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 Welcome to Www.Ham.dmz.ro 18 March 2005, 4:57 
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News
New Icom IC-756PROIII transceiver !
New Kenwood TH F6/7 Mod:Service Menu switch!
New Kenwood TH-F6/TH-F7 conversion!

Icom IC-2720H (IC 2720 H IC2720H)
IC-2720H
Programming interface schematics for Icom:
Programming software for Icom IC-2720H (IC 2720 H IC2720H) :
PDF User Manual for Icom IC-2720H (IC 2720 H IC2720H) :
PDF Service Manual with schematics for Icom IC-2720H (IC 2720 H IC2720H) :

Mods for Icom IC-2720H (IC 2720 H IC2720H) :
    Icom IC-2720H (IC 2720 H IC2720H) crossband repeater
    Icom IC-2720H (IC 2720 H IC2720H) Adjustment Method by CS-2720 Cloning Software
    Icom IC-2720H (IC 2720 H IC2720H) RFI in mike
    Icom IC-2720H (IC 2720 H IC2720H) Reducing the RFI on microphone PTT line
    Icom IC-2720H (IC 2720 H IC2720H) out of band mod
    Icom IC-2720H (IC 2720 H IC2720H) repeater function

Icom IC-2720H (IC 2720 H IC2720H) technical specifications :  Icom IC-2720H (IC 2720 H IC2720H) technical specifications

Icom IC-2720H (IC 2720 H IC2720H) Reducing the RFI on microphone PTT line

While working on 2m band and high power, when the microphone is held too close to the antenna, the PTT 'hangs' in TX mode when going over to RX and/or there is sometimes no modulation during TX.

This is due to RFI on the PTT line going into the display/controller unit, and can be particularly annoying when working mobile with an antenna affixed to the front windshield (like PROCOM 'Glassfix' dualbander).

Solution :

RFI can be drastically reduced by inserting a 10 to 22nF capacitor between PTT line and ground (scratch a little bit of the PCB varnish), on the RJ-45 plug in the controller unit. See picture. If SMD capacitor not available, then try with a chip capacitor, solder the 'ground' side on big solder pad (solder of the potentiometer casing).

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