N1GY- The simple Approach to Ham Radio
Since this page was originally written, there have been some changes. The mast setup behind the seat of the scooter has been abandoned and a dual band antenna mounted on a bracket attached to the front of the basket. Two "Tiger tails", one for 2 meters and another for 70 centimeters have been secured to the same bracket and in testing with a antenna analyzer both bands have an SWR of less that 1.2 to 1. The mast presented some significant problems when dealing with any event that occurred both outdoors and indoors as the mast would have to be lowered to get through the entryway. Now there is no problem at all. I did discover that for transmitting while in motion, the 70 centimeter band is much preferred. On 2 meters there is a lot of RFI from the scooter motor and I have not been able to clear that up as yet. The scooter is still under warranty so no messing with the motor until that is out of date.
Finally a picture of the entire rig all hooked up and ready to carry up to 150 pounds of radio gear off to a public service event or a Field Day. Alternatively, it can carry hamfest buys or flea market finds back to the car. The wagon not only tows very well behind the scooter but it also folds up into a relatively small package that even I can toss into the car when needed. For those of us who are getting a little long in the tooth and whose medical or physical conditions require the use of a mobility scooter, being able to haul gear around without having to make multiple trips to and from the car makes participation in activities whether ham radio connected or just shopping or other human activities much, much easier and more enjoyable.
Here is a closeup of the hitch and bracket installed on the scooter and with the handle of the "beach wagon" connected to the hitch. A locking pin ensures that the wagon will not accidentally separate from the scooter. .
Above is a photo of the hitch partially installed on the bracket that holds the antenna for the scooter. Later I added a second smaller bolt through the upright portion of the bracket to ensure that the hitch would not move vertically either up or down.
This is a picture of the adaptor. I have to wait until it gets here to determine exactly how to mount it to the L-Bracket that holds the antenna. I will post pictures of the wagon and the scooter as soon as I have the project completed.
There has been an addition to the scooter. While not precisely a radio project in itself, the addition of a "beach wagon" that I purchased at Dick's Sporting Goods will allow me to tow the wagon loaded with all of the gear that I would need at Field Day or a public service event. This saves multiple trips back and forth to the car. I found a web site http://jcv-tow-hitch.com/ The manufacturer has a great line of hitches that attach directly to the receiver that is on many mobility scooters. Since I already use that receiver to mount the antenna for the radio in my scooter, he was kind enough to design and build a one-off adaptor that will attach to the L-Bracket that provides the base for the antenna. I modified the handle of the wagon by adding a large eye-bolt secured to a heavy-gauge aluminum bracket. This allows me the option of towing with the scooter or pulling the wagon by hand if the distances involved are close. The "beach wagon" has relatively large wheels and tows easily behind the scooter. It also folds up into a compact package which stores easily in the minivan. I had to cut a rectangular hole in the cover for the eye-bolt and mount, so my eldest daughter is going to surround the hole with "binding tape" so it doesn't wear out to soon.
This antenna worked fine but I felt it was a bit too risky if there were a lot of people close by. I wanted to get the antenna behind the driver and over most peoples heads if possible.
Below is the original scooter radio set-up. It only had one battery and the antenna was in the wrong place and of the wrong design.
An early antenna that did not work as hoped. It turned out to be too close to the operator and did not have enough of a ground plane to transmit well..
This is a close-up.of the battery system. The two 7 AH SLA batteries are connected in parallel via the Bat-Pacs on top of each battery. The Bat-Pacs provide an easy way to track the power usage of the system because each one has a built in voltmeter and one fused lead (5 amp) and one un-fused lead which is used to connect the two batteries in parallel and to recharge the batteries as needed. Also in the basket are the operating manual for the radio, the charger for the batteries and a headset built specifically for the JT-270M
Here is a close-up of the radio and power supply. The radio is a Jetstream 270M which is sold as a Leixen VV-898 in other parts of the world. It is powered by a pair of 7 AH SLA batteries in parallel through a feeder box that combines an ON-OFF switch and a voltmeter/ammeter from Quicksilver Radio Products.
This is how the mast is secured to the scooter. A preexisting mount under the back of the seat is connected by an "L" bracket from the scooter manufacturer to a socket made from PVC pipe to hold the base of the mast. Clevis pins hold both the bracket and the mast in place
This is an overall view of the scooter. The mast is at full elevation but can be easily set at an interim height for use in areas with a height limit.
The diagram on the left is of the stock wiring that is found on the stock hand mic that comes with the JT-270M. The diagram is looking at the top of the RJ-45 with the locking clip away from the viewer. The blue wire is not used (NC). The Orange wire is the VCC or V+ which powers the electret element. The white wire is chassis ground. The black wire is PTT. The Grey wire is Mic ground. The Yellow wire is Mic +. THe Red Wire is RXD and is not used in the adaptor. THe green wire is called Key and is also not used in the adaptor. Now to translate that color code into the color code for the CAT-5 cable.
