small sidewalk that goes along the side of the house. The edge of the roof overhang is directly above the edge of the sidewalk. Consequently the antenna pole would go straight up past the roof where it could be attached.

I next cut a four foot section of 1 3/4″ PVC pipe from Ace Hardware. That slipped over the dowel. The dowel stood about 2 1/2 feet above the ground. The painter pole would be inserted into the PVC pipe and rest on top of the dowel. The painter pole is about 1 5/8″ in diameter, a nice tight fit into the PVC pipe.

The painter pole is inserted into the PVC pipe, attached to the roof, and stands about 18′ tall. Two guy ropes go from the top down to the edge of the roof to provide additional stability (the picture was taken after the pole was secured to the roof.). The guy ropes are hanging down in the picture and were attached to the edge of the roof after the picture was taken. The ropes from the pulley are for the HF dipole antenna that will be put up next.

There are three repeaters in the area that can potentially be reached from my location. One is about a mile away at BYU-Hawaii campus. Another is thirteen miles west. That repeater is currently running low power because of a problem with the amplifier. When that gets fixed (it’s been down for several months) and I can finally hear it again, that repeater is linked into the state-wide emergency network of repeaters. Finally there’s another repeater nineteen miles south which I can now reach with this antenna.

2 Meter Ground Plane Antenna

Because of the move from Laie to Hau’ula a couple of weeks ago, I had to take down my antennas and put them back up again in the new location. The first antenna to go back up and into operation is a 2 meter ground plane antenna.

I took the original idea for the antenna from an article on hamuniverse.com. I bought some 14 gauge bar wire and some small bolts and nuts from Lowe’s along with 25′ of RG58 coax and an SO239 panel adaptor from Radio Shack. I built it as described in the link.

I threaded the coax up through a two foot section of 1″ PVC pipe from Ace Hardware. I used Gorilla Duct Tape (also from Ace) to hold the SO239 down on the top of the PVC pipe. Since the coax has PL259 connectors on either end, it mated up very nicely with the ground plane antenna.

The PVC pipe is attached to a 12′ painter pole that I bought at Lowe’s for this purpose. I drove a 1 3/4″ piece of PVC pipe (also from Ace) into the ground so that about 18″ were above the ground and stuck the bottom of the painter pole into the PVC pipe and the attached the pole to the fence. It has very low wind loading and has stood quite firm during the recent tropical storm that came through.

This antenna is one of four antennas going up at my new address in Hau’ula. This antenna is connected to a Motorola 2 meter radio operating simplex on 147.450 Mhz attached to the AllStar network via a Raspberry Pi. See the AllStar category for information on that setup. The antenna has been an excellent performer. Together with the 20 watts output from the Motorola radio, I have excellent coverage throughout the Hau’ula and Laie area.

Recently on Ham Radio 360

I recently discovered this podcast and listen to it on my iPhone. The recent two Workbench segments sold me on the podcasts. They were about bench power supplies (I bought one based on this podcast) and the first of a two-part series on oscilloscopes. I’ve always been fascinated by ‘scopes and have a very incapable one that uses an Android tablet. I’ve also got two other (very cheap) DIY kits that I haven’t put together, yet. I’m not expecting much from either of those kits, but I should begin some actual learning guided by what I’ve learned in the oscilloscope series.

Cale Nelson’s episode on ham radio satellites was excellent. I’ll be listening to that one again when I get a capable antenna and can actually try to work someone on a satellite.