I currently have alpha 60 and I recently purchased an Ultra Stick .60 and I need another receiver for it. I have a JR XP6102 radio. It came with a PCM R770 receiver and I was wondering is that the only receiver I can use with my radio are is there other models that I can use. Those run around $100 and I been looking, it seems that the futaba receivers are a good bit cheaper. I just dont know if you can mismatch receivers are what. Do you think I should stick with the R770? Any help would be appreciated.

Thanks, Mike

You can go buy a Hitec receiver at your local hobby shop. They make good receivers - I have several with no problems. Futaba doesn't work with JR.

You can't use Futaba because the frequency shift is wrong.

If you are willing to go FM instead of PCM then JR offers their R700 and R720 recievers.

There are also aftermarket units available.

Note: if you want PCM you will need to stay JR as the coding is proprietary.

I'm not sure what the PCM is. Is that the option to chose what channel you use are what? I am new to this and still learning so much. So it sounds like the best thing to do would be to stick with the R770 right?

PCM stands for Pulse Code Modulation. It is IMO a slightly better method of transmitting the signal to the plane that uses a coding method different than normal FM. Both are FM (Frequency Modulation). I'd say PCM is better for more expensive planes but I personally feel it not necessary for small planes.
Only you can decide if you want to spend the extra money.

Hi Madrigger,

I know PCM is basically Pulse code modulation the signals send to Rx(Receiver) are mostly glitch free and are digital as compared to FM which are analog. It also offers Fail Safe Mode option by activating that option all servos come to neutral position. Hitec's Electron 6 is the best Rx I ever had any. It's compact good in price and very reliable. As PCM is compatible with FM, so Im sure Electron 6 is the best choice and Im still using it with my JR's XF421Ex Tx.

Mody

Another point - the R770 has been dis-continued. Consider the R790 as a replacment in PCM @ $100.

The Electron 6 is not PCM.
This is the RX Armody was speaking of
http://www2.towerhobbies.com/cgi-bin...?&I=LXCXM9&P=6

Yeah I did notice that the R770 was gone and the R790 took it's place. It is the same price as what the R770 was though. I think I will go ahead and order a R790.

You'll always come through for me. I don't know what newbies would do without helpful people like yourselves.

Thanks again, Mike

Bruce,

You are right, its not PCM, but it can be used with PCM Tx right, naturally it won't offer the features of PCM Rx.

Mody

The TX will need to be switched to transmit in the PPM FM mode. I was wanting to make sure he understood that it was NOT PCM.

United Hobbies carries the GWS RD8SL receiver. It's an 8-channel full range dual conversion receiver. It's also shift selectable so you can fly it with Airtronics/JR or Futaba/Tower radios. The receiver is $24.99 and the receiver crystal is $3.99. United Hobbies is located in Hong Kong, so a typical order will take about 3 weeks to arrive. What's amazing is they can ship a pair of these receivers and crystals from Hong Kong to Omaha, NE via International Air Mail for $5.00 shipping and handling.

Edit: United Hobbies ships worldwide, so make sure you're ordering the 72Mhz FM receiver and the 72Mhz FM dual conversion crystal if you live in North America. If you don't live in North America, United Hobbies also stocks receivers and crystals for 35/36Mhz and 40/41Mhz.

They charge a 3% fee for paying via PayPal to cover the cost of credit card processing. Overall I'd rate their customer service as exceptional.

http://www.unitedhobbies.com

Try not to tell anybody else about this incredible deal, or pretty soon everyone will be ordering them!

What it comes down to is this: You need a positive-shift PPM receiver, or a JR PCM receiver. You have many, many choices among positive-shift PPM receivers (including JR's own offerings) and much less choice among JR PCM receivers (there aren't as many models/prices).

The first thing to really understand is that people often confuse their terminology. The companies themselves contribute to this. The biggest bit of confusion is what FM means. It's frequency modulation. FM receivers can be PPM or PCM, generally. PPM is analog encoding. PCM is digital encoding. Both are transmitted via FM. Manufacturers rarely us the term "PPM", instead calling it "FM". That's because most modelers aren't clear--for most people, the choice is between "FM" and PCM. Let's hope I haven't confused this issue for anyone.

PCM, being digital, involves checksums. What's a checksum? It's a way of validating the data the receiver decodes, just like your computer does when you download something from the Internet. Bad data happens, and with PCM it throws away the bad data (packets of data are called frames). If no data or enough bad data is received, that's when a PCM receiver goes into "failsafe". Failsafe isn't all servos returning to neutral, as was stated by another poster. It's the servos going to a pre-set condition. People argue about what that should be, most only agreeing that the throttle should be cut. You'd be surprised how many people never program their failsafe positions, and many people have a misconception that failsafe will somehow save their model. Failsafe is primarily to make a crashing model safer (the engine being cut) rather than save the model from crashing.

