You probably have an older AM system. Check the transmitter and its crystal for frequency. It may be 26.995, which
is part of the 27 Mhz band.
Receiver crystals are often marked with their basic frequency, which is not the same as the frequency the receiver
will work at. An internal frequency called the "intermediate frequency" (IF) is added or subtracted to the crystal frequency
to arrive at the operating frequency.
The IF is usually .455 KHz. In this case, adding that to 26.54 gives us 26.995 - the probable operating frequency of the transmitter.
Installing batteries and a servo and turning the system on will not harm anything if they turn out to be on different frequencies.
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