Dave trimmer

My reciever has the ability chang its shift, what does positive or negative shift mean?

Thanks, Dave Trimmer.

piper_chuck

My Feedback: (12)

It has to do with the way they encode the signal. Which to use depends on who made your transmitter. Futaba and Hitec use negative, while JR and Airtronics use positive shift.

Dave trimmer

Thanks, but what happens if you take a reciever with a channel 18 crystal and stick in a channel 58 crystal, if I turn on my reciever will this wreck the reciever. lastly do you have an idea what dual convertion means?

Thnks a lot, Dave Trimmer

bruce88123

What happens depends upon the make and models of the receivers and crystals in question. For Futaba, they have Hi and Lo band Rx receivers. In YOUR scenario (if Futaba) it MIGHT work but you would have a weak receiver because it would not be tuned properly for the hi/lo condition. JR (and some others do not operate this way).
Also, you can not/should not swap crystals between brands or between single/double conversion receivers.
Dual conversion RX have what is called 2 mixer stages in which the signal is processed. (terminology simplified for ease of understanding). Single conversion RX have 1 mixer stage. If you use a single conv xtal in a dual conv xtal unit the rx will not work because the internal freq's will be so far off that it won't even be funny.

ALWAYS take the time and spend the small amount of money to purchase the correct equipment. It will be cheaper in the long run.

Missileman

I learned this all the hard way.
Dual conversion= you MUST HAVE a dual conversion crystal
If Futaba= No you cannot put a channel 58 crystal in a RX that had a channel 18 in it. You will need a High Band reciever for channel 58.
Keep in mind I am only refering to Futaba because I don't have experience with other brands.
I can say with absolute certainty that missmatched radio gear may work on the ground but once you fly out of the deminished range of your gear you can wave goodbye to your airplane.

carrellh

Unless the receiver is a Futaba, changing from ch 18 to 58 is not a problem. Futaba spilts the 72 mhz band in half (11-35 and 36-60) and doesn't recommend changing channels between the halves. The crystal needs to be the correct brrand and type for the receiver.

Single conversion and Dual conversion refer no the way interference is filtered (I think). What I do know is that you have to use the correct type of crystal for the type of receiver.

I do not think anything will blow up from plugging in the wrong kind of crystal; most likely:
1. It will not work at all
2. It will act very erratic
Either way you'll know you have a problem long before you put a model at risk.

Dave trimmer

When you think you knowit all in this hobby you can easily get new information and confused all over again!!!

bruce88123

"Dual conversion" usually gives better "selectivity" and "adjacent channel rejection". This boils down to mean that "it works better with less interference".

I used the word "usually" to allow for poor design and worse tuning. Dual conversion also "usually" takes up more space than single conversion. This is one reason most park flyers will have single conv. Smaller,cheaper,lighter,less range.

Hill202

My Feedback: (24)

Does a Hitec receiver split the band?

piper_chuck

My Feedback: (12)

You mean to high/low like Futaba? Nope, Futaba is the only one who does that. And just to clear up some information, the Futaba high and low band receivers are the same, they're just tuned different. So, while it's a bad idea to just put a low band crystal in a high band receiver, you can send the receiver in and have it retuned to the other band.

bruce88123

When Futaba tunes the basic RX they align the components to optimize performance in the middle of the "band" whether it is Hi or Lo. They feel this gives better performance from THEIR RX.

From Futaba web site:
Most of our 72Mhz receivers are now tuned to the center of either a low band frequency (channel 11 to channel 35) or high band (channel 36 to channel 60).

By tuning to each band, you can easily and safely change your receiver crystal to anywhere within this high or low band range, without having to send it in to be retuned.

If you have a receiver that is not marked as to which channel it is, or if it is not marked with a sticker that says if it is High or Low, you can check inside the crystal slot to see if there is a red mark. If there is a red mark, this indicates that the receiver is High band.

JollyPopper

My Feedback: (6)

I have a Futaba eight channel dual conversion receiver on channel 52. I would like to use a Hitec transmitter that is on channel 41 to control it. Does anyone see any problem with putting a Futaba channel 41 crystal in the receiver and using the Hitec transmitter with it? Oh, the Futaba reciver and transmitter are PCM technology, but the Hitec transmitter is FM. Any problems?

piper_chuck

My Feedback: (12)

Everything sounded fine until you got to PCM. A PCM receiver with a PPM only (a more appropriate description of the way your Hitec transmitter encodes the signal) transmitter, isn't going to work. The transmitter and receiver need to speak the same language. Most (all?) PCM transmitters are bilingual, they can also speak PPM. However, most PCM receivers (at least the ones I know of) only speak PCM. Trying to have them talk together is like sending me to China and expecting me to be able to give directions to a cabbie! Oops, bad example, I do give directions to the cabbies over there!

JollyPopper

My Feedback: (6)

Thanks, Piper Chuck. I was afraid that was the case, but I was hoping against hope that it wasn't. Guess I will have to procure a Futaba PPM receiver to do this or fix the Futaba transmitter. It is an early version of PCM and computer technology that has adjustable travel feature, but I haven't figured out how to adjust it. Everything works except left aileron. It only travels about 1/8 inch and I have not yet figured out how to adjust the travel. Right aileron seems to have plenty of travel, and another servo does the same thing, so it isn't a servo problem. Has to be either transmitter or receiver problem, and I'm guessing transmitter. Could be using it soon as a boat anchor. [&o]

Max

piper_chuck

My Feedback: (12)

Post the model number, perhaps in a new thread so we don't hijack this one, someone may know how to fix it.

bruce88123

You can go to www.futaba-rc.com and download just about any manual. Sometimes it helps to just reset to factory defaults and start over because a previous owner (or you) has gotten things so screwed up it will take forever to fix it. Or sometimes it's just one switch too.

Default is a lifesaver though.

BTW - if it is the 8UAFS, it is a nice unit . I have a 7UAFS.