Should I "overbuy" my first radio?

[JWeb]

Hi Gang:

Although I have been interested in RC flight for many many years, and even managed to crash my 0.049 Cox "EZ Bee" 2-ch plane many times when younger (that is, when I could get the 0.049 started!), I am just now ready to really "pull the trigger" on the hobby.

My current plan is to purchase the Hobbico Avistar (on the many recommendations I found here) and an OS 0.46 engine. My question is regarding the purchase of radio equipment.

I know that I will soon graduate from a trainer to a more complex model. Also, I have not yet decided if I would also like to try flying helicopters. Thus, it seems to me that I want to overbuy my first radio. I am currently looking at the Futaba 7CAF (7-ch) radio system. It has basic heli capibilities, trainer mode, dual-band capabilities, and a host of other attractive features. Would this be a wise decision for an initial purchase? I definitely don't want to have to upgrade the radio in the near future.

I still have much to learn, so please forgive any apparent ignorance!

Jeff

[Joe Ford]

I did...I went with the Futaba 6XAS (the one the 7CAP replaced)...now I'm about 2 years into powered models and find myself needing something more powerful w/more features, channels, model memory, etc. But still 2 years on a $200 investment isnt bad at all. I say go for it. :)

[ivanc]

The 7C is a nice radio with a lot of features, some of which you might use in the future. If your budget allows, buy it.

[JWeb]

Thanks for the responses.

The next question is: do I want FM or PCM? Also, please help me to understand: I believe the TX is capable of both... when I select FM or PCM at buy time, I am selecting the RX, correct? I have read that FM = faster response, potential "glitch" and PCM = slower response, no "glitch". Is it as simple as that?

[Ken-Ohki]

I persoanly believe in buying more/better then you need.

But I would base my descision on your expected learing curve.. 5 or 6 chans will last you a long time. but not be good for a heli. The only reason I say this is,,,By the time you are ready for more, there will most likely be better cheaper radios available, So, you will most likely end up buying another one in a few years anyway... My suggestion is to buy a little more then you need now, then in a few years, Buy your "last radio" so to speak. it will also give you a bit of time to actualy figure out exactly what "you"want.
Some will agree with that some wont. it really boils down to your budget.

If I am not mistaken,, a PCM ( pulse code modulation ) radio is tecnicaly like a scrambler, (tecnicaly ) allowing more protection from interfearence from other radios or other things that may or may not be in you flight area. If you have the money, Go for it, But, IF I am also not mistaken,, your recivers will be more expensive.

Ken-Ohki
"I make things do what I want them too, The Hell with what they are designed to do."

[JWeb]

As I understand PCM is not necessarily scrambling, but the addition of "headers", "control packets", and "trailers" in a more digital format (as opposed to the analog PPM format) to aid in disregarding interferences. But, my real question is: the Futaba 7CAF TX is capable of BOTH (via a switch?) and the RX is really the distinction, correct?

Also, how do I choose a frequency? I am not an AMA member and have only just began looking at local clubs... so I suppose I should just pick one at random, correct? Are they changeable via crystals (cheaply) at a later date?

[ivanc]

The 7C is set up for PPM or PCM through programming it per model (there's no PPM/PCM switch). The difference between 7CAF (PPM) and 7CAP (PCM) is the Rx it comes with. The main difference is that PCM has failsafe programmable at the Tx end. But there are many PPM receivers that have built-in failsafe systems. IMO PCM is not worth the price difference so I would recommend to stick with PPM. Another reason is that different brands of PPM equipment are interchangeable while with PCM each manufacturer has its own PCM format not compatible with others.
In USA you're NOT ALLOWED to change the transmitter crystal, but you can change the receiver crystal providing it's in the same band (27MHz xtal in 27MHz Rx, 50MHz xtal in 50MHz Rx, 72MHz xtal in 72MHz Rx, 75MHz xtal in 75MHz Rx). This is described in the stickies by Steve Lewin on top of the radio forum - http://rcgroups.com/forums/forumdisplay.php?f=135
You should first check with the local club and fields you're planning to use to see which channels are not used or rarely used and get your radio on one of these channels.

[JWeb]

Ivan, very helpful information.

Although those links answered the majority of my questions, I am still unclear on channels: If I buy my 7C, for example, on channel 15 and decide that I really need to be on channel 19 at a later date, what do I do? Is this a software programmable option or a crystal change? I remember my really old Cox EZ Bee radio seemed to have a "chip" or crystal on the RX and TX that I could swap...

Am I way off?

[geofb]

I got back into the hobby about 18 months ago, after many years doing other things. I "invested" in a Futaba FF9. I decided I wanted the extra protection from interference that PCM gives and the other features which I knew I would grow into. The additional cost is much less than the cost of the planes I would be flying, so I saw it as insurance. I quickly found exponential extremely useful and have recently started to use some of the other "computer" features.

I still only currently use 4 channels and may never use all 9 - so what?

I have never regretted the extra cost of the intial investment and would strongly recommend a similar approach if your budget allows.

