Product manual

Setting FFSK Levels in a Radio-based System
113
Note
In a radio system, the volume of the receiving radio may have to be
adjusted. Ideally, the FFSK signal should cause 2-3 kHz of deviation in
FM type radios. However, the significant parameter is the voltage at
the receiving entity’s input terminals for a continuous FFSK signal
generated by the transmitter in the Test Mode. Most radios have more
than enough receive gain to accommodate this requirement. The gain
(volume) of the receive radio must be locked in and maintained at
whatever level is settled upon. Changes in this gain could alter the
performance of the system dramatically.
Additionally, most radios exhibit a roll off of the audio at higher
frequencies. In order to determine the effect of this roll off, use an
oscilloscope to view the input signal to the Model 6. When the test
tone is transmitted, it is a series of tones corresponding to logical 0
and logical 1. If these tone waveforms show alternating large and
small peaks, measure their amplitudes. If the large peaks are more
than 1.2 (120%) times the smaller ones, then data integrity may be
compromised.
Table 7: Model 26 Pots
Reference Name Description
Initial
Position
R-30 MIC XMT Level of Handset Mic to Line & Handset Ear Mid
R-31 VOX Active Threshold level of VOX Mid
R-32 COR Active Threshold level of COR Mid
R-63 TONE XMT Level of Tones to Line & Handset Ear CW/CCW
R-64 EAR POST RCV Level of Line Audio to Handset Ear Mid
R-68 EAR RCV Level from Line, tones or Mic to Handset Ear Mid
R-69 4W RCV Receive Signal Input Level - 4-Wire Mid
R-78 FSK POST RCV Secondary FFSK Input Level Adjust. Mid
R-79 FSK XMT FFSK XMT Level CCW
R-81 2W RCV Receive Signal Input Level - 2-Wire CW/CCW