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Discussion Starter · #1 ·
Hi Guys,


I have a 27mhz 2 channel radio (smartech), can you use 29mhz crystals in it?


Thanks


Sikm8
 
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hmmm from what i have heard the 27am is pretty ####!!

might want to invest in a 29am radio set, ...im pretty sure a 29 wont work in a 27,



welcome aboard too

Nismo
 

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I personally wouldn't consider 29am as an upgrade to 27am. There might be less interference (CB radios?) but I've gone from 29AM to 27FM and have less radio issues now.

It could be due to the FM controller being far superior, and that's where I would recommend upgrading if you want.

Answer to your original question, I don't know.
But if you want to grab some 29MHz crystals and try it out, I don't think it would hurt anything.

If you're anywhere near Parramatta in Sydney, I've got a 29MHz crystal set you can test on it if you want.

Cheers, Oggy.

p.s. 29MHz seems to be the most common frequency - all the RTR cars in the hobby shops seem to have 29.825!!
 

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No you cannot use 29Mhz crystals in a 27Mhz Radio.


I disagree with Nismo however, I think 27Mhz is no different to 29Mhz as far as quality goes.


27Mhz is a fairly common frequency in Australia these days, and while 29Mhz is the "official" one, you shouldn't have any difficulty finding crystals locally. If it is 27Mhz FM (the same as mine), crystals may be more difficult to find in Aus.


Regards,


Chris
 

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27mhz is not the best as your signal can get flattened by people using CB radios near by
 

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Discussion Starter · #6 ·
Thanks very much for the info guys..


Ogier, thanks for the offer but I am in Geelong, a fair drive.


Anyway, think I may have found someone with 29mhz crystalI can test with.


Hope to be back soon


Sikm8
 

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I'm fairly certain it won't work - but if it did, that'd give me a
whole range of more channels to use with my stock AM radio set.
 

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sikm8 said:
I have a 27mhz 2 channel radio (smartech), can you use 29mhz crystals in it?

Nope.


Although sometimes it *might* seem to work on your benchtop if the 2 bands are closeby, but using wrong xtals will detune your equipment and the range will be severely crippled. Don't risk it.
 
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nismo if your gunna fork out the money from 27 to 29 u would get FM and stop p faryting around with toy'ey AM


there is nothen wrong with AM radio's, ive been using a futaba wheel radio 29AM and have had no probs, why bother upgrading yet?



fair enough if it died on me, id go and get a FM maybe, but the most cars i have ran against is 2, hmmm



Nismo
 

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Nothing wrong with AM radios, those that say FM is better can't tell the difference between marketing & the truth!



FM has its uses and maybe the signal filtering is a bit better, but in 95% of the cases AM works fine.


AM gear is also cheaper, more robust because its simplerand the xtals are $20/pr instead of $40-50.
 

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i have the cheapest radio i could find..its the futaba attackAM29mhz stick radio..i bought it for $90...they are selling for $69 at my LHS now..hmm...


thecheapest wheel radio i could find was around $140..hmm


but it seems that all professionals use wheel radios?


i've never seen a video clip with stick radios...they are all standing there holding their wheels...ahahhhh
Edited by: migoreng
 
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they are all standing there holding their wheels...ahahhhh


ahahah good way to put it..i first had a stick radio, then i got a wheel radio and have never touched a stick one since..



Nothing wrong with AM radios, those that say FM is better can't tell the difference between marketing & the truth!
</font>



FM has its uses and maybe the signal filtering is a bit better, but in 95% of the cases AM works fine.</font>



AM gear is also cheaper, more robust because its simplerand the xtals are $20/pr instead of $40-50.
</font>


spot on there zoomer, ive had no radio glitches or
anything at all, there was only the once when all the RX and esc where
wrapped up around the arial..hmmm

</font>


Nismo

</font>
 

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yes maybe but if u r gunna stuff around with crystal and rubbish get yourself a jr xs3 or hitec dsx or the new futaba 3pm and be done with crystals with the onboard synthesiser, all retail around 200USD aka 300aud
 
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whats so hard about changing crystals..., its a 20second job,

yes it would be nice to have a "expensive" radio set, same as its nice to have an "expensive" car, and etc etc etc...



a $300 radio set is on my "wish" list, not my needs list, and anyhow i have a habbit of dropping my TX,







Nismo
 

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Why wont it work if you replace both crystals? The one in the reciever and the controller, can someone explain to me why it wouldnt work?
 

