RE: Dual band Transmitter w/Single band Reciever?
No you would not touch the TX crystal. The single/dual consversion senarios only apply to the type of filter system used in the Rx, it has nothing to do with the Tx. If you use a single conversion Rx, you would also use a single conversion crystal of the same brand as the Rx ordered on the desired channel, in this case the same channel that your Tx is on.
Use only the same brand and single or dual conversion crystal as the type Rx your plugging it into.
A band is a block of frequencys (channels) some where in the frequency spectrum do keep in mind there are park flyers in the US that use the 27Mhz band and also the 72 Mhz band and in this case you can only use flight packs on the 72 Mhz band, the same band your Tx is on. You cannot us a 27 Mhz band crystal for instance in a Rx intended to be used on the 72 Mhz band.
John[8D]