RC India

Hello guys, :)

I just want to compare some rx below .Which one is better and gives more range and why :headscratch:??

1)R156F
2)Corona Synthesized Receiver 6Ch 72Mhz {{Form H.K.}}
3)Corona Synthesized Dual Conversion Receiver 6Ch 72Mhz {{Form H.K.}}
4)Corona Synthesized Dual Conversion Receiver 8Ch 72Mhz(why would i need this one as i will be having 6 ch tx??)                {{Form H.K.}}
5)R168DF (Dual Conversion)
6) MKS 9Ch Synthesized PPM/PCM Receiver (72mhz) R9000S {{Form H.K.}}

Is corona (synthesized) rx compatible with futaba exp.( As it says it does not need crystals ,but the tx futaba exp is having crystal!! )

Thnks
Snehal

I would think all would have adequate range but can only speak for Corona as I have used the same, and it works fine. The synthesised receivers do not need a crystal as the Rx will scan and set itself to the frequency of your transmitter. Do note, however, that the frequency BAND of the Rx must be the same as the TX (i.e. 72, 35, 40 MHz, etc.). Also, these work only on PPM mode. You will have to set the Tx to this mode.
.

Is there any difference between
Corona Synthesized Receiver 4Ch 72Mhz (v2) $15.99 (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5781)
and
Corona Synthesized Receiver 6Ch 72Mhz (v2) $16.24 (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6599)
other than number of channels and the negligible cost difference ???

You will have to do some research.  Resolution (number of steps in servo movement) AND accuracy in centering are the key things to look out for.

Corona and Futaba have more or less the same front end and If section or IC, but Corona RX are much better than Futaba as they have DSP (Digital signal processing)in the decoder section ,which improves the performance when signal gets weak at long distance..

Jitender

Wouldn't centering accuracy be a function of the servo?

Centering can be affected by what signal (PWM width) is sent out by the receiver too, right ?

The receiver will send out whatever is transmitted and, of course, received. The pulse width (in PPM mode) is not decided by the receiver.

Not really... what you are talking about is an IDEAL world ;)

It is the precision of the components in the receiver that decides what is the exact the pulse width that the servo sees (regardless of what is being transmitted by the TX).  You can see what I mean if you think about the step/resolution issue along with this.

PPM is decoded into various PWM signals for each channel in the receiver, and the precision of this process is the issue in question.

Anwar, I think you are mixing up PCM with PWM coding. With the former, the signal (position of the pot) is converted from analogue to a 10 or 11 bit digital code (1024 or 2048 resolution). This (code) is recovered by the receiver and then decoded/converted to a PWM signal. In this case the components could, possibly, have a bearing on the accuracy of the signal.

But with straight PPM, the signal is ONLY modulating the carrier. This carrier is received and "demodulated". Which means the signal is "extracted" from the carrier. There is no processing involved so tolerances cannot creep in.

The problem of poor tolerance components could be an issue in the transmitter, though, in both cases.

It is the extraction/demodulation into individuals channels that I was referring to (even though I used the word "decoding"), not talking about PCM at all. The component tolerance is probably the issue, and I am not sure why it is mentioned as an issue in the transmitter alone... it can very well be an issue in the receiver too.

I do remember people saying some of these receivers having very low number of steps, that they are not viable for use on precision setups.  Will try to find the link.

The product reviews themselves talk widely about centering issues on these, and some Corona models are said to be better in this aspect.

Note that these do employ DSP for filtering, and such processing could be the source of the issues.

Please do find the links, if possible. Would help shed some light on the actual process involved and the possible problems.

Maybe it does have something to do with DSP - which is not used by Futaba for sure.

There is some discussion here :

http://www.rcindia.org/radios-and-receivers/need-help-in-selcting-a-corona-rx/msg14424/#msg14424

A quick search leads to stuff like these :

http://www.rcgroups.com/forums/showpost.php?p=8782129&postcount=4

http://www.rcgroups.com/forums/showpost.php?p=8898973&postcount=37

http://www.rcgroups.com/forums/showpost.php?p=8899003&postcount=38

http://www.rcgroups.com/forums/showpost.php?p=8899933&postcount=41

I guess there are a lot more, stopped looking for now.  The HK product pages does seem to have many comments about centering.

After checking corona website,  i have come to a conclusion that both these Rx have the same specification and run the same algorithm. Also as Anwar pointed out, there are some negative reviews about centering issues in 4ch rx. Weight difference is also just 2 grams. So i am going ahead with Corona Synthesized Receiver 6Ch 72Mhz (v2).
Thanks for the help guys  :thumbsup: