Icom IC-720A (IC 720 A IC720A) transceiver mods reviews software and diagrams

   
 
ham | what is new | links
 Welcome to Www.Hampedia.net  submit to reddit
22 November 2019, 14:55 UTC 


SDR


ELAD
SDRplay

Transceivers


Kenwood
Midland
Yaesu
Alinco
Icom
Other

Antennas


M2
Par
Gap
Sirio
Araki
Maco
Nil-Jon
Maldol
Comet
Hustler
Nagoya
Watson
Hy-Gain
Dressler
Cue Dee
Solarcon
Diamond
Cushcraft
Quicksilver
Moonraker

Power supplies


Powerbox
Kenwood
Diamond
Samlex
Mascot
Daiwa
Yaesu
Alinco
Icom
H&H

Rotators


M2
CDE
Yaesu
Create
Kenpro

Antenna tuners


MFJ
LDG
SGC
Icom
Yaesu
Mizuho
Dentron
Kenwood
Sommerkamp
Barker & Williamson

Repeaters


GME
Icom
Zodiac
Kenwood

Transverters


Microwave Modules
Tokyo Hy-Power
SSB Electronics
Tecnostudi
Kenwood
Yaesu
Minix

Meters


Diamond
Comet
Bird
MFJ

Ham resources


Propagation:
  Sporadic E skip (Es)
  Backscatter
  Tropo
  Meteor Scatter (MS)
  F2 Skip
  Aurora
  Trans-equatorial scatter (TE)
  Lightning scatter (LS)

Icom IC-720A (IC 720 A IC720A)
IC-720A
Programming interface schematics for Icom:
Programming software for Icom IC-720A (IC 720 A IC720A) :
PDF User Manual for Icom IC-720A (IC 720 A IC720A) :Icom IC-720A Instruction Manual
PDF Adjusments Procedures Manual with schematics for Icom IC-720A (IC 720 A IC720A) :
Schematics for Icom IC-720A (IC 720 A IC720A) :

Mods for Icom IC-720A (IC 720 A IC720A) :
    Icom IC-720A (IC 720 A IC720A) Rotaryswitch mod
    Icom IC-720A (IC 720 A IC720A) extended xmit
    Icom IC-720A (IC 720 A IC720A) Modifying IC-720A to get rid of rotary relay
    Icom IC-720A (IC 720 A IC720A) Amtor mods

Icom IC-720A (IC 720 A IC720A) technical specifications :  Icom IC-720A (IC 720 A IC720A) technical specifications



Icom IC-720A (IC 720 A IC720A) Modifying IC-720A to get rid of rotary relay

I have just finished modifying an old IC-720A HF transceiver to replace the rotary relay filter control with a set of reed relays and a small digital circuit to select the appropriate relay and provide feedback to the existing CPU in the radio so it thinks it's still on the rotary relay. The cost for parts was about $25; the cost of my time was slightly more than that, but it was "fun".

The modification is so far successful, and the radio is much quieter in band switching as well as being more reliable (the old rotary relay was impossible to get mechanically aligned correctly, leading to poor connectivity between the rx/tx and the antenna, as well as many missed stepping pulses).

Summary: Use the step-pulse line to drive a small SPDT relay; use the SPDT relay to drive an R/S flip-flop (built from two nand gates) to provide a clean step signal (the existing step signal has some kind of very high speed clock train superimposed on it and therefore was not usable directly). Feed the pulse train into a CMOS decade counter type 4017. Take the appropriate decade outputs (active high) and recreate the switch-position feedback signals using a small diode matrix ala the original design. Also use the decade outputs through 33K resistors to turn on 2N3904 NPN transistors, which are used to select the appropriate (1 of 7) DPST reed relays. The CMOS chips (the nand gates and the decade counter) can be had at Radio Shack and must be powered from 9V (or so) because the radio does not use 5V logic (of course...)

I mounted the reed relays inside the original low-pass filter subassembly, and the rest of the circuitry on a small perf-board near the SWR module (connected by ribbon cable).

This is not a detailed design description but if you are interested I will provide more details. This project did ssalvage an otherwise-worthless IC-720A, but I don't think I'd do it again (rather time consuming, but perhaps you can benefit from my experience and save some time).

CB Equipment


President
Midland
Uniden
Zodiac

 Power amplifiers


Beko
Icom
Alinco
Drake
Yaesu
Daiwa
Collins
Kenwood
DanAmps
Ameritron
Autophon
Eto/Alpha
Command Technologies
E.F.Johnson
Dentron Radio Co.

FRS/GMRS


Bell
GPX
ENC
Tekk
Icom
Sony
Alinco
Drake
Cobra
Maxon
Vertex
Conair
Uniden
Jenson
Ranger
Midland
Whistler
Magnum
Unwired
Coleman
Motorola
Audiovox
Memorex
Columbia
Samsung
Standard
Kenwood
Cherokee
Panasonic
Freetalker
Vtech Vtalk
RadioShack
Fanon Courier
Sharper Image
General Electric
Oregon Scientific

PMR446


Sommerkamp
FreeQuency
Goodmans
Kenwood
Lafayette
President
Binatone
Motorola
Multicom
Albrecht
Maycom
Topcom
Xtreme
Ondico
Telcom
Maxon
Vertex
Zodiac
Yaesu
Cobra
Alinco
Icom
Alan
ITT