WTA Crystal - from diff Tx and Rx

[Shark]

asked many diff LHS, but no one can give me a 100% answers
so come here and seek advise.

Can we use diff Tx with any brand of Rx but crystal are the same make
eg. Can I get a Futaba Tx to work with my Wing Dargon Rx by fixing the same crystal into both.

[Daniel Wee]

Well, it depends. You see the so called crystals have to be cut for specific frequencies depending on whether the receiver is single or dual conversion, and what the IF frequency is. If the number of conversions, and the IF, and the shift is the same, you should be able to use the same crystal. So, although a Futaba crystal is marked 29.100 MHz for example, it's actual resonant frequency may actually be 28.645 MHz but for a JR crystal marked 29.100 MHz it may actually be 29.555 MHz. On the other hand for a single conversion receiver marked 29.100 MHz, the resonant frequency may actually be 29.100 MHz. The reason for this is due to the different ways the receivers are designed. If you knew what the actual resonant frequency of the crystals are, you could theoretically go to Sim Lim Tower and buy REALLY cheap crystals that work. You only need to make the crystal fit because the RC crystals use thicker connectors. I used to have a little circuit to test crystals but I don't know where I've put it now. So basically the factors to consider for crystal compatibility are:-

1. Single or dual conversion
2. Positive or negative IF shift
3. Type of crystal - fundamental or harmonic frequency (most are fundamental)

Daniel

[Shark]

thank for the explaination. so does that mean I can use any TX (any brand) with any Rx as long as the crystal from Tx and Rx are paired (brought togther in a pair)

[HZM]

At one time, I am using futaba Tx, GWS receiver w Berg crystal

Mike

[Daniel Wee]

As for the pairing, there is a good chance it will work actually but it assumes some symmetricity between the Rx and Tx design. This is not always the case however, and different manufacturers may use different IF frequencies, especially when dual conversion receivers are concerned so I would not really want to risk this. Actually some of these crystals are pretty cheap at Sim Lim Tower so you can always give them a test. The key is to find out what exactly those frequencies are. Basically what you need is a crystal tester and a frequency counter. That will solve the mystery of the crystals once and for all, and of course, publish the results here afterwards. Maybe I will go try and dig up my crystal tester to see if I have it in the office. That way I can test all these crystals and solve the problem. Have to go look in my equipment pile at my office.

Daniel

[nic]

Forget about using the crystal from Wind dragon's Tx. Just get another Tx, but specify the same frequency.

Eg If Rx is 40.123. The futaba Tx also must be 40.123. It is better to use Futaba crystal on Futaba Tx.

There is only 1 exception... for 72MHz, there is positive shift and negative shift.... so.. if you are not on 72MHz... you don't need to worry about that.

I am using Futaba Tx, I have Hitec receiver, Berg Reciever and Futaba Receiver, each receiver using their respective brand's crystal.

Mike: I still have 1 spare Dual Conversion Hitec crystal (brand new in packaging).. let me know if you want...

[pilot_bear]

If the number of conversions, and the IF, and the shift is the same, you should be able to use the same crystal. So, although a Futaba crystal is marked 29.100 MHz for example, it's actual resonant frequency may actually be 28.645 MHz but for a JR crystal marked 29.100 MHz it may actually be 29.555 MHz. On the other hand for a single conversion receiver marked 29.100 MHz, the resonant frequency may actually be 29.100 MHz. The reason for this is due to the different ways the receivers are designed.
Daniel

Hi Daniel, one question,
quoting the above as an example,
does that means if i am using a futaba 29.555, and another guy using a JR 29.100, there is a likely chance that he could be interfering with my signal ? or put it another way, if both using 29.100 of different brand, we might not face any interference problem at all?

Thanks,
PilotBear

[Daniel Wee]

Well, not really because the shift usually takes place within the receiver side. The transmitter will transmit on the stated frequency regardless of the shift of the receiver so there should not be any conflict in frequency unless they both state the same frequency.

Daniel

[pilot_bear]

Well, not really because the shift usually takes place within the receiver side. The transmitter will transmit on the stated frequency regardless of the shift of the receiver so there should not be any conflict in frequency unless they both state the same frequency.

Daniel

OIC , thanks for the info.

PilotBear

[Shark]

sorry I still dun really get it.. can anyone explain in more "layman" terms. ok let say for my case..

I am getting a Futaba Tx (2nd hand), 29Mhz freq. so can I use it on my Wing Dargon Rx? if I take out the 29Mhz from the Futaba and rplace with my original crystal from my Wing dargon Tx?. Since now the Futaba Tx is at 40Mhz (crystal from Art-tech) and the Rx also on 40Mhz (Art-tech rx and Crystal).. will this confiuration work?

Or does it mean I have to replace my Wing Dargon Rx with Futaba Rx then it will work? (of cos both in same freq)

[nic]

sorry I still dun really get it.. can anyone explain in more "layman" terms. ok let say for my case..

I am getting a Futaba Tx (2nd hand), 29Mhz freq. so can I use it on my Wing Dargon Rx? if I take out the 29Mhz from the Futaba and rplace with my original crystal from my Wing dargon Tx?. Since now the Futaba Tx is at 40Mhz (crystal from Art-tech) and the Rx also on 40Mhz (Art-tech rx and Crystal).. will this confiuration work?

Or does it mean I have to replace my Wing Dargon Rx with Futaba Rx then it will work? (of cos both in same freq)

In layman:

Frequency Bands and channels:
1) Frequency bands: 27, 29, 35, 36, 40, 50, 72, 75
2) Channels: .xxx i.e. the decimals behind the bands.

Note 1:
-- A Rx cannot switch from one band to another by swapping the crystal. It only can change channel.
-- Most Tx cannot switch from one band to another too. Unless the high ends one that comes with removable modules, usually 7-9 channels Tx

Note 2:
-- Don't worry about shift unless you are on 72MHz. You wont be able to find shift sensitive receivers on other bands.

Note 3:
-- Channels can be swap by changing crystals. It is however not advisable to use a different brand's cystal on a different Tx/Rx. Put it this way.. this is not a toy, and "DUN PLAY PLAY". Anyway, a lot of times you will find it will not work.

Note 4:
-- You can use different brand recivers with different Tx as long as the the band+channel is the same. Look around at the FF, you will see most who are using Futaba or JRs are not using Futaba and JR receivers

[Shark]

thank nic for the explaination.

so now I know, which mean I can use my Tx on diff planes, only thing is change the crystal to match the band + channel.

[nic]

thank nic for the explaination.

so now I know, which mean I can use my Tx on diff planes, only thing is change the crystal to match the band + channel.

Eh.. see note 1... change crystal on receiver can only match the channel.. so you need to make sure the receiver you buy is on the same band...

[pilot_bear]

maybe i can help shark here.

He intend to use a futaba Tx for his WD, but still want to use back the WD Rx.

So the question is can he use back the the same WD Rx ,RX x'tal and use back his WD Tx x'tal on a futaba TX
or
do he need to buy a pair of matching futaba x'tal for both the WD Rx and Tx ?

note: the example above i use futaba to simplified thing, ofcourse he can also use JR/Hitec/etc Tx
assuming also the band / ch is same.

Hope this is your question.

[Shark]

think I got it now..

Basically we cannot anyhow buy any Rx and Tx and use the same crystal. It wouldnt work!!!. we need to buy the same band of Tx and Rx and crystal but can choose from diff channels. The sticker on the Tx and Rx must hv the same Number (eg 72, 29 etc) ..

thank all..now I know liao..