Go Back   WorldwideDX Amateur Radio Forums > Amateur Radio Related > Amateur Radio Modifications > Icom


Amateur Callsign Lookup
Enter Callsign:

ICOM IC-2820 TX audio modification

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 05-23-2010, 09:54 AM
AudioShockwav's Avatar
Extraterrestrial Admin
iTrader: (2)
 
Join Date: Apr 2005
Location: High Sierras Near Yosemite Nat Park
Posts: 5,049
AudioShockwav has disabled reputation
Default ICOM IC-2820 TX audio modification


We all know that the ICOM IC2820 has an squeaky TX audio response in FM mode with a lot of exaltation of the high frequencies.
This audio response is really not comfortable to hear.
In order to solve this problem (that isn’t really a problem….)
I decided to check the schematic diagram and open the bottom cover of the radio and find where to put the fingers.... or better where to put the soldering iron.
There are three HPF “high pass filter” stages on the MIC path, so I tought to eliminate one stage and hear the difference.
I bypassed the first HPF stage right behind the MIC connector on the front panel with a 10 uF 16 V capacitor.
I put the capacitor with the positive lead on PIN 3 of the MIC connector and the negative lead on the joint between C624 and R545.
In order to have the right effect on the audio response you have to remove the 1 uF C624 capacitor from the PCB.
The following drawing and pictures well explain the modification.

This is the first stage that acts as HPF

This is the PCB area where the first HPF stage is located
In this last picture there are all the information to perform the TX audio modification on the 2820.
The modified radio has been checked in DV mode too to verify that the now broaden audio frequency response doesn’t affect the audio quality in GMSK modulation.
Now the question is…….Why the engineering staff from ICOM put this third HPF stage on the AF path?
I really don’t know but by now it doesn’t matter!
Now enjoy your NEW IC2820 but pay attention to set the audio setting as follow:
MIC sensitivity: HIGH
ALC: OFF
With the above settings the transmitted audio will be more powerful and comfortable.
__________________
Radio-active

NASA/SOHO


When I was a child
I caught a fleeting glimpse
Out of the corner of my eye.
I turned to look but it was gone
I cannot put my finger on it now
The child is grown,
The dream is gone.
but I have become comfortably numb.


Reply With Quote
Reply

Bookmarks
Worldwide Radio Forum



Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Icom IC-2200H TX preamp modification AudioShockwav Icom 0 05-23-2010 09:43 AM
ICOM IC 2200H Mic output modification AudioShockwav Icom 0 05-23-2010 09:42 AM
ICOM IC 2200H Airband (AM) audio level modification AudioShockwav Icom 0 05-23-2010 09:38 AM
Stock Cobra 2000GTL "air noise" on TX Crazy_D General CB Services Discussion 13 09-30-2007 01:33 PM
Icom 718- ALC modification for AM possible? High Miler HF Bands and HF Rigs 19 02-04-2007 10:43 PM


All times are GMT -7. The time now is 02:54 AM.


Powered by vBulletin®
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.0
Worldwide Radio Forum