A.T.

Near the point where the antenna connects to the circuit board is an adjustment most receivers. It is used to peak the RF input to the exact frequency desired. Shops which do this will know where to monitor the signal with an oscilloscope.
Unfortunately, in your case the Futaba R122JE has no provision for retuning. [Of 10 tested new out of the box, only 2 had range close to that of a Hitec 2ch RX, the rest with various range tests down to only 4m - not recommended for sailplanes] As the aerials often corrode and or break when typically used on cars or boats, a failing R122JE may be revived by simply fitting a new 50cm aerial . Also open the case, remove board and brush pins and bottom of the board with a dry toothbrush to remove all built up dirt or corrosion which also impair operation of an RX.
It is possible to get quite close by monitoring the sensitivity of other RX using a servo, as set out below in previous comment ex rec.models.rc.air.
Alan
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Just connect a servo to the open receiver, turn on your transmitter with the antenna retracted and some distance away. Adjust the can until the servo jitters in one direction and then the other. Readjust to the center of the range.
(For 72 MHz) Futaba adjust their receivers for a peak at about channel 25 or 50 depending on whether crystals below or above channel 38 will be used. It usually isn't necessary to retune at all if your crystal is between the two tunings. You don't need to retune if you stay within the low
or the high band either. Retuning may be a good idea if you are moving from one end of the band to the other. But, don't get too hung up on it. If you get a good range check, don't worry about it. Jim - AMA 501383 "James D Jones" 05.05.03
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"There is a range of Rx which can be purchased in the UK as a ready built Rx or as a kit. If you buy the kit version then the instructions for *peaking* the Rx with the crystal to be used is exactly as stated above. Leave the aerial down on the Tx and keep trimming for no servo chatter while steadily increasing the distance from the Tx. Range with Tx aerial down is about 40 yards and many people have built and used these receiver kits and are very satisfied with them.
It is not exactly rocket science after all, the crystal determines the frequency. You plug in a servo after gently turning it so the arm is to one side. By trimming one of the coils the servo should centre and then be capable of being operated with one of the Tx controls.
The other coil is then adjusted for maximum range as above. Should be easy to determine as this last coil is adjacent to the aerial lead on the PCB.
Lots of people build and use these Rx, most of them will have no experience of radio equipment, they just follow the instructions supplied. I use them in fairly large gliders which I fly at quite long range. The firm that sells them has been around quite a long time now. Reg 06.05.03
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Regardless of who tunes it, be careful that you dont break the core slug if it is of this type. Try not to use a metal screwdriver or a hex wrench. ONce cracked, it looses its effect and you are down for a repair. Some cores are waxed in place to prevent movement from vibration. If it is a variable capacitor it isnt so bad but you still have to know what to look for. - Jim Breeeyar
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Much more under "Radio Systems, Accessories, Alterations and FAQ" on my web page.
Regards
Alan T.
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