Bolter

Can anyone tell me if a JR 9303 transmitter will run my Hitec receivers ?

Thanks,
Bolter

carrellh

It depends.......
If the receivers are positive shift - yes
If they are select shift - yes
If they are negative shift - no
If they are PCM - no

aeajr

My Feedback: (2)

Let me just confirm that is is correct.

All Hitec receivers can be ordered new in positive shift, which is the JR standard. Some Hitec receivers can be adjusted, and some are self adjusting to the radio's shift.

aeajr

My Feedback: (2)

This article may be helpful.

WHAT YOU NEED TO KNOW ABOUT RECEIVERS
by Ed Anderson
aeajr on the forums
Revised 7/7/06

You control the plane by moving controls on the radio, but it is the
receiver that "hears" the radio and directs those commands to the proper
servos to move them according to your wishes. So, what do you need to know
about receivers when preparing and flying your plane?


FREQUENCY AND CHANNEL

Receivers are specific to a given frequency. For example, in North America,
NA, our planes can be flown on 27 MHz, 72 Mhz, and perhaps others, but these
are the most common. Your receiver has to match the frequency of your radio
in order to be able to hear it. In NA 72 MHz is considered the RC aircraft
hobby channel it is split into 50 sub frequencies, or channels so that we
can have more than one person flying a plane at any given time. In NA, 27
MHz is typically only seen in low end RTF planes and is shared with low end
cars and boats and is limited to 6 channels.

Normally you need to get a crystal with your receiver that matches the
channel of your radio. In RTF packages, this is already done, so you don't
need to worry about it. However if you are buying your own receivers, you
must match them to the frequency and channel of your radio when you buy
them. Your supplier can help you with the details. One suggestion is that
you not mix crystal brands. They may work but this introduces a risk that
you are better off avoiding. If you get a Hitec receiver, get a Hitec
crystal.


AM and FM and FM SHIFT

Just like your car radio, RC radios can use AM or FM to transmit their
instructions to the plane. AM is an older technology but it is still in
use, primarily in low end 2 and 3 channel radios. However most new radios
are FM. Both work!

In North America, FM radios are grouped by those using positive shift and
those that use negative shift. Typically we speak of JR and Airtronics as
positive shift. Hitec and Futaba are negative shift. In some cases these
brands can be made to change shift through a function called shift select or
reverse shift. Apparently this issue of shift is not unique to North America.

Shift refers to how the radio codes instructions for the receiver. One is
not better than the other, they are just different. This is only important
when you are buying a new receiver as you need to be sure that your FM
receiver and your FM radio are using the same shift. Shift does not apply
to AM radios.

Crystals are not specific to shift, but they may be specific to AM vs. FM.
Be sure you get the right type of crystal for your receiver.


PPM and PCM

PPM and PCM further define how the radio codes commands to the receiver. If
you have an AM radio, you don't need to be concerned about how the radio
encodes. AM radios sold in North America use PPM as far as I know.

FM receivers can be either PPM or PCM. When people say FM, they typically
mean FM/PPM. If they say PCM, they mean FM/PCM. \

As long as the shift is right, you can mix brands of FM/PPM radios and
FM/PPM receivers. On the other hand, PCM receivers are highly brand
specific. If you have a Futaba radio capable of PCM transmission and you
wish to use a PCM receiver, you must have a Futaba PCM receiver that is
compatible with that model radio. No mixing brands in PCM.

As far as I know, all FM radios can transmit in FM/PPM. Some can transmit
in FM/PCM also. I don't know of any that are FM/PCM only, but there may be
one out there. If PCM is listed, it is normally an extra feature, not a
requirement you use PCM.

Some will say that PCM is better and more reliable. I can neither confirm
or dispute this point as I have not used PCM receivers. I will point you to
a couple of articles that discusses PCM, how it works and their opinion
of the advantages.

Futaba FAQ on Advantages of FM/PCM over FM/PPM
http://www.futabarc.com/faq/product-faq.html#q102

Article on PCM vs. PPM
http://www.aerodesign.de/peter/2000/...ml#Anker143602

PCM receivers tend to be more expensive, larger and heavier. From what I
gather FM/PPM is what the overwhelming majority of flyers use. FM/PCM seems
to be most popular in the high performance world, giant scale and
competition planes. Choose whichever you like as either will fly your
plane.

