Spectrum Management - From the Early Years to the 1990s

by Laval Desbiens

Page 23 of 26

Measuring Frequencies with the Racal RA17C12

 


Frequency

standard

Output

 

1 MHz standard input

00 kHz to y fine tuning
1 MHz to RX RACAL RA17C12 receiver
5.1 MHz mixer

100 kHz

IF out

to x

2nd VFO out

to the mixer

  y Scope x  
NOTE:

When the fine tuning is adjusted so that a 1:1 Lissajous pattern appears on the scope, the receiver is tuned exactly to the incoming frequency.



5.1 MHz Mixer

 

2nd VFO
 

1 MHz

standard

Frequency counter

Example a) -

RX in

3.780123

14.100546

b) -

VFO 1

43.500000

54.500000

c) -

1 out

39.719877

40.399454

d) -

Fixed osc.

37.500000

37.500000

e) -

2 out

2.219877

2.999454

f) -

VFO 2

2.319877

2.999454

Last IF g) -

3 out

0.100000

0.100000

At mixer output, there is a difference of 5.1 MHz minus f) of which only the significant,

or last six (6) digits are retained, since the "MHz" are read directly on the receiver.

2.780123

2.100546

 

Spectrum Management - From the Early Years to the 1990s

by Laval Desbiens