PPM just takes it all in. Bad data, no data, the receiver doesn't do anything about it. If your signal is lost or someone turns their transmitter on with the same frequency as yours, there's no "failsafe" position for the servos--they kind of do whatever they want to do. That might sound bad, but in reality either way the model is likely be done in one way or another if there's no good signal.

Far more people use PPM than PCM. PPM is cheaper, you have lots of choices in terms of the receiver you use, and for regular sport flying there are few true advantages to PCM. It really comes down to you making an educated purchase about what your needs are and what your budget is. If you want to stick to PPM, buy from a reputable brand name such as Hitec, JR, Airtronics, or FMA Direct. Saving $10 on a no-name knock off may not be the wisest of choices.

"If you want to stick to PPM, buy from a reputable brand name such as Hitec, JR, Airtronics, or FMA Direct. Saving $10 on a no-name knock off may not be the wisest of choices. "

I couldn't agree more. Your radio equipment is the most important part of your aircraft. That's why I was so thrilled to find a GWS receiver for such a great price. GWS is one of the most recognized brand names in RC flying the world over. I've used their single conversion micro receivers on my park flyers and have been very happy with their performance.

Interestingly enough, the JR FM/PPM receivers are single conversion rather than dual conversion like the GWS RD8SL. JR says that they incorporate advanced signal processing circuitry in their FM receivers to give them comparable performance to dual conversion systems, however.

GWS is a great brand and a company known for making solid products at very reasonable prices.

I just don't have any experience with GWS receivers. When I recommend things, I try to stick to brands that I have direct experience with. It keeps me out of trouble.

Well, Now my knowledge certainly has been increased and I learned the true concept of Fail safe as described by the poster. Mostly radios are 72 Mhz, My radio is 72 Mhz, and on the box of JR XF421EX channel 51 was written. What is the meaning of 72 Mhz, is radio transmitting signals on 72 Mhz wavelength?? and what is 51 channels? Also as spread spektrum technology has been introduced where it is used as 2.4 Ghz is it more powerful and glitch than Mhz technology as from 1 to 79 channels are free and user can lock on any channel with having a conflict. But what about those synthesized Rx which don't need crystal in it, are these synthesized crystal free Rx capable to work with 2.4Ghz radio? Please clarify.

Thanks

Mody

OK, 72 MHz refers to a BAND of frequencies.
Channels 11 thru 60 make up this band and range from 72.01 MHz thru 72.99 MHz.
Channel 51 is on 72.81 MHz.

For the 2.4 GHz band there are approximately 45 different (maybe 80 can't remember off the top of my head) ranging from 2.4 GHz thru 2.485 GHz.

You need a RX designed specially for 2.4 GHz to operate on 2.4 GHz. No way to modify a 72 MHz RX.

There's a lot of difference between the different 2.4ghz systems. One thing that doesn't differ is that you don't have to pick out a channel, and they're supposed to sort out any frequency conflicts amongst themselves. SS as it applies to models is a pretty new innovation, and I don't think there are many people that have a handle on the specifics of each available system, let alone a solid understanding of the differences between them. Some use one frequency selection in each flying session, while others hop from frequency to frequency during a session. The theories in play are pretty different from 72mhz, which is a fairly simple thing to understand. As time goes on we'll all get more familiar with SS.

One thing a lot of people are doing is using "spektrum" in place of spectrum. Spektrum is a proper noun. It's become a lot like kleenex, where people refer to tissues as kleenex whether they're Kleenex brand or not. Even though a lot of us refer to 2.4ghz radios as spread spectrum, the word spectrum shows up only on Futaba's home page for their SS products--no place else that I could find. It's interesting to watch the marketeers do their work. Each time a Futaba piece of literature or representative would say "spread spectrum" they'd be saying a word that's phonetically the market leader at the moment. Pretty insidious, eh?

Thanks Bruce for your reply,

Im using JR XF421EX with 72.810 frequency. Hopefully upon my arrival to USA, as I don't know much about Futaba, as I never used it and JR's radio is my first radio. I have a plan to buy JR's XP7202 with synthesized receiver. About 2.4Ghz, Spread Spektrum or this technology, I would jump into it later, but still who knows when Im gonna jump into it. JR 9X with 2.4 Ghz spektrum is pretty expensive, which I don't think I would be able to buy in the first place, but as I would grow, I'd probably jump into Spektrum technology, which seems to be the upcoming future.

Mody