RANGE

For practical purposes, range is determined by the receiver, not the radio.
It is a function of sensitivity of the receiver and its ability to pick out
the radio signal and filter out noise. Many brands state the rated range of
their receivers. Some do not. I suggest you stick with brands that state
their rated range or you could end up flying beyond the range of your
receiver.

How much range is enough? That depends on the application. You can
NEVER have too much range, but you can have too little. If the plane
gets out of range it will crash or fly away. More range is always better.

Here are my suggestions for minimums:

Indoors

Indoor planes are usually very weight sensitive, every gram counts.
To get extremely light weigh, sometimes range has to be sacrificed but that
is OK indoors as long as you know what it is. I suggest 200' minimum and
more is better but you may be fine with less. Many indoor flying spaces are
less than 100 feet along any span and you are not going to accidentally fly
past the walls.


Outdoor - Planes

Slowflyers, micro helis and small electric planes under 36" wing spans can
often get by with ultra light receivers with ranges of as little as 500
feet. This is adequate if you have a small model or fly in a small field of
under 500 feet in span. Many of these small models can be hard to see at
ranges of more than 350 feet, approximately the length of a football field.
I prefer more range, but many people do fine with 500 foot receivers. The
GWS pico 4 channel is a good example of this kind of receiver.

Today there are plenty of micro receivers with 1000' or greater rated range
that are under 1/3 ounce, about 9 grams. I have a large field that is 1600
feet long so it is easy for me to get a plane out beyond 500 feet without
realizing it. While it can become hard to see them at that range, I don't
want to lose it because I ran out of receiver range.

If you can tolerate up to 1/2 ounce, about 14 grams, for your receiver, then
there is no reason to use a receiver with a 500 foot range limit, except
price. The Spektrum DX6 receivers are good examples. Tiny in size they are
a safe working range of 1500 to 2000 feet. The Hitec Micro 05S at .3 oz,
about 8 grams, has a range of 1 mile. Berg, FMA Direct and others make tiny
receivers with over 1500' range ratings. Why limit yourself with short
range receivers and take a chance of losing you model?

For gliders, sailplanes, fast electrics or glow planes with wing spans of 2
meters, about 80 inches or less, I recommend a minimum of 2600 feet, 1/2
mile or 1 KM depending on how your receiver specs are given. More is ALWAYS
better.

Planes with greater than 2 Meters or 80 inches, and especially thermal
duration sailplanes, I recommend you use a receiver with a 1 mile, 1.5 KM or
5000 foot + rating. It is quite easy to get these planes out 3/4 of a mile,
especially the larger sailplanes, and you don't want to have signal problems
with a plane this large that is out that far. This will give you good
signal strength for the likely distance you will fly the plane which is
probably no more than 75% of that range.


SIGNAL PROCESSING - Single and Dual Conversion, DSP and more

In addition to range, receivers will usually specify if they are single
conversion, dual conversion, or that they use some other method of signal
processing. I will leave it to the engineers to go into depth here.
However, as a general rule, dual conversion is better than single but there
are excellent single conversion receivers that have digital signal
processing and other ways of making sure they pick up the right signal.

I have no hesitation to use single conversion receivers with 2600 foot, (
1KM or .6 mile) rated ranges in my models that will be flown less than 1500
feet out. Most of my electric planes can't be easily flown further than
that and
since I am operating at less than 70% the raged range I feel comfortable
that good quality single conversion receivers should be fine.

For my 2 meter and greater wing span planes, I use only dual conversion
receivers. Here I am flying planes, typically sailplanes, that may be over
1/2 mile out and 1000 feet or more in altitude. I need every bit of signal
processing I can get to insure I get clean control. I can't afford even a
single glitch.

You make decisions based on your type of flying. This is what I do.

Some receiver brands offer single conversion, dual conversion and perhaps
other types of receivers. Be sure you get the right kind of crystal based
on the receiver. For example, Hitec dual conversion receivers and single
conversion receivers take different types of crystals. I don't know what
makes them different but you can not interchange them. They won't work.


