EMRFD Message Archive 7909

Message Date From Subject
7909 2012-10-27 05:01:51 ha5rxz Phase Modulating A Carrier
In the Files section you will find a section of the TS-480 schematic under the title "Kenwood Phase Mod.jpg". Operating at about 8.8 MHz it will phase modulate a carrier but I cannot understand the component values used.

A 2.2 uH inductor needs about 150 pF to resonate at 8.8 MHz but in the circuit we see 2 x 330 pF, 1 x 220 pF and a varactor diode that has a maximum capacitance of about 100 pF.

Please could someone explain what is going on?

Peter HA5RXZ
7910 2012-10-27 16:38:02 kb1gmx Re: Phase Modulating A Carrier
7911 2012-10-28 06:50:15 ha5rxz Re: Phase Modulating A Carrier
OK, thanks Allison. My final goal here is to use this circuit or something similar to phase modulate the output of a 45 MHz oscillator but in order to do that I need to understand the component values. Normally I'd use a varicap but the 45 MHz oscillator is ovened and I don't want to spoil the spec.

Peter HA5RXZ

7912 2012-10-28 08:45:39 kb1gmx Re: Phase Modulating A Carrier