N1GY- The simple Approach to Ham Radio
Finally here is a picture of the new antenna mount. It still has the "Tiger Tails" and the same stud mount, only the bracket and the location has changed. Now the lid of the box can be opened without having to disconnect the coax jumper.
Also removed the two battery covers since the closed box makes it impossible to read the meters that are mountedon the covers. I simply built a new wiring harness to duplicate what was built into the covers and placed one battery terminals up and one terminals down. Due to the confines of the box they will never touch.
Just barely visible on the top of the antenna bracket is the Powerpole set that allows checking the voltage of the batteries and charging of same. No shown in this image, I have added a small extension to the Powerpole at the base of the antenna that doubles the available Powerpole sets so that charging and monitoring voltage can take place simultaneously.
Most of this article has been about the JT-270M as a mobility scooter radio, however it also lends itself to creating a "manpack" radio quite easily. Because the radio is so small it could easily be mounted on the chest strap of a back pack with a mic clip for the hand mic on the other chest strap. A couple of 7AH batteries in parallel could be carried in the back pack and an antenna could easily be attached to the pack frame or to any rigid panel attached to the pack. The use of "tiger tails" makes the need for a ground plane superfluous and the whole package does not weigh all that much. There would still be room in the pack for the other necessities of the situation like clothes, food, maps and other essentials. By changing the batteries to a different shape one could easily package it as a shoulder bag portable as well.
The mic clip was mounted on the side of the basket.
This is a shot that is taken pretty much from eye level as I would view the radio when sitting on the scooter. I did discover one limitation after I made the current installation. I cannot drive the scooter forward off the lift. The radio box runs smack into the lift arm. So, now I have to back the scooter off the lift. I did think about turning the scooter 180 degrees.and thus putting the radio box on the outside away from the lift arm but there may not be enough room between the scooter and the tailgate to do that.
Here is a side view of the new set-up. I may yet move the antenna which right now is behind the radio mounted to the lower portion of the box. I did rebuild the rig so that the installation was a bit neater. I moved the external speaker a bit to the right in the picture so I could aim it more vertically. I did try to take a shot of the antenna but I could not get it to stay vertical when placing it on the web page. It kept wanting to display sideways which was not the shot as I took it. I will try again later.
The JT-270M as a Portable Go-Kit Radio and as a Mobility Scooter Radio.
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.
A few days ago, I got the usual monthly newsletter from Quicksilver Radio Products. In it, John Bee, the proprietor and a good friend of mine, announced that in spite of statements to the contrary made a few years ago, he was now going to sell a limited number of transceivers. The new addition to his product line was the Jetstream JT-270M. This is a new radio manufactured in China and its claim to fame is that it is a 10 watt mobile rig. It comes complete with it's own programming software and USB cable. Since I am now the owner of what is referred to as a "mobility scooter" after my medical problems earlier in the year, I thought it might make a neat way to add ham radio to the scooter. The scooter came with a plastic basket that attaches to the front of the scooter. The basket looks sturdy enough, however, in order to load the scooter into my minivan, (another new purchase) the basket must be removed from it's mount and stored separately.
This is no big problem, but it did give me the idea that if I were to mount the JT-270M and its associated accessories like a battery and an antenna on the basket, it would make a relatively light portable rig with twice the power of the usual HT. The antenna connection on the JT-270M is the usual SO-239 connector so the radio can be easily connected to an external antenna such as the ones that are found in every severe weather shelter in our local county school system. This would certainly be more powerful than an HT with a "rubber dummy load" antenna. I will not go into the specifics of the actual construction since every setup will be unique to the operator and his or her needs. I have placed a few pictures of the "Radio in a Basket" so that you might see some aspect that would work for your situationType your paragraph here.
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.
I made a couple of changes today to the rig shown above. I added a pigtail to the power wiring to allow me to recharge the batteries without having to dismount the box from the scooter. I also moved the antenna set up from the forward end of the right side to the aft end of the same side. No changes were necessary in the coax jumper but a new mount was built that screws to the top of the lid of the box. This places the antenna clear of the radio since it now is aft of the external speaker. I had a scrap of 1/8" thick x 1" aluminum flat stock that already had holes drilled in it from another antenna project long forgotten. The antenna mount and the tiger tails transferred over easily and the project was back on the scooter in almost no time at all. Another little gadget that I made today was a voltmeter. I used a very inexpensive digital voltmeter from All Electronics and wired it up to a short length of 16 gauge zip cord with Powerpoles on the far end. THis can be plugged into the charging pigtail that protrudes from the box to check voltage and then removed and stored in the pocket behind the seat along with the antenna radiator when not in use.
Today, October 11, 2018, I made a MAJOR CHANGE to the scooter radio. It has been removed from the basket where it has resided since 2014. I added a plastic "ammo" box to the cane holder I built. on the right side of the seat. I will add pictures as soon as I can take them, (it is dark right now).
The "ammo" can is one of the smaller ones sold by Harbor Freight but it carries both 7 AH SLA batteries quite easily. The radio and the external speaker are both mounted on top of the lid since the batteries take up all of the space inside the box. THe same antenna system is used, mounted on the right side of the box away from the operator. I have also eliminated the external switch since the power switch is right there on the radio.
Believe it or not, the whole thing fits into the van on the scooter lift with one exception. I do have to unscrew the antenna radiator from the mount. It is a bit too tall to fit inside the van. The ammo box is one I have had around for several years, complete with several holes that were drilled to accomodate a previous project. Most of the holes have been covered by the installation of the radio and the external speaker. The holes that did not get covered that way have been blanked out with small pieces of ABS plastic. The radio is mounted vertically, with the controls and display on top mainly because it is positioned near my right side and I would not be able to see the display if it were mounted horizontally.
I was going to try to create a fold over mechanism for the antenna mount but for now it is easier just to dismount the radiator and store it in the pocket at the back of the seat until it is needed. The basket has now been returned to the job of carrying all the freebies and other goodies one picks up at any major hamfest. As I have said a number of times on this web site and elsewhere, few projects stay as they were originally designed for very long. As we see how our projects work in the field, change is about the only constant.
Assuming decent weather tomorrow, I will take some pictures and do some testing, the result of which will wind up here.
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.
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.
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 translate 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: