Using a receiver with the "wrong" crystal

What would happen if someone used a 72MHz high-band receiver (like the
high-band Futaba FP-R127DF) with a 72MHz low band crystal (channel 24)?
I've accidentally pulled a receiver that had been bought with a channel 54
crystal (from Tower as part of a radio system so I'm assuming they picked a
high-band receiver) and not knowing any better put a channel 24 crystal in
it. I've flown successfully with it, but just found out today that the
127DF is tuned for high-band or low-band and now realize I may have screwed
up.
My guess at the potential consequences is that the range of the receiver
would be dramatically reduced. Is this correct?
Thanks.
Jim
Reply to
Joe Bill
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You may have caused a flux in the time-warp continium.............. or just reduced your range. It can be retuned to ch 24. mk
Reply to
MK
That will only occur if the flight pack battery is capable of outputting 1.21 GigaWatts
Seriously, as the other "Mike" mentioned, the worst would be a slight decrease in range. This hi/low band stuff is a recent R/C radio manufacturer idea. Not that's it's a bad idea, but just relatively new.
Mike
Reply to
Mike
Let me tell you...if that thing will pass a range test I'd fly it till the Sun went down. If there is any reduction in range you'll probably never know it as it would be very small. You'll here all kind of gloom and doom before you get all the replies in. I have my flame suit on and am ready for the worst!! Eddie Fulmer AMA 63713
Reply to
Efulmer
I have an older 127DF that came with a Conquest FP-7NFK. Back then there was no choice of high or low receivers, just the full range of channels to choose from.
Reply to
Tim
No flames from me Eddie.
Who do you think starts this stuff with the hi-low band radios, when we got along without it for years and no problems?
If you want to start flames ---- I flew for years at busy fields with Futaba Attack AM radios. Can anyone imagine doing that now days? GRIN
Happy Flying
Mike
Reply to
Mike
Correct.
I don't recall Futaba or Airtronics doing it, but Hitec would ship radios to hobby shops without crystals. They would include sets of Tx/Rx crystals to be installed at time of purchase for whatever channel the customer wanted. I don't ever recall a problem with that method.
Must be progress these days huh? Mike
Reply to
Mike
If the MANUFACTURER says you need to do a certain thing and you think you know better than them, they you are in for a rude awakening if something should happen.
Accident investigator to judge: The only thing we found was that the wrong frequency crystal was in the receiver. The receiver was designated as a high channel one but there was a low channel crystal in it.
Judge to you: The people who design and make these things say that is wrong. Why did you do that?
You to judge: Because I know more than they do. I did a range check.
Reply to
Paul McIntosh
Good point!
I also tried this with my hitec stuff - changed the crystal and ended up with a loss of my aileron channel...only the aileron. Everything else was fine. Switched back the crystal and everything was back to normal. This was from channel 28 to 52 and back.
FredD
Reply to
RedFred1
And a recommendation from Futaba that you have your transmitter and receiver tuned if you changed crystals from what came with them.
Reply to
Paul McIntosh
Perhaps Futaba changed their receiver design and now they are supposed to work like that.
Reply to
Paul McIntosh
Hitec openly advertized that their receiver design allowed you to change crystals without retuning. Futaba always recommended having the sets tuned if you changed frequencies from what was originally supplied.
Reply to
Paul McIntosh
Some manufacturers will tune a receiver to the center of the entire 72MHz band we use. Some split the band and tune their receivers to the center of the high or low half of the band. Why? This way they get some sort of better performance from the receiver. Perhaps they can tune it tighter with better rejection or perhaps this reduces drift in some way. But I'm sure they have a reason related to performance.
Does this mean a so called low band crystal will not work in a high band receiver? Nope! But in theory, the low band crystal in a high band receiver will not provide as good performance as you would get by staying within the band it was tuned for. Chances are you can get away with it. Especially if the range check looks OK. But in the event of a crash, it adds just one more contributory variable you'll have to consider. And as has been pointed out, if it ever were to make it to a court case, it could prove your undoing.
You buy your ticket and take your chances!
Chuck
Reply to
C.O.Jones
Speaking of Futaba radios; how do you tell a high band receiver from a low band one? I have a couple receivers without crystals in them. Is there a model number on them so a person can identify one from the other? Thank you, Ed
Reply to
ZEMSKI
That would emply that Futaba used to tune each receiver for a specific channel. Now that they only tune to a high side or a low side, it would seem that the channels on the extreme ends of the high or low side would be much less in tune than the earlier receivers that came tuned for a specific channel.
Reply to
Tim
======================= They are typically not marked in any way. If it came with a crystal, it has a sticker with the original channel. If not, I guess you have to have it checked.
Reply to
Carrell
Acording to Futaba, from their FAQ:
Please explain Hi and Low band to me? I am not sure what the difference is between them.
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.
hth
J.D. to e-mail, pull the post
Reply to
J.D.
In theory, it MAY work. And a range check is a poor indicator of tuning status especially if the range check is in the absence of any kind of potential interference.
Reply to
Paul McIntosh
The only manufacturer selling high and low channel receivers is Futaba and they have different part numbers for them. They are also clearly marked.
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Reply to
Paul McIntosh
Depends upon the design. Some receivers do not use an RF stage and go straight to the mixer for conversion to the first IF. For these no tweeking is required. Some use an RF stage which has a passband to amplify the signal to the mixer. It's difficult to wideband tune the RF stage to cover the entire band so the manufacturer either tunes for low or high in the band. Usually, it is only a small tweek of a tuned cap. Without this, the range may be degraded but still usable for our short range control. Many would not notice the degraded performance.
Just my 2 cents.
Ray S.
Reply to
Ray Shearer

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