CHANNELS

We spoke of channels above in terms of frequency. We also use the word
channels to describe how many servos/devices you can control. So a 4
channel radio can control up to 4 devices, for example. It is OK to have
more channels in the receiver than your radio has as some slots are used for
things other than channel control. For example, if we have a 4 channel
radio and are flying a 4 channel plane your slots might be used like this:

1 per control channel = 4
1 receiver battery
1 for plane locator or battery monitor

In this case you might want a 6 channel receiver to give you 6 slots. Or you
can use one or more Y cables to share slots. However I prefer to have a
receiver with extra slots rather than use Y cables. I feel it will give me
greater reliability. Rather than putting money into Y cables I would rather
put the money into the receiver.

If you have a 3 channel electric plane, you need a minimum of a 3
channel receiver. You don't typically need a separate slot for a receiver
battery as your electronic speed control normally provides the receiver with
battery power from your motor battery. You can use a 3, 4, 5, X channel
receiver, but it must have at least 3 channels.

You can also use a 2 or 3 channel receiver with a 4 or more channel radio,
but you will only have 2 or 3 channels of control available. An example
might be to use a 3 channel receiver for your R/E/T plane but use a 4
channel radio to fly it. That works!


COMPUTER RADIO AND CHANNEL MIXES

If you are splitting functions using mixes in a computer radio your
receiver may need more channels. For example, if you have a computer
radio, you might be able to use two servos for your ailerons and have each
work from its own channel. Each aileron will be controlled its own channel.
Some radios can put the second aileron on any channel and some require they
be on specific channels. Consult your manual for guidance here.

Here is an example where we use more than one slot for a function because we
have individual servos on each surface. This is the layout of one of my
gliders and is controlled from my Futaba 9C computer radio. I use an 8
channel receiver and 7 servos.

Ailerons - channels 1 & 7
Flaps - channels 5 & 6
Elevator - channel 2
Rudder - channel 4
Tow hook release Channel 8
Battery - uses channel 3 slot
Plane Locator - Shares channel 8 slot with the tow hood release servo
via a Y cable


Summary

The receiver is the most critical of all the electronics you will put in
your plane. The most expensive radio with the wildest features is just a
paperweight without a good receiver to carry out its instructions. While
the terms can be confusing at first, you should now be prepared to choose
a receiver with confidence. Remember to always consult your radio manual
for any specific needs of your radio system.

A key point is that it is the receiver and not the radio that really
dictates the range you can expect. I encourage you to be very aware of the
range rating of your receivers so you don't lose a plane by exceeding your
safe range.

Your receiver has to have enough channels to accept commands from your radio
and to accommodate the number of servos/devices you have in the plane.
However the number of channels in the receiver does not have to match the
number in your radio.

Your receiver needs to match your radio in the areas of shift, frequency and
channel as well as FM/PPM or FM/PCM features. For FM/PPM you can mix and
match receiver brands, but with FM/PCM you can't!

That's about it. Treat your receivers with care and they will take care of
your planes for years to come!

Good article on radios by the Torrey Pines Gulls Web Site.
http://www.torreypinesgulls.org/Radios.htm

edited 7/8 - to correct a statement about shift.

Bolter

Thanks to both replies ! A wealth of information here :-)

Bolter

Deyrick Gibbins

" In most of the rest of the world, all radios are positive
shift, as I understand it."

Not correct in my opinion, in the UK on 35Mhz FM all equipment is negative shift in my experience. Mine is at least, Futaba and Hitec Transmitters, my Optic 6 is Negative by default although is selectable within Model settings. My Futaba is not selectable and is -ve.
Bought a JR receiver to go with it recently which is also negative shift. I selected +ve shift on Optic 6 for it at first ( as i had read JR were +ve shift) and it did not work at all, switch to -ve and all is fine.

Del

aeajr

My Feedback: (2)

Thanks Del!

I will amend the write-up. If it is not true in UK, then it is probably not true in other parts of the world too.

I appreciate your help.

iflyj3

My Feedback: (7)

If my memory serves me correctly, a few years back Futaba made a single stick transmitter that was only PCM. I believe it was a 512 system.

