Red Jacks

A newbie question concerning crystal sets.
I have been told that you can not change crystal sets from one brand of radio to another.
Is this true or not? Someone also told me he changed sets from one brand to another and
there was no problem. Everything worked fine.

Scar

My Feedback: (3)

In the US, the FCC sells licenses to people so they can mess with frequency generators. If you don't have a license, you're not supposed to fiddle with the transmitter. You can change the receiver crystal all you want, and they're easy to come by.

Transmitter crystals are less easy to come by, and the Professionals will tell you that after a crystal change you need to "tune" the unit. Except for Multiplex, which sells crystals.

Other transmitter manufacturers get around that by selling frequency "modules" that you can swap in & out, or "Synthesizer" modules, which can be set to any frequency.

Now, your question involved Brands, specifically. I don't know about transmitters, but I've used HiTec crystals in Futaba & Airtronics receivers without problems. I've been told they won't work in JR, but I never tried one.

Good luck,
Dave Olson

Red Jacks

Thanks for the reply Dave.

I suppose I could purchase a set or two and try them on several brands of radios.
What does concern me is there a potential to damage the radio from using different
brand crystals than what originally came in a particular radio.

coolguy234

Well im not in the US, and here there's no restriction. We change crystals in both the Tx and Rx without any problem. Just dont put a 26.xxx into a 27.xxx Tx/Rx or 72.xxx etc...

Spoiler

Just read an article on this. As manufacturers make their Xtals with slightly different capacitance values, the external circuitry in each manufacturers Rx and Tx is slightly different and tuned to compensate for their Xtals capacitance value. This results in incorrect reception or off frequency transmissions if say JR Xtals are used in Futaba and increased intereference for others as well probable reduced range. The rule is therefore to use the manufacturers Xtal in its RC equipment. This allows you to use say Hitec Rx's with a JR Tx provided the correct Xtals are used in each.

$n4IL

On a slightly related note, is it OK to use a transmitter from one manufacturer (say Airtronics) and receiver/servos from another (Hitec)? I'm planning on purchasing a sightly better transmitter than my current one, and all my planes currently use Hitec gear. I was thinking of buying an Airtronics transmitter. Thanks!

JohnBuckner

My Feedback: (1)

Unless the airtronics Tx you select has modulation shift select feature then this combination will not work. Modulation shift must be the same for the Rx and Tx. Hitec normally uses negative shift and Airtronics normally uses positive shift. I beleve Airtronics has one tX that is shift selectable but cannot tell you which model it is. Hitec does sell Rx's on both shifts for use with JR and Airtronics Tx's but if it was bought as a package with a Hitec Tx then it will be negative shift.

John

$n4IL

Thanks, that's just the info I needed. Looks like I'll be staying with Hitec just to keep my "shift" as simple as possible.

hilleyja

My Feedback: (3)

$n4IL,

Actually, I won't swear to this, I think most of the CURRENT Airtronic TXs come with the ability to switch from Positive to Negative shift. Hitec TX's also have this capability (at least my Hitec Eclipse 7 does and my old Prism 7 did as well).

NOTE: Hitec is in the business as a 3rd part RX vendor. Because of this most of their RXs can be purchased as POSITIVE or NEGATIVE shift. They also market a 7-channel RX that you can change the shift with a wire strap.

BasinBum

My Feedback: (2)

The AMA position is don't change the TX crystal but the actual FCC rule (95) is rather vague on this issue. As for Scar's explanation of a "license" to work on radios that's not true and there is a vague description of who is qualified to do internal work on a transmitter.

Regarding JR crystals in Futaba radios for example....Jr mostly uses single conversion receivers whereas most other manufacturers use dual conversion so the crystals are not interchangeable. I have swapped Hitec and Futaba receiver crystals with no problems.

If you want to change the channel of your transmitter it is easy, cheap and wise to just send it in for the manufacturers service dept. to do it and have some peace of mind.

Digger44

My Feedback: (4)

Just wondering , if anyone has used the SEEKER II (8 channel) or the SEEKER 6 receivers, and if so, do you feel safe changing frequency. This would be an advantage if the technology is solid. Match these receivers up with a synthisized transmitter and your options are virtually unlimited. They claim to work with any FM Transmitter. Polks Hobby sells them for 60-70. Not bad if it works.