User manual HAM INTERNATIONAL MULTIMODE II

[. . . ] 9 to 15 of IC1 ] on the programmable divider in [ C l , to preset the divider. The two signals, the crystal oscillated signal [10. 24 MHz] from Q3, and the signal from the VC0 via the lowpass filter [LPF] and buffer [in the IC1 1, are compared in the phase detector of IC1 and the phase detector produces a DC output voltage derived from the phase diiference in the signals fed to it. This DC voiraae applied to the VC0 causes ~t to shift freauency untll its outout s~onal locks up w t h the count. donVvn frequency provided from reierence oscillator Q3 [;vnen two signals are in phase] ~t which point no DC output is prociuced in the phase cietector, and t h VC0 rerna~ns locxed on freouency. When a new channel is seiected a ne*:t N ccode is apolied to the programn?aol"evider. [. . . ] Also fed to the second mixer i s the second local oscillator signal, 10. 24 MHz, from Q3. Mixing of these two signals result in a signal at a frequency of 455 kHz in T14. This is the second intermediate frequency for AM or FM mode of reception. In AM mode, the 455 kHz signal passes through the ceramic bandpass filter CF, and fed to. 1F amplifiers 027, 28, and 29, which include IF transformer T15. The output of Q29 is applied to 025, the AM diode detector, while in FM receiving mode, the 455 kHz signal amplified only through Q27 i s led to FM demodulating IC, IC3 on the PTOSOO6 through T4. Resultant demodulated audio i s acheived from the IC pin = l 2 and input to AF gain control VR, VR1. In the SSB mode of reception, the signal obtained a a s result of the mixing of the RF input and IC2 VC0 signals, 10. 695 MHz in the USB, and 10, 692 lLlHz in the LSE mode, is not converted down to lower intermediate frequency, but. is passed ttiroucjh the crystal filter, XF, and fed to the SSB IF amplifiers, 014, 16, and 17, which inciudes T11, and 12. The signal at the secondary side of T12 is fed to 019, the product SSB detector and beat with the BFO [beat frequency oscillator] signal from the Q12 and finally rectified to audio frequency signal. The audio signal output from detectors (for AM [D25], FM [IC2], and SS8 [Qlg]), i s passed through the AF Gain Control, V R l , to the input of the audio amplifier, IC5. The audio output, is transformercoupled to the internal speaker, or to an external speaker through External Speaker jack, J3. R X Diagram to. 2 1 nnz PLL C IRCUIT 57. 66- 10. 695 39. U) MHz XF nnz 012 -in 0 16/11 SS0 IF OSC 0 20 ANT R F AMP 0 !GET. t 0 22123' AM M I X 121 AF 025 AM POWER OUT IF &M DET. Squelch 032, 33, and 34 are the squelch amplifier transistors. At low [or no] signal levels Q34 collector conducts to ground and i t s output connected to pin number 6 of 1C5 results in no signal output from the audio amplifier. As the incoming RF signal increases it results in opening up the AF amplifier and output is activated. The point at which Q34 cuts off i s determined by setting of the Squelch Control, V R2. Nois2 B l a n k e r C i r c u i t N o i s e s c o n t a i n e d i n t h e o u t p u t from 4-20 p a s s C-112 and f e d t o 4-23, n o i s e a m p l i f i e r . The n o i s e s a r e r e c t i f i e d by D-20 and D-21 t o t u r n on 4-24 (FET) which i n t u r n t u r n s on 4-25 and 4-26. This causes the I F s i g n a l (10. 695 and 10. 692 MHz) a t T-10 t o s h o r t o u t t o ground through C-21 and 4-26, d u r i n g the presence o f t h e n o i s e impulses, v i r t u a l l y b l a n k i n g o u t t h e n o i s e s from t h e a u d i o o u t p u t . s i l e n c e d i s of s u c h s h o r t d u r a t i o n o f 10 microsecond o r l e s s t h a t t h e r e i s v i r t u a l l y no a u d i b l e e f f e c t on the o u t p u t . ) 'Tune' C i r c u i t The t u n e c o n t r o l f a c i l i t y a l l o w s betweenc h a n n e l o p e r a t i o n by s h i f t i n g b o t h t h e t r a n s m i t a n d r e c e i v e f r e q u e n c i e s 4. 5 kHz above o r below t h e a s s i g n e d c h a n n e l f r e q u e n c y . The a c t i v e e l e m e n t s of t h i s c i r c u i t a r e t h e v a r i a b l e - c a p a c i t a n c e d i o d e s D-4, D-5 and VR-2 ( f r o n t p a n e l ) . The c a p a c i t a n c e of b o t h diodes w i l l vary i n accordance w i t h t h e b i a s l e v e l d e t e r m i n e d by VR-2 a d j u s t m e n t , t h u s i n c r e a s i n g o r decreasing the p a r a l l e l c a p a c i t a n c e t o R-14 a t 4-4 e m i t t e r t h r o u g h C-25, a n d t h e e x t e r n a l c a p a c i t a n c e t o X - l , X-2 o r X-3 (D-5) s i m u l t a n e o u s l y . [. . . ] Comparing t h e e x t e r n a l RF power a n d t h e b u i l t i n meter, a d j u s t RV-3 (PTBM059) f o r e q u a l i n d i c a t i o n on t h e power m e t e r s . 1 2 - T r a n s m i t t e r Alignment Connect t e s t equipment t o u n i t a s shown: EXT ANT SP JACK /' A JACK a0 ' +\ i Durnrn y Plug DC Power < . D . ( VTVM A SUPP~Y Receive M o d e AGC Connect d i g i t a l v o l t m e t e r t o c i r c u i t b o a r d PTB?1059 t e r m i n a l 1 5 (4-20, 4-22 AGC i n p u t ) and c h a s s i s ground. 2 - S e t t h e t r a n s c e i v e r t o c h a c n e l 60 (MID b a n d ) . 4 - A d j u s t RV-8 f o r 2 V. 1 - AM r e c e i v e r s e n s i t i v i t y 1 - S e t s i g n a l g e n e r a t o r t o 27. 655 MHz w i t h 1 kHz 30 % m o d u l a t i o n . [. . . ]