JohnBuckner

My Feedback: (1)

Two other examples of PCM only Tx's to add to the list: Futaba Conquest PCM FP-T6NPK, a simple non computer 512 PCM version of the Conquest series and the Airtronics Spectra PCM 7P (the spectra name was used by Airtronics long before Hitecs use of the name for their synth module. This Tx was a single airplane Tx with no model storage however had most of the features and mixs of modern computer types and was programed through 48 pots and dip switchs.


I am sure there are others out there also but I own examples of both and still use them.


John

oliv007

Hello John

I am a dinausore and still using my SANWA (=Airtronics in Europe) SPECTRA 7H !...
However, I stopped using it almost 10 years long and I can not find back the instructions manual... Could you help me with a copy of your Spectra 7P manual ?
Do you think I can still find a compatible receiver ? I want to switch from my old 100 times crashed Hirobo Shuttle to a brand new T-Rex and I am hesitating to change also the transmitter...

Best Regards

aeajr

My Feedback: (2)

With the rise of 2.4 GHz, new flyers may never have to deal with the AM, FM, PPM, PCM discussion above. Of course then you have to deal with

spektrum/JR vs XPS vs Futaba 2.4 GHz as they are not compatible with each other. So we avoid Pos vs neg shift and ppm vs PPM, but we now have 3 kinds of 2.4 GHz.

Such fun!

Here is a broad overview of what is going on in the 2.4 GHz market:
http://www.rcuniverse.com/forum/m_6130963/tm.htm

A.T.

Negative shift is used outside USA - This has been advised a number of times in the past, for example Positive - Negative Shift extensive thread on history, Discussion - any JR radio can use futaba receiver, Positive - Negative Receiver productions
With regard to PCM only TX, add:
Futaba FP-T5NP "Challenger" which used a unqiue receiver "FP-R105IP" which activated a pre-set throttle cut only.
JR early PCM TX such as the Apex 7, known as the Century 7 (with fewer features) in the USA, were available as PPM or PCM only - not changeable by user.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

aeajr

My Feedback: (2)

I am not sure what you are saying.

In the US, JR transmitters can not talk to Futaba receivers.

Most Airtronics and Hitec transmitters can talk to either.

A.T.

Please re-read the entire post which does not say that JR transmitters can talk to Futaba receivers in USA (as they do in other countries). The original thread header was simply used to highlight the rebuttal shown within that link and read remainder of the thread if any reader so wished.
Regards
Alan.

aeajr

My Feedback: (2)

Thanks. As I said, I was not sure what you were trying to convey.

Imac Kiwi

On 72 Mhz JR and Airtronics use positive shift, Hitec and Futaba use negative shift. This only works for fm (ppm) modulation. Each radio manufacturer uses different encoding for PCM modulation. Outside of USA, we use frequencies other than 72mhz. On PPM they work with each other in my experience. I am not a radio tech, so further input from qualified persons would be welcome.

iflyj3

My Feedback: (7)

You are correct for the USA. The ACE MicroPro 8000 was natively negative shift also, but the latest firmware allows selection for the shift. Some Airtronics and Hitec do also. Only JR and Futaba have been hardheaded about allowing the user to select. BTW, it is interesting that Futaba is negative shift on 72 MHz but positive shift on 50 MHz.

It is my understanding that outside the USA all radios shift the same way.

A.T.

Hi Alan, as referenced in my first post, regardless of frequency, all shift select TX are to be set on "SFT.N" i.e. 35 Mhz, 36 Mhz, 40 Mhz & 41 Mhz except when used with JR or Sanwa(Airtronics) RX operating on 72Mhz and 75 Mhz. Reference in need, "Transmit Shift SFT.N SFT.P" Eclipse manual page 11 download manual .pdf . Negative shift being factory default for all Hitec transmitters.
Much more information under "Radio Systems, Accessories, Alterations and FAQ" sub section "Receiver - FAQ, guides and aids to best reception" and "Transmitter - FAQ - Additions, Adjustments, Clonepacs & Repairs" amongst others on my web page.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

mousebengal

does anyone know if i can swap the crystal from my eflite cx and use it with the eflite controller on a generic x-ufo[8D]