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Evilhomer,


The crystals simply modify the fixed modulation of the TX and RX. In other words the TX and RX is either 27 or 29Mhz. The crystal then sets the frequency within that band.


Regards,


Chris
 
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found this on a rc forum, RC group discussion or something,.



<div class="smallfont">

What type of crystal do you need ?
</div>


<hr size="1" style="color: rgb(167, 167, 167);">





<div>Since this seems to be a rather frequent question I'll attempt a general answer to it.



First the basics, pardon me if you already know this. In most of our
R/C equipment it is a crystal that determines the channel or frequency
that the equipment is working on (the exception is equipment with
frequency synthesizers like the Hitec Spectra module). With no crystal
a transmitter will not transmit at all. With the wrong crystal it will
transmit on the wrong frequency. A receiver with no crystal will pick
up garbage from the air and with the wrong crystal it will be
"listening" to the wrong transmitters. Both the transmitter and
receiver must have crystals with exactly the same channel number.



There are 3 main types of R/C crystal. These are Transmitter crystals,
Single Conversion receiver crystals and Dual Conversion receiver
crystals, commonly called Tx, SC Rx and DC Rx for short.



These are all very different and you must not mix them up. A
transmitter crystal will not work in a receiver, a DC Rx crystal will
not work in a SC Rx etc.



PCM receivers do not need special crystals. All PCM receivers are
either Single Conversion or Dual Conversion and use a standard crystal
of the correct type.



The different manufacturers sometimes use different specifications for
their crystals so the only safe advice when you are changing a crystal
is to use one sold or recommended by the equipment manufacturer. Hitec
equipment, Hitec Crystal, JR equipment, JR crystal, Futaba....you get
the picture. Some aftermarket manufacturers don't sell their own
crystals but say to use a Futaba or other make crystal. Do as you're
told
.



Note: the crystal you use in a receiver is not affected in any way by
the make of transmitter you are going to use it with. If it is a Hitec
Rx it uses a Hitec crystal no matter if you're going to use a
Futaba/JR/Hitec/Sanwa/Airtronics transmitter with it (or any other I've
missed).



You'll probably see people telling you that a Brand X crystal works
fine in a Brand Y receiver. They may be right but it's up to you to
decide a) how much you trust them and b) if their advice will
definitely work for your equipment. Just as one example, I've often
seen people making a general statement that one brand of DC Rx crystal
will work in a different brand receiver. It may be true in North
America on 72MHz where they are (I don't know I've never tried it) but
it is completely untrue for the 35MHz European equipment I use (I do
know I have tested it). Beware of wide-ranging general advice given by
people with only limited knowledge.



I'm going to freeze this note at the top of the Radios forum. If you
want to debate any of the advice or it hasn't answered your questions
feel free to start a new thread any time.



Steve


Nismo

</div>
 

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Just a quick update, i tried 29mhz crystals in my ACOMS 27mhz AM radio system and it worked! So some do work with bith crystals, didnt lose any range what at all as well, so it was working at its full potential.
 

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What kind of range test did you do?



The only one that is any use is... get a friend to hold the car while you walk away holding the TX with the antenna down. Keep twiddling the sticks until the car stops responding & your friend calls out to you to stop walking.


Test the difference between using 29 & 27...






Honestly I wouldn't risk using 'wrong' xtals on a gas car, unless you've got a fail safe at the very least. You're playing it very risky.





If you want to do risky things... you can also run xtals "reversed". Put TX xtal in RX and viceversa... and it'll still work!! It'll be running on a different frequency to the original too... so you can run 2 sets of the same freq at the same time.


Again *range* is reduced... but if there's enough for what you're doing & you know the limitations, it'll work - as long as you're happy taking the risk.
 
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