Because the two diagrams are inverted relative to each other I will simply call out the color codes in this manner
Blue (NC) Brown (NC)
Orange (V+) Brown/White (V+)
White (Chassis Ground) Green (Chassis ground)
Black (PTT) Blue/White (PTT)
Grey (Mic Ground) Blue (Mic Ground)
Yellow (Mic +) Green/White (Mic +)
Red (RXD) Orange (used for receive audio + from Ext Spkr Jack)
Green (Key) Orange/White (used for rec. audio ground " )
My method for constructing the cable is relatively simple. I take 1/2 of a stock 7 foot Cat-5 jumper and slice through the outer sheath about 4 inches behind the RJ-45 for about 1 inch. I fish out the orange and orange/white pair of wires and cut them close to the RJ-45 end of the slice. I then use heat shrink to repair the slice leaving the two wires outside. I then take a mono 3.5 mm plug and solder it in the usual manner to a 12" length of RG-173 cable or any cable with 2 concentric conductors. I then solder the ground side of the plug and cable to the orange/white wire from the CAT-5. I use another very short length of heat shrink to cover that joint. Then the orange wire from the CAT-5 is soldered to the center conductor of the plug/cable and that joint is secured under heat shrink as well. This last piece of heat shrink is slid over the entire junction of the receive audio cable and the CAT-5 cable to reinforce the junction. THen the other end of the CAT-5 cable can be dressed and an anti stress grommet is placed on the cable to secure it to the enclosure.
Inside the enclosure the holes are drilled. two holes in one end of the enclosure are 1/4" for the two 3.5mm stereo jacks that will connect to the PC headset. One 1/2" hole is drilled in the opposite end for the CAT-5 cable and one more 1/2" hole is drilled in the center of the lid of the enclosure for the PTT push button switch.
The jack for the mic side of the headset has a 2K ohm resistor soldered to the terminal at the back of the jack that is closer to the ground terminal of the jack. A 10 mf polar capacitor's positive lead is soldered to the other terminal at the back of the jack. The brown/white wire is soldered to the free end of the resistor and the green/white wire is soldered to the free lead of the capacitor. The blue wire is soldered to the ground terminal of the mic jack The blue/white wire is soldered to one side of the PTT switch and the Green wire is soldered to the other side of the PTT. This completes the mic side wiring.
The jack for the earphone side of the headset gets the remaining two wires. The orange wire is soldered to both of the back terminals on the jack and the orange/white wire is soldered to the ground terminal on the jack. The lid can now be secured in place with the screws provided with the enclosure.
Make sure that the JT-270M is turned off. This is important because connecting and/or disconnecting things from the radio while it is on will cause problems. Don't ask me how I know. Plug the headset into the adaptor and plug the RJ-45 plug into the mic jack of the radio. Plug the 3.5mm mono plug into the external speaker jack at the rear of the radio. Now you can turn the radio on. Key the PTT and ask for a radio check (Identifying your station of course).
Anyone needing more information or a parts list with sources please email me via the Contact Me Page and I will be happy to answer any questions.
UPDATE 9 Recently I modified the PVC mast that holds up the antenna. Actually several changes have been made over the past several months. First the short mast in the front of the basket was abandoned in favor of a taller PVC mast that slots into a bracket under the seat so that the mast extends above and behind the rider. This places the antenna further away from the rider. The problem with this approach was that the mast is harder to store properly in the vehicle because of it's size. To deal with that, I cut the mast in half (about 32" each) and added a PVC coupler to keep the two halves together when in use. This solved the storage problem, but weakened the mast to the point where I was not happy with it's appearance.
The solution was to abandon the idea of a PVC mast altogether. A trip to my local hardware store provided a telescopic painter's extension pole that was about 36"long retracted and expanded to about 61" when extended. As a plus, this is a one hand operation. A cheap paint roller provided a method of attachment for the antenna. I got considerable help from the staff at the hardware store who removed the unnecessary parts (the roller and the metal frame it rotates around) allowing me to add a 1/4-20 bolt and Nylock nut to secure the crossbar of the antenna.
A bit of detective work at the hardware store located a 12" piece of 1-1/4" PVC pipe and the necessary bits to adapt it to the metal fitting at the back of the seat on the scooter. Some PVC cement to glue the bits together and a clevis pin and a hole drilled through the PVC to secure the bottom of the telescopic mast finished the mast part of the project. The clevis pin is removable to separate the mount from the mast for storage
Since the coax from the antenna can no longer be hidden in the mast, a few velcro straps were used to secure the coax along the length of the mast.
As soon as I get daylight tomorrow I will add some photos of the new mast in use on the scooter. This is turning into a never-ending project all by itself. Hopefully things will slow down for a while.
