KrazyKraut

Hello Everyone!
I am going to ask some questions that perhaps have been answered previously, but I have not found them in the forum area. Forgive me if this is repetitive.

1) I want to buy at least a 4 ch. radio. A computer model is not necessary at this point. A 4 ch. because I want to get something to grow into and be useful down the road. Are all mfg's the same... meaning, this is personal preference like whether you like Ford's, Chevy's or Dodge?

2)Are there any distinguishable differences that may be an advantage for someone like myself?

3)Are the servo's tuned to each radio frequency or does the RX take care of this?

4)The servo's don't come with the radio, right?

5)Are there analog and digital radios/units? Is there a difference in cost? How about reliablility of signal? Are the digitals multiplexing all servo signals on one carrier? (I work in wireless telecom, forgive me if this doesn't apply)

Thanks for all of the advice! It has been a pleasure thus far conversing with all of you! You all have been very courteous and helpful!

KK

JohnW

My Feedback: (6)

1. You will find Ford vs. Chevy arguments. There are a lot of decent radios available at the low end. I suggest you at least look at 6ch computer radios. They are much more flexible than a 4ch. Computer radios are also easier to setup with respect to throw end points, dual rates, etc. The big four in the US are Futaba, JR, Hitec and Airtronics. My personal pref really doesn't matter as it is mainly a Ford vs. Chevy thing.

2. Again, look at low end computer radios. They will cost a little more than a standard 4ch, however, for most pilots, a 6ch computer radio is all they ever need. Some like me need higher end radios, others can get by with a 4ch. You may find quickly that the 4ch radio just isn't enough. Also look at features, can the radio in question support helis and planes (if that is important to you), ease of programming, features like mixes, expo, etc. While you won't use a lot of this your first year, as you progress you will want to use some of these features.

3. Only the RX cares about the radio frequency. For the most part, any servo will work with any RX. You may have to move some lines around for this to happen.

4. Depends. Sometimes you will find the servos and rx bundled with the radio, sometimes not.

5. Yes and Yes. PCM can be considered "digital" and it does cost more. Most midrange and up radios will support PCM but they may not ship with a PCM receiver. Quite honestly, I wouldn't worry too much about that now. You'll find arguments either way on this subject. PCM has a slightly better effective range and is more predictable. This is directly due to the digital encoding being easier to decode at higher signal to noise ratios and has nothing to do with tx power. It is more predictable because the digital encoding is followed by checksums. Both PCM and PPM/FM are subject to "hits" but they react differently. PCM has the ability to throw away packets that are hit. Standard PPM sees the hits as commanded positions and moves the servos to "random" positions. Some will argue PCM is good and others will say it is bad. I personally only fly PCM, but thats me (Ford vs Chevy again.) PCM is proprietary to each manufacturer and each works a little different. Most send a full and/or differential packets that contain commanded servo positions. Everything is on the same carrier. OK, short answer, start with a standard PPM FM receiver. You might want to verify your radio will support PCM if you decide to get a PCM receiver down the road.

RobStagis

When you buy a radio, if the advertisement doesn't specifically say that something is coming with it, then it's NOT coming with it. Typically (and for whatever reason) a 4-channel radio will come with 3 servos.

As a newbie, one of the most fun things you can do is charge the batteries, lay the entire radio and its accompanying rats-nest of wires out on a table and start plugging things in, flipping switches and moving levers. Maybe, as a lead-in, use scraps of paper to label which servo is going where.

Without a computer radio, you have to use mechanical means to set your throws. What this means is that you have to determine which hole on which end of a pushrod you plug things into to make the surface waggle in the direction you want and the AMOUNT that you want. While not as easy as setting throws with a computer radio, it will give you a good grounding (unfortunate reference to crashing there) in how to set up a plane.

The traditional way of setting up a plane was to get everything as close to perfect as you could get with mechanical means, then fine-tune with end-point and centering adjustments at the transmitter. I've never owned a computer radio, so this is the way I still do it.

Servos, as long as they match the brand and plug, are nothing more than electro-mechanical devices driven by electrical signals from the receiver.

They still sell AM radio, but FM is preferable from an interference standpoint, then dual-conversion FM, then PCM, then..... (I'm not really current with the state of the art).

It's all fun

HarryC

My Feedback: (1)

It is still correct to set travels by mechanical means, then only use the computer to fine tune the travels. Otherwise if you do large reductions on computer travel you lose resolution, torque is wasted leading to increased blowback, more slop is introduced etc. Large increases in travel have diminishing returns due to the rotary nature of the servo output.

Harry

JohnW

My Feedback: (6)

Ditto on what Rob and HarryC said. I didn't mean to give the illusion that a computer radio frees you from designing strong mechanical links when setting up control surfaces. You MUST have a good mechanical link between the servo arm and control horn. Don't fix major throw problems by dialing down your endpoints or ATV, etc. When ever possible, use as much "radio" throw as possible (ATV, end points, etc) and adjust your mechanical link accordingly. This is where a computer radio helps. You can easily fine tune your throws and center points.