bako

hallo. can someone tell me whats difference between negative and positive shifts in FM radios? for examle I have eclipse7

A.T.

The shift is the way the FM signal is modulated. Because the modulated signal is different, you cannot use a negative shift transmitter with a positive shift receiver or visa versa. Hitec and Sanwa transmitters are shift selectable and can be changed to match another brand of receiver in use whilst JR 72 Mhz & 75 Mhz TX are fixed positive shift and Futaba are negative shift. Hitec used to produce two types of receivers marked for Hitec/Futaba use with negaitive shift and the other marked positive shift for use with JR & Airtronics 72 & 75 Mhz TX. New Hitec 72 & 75 MHz RX now have auto shift and automatically change shift to match the Transmitter (caution = Golden rule applies now more than ever with auto shift, PLL and IPD receivers = TX On First - TX Off Last or the receiver may not lock on to your TX - picking up some other close to frequency signal instead). JR also now produce some receivers with either positive shift as used with 72 MHz for JR and Sanwa (aka Airtronics) and Negative shift for use by Futaba and Hitec on 72 Mhz. and 75 Mhz.
Regardless of frequency, all shift select TX are to be set on "SFT.N" i.e. 35 Mhz, 36 Mhz, 40 Mhz & 41 Mhz except when used with JR or Sanwa(Airtronics) RX operating on 72Mhz and 75 Mhz. Reference in need, "Transmit Shift SFT.N SFT.P" Eclipse manual page 11 download manual .pdf .
Much more information under "Radio Systems, Accessories, Alterations and FAQ" sub section "Receiver - FAQ, guides and aids to best reception" and "Transmitter - FAQ - Additions, Adjustments, Clonepacs & Repairs" amongst others on my web page.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

bako

thanks, nice explenation
so it means I can use any reciever for my 40mhz eclipse? (of course 40mhz recievers and not 72 ones)

A.T.

Yes, with proviso:
1. Eclipse can operate with all known PPM/FM receivers on same frequency. Whilst using receivers on 35, 36, 40 & 41 Mhz, both the Eclipse and Optic 6 must use Negative shift for all brands of receivers.
2 PCM is proprietary to each brand and cannot be used with any other brand. Hitec PCM receivers work only with the old Prism 7 transmitters whereas the Eclipse and Optic 6 operate a new system designated QPCM which operates only with the Hitec HPD-07RH 7Channel QPCM Receiver. Eclipse may have a mixture of models in memory pre-set to operate as QPCM or PPM. Each time you turn TX on, RF will automatically be QPCM or PPM as programmed and saved. Eclipse/ Optic Transmitter FAQ
3. Crystals used in other brand receivers must be the same brand as the reciver or confirmed by the receiver's manufacturer to be compatible with that brand as per Crystals - Swapping brands in RC Transmitters and Receivers.
More information available under "Radio Systems, Accessories, Alterations and FAQ" sub section "Receiver - FAQ, guides and aids to best reception." on my web page.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

A.T.

add addendum for Optic Sport Manual (also applies to Optic 6FM) = Set to Negative Shift for use with 35, 36 * 40 MHz receivers.
& copy from Eclipse Manual
{provide link and document as original URL down whilst original web page is being fully rebuilt}.

Alan T.

Dick T.

My Feedback: (243)

I believe the Futaba 12 and 14 series transmitters are shift selectable in PPM mode also.