To the left is a photo of the inside front cover of the user manual for the JT-270MH. I typed a copy of the frequency list and stapled it to the inside front cover of the manual. I had to go down to size 8 so the font would fit but it is still readable.
The changes were numerous. First I was able to place two 7 AH SLA batteries in parallel. I installed a speaker with a headphones jack inside the box rather than attached to the outside of the box as before. The taller ammo can provided space above the batteries for the charger, the microphone, the manual and the portable antenna. The headphone jack automatically switches the receive audio from the speaker to the phones when they are plugged in. I also added a voltmeter in parallel with the radio. The current draw of the meter is between 5 to 15 ma. so power drain is not a problem. A switch controls both the meter and the radio. Two sets of Power Pole connectors allow for recharging the batteries and also for supplying power to various accessories like USB lights or USB chargers.
It is somewhat unusual for me to do such a complete redesign after so little time, but when I added the speaker to the old setup I realized that that way just did not work properly. A complete redo was the only option. The ABS panel covers not only all the wiring but also hides the batteries and allowed me to add a fairly professional looking speaker installation by drilling a series of holes through the ABS panel following a grid drawn on the back of the panel. A couple of small scraps of the same material were heated and bent to form a pair of clamps to hold the speaker in place. More scraps, this time of 1/2" plywood were screwed to the sides of the can to brace the batteries and to provide support for the ABS panel which was secured with small screws.
This turned out to be a really simple project that anyone with even a rudimentary set of tools can accomplish. I used a simple hacksaw to cut the aluminum angle and even a standard set of drill bits will get through the metal of the ammo can. A pair of metal shears was used to trim the lid to clear the bolt heads. I added a couple of pull tabs made of vinyl tape for the manual and a wire tie for the Altoids Tin. That removes any difficulty in retrieving these items since the can is kind of deep
It is a couple of days since I wrote the above and I can now report that the antenna I ordered has arrived and been put into service. The results were just what I was hoping for. The radio puts out full power with the antenna on both bands and it would appear that the counterpoise wire is not really needed. I also procured a charger for the battery from my local Batteries Plus and the battery charges up easily. The latter was a bit of a surprise since the battery has been sitting around my radio room for a long time. I did consider mounting this new unit on my mobility scooter but after some thought I decided to leave well enough alone. One of my pals did suggest a visit to Lowes to get a shoulder strap for a gas trimmer as an addition to the ex-ammo can that provided the start to this whole project. Maybe tomorrow....
I wound up ordering a new strap from a company on the west coast called Strapworks. It is bright dayglo orange and the fittings match the ones on the ammo can well. It has occured to me since I wrote this page that one could call this "Radio in a box MK III" It certainly is the smallest of the three and probably the lightest as well.
When we used this radio to do a little "railroad mobile" operating at the Florida Railroad Museum several weeks ago, we discovered that there was a significant amount of noise because of operating from an open train car. It is simply not feasible to use a closed air conditioned railroad car as there would be no way to get an antenna into a usable position. Therefore, a few mods needed to be made to the 25 watt portable radio to alleviate the noise problem.
I decided to add an external speaker that I had purchased at the same time I purchased the 25 watt radio. Space considerations meant that the speaker had to be mounted on the outside of the ex ammo can I had used as a carrying container for the radio and battery. An 3.5 mm mono earphone jack was added to the speaker enclosure so that the operator can block out the engine noise by using headphones. This is not the most sleek arrangement, but it will alleviate the problem of hearing contacts while the train is moving. Here is a photo of the added speaker with the phones jack.
This photo shows the external speaker with the phones jack on the enclosure. Plugging the earphones into the jack automatically shuts off the speaker so that the full audio energy is sent to the earphones.
The other side of the box shows the pigtail mounted to the box to permit the addition of a counterpoise if needed.
UPDATE: Big changes to the portable 25 watt rig I wrote about above. The other day I realized that I could pick up a much larger surplus ammo can in which to place the JT-270MH. For less than $16 I became the proud owner of a brand new 50 cal. ammo can. The old container pictured above was deconstructed and I spent a pleasant Sunday designing and building the new unit.
The other day I chanced upon a new offering from an old friend at Quicksilver Radio Products. John has been a good friend for many years and he often has new and useful products for the amateur community. The item in question was a "radio in a box" complete with battery power and an antenna. Now I have no argument with the cost, it is a great little product and I buy from John on a regular basis. In this case I looked around the radio room at N1GY and discovered that I already had almost all of the components on hand. An empty ammo can, a 7 AH SLA battery, a 25 watt dual band radio that I bought at Orlando Hamcation this year, programmed and then put away as a spare, some aluminum angle material and most of the little bits like a switch, an SO-239 and I obviously had enough Powerpole connectors since I had just received an order from Quicksilver of 100 sets.
In fairly short order the project was begun. After verifying that everything would fit, I fabricated a piece of aluminum angle to form a battery hold-down. Another chunk of the same aluminum made a bracket for one side of the radio and a hole through the outer ammo can provided the mount for the other side of the radio. Yet another chunk of the aluminum angle material was drilled to mount an SO-239 mount for the antenna with a short run of RG-8X coax to the back of the transceiver. Also mounted on this last piece was a switch to turn the radio on and off, and a Powerpole connection to allow recharging of the battery and/or external power.
Once the parts were assembled, I used nail polish remover to remove most of the markings on the outside of the ex ammo can (with somewhat underwhelming results, I might add) and added a label made with glossy photo paper identifying the contents lest anyone see the old ammo can and get paranoid. On the other side of the can I added a short pigtail with a single powerpole on it so I could add a counterpoise (if necessary)
Some thoughts about the choice of radio. The unit is a Jetstream JT-270MH a 25 watt version of the same radio I have written about before when I radio-equipped my mobility scooter. The current draw for the higher powered unit is about 3.5 amps on transmit at full power. However, it can easily be turned down to a lower power level at which point the current draw is about 1.8 amps at 10 watts or even 1 amp at 5 watts. Also that is only on transmit, the draw on receive is 78 milliamps so one 7 amp SLA battery should be good for at least 24 hours.
The box is open. Over the battery on the left I have taped the programming CD just in case. The microphone is stored down in the middle with the coil cord tucked between the radio and the controls and connections above it. The manual with the frequency list is tucked underneath the radio at the bottom right. Beside the battery is an Altoids Tin with the counterpoise wire, the programming cable and a right angle adapter for the SO-239 at top right. To the right is a photo of the contents of the Altoids Tin.
N1GY- The simple Approach to Ham Radio
Here it is with the mic connected and turned on. The only thing missing is the antenna which will arrive tomorrow by UPS.
Here is the outside of the ammo can with the new label. Note the cutouts in the edge of the lid to accommodate the various bolts used to secure parts on the inside
A Portable 25 Watt Dual Band Transceiver OR
The Radio In A Box Mk. III