Notices
Marine Electronics Forum

What is TVG?

Old 10-09-2014, 12:04 PM
  #1  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Aug 2009
Posts: 12,561
Likes: 0
Received 324 Likes on 222 Posts
Default What is TVG?

Can somebody tell me what it is and what it does? On my evo2 if I turn it up to 6 I can clear the "noise" up, but I'm not sure if this setting is stopping me from seeing bait maybe?
Old 10-09-2014, 12:09 PM
  #2  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Aug 2009
Posts: 12,561
Likes: 0
Received 324 Likes on 222 Posts
Default

In english please. lol
Old 10-09-2014, 12:11 PM
  #3  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Aug 2009
Posts: 12,561
Likes: 0
Received 324 Likes on 222 Posts
Default

I found this, but I'm not sure how it corresponds to the Simrad unit. http://www.furunousaforum.com/viewtopic.php?f=7&t=125
Old 10-09-2014, 12:35 PM
  #4  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2008
Location: Plymouth Ma.
Posts: 8,105
Received 254 Likes on 156 Posts
Default

Time Variable Gain

TVG is intended to compensate for the fact that close-in returns provide a louder echo than further-away ones by using a lower gain level in the period immediately after the sounder stops transmitting its ping (echoes from nearby objects) and then ramping up the gain level over time as the ping travels into deeper water, attenuating as it goes.
You cannot turn TVG off completely, but the TVG control allows you to adjust the extent of the effect of this compensation.
The ideal end result of using TVG appropriately is that if you increase Gain until you see a lot of clutter on the screen, the amount of clutter seen is about equal throughout the depth of the water column. That is, if you use A-scope Mode 2 (and I always recommend using A-scope Mode 2 for sounder tuning) then the clutter signal level should be a straight, vertical profile on the A-scope without 'peaks' and 'troughs.'
Old 10-09-2014, 12:37 PM
  #5  
Closed Admiral's Club Member
THT sponsor
 
Join Date: Jan 2014
Posts: 2,771
Likes: 0
Received 0 Likes on 0 Posts
Default

TVG is time variable gain.
Old 10-09-2014, 01:00 PM
  #6  
Admirals Club Admiral's Club Member
THT sponsor
Marine Advertiser
 
Join Date: Oct 2009
Posts: 23,882
Likes: 0
Received 1,694 Likes on 927 Posts
Default

Originally Posted by CMEBoston View Post
Time Variable Gain

TVG is intended to compensate for the fact that close-in returns provide a louder echo than further-away ones by using a lower gain level in the period immediately after the sounder stops transmitting its ping (echoes from nearby objects) and then ramping up the gain level over time as the ping travels into deeper water, attenuating as it goes.
You cannot turn TVG off completely, but the TVG control allows you to adjust the extent of the effect of this compensation.
The ideal end result of using TVG appropriately is that if you increase Gain until you see a lot of clutter on the screen, the amount of clutter seen is about equal throughout the depth of the water column. That is, if you use A-scope Mode 2 (and I always recommend using A-scope Mode 2 for sounder tuning) then the clutter signal level should be a straight, vertical profile on the A-scope without 'peaks' and 'troughs.'
Excellent explanation..
Old 10-09-2014, 03:03 PM
  #7  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2008
Location: Tampa, FL
Posts: 979
Received 30 Likes on 17 Posts
Default

It's like turning the volume on your hearing aid down, the closer someone is to you.

Imagine your wife screaming at you in your face. Now imagine her screaming at you from across the yard. If you were a sonar, you would think she was a lot fatter when she was in your face. So, you turn your hearing aid down as she gets closer. Now you (as the sonar) see her as equally fat regardless of how far away she is.

More TVG is more hearing aid adjustment.

No TVG is no hearing aid adjustment.

So (theoretically) with the right amount of TVG, a 10 lb fish will look the same at 10ft as it does at 50ft.

Last edited by tainted; 10-10-2014 at 12:07 PM.
Old 10-09-2014, 03:12 PM
  #8  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2011
Location: Boston/Cape Cod
Posts: 1,285
Received 14 Likes on 11 Posts
Default

CME - what is a good setting for this …..oh I don't know lets just say around below numbers - lol ? I'm having hard time really understanding what I'm looking at sometimes.

Old 10-09-2014, 03:26 PM
  #9  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Aug 2009
Posts: 12,561
Likes: 0
Received 324 Likes on 222 Posts
Default

I'm pretty sure that's small fish Captain Frosty.
Old 10-09-2014, 03:37 PM
  #10  
Admirals ClubCaptains Club Member Admiral's Club Member
THT sponsor
 
John_Madison CT's Avatar
 
Join Date: Aug 2001
Location: Old Saybrook, CT
Posts: 14,470
Received 741 Likes on 402 Posts
Default

This looks exactly like the nightmarish Chirp screens I've seen. There's just stuff all over the screen. Don't know what's clutter, bait, fish, plankton, thermocline, etc.....







