SSB and over modulation? - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 07-04-2006
Member
 
Join Date: Nov 2000
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
aphil138 is on a distinguished road
SSB and over modulation?

I was finally able to call in to Cruiseheimers this morning on my SSB radio. It was explained to me that I could be heard loud and clear, I was over-modulating. Can anyone explain that to me?Alan
Reply With Quote Share with Facebook
  #2  
Old 07-04-2006
gc gc is offline
Member
 
Join Date: Feb 2003
Posts: 63
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
gc is on a distinguished road
Over modulation is a distortion of the audio being transmitted. The audio (your voice) is mixed with radio waves to form the transmitted signal. It is then unscrambled on the receiving end. This mixing is done by modifying the radio waves strength according to the audio wave. When you overmodulate it is trying to reduce the radio waves strength below zero. Obviously this does not work and generates distortion by the time it is de-modulated on the other end. The fix is to lower your voice or move the microphone further away from your mouth. This reduces the audio volume going into the mixing process and gets things working the way they are designed to work.
Find someone to work with and try several transmissions with different voice levels to find which gives the clearest reception.
Reply With Quote Share with Facebook
  #3  
Old 07-05-2006
Member
 
Join Date: Nov 2000
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
aphil138 is on a distinguished road
Thank you.. so the problem is with me rather than with the gear. Comforting, at least I know the installation is working.
alan
Reply With Quote Share with Facebook
  #4  
Old 07-05-2006
Senior Member
 
Join Date: Jul 2001
Posts: 1,174
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 14
k1vsk will become famous soon enough
Not to get too technical but it's not actually over-modulation which is a term commonly used on FM and AM but is distortion of the audio. You can't over-modulate an SSB signal as the signal is essentially all voice audio, i.e., the signal level rises and falls with the level of your voice.
Long story short - rather than figure out how loud/soft near.far away to speak, just pick a comfortable voice and distance from the mic and adjust the mike gain control such that the audio is clear. Obviously, it helps to have someone listening...
Reply With Quote Share with Facebook
  #5  
Old 07-06-2006
Member
 
Join Date: Nov 2000
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
aphil138 is on a distinguished road
OK, This is a SGC2000 with an auto tuner. It has no mic gain that I know of. Is there a good frequency to use to find someone to test things out with?
alan
Reply With Quote Share with Facebook
  #6  
Old 07-06-2006
Senior Member
 
Join Date: Jul 2001
Posts: 1,174
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 14
k1vsk will become famous soon enough
Testing radio

If you are at a marina, what I'd do is walk the dock looking for someone who has an antenna (other than ther typical VHF) and ask them to monitor your transmission. Their close proximity will help ensure that they are hearing your signal without any interference. The goal is to "modulate" the signal at the strongest level without causing distortion as SSB transmitted power is a function of audio level. Any frequency will suffice.
Don
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



All times are GMT -4. The time now is 01:24 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.