UPDATE: I noticed that the power output on 2 meters was less than the output on 440. I traced this to the antenna pictured in the second picture from the top above. A recheck of the SWR on 2 meters showed it was about 4:1. After several failed attempts to improve the performance of the pictured antenna I built a completely different setup. The new antenna is a vertical dipole made with two OPEK 19.5" dual band antennas. One is connected to the coax in the normal way via a standard stud mount. The other is bolted to the supporting metal that also secures the stud mount. I will post a picture tomorrow. The only downside of the new antenna is that the lower element must be removed when storing the basket. I plan on having a welder add a finger flange to the 3/8" x 24 nut that secures the element. That will make it a "no tools required" operation.
UPDATE 2: I had reasonable SWRs on both bands with the antenna set up as stated above. The problem of installing and removing the lower element made me look for a better solution. I designed and built a 18" mast which I attached to the front of the basket and mounted the feed point of the antenna on top of that. That way I would not need to assemble and disassemble the antenna. Unfortunately, for some unfathomed (as yet) reason, the SWR on both bands now reads about 2.6 to 3.5 to 1 on both bands. Obviously, this antenna project is not anywhere near completion. However, I am sure that eventually I will find a solution that works. It just remains to be seen how long that will take. Check back, I will post the results as I find them.
UPDATE3 I finally built an antenna that works with the JT-270M! This morning I went shopping at my local hardware store and constructed a new antenna mounting system based on further research that I did on line last night. The problem that had to be solved was keeping the coax far enough away from the antenna elements, particularly the lower one. Extending the antenna about 12" to the front of the basket and having the coax start its downward path at least 12" away from the antenna solved that problem. The other difficulty was that the stud mount I was using made the upper element at least 1.2" longer than the lower element . I solved that by mounting both elements to a plate of ABS that was secured to the PVC pipe extention as you can see in the bottommost picure above. Instead of using a PL-259 to connect to the antenna, I simply dressed the coax and connected each element with a soldered and crimped ring terminal. The SWR on 2 meters was less than 1.7 to 1 across the entire band and the SWR on 70 centimeters was less than 1.4 to 1also across the entire band. I think I will call that one DONE.
UPDATE 4 One last modification or accessory was added to the "radio in a basket". Because one cannot control where one might be sent during an emergency, I was concerned that the lower element of the vertical dipole was only about 1/2" off the surface that the basket might be on. So, an extention was constructed out of the same 1/2" PVC to lift the antenna about 3 feet higher. If that is not enough then an external antenna can be used. I plan to add a newly available Battery Monitor to the 7AH gel-cell battery as soon as it arrives from Quicksilver Radio Products www.qsradio.com. The owner, John Bee, N1GNV is a personal friend of mine and a vendor who most certainly has the best interests of his fellow ham radio operators upermost in everything he does. I might just add a second gel-cell to the basket just to double the endurance of the set-up.
UPDATE 5 I have added one more photo above to demonstrate a pair of new gadgets that I picked up at the Stone Mountain Hamfest. Quicksilver Radio calls them Bat-Mons but whatever the name they are pretty neat. They are best described as a plate of heavy duty plastic material which has been CNC machined so that a voltmeter, a 5 amp fuse and two Powerpole connectors can be installed along with the normal connections to a 7-9 AH Gel-cell battery. The manufacturer also mkes a larger design for a bigger gel-cell. One of the two Powerpole connections is fused, the other is un-fused. The included voltmeter is operated by a switch that is installed at one end of the device. The unfused connections are used for charging the battery and/or connecting to another battery as illustrated to make a 14 AH battery system. The company, Hardened Power Systems, makes a variety of accessories in addition to many other devices. As you may be able to tell from the last photo, I have slightly modified the "Radio in a Basket" again, raising the radio bracket a few centimeters to clear the dual batteries better. BTW- I had this unit on my scooter at the hamfest and got many compliments on the installation.
UPDATE 6 I have added a photo of the digital meter that I added to the scooter basket. It ia the one at the bottom of the photos, (thanks, Captain Obvious) Details of it's construction can be found on the "UPDATES from the Radio Room Page 2" page. I can now turn the radio on and off with the switch that also controls the digital meter. This prevents the meter from draining the battery when the unit is not in use.
UPDATE 7 The enclosure for the digital meter and switch has been updated to a standard 1"x2"x3" ABS plastic box. This allowed the enclosure to be mounted on top of the radio where it is much easier to access.
UPDATE 8 I have, with the help of the Leixen factory in China, been able to build a working headset adaptor for the JT-270M. Leixen is the company that actually makes the radio which they call the VV-898. In this country it is sold under the Jetstream brand as the JT-270M. Having obtained the proper diagram of the mic pinouts in the RJ-45 connector, I was able to tranlate those to the proper wire color code for a standard CAT-5 cable as I use in most of my headset adaptors. Here are the illustrations