[ivanc]

I am still unclear on channels: If I buy my 7C, for example, on channel 15 and decide that I really need to be on channel 19 at a later date, what do I do? Is this a software programmable option or a crystal change?
You'll need to send it to Futaba (Champaign, IL) to be retuned for channel 19, so you will not be able to use it for channel 15 any more. There are Txs with replaceable RF modules (you can change modules for the different channels) or with a frequency synthesized RF modules (you can select the channel the module works on). Such radios are Hitec Prism, Eclipse, Optic, Futaba 9C.

I decided I wanted the extra protection from interference that PCM gives and the other features which I knew I would grow into.
That's a myth - a good PPM receiver is not susceptible to interference and a PCM receiver will stop working (go into failsafe mode) if it gets hit with high levels of interference (a Tx in PPM mode on the same channel that is closer to the model than the PCM Tx). Multiplex do not use PCM any more although they were the first to implement PCM in RC. Instead they use high quality receivers with built-in failsafe.

[LostMyPlane]

When buying a pcm or ppm radio, the difference is the RX since the radio does both. I think if you live in an industrial area that may have a lot of radio traffic ( industrial radios have a very bad habbit of being on our radio frequencies ) you may want to spend the extra for PCM.

A Futaba Radio has to be sent back to change the channel. A JR radio doesn’t. You can order crystal packs for the JR radios. The 6102 radio that my friend uses is a great radio and he does 3D with it (has expo, dual rates, sub trims and much more) The JR 8103 that I have is great. I bought it with the PPM RX for about $380.

[ivanc]

A Futaba Radio has to be sent back to change the channel. A JR radio doesn’t. You can order crystal packs for the JR radios.
According to FCC (valid in the USA ONLY) Part 95:

Sec. 95.645 Control accessibility.
(a)...
(b) An R/C transmitter which incorporates plug-in frequency determining modules which are changed by the user must be type accepted with the modules. Each module must contain all of the frequency determining circuitry including the oscillator. Plug-in crystals are not considered modules and must not be accessible to the user.

Sec. 95.653 Instructions and warnings.
(a)...
(b) The instruction manual must contain all information necessary for the proper installation and operation of the transmitter including:
(1)...
(2)...
(3) Warnings concerning the replacement of any transmitter component (crystal, semiconductor, etc.) that could result in a violation of the rules.

It's obvious to me that changing the transmitter crystal by the user is illegal in the USA no matter what brand Tx is used. BTW Futaba sells crystal sets (Tx/Rx pair) too - http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXH260**&P=0

[JWeb]

Interesting, Ivan. So, if I understand this properly, I would have to buy the Futaba 9C radio system if I were interested in having the capability to change band/frequency/channels (since it employs the "plugin" module). With some additional reading, I was able to learn that if you simply change the crystal and move more than two or three channels, it is possible to produce a TX setup that could interfere with neighboring channels. Changing the crystals is only part of the equation - as you suggested early, there are other components that must be "tuned" in the system.

Thanks for the great information today... you have helped me understand the technology better and make an informed buying decision.

[JWeb]

Another question regarding "overbuying" of the radio system. As I browse the towerhobbies website, I am intrigued by the park flyers and the glide planes. I am assuming (since many of those kits require 3-4 servos and a micro/nano receiver) that I could employ a radio system such as the Futaba 7C by simply buying the servos and matched receiver. Is this correct? I feel better about the steep price tag if I know that it is truly versatile (not only in that it supports up to 7 channels, but that it can be used with multiple flying machines).

Just attempting to confirm...

[ivanc]

There are other Txs using frequency synthesized modules at less $$$: Hitec Prism 7, Eclipse 7 and Optic 6. Recently I purchased a used Prism 7X with a Spectra module - a great radio that has only one downside for me - it has memory for 3 models only. The Eclipse has more though. The Optic has an 8-model memory.
What you normally do is buy the radio with or without a receiver and/or servos. For each model you buy a receiver crystal on the same channel and a flight pack (Rx and servos) or buy receiver and servos separately.
For my first plane (Hobbico SuperStar EP ARF) I bought a Hitec Flash 5X - the sailplane version with the 5-channel 555 receiver and 3 micro servos. For my next plane (Hobbico HobbiStar 60 ARF) I purchased a Hitec flight pack - Rx, 4 HS-425BB servos, switch and battery pack and a receiver crystal on the same channel as my Tx. For my next planes I purchased the receivers and servos separately.

[fhhuber506771]

There's something to be said for buying the $100 - $120 4-ch basic set, even knowing that you WILL buy the computer radio within 6 months:

That 4 ch basic comes with 4 servos ($40 value) an RX ($60 vlaue since they generally come with the 7 ch RX anyway...) Nicd flight pack ($18 value), Switch harness ( $10 value).... The darn TX is FREE! and has an 8 cell pack that can be split for 2 RX packs...

Then you buy your better radio on the same frequency, and you can donate a buddy box to the club. and have the second charger still to plug 2 models in for overnight charging.

You can keep the low cost system's flight pack in your fixed wing.. and order the 7Ch computer system with the better servos REQUIRED (Futaba 3003/3004 are NOT good for heli at ALL!!!! Helis destroy thier centering pots!)

You just can't lose by buying the 4 ch AND the 7 Ch when planning to do both fixed wing and heli :D