The Hull Truth - Boating and Fishing Forum

Go Back   >
Search


Reply
 
Thread Tools Search this Thread
Old 04-10-2016, 05:53 AM   #1
Admirals Club
Thread Starter
 
Join Date: Apr 2007
Location: Alexandria Virginia
Posts: 418
Default Simrad BSM-2 Impedance Selection for B275LH-W

All:

The other day I called Simrad technical support regarding this question. The technical support person I spoke to did not seem to understand the difference between a pure resistive temperature shunt value, and a conjugate matching circuit which is reactive in nature.

The first answer he gave me was 10K Ohms, which made no sense with regards to reactance. When I finally told him I was working around the area of L47 and L36, which from my experience look like impedance matching transformers, he finally put me on hold to find the answer. When he returned to the line he told me for the BSM-2 the selection should be Z1 (100 Ohms) on both the low and the high transducer jumpers.

I have since called Airmar to determine the impedance of their elements. Airmar informs me the low frequency element is 203 Ohms, and the higher frequency element is between 165 - 169 Ohms (depending of frequency). If this is the case, than should I not be using the 270 Ohm selection (Z2) on both the low and high transducer jumper settings?

Rich
av8torrich is offline   Reply With Quote
Old 04-10-2016, 06:11 AM   #2
Senior Member
 
Join Date: Feb 2005
Location: Norway
Posts: 11,498
Default

When BSM-2 was released the impedance tap recommendation for x265LH was (x275LH-W didn't exist at that time) Z2 for High and Z3 for Low. Later a technical bulletin was issued recommending Z1 for all transducers, I've heard this was something Navico and Airmar concluded together to avoid overpowering certain transducers. I've been reading transducer element documentation and done testing and concluded Z2 is best for both Low and High for x265LH and also x275H-W (I've been then testing with B175H-W which has the same High element as x275H-W).
abbor is offline   Reply With Quote
Old 04-10-2016, 06:38 AM   #3
Admirals Club
Thread Starter
 
Join Date: Apr 2007
Location: Alexandria Virginia
Posts: 418
Default

Quote:
Originally Posted by abbor View Post
When BSM-2 was released the impedance tap recommendation for x265LH was (x275LH-W didn't exist at that time) Z2 for High and Z3 for Low. Later a technical bulletin was issued recommending Z1 for all transducers, I've heard this was something Navico and Airmar concluded together to avoid overpowering certain transducers. I've been reading transducer element documentation and done testing and concluded Z2 is best for both Low and High for x265LH and also x275H-W (I've been then testing with B175H-W which has the same High element as x275H-W).
Arbbor-

Thanks, yes I can see how Z1 (100 Ohms) would be a safe bet from a standing voltage perspective. That being said, I think for these elements you really need to be a bit higher to achieve the best transmit and receive coupling.

Since they don't offer schematics, its hard for me to guess as to the TX/RX chain topology, but in RF circuits this would be the way I would proceed.

Rich
av8torrich is offline   Reply With Quote
Old 04-10-2016, 09:21 AM   #4
Admirals Club
 
Join Date: Feb 2011
Posts: 566
Default

Quote:
Originally Posted by abbor View Post
When BSM-2 was released the impedance tap recommendation for x265LH was (x275LH-W didn't exist at that time) Z2 for High and Z3 for Low. Later a technical bulletin was issued recommending Z1 for all transducers, I've heard this was something Navico and Airmar concluded together to avoid overpowering certain transducers. I've been reading transducer element documentation and done testing and concluded Z2 is best for both Low and High for x265LH and also x275H-W (I've been then testing with B175H-W which has the same High element as x275H-W).
Sounds like I should have my old BSM-2 back which my dealer exchanged without charge for BSM-3 when it was launched and we were still trying to achieve some measure of acceptable sonar performance from 175C-L and 175C-H.

Another THT'er was able to buy that BSM-2 at a bargain price
BCTony is offline   Reply With Quote
Old 04-10-2016, 10:27 PM   #5
Senior Member
 
Join Date: Feb 2004
Posts: 734
Default

Out f interest does anyone know what impedance the Bsm-3 is set at for high and low
ozmako is offline   Reply With Quote
Old 04-11-2016, 07:47 AM   #6
Senior Member
 
Join Date: May 2003
Location: Gibsons B.C. Canada
Posts: 171
Default

come now, Tony you know your a dedicator follower of fashion
besides the BSM looks so good on my boat now.....lol

believe Abbor has stated the BSM-3 has S/W fixed taps and is set at Z1
not sure but i set Tony's old BSM-2 at Z2 on both Hi and low
on both NSS-8's gen 1
SS175's are seen and greyed out and both give temp readings

Name:  060.jpg
Views: 0
Size:  181.2 KB
wildthing is offline   Reply With Quote
Old 04-11-2016, 08:17 AM   #7
Senior Member
 
Join Date: Feb 2005
Location: Norway
Posts: 11,498
Default

I assume Z1 is hardwired on the PCB for BSM-3, but I don't have this verified.
abbor is offline   Reply With Quote
Old 04-11-2016, 08:18 AM   #8
Senior Member
 
Join Date: Feb 2005
Location: Norway
Posts: 11,498
Default

Quote:
Originally Posted by BCTony View Post
Sounds like I should have my old BSM-2 back which my dealer exchanged without charge for BSM-3 when it was launched and we were still trying to achieve some measure of acceptable sonar performance from 175C-L and 175C-H.

Another THT'er was able to buy that BSM-2 at a bargain price
Your box may have a fancy color, but we probably have the best sounder
abbor is offline   Reply With Quote
Old 04-11-2016, 11:45 AM   #9
Admirals Club
Thread Starter
 
Join Date: Apr 2007
Location: Alexandria Virginia
Posts: 418
Default

One way to check this would be to look for continuity between IMP SEL, and Z1. If there is a short between these two terminals, then Z1 is hardwired.

I just looked at the BSM-3 Manual, and it appears as though the terminal board layout is identical to the BSM-2. I would look to see if L36/L47 reside above the terminal boards for the transducer connections. If they do, this would indicate to me they plan on tapping those transformers in some fashion to obtain the best impedance match.

Rich
av8torrich is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 Off
Pingbacks are On
Refbacks are Off

Forum Jump


All times are GMT -7. The time now is 01:06 PM.


©2009 TheHullTruth.com

Powered by vBulletin® Version 3.9.3.0
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.