Radio Technique
EVERY so often someone asks, "How can I be sure what current is being fed to my batteries by my charger?" The simple answer is: "Use an ammeter." But nothing is really simple. "What ammeter, and where do we connect it?" are the usual rejoinders. Let's answer the simple question first. The best way to connect an ammeter to your system is by cutting into a spare aileron extender cable, as shown in Fig. 1. Most sets are delivered with at least one extender cable, which is seldom used. So cut that one up. If you need the one that came with the set, or didn't receive one, contact the manufacturer. It should cost less than $5. The important thing to remember about cutting into the cable is that you only cut one wire, and then you connect the cut ends to the ammeter. Leave the other wires intact.
Radio Technique
"HEADS UP! I ain't got it!" Crunch. Now you turn off the transmitter, collapse the antenna, and walk slowly to the crash site . . . right? Wrong! Leave the transmitter on, and the antenna extended. If your airborne unit is still operating, the transmitter's signal will keep the servos centered. When you turn off the transmitter, you take a chance on having some other signal drive your servos hard against the stops, thereby destroying what was otherwise a crash survivor. Now you are the scene: The first thing you do is stir the sticks to see if the receiver is still working. Another mistake. Leave the testing for later. For now, disconnect the airborne battery pack, taking care not to get a bad burn from the wires, should a short-circuit occur somewhere. Then turn off your transmitter.
Radio Technique
You might begin with the manufacturer's literature. Idle currents are usually specified in either the sales brochure or the Owner's Handbook, or both. Typically, you will find idle currents listed for each type of servo, and for the receiver. Make a list of the equipment in your plane, then list the idle current next to each item, then add it all up, as in Fig. 1. You can't find the data in the literature you have? Get hold of back issues of Flying Models magazine. My buddy, Bob Aberle, goes to a lot of trouble to put that info into every review he writes. Bob has reviewed just about every RC system there is. He's sort of the P.G.F. Chinn of the RC crowd. You don't subscribe? Try the local library and/or your flying buddies. Still can't find out what those blasted currents should be? Refer back to Radio Technique, Model Aviation, August '79, pp. 22, etc. That's where I showed you how to make an ammeter adapter from an aileron extension cable. Make one. You will find it to be one of the most useful pieces of test equipment that you can make at home. See Fig. 2.
Radio Technique
THE Novak Radio and the Q500M: This column will be a bit different from what usually is seen here. First, I bought a flight pack from Novak Electronics (1915A South Evergreen St., Santa Ana, CA 92707), and I want to talk about that. Then I put it in a modified Quickie 500, and guess what? Let's start with the flight pack. The leading question: Why spend as much on a flight pack as the mail-order houses charge for a complete 6-channel system with nickle-cadmium batteries, charger, transmitter and four servos? When you open the box, you draw out a small, rather ordinary-looking group of components (Fig. 1). They are well made and rather light. A 4-servo flight pack, with the customary 500 maH battery pack, weighs in at only 8-1/2 ounces. That is an ounce or two less than most. Switch to a 100 maH pack, as is frequently used in Formula I, Quarter Midget and other racing, and the weight drops to 6.15 ounces. The 1/2A package weighs only 4-1/2 ounces. That's not anywhere near the lightest available, but it's quite a bit smaller and lighter than most. Let's look further.
Radio Technique
REPLACING Transmitter Batteries: Here I sit on a rainy Saturday morning, looking at three transmitters and a $75 pile of new batteries. The thought occurs to me that almost anyone can do it, with a little of the right kind of information to help. The first thing to know is whether or not the batteries NEED to be changed. Here are some guidelines: 1. If you have been using some kind of battery tester and the test time has dropped to half of what it was when the transmitter was new, it's time for a change. The same is true if your only test equipment is the panel meter on the transmitter. 2. If your transmitter comes off charge with the meter needle pointing to the usual place, but it drops rapidly to a much lower value as soon as you put the transmitter in service, you have at least one bad cell. Further evidence of this situation will be the fact that the transmitter will operate for a long time with the meter pointing to the low reading. This might lead you to think that the meter is defective, but you'd be wrong to think so.