Originally Posted by Captain Frosty View Post
CME - what is a good setting for this …..oh I don't know lets just say around below numbers - lol ? I'm having hard time really understanding what I'm looking at sometimes.

Old 10-09-2014, 03:54 PM
  #11  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Aug 2009
Posts: 12,561
Likes: 0
Received 324 Likes on 222 Posts
Default

It's hard to see from the screen, but it looks like you have your gain set to auto +6 and color at 33? It looks like there is a ton of surface clutter too, like you can't see anything between 0 and 50 ft? What is your tvg on? Do you have any noise reduction on?
Old 10-09-2014, 04:07 PM
  #12  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2011
Location: Boston/Cape Cod
Posts: 1,285
Received 14 Likes on 11 Posts
Default

well thats why i'm asking ….the bait is the yellow and red - I zoomed in on it - obviously enhances it . I think the TVG is 4 or -4 I don't remember . What are the squiggly lines ? Every now and then I'd get a cluster of red squiggly lines a lot bigger …..then I'd get some nice red arches ….. I want to get rid of the BS and see the red arches and bait - thats it . Its hard to play with when you have no idea if the fish your targeting are there and what they look like on this sounder nss9 /b175w …I think CME has this setup and is familiar with it because he installs them and he knows what i'm looking for here at this spot .
Old 10-09-2014, 04:22 PM
  #13  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Aug 2009
Posts: 12,561
Likes: 0
Received 324 Likes on 222 Posts
Default

There is no -4 tvg. Is your gain at auto+6? Try turning it down and the color up. That's just my opinion with very limited experience with my unit so far.
Old 10-09-2014, 04:24 PM
  #14  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Aug 2009
Posts: 12,561
Likes: 0
Received 324 Likes on 222 Posts
Default

What were you trying to catch at that spot?
Old 10-09-2014, 06:15 PM
  #15  
Senior Member
 
Join Date: Feb 2013
Location: East central Fla
Posts: 657
Received 64 Likes on 47 Posts
Default

Originally Posted by VanW View Post
It's hard to see from the screen, but it looks like you have your gain set to auto +6 and color at 33? It looks like there is a ton of surface clutter too, like you can't see anything between 0 and 50 ft? What is your tvg on? Do you have any noise reduction on?
The x6 is the zoom level not the gain and the unit is zoomed in the upper water colmn.. looks like 40-100'.
Squiggly lines look like fish.. maybe bait type fish. Why are you zooming in to that particualr segment in the water column... what are you looking for? Id say you could use to turn down the TVG some more to clean up the screen some, by the sounds of it that much info is confusing you.
Old 10-09-2014, 07:12 PM
  #16  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2011
Location: Boston/Cape Cod
Posts: 1,285
Received 14 Likes on 11 Posts
Default

i zoom it in because at full screen everything looks the same size =micro . also it seemed the fish I was chasing were hanging around 60-100' (BFT)
Old 10-09-2014, 11:00 PM
  #17  
Senior Member
 
Join Date: Apr 2013
Location: Norway
Posts: 651
Received 33 Likes on 24 Posts
Default

Turn down sensitivity to around auto. Turn up colour to around 60-ish. TVG around 4. Then post a new screenshot, if possible one from the NSS itself. (You need a memorycard to transferr screenshots from the unit to your PC/ Mac/ phone/ tablett.)

Great input from CMEBoston!
Old 10-10-2014, 01:06 AM
  #18  
Senior Member
 
Join Date: Feb 2005
Location: Norway
Posts: 16,430
Likes: 0
Received 1,128 Likes on 918 Posts
Default

Team Colibri is using Lowrance, Lowrance Color gain of 60 is 30 for Simrad. The Lowrance Color gain goes to 100, Simrad goes to 50.
Old 10-10-2014, 03:07 AM
  #19  
Senior Member
 
Join Date: Apr 2013
Location: Norway
Posts: 651
Received 33 Likes on 24 Posts
Default

Originally Posted by abbor View Post
Team Colibri is using Lowrance, Lowrance Color gain of 60 is 30 for Simrad. The Lowrance Color gain goes to 100, Simrad goes to 50.
I stand corrected.
Old 10-10-2014, 04:38 AM
  #20  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2011
Location: Boston/Cape Cod
Posts: 1,285
Received 14 Likes on 11 Posts
Default

will do this weekend ….any other color gain settings to try -send em over .
thanks

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.