skrez

My Feedback: (15)

Hi guys,
This might be a dumb question , but can I use a low band cystal in a hi band transmitter? I did a range check witha low band receiver and cystal in a high band transmitter and checked okay. Would I have greater chance of getting interferance and crashing?
thanks,
Frank

Dsegal

First, you cannot change the crystal in the transmitter yourself. It can only be done by a licensed technician. As far as I know, Low and High band refers only to Futaba receivers and you can change crystals within the respective band ranges.

ecmiller

I beg to differ. From what I have read, you can change crystals in the transmitter as long as the crystal is within the high or low band the radio was set up for. A licensed technician will need to change the crystal if the user wishes to change from the high band to the low band or visa versa. In such cases, the transmitter will need to be tuned.

Also, the high and low band is a universal characteristic of the 72MHz band. It's not exclusive to Futaba.

Anyway, since the safety factor depends so heavily on the radio, I would ask the mfg of the radio before I start interchanging crystals.

Ed

piper_chuck

My Feedback: (12)

The FCC REQUIRES that any crystal change in a transmitter be done by a licensed technician. It's not a high/low thing or specific to a manufacturer, it is any change. This requirement is in place to ensure that the transmitter is operating correctly with the new crystal. This is not a case of the government placing unnecessary regulatory burdens on us, it is there to protect the rest of us from a transmitter that's operating off frequency.

Will it work ok without being sent in? Probably. Is it worth placing other people's planes at risk, and potentially risking property damage or worse, bodily harm, because a person wants to save a few $$$? Definitely not!!!

Scar

My Feedback: (3)

This is a troll, right? If not, I have questions.

1. What's a 'high band transmitter' ?
2. What brand are you talking about, and how did you obtain a transmitter crystal for it?

With respect to question #1, I've heard of Futaba's designation of receivers as low- and high- 'band', but not transmitters of any brand. Of course, with HT or JR & others, you can use any crystal with your receiver.

With respect to question #2, I don't see a lot of crystals for transmitters for sale in the US. Modules, yes, but crystals.... well, thus my question.

Now, Multiplex used to sell crystals for their 72 MHz transmitters in the US. I happen to have one, and crystals for #47 and #31, but they don't designate low- and high- band.


Just wondering.
Dave Olson

famousdave

My Feedback: (61)

I have had numerous conversations with the JR lab techs, Danny Snyder, as well as JR Radio users at the various events like the Scale Masters and Shootout.


The info below pretty much holds true for any radio manufacturer these days as the frequency control circuitry is amazingly accurate.

There are usually 3 dots or markings on the crystals, left, center, right. These dots indicate where the crystal tunes in relation to its ideal center frequency. It is the same as high, center and low band.


Here is what Danny has to say about it: http://www.rcuniverse.com/forum/fb.asp?m=2371965


Just for the hell of it I popped the module off my 10x and looked at where the crystal was compared to my RX crystals - one is left the other is right! I have been flying that radio non stop for 3 years and have never had a range issue.

I would install any band crystal in the RX, but don't change the crystal in the TX. If you do have to change the TX crystal for any reason send it back for a bench alignment.

If you do change your tx crystal without a bench test, PLEASE don't fly near me!
DP

famousdave

My Feedback: (61)

*Deleted - duplicate post*

cassidy

My Feedback: (5)

I have JR transmitters such as the 4 and 6 channell MAX seies and the Max Computer radios that have the bottom of the TX clearly marked with a label that say low band or high band. This equipment is 20 yrs old.

sfsjkid

At our club, one guy changed from 50 something to 15, and caused problems with another flyer on 16. Range check was OK, but it can't check for adjacent interference.

Rodney

You can cause other people to have problems when you change the crystal in your transmitter without having it checked for proper operation. While it may appear to work your receiver okay, it may also be transmitting spuriouse radiation that effect other receivers on adjacent channels. No two crystals are exactly alike, they are simply ground quartz that will in most cases require some slight adjustment of the associated inductance or capacitance in the oscillator circuit to insure that no side bands are generated and that it is within FCC specs. Besides, this will nullify any insurance you have should you be responsible for an accident due to interferance.