Rigol DSA815 - VSWR-Bridge tear down... - Page 1
Forum section: electronics / testgear

author: seahood
author_rank: Newbie
timestamp: February 05, 2014, 08:33:48 am
content: Hello,does anybody know what exactly is inside the Rigol VSWR Bridge VB1020 for the DSA815 Spectrum Analyzer ?http://www.batronix.com/pdf/Rigol/UserGuide/VB1020_VB1030_Manual.pdf

author: KJDS
author_rank: Super Contributor
timestamp: February 05, 2014, 09:18:26 am
content: It's almost certainly a wheatstone bridge autotester, some intro reading herehttp://www.anritsu.com/en-US/Products-Solutions/Solution/Understanding-directivity.aspx

author: seahood
author_rank: Newbie
timestamp: February 05, 2014, 09:32:02 am
content: Nice ! I ask me how hard it is to build such a device... studying details... --> No Details about the inner organs of the device...

author: babysitter
author_rank: Frequent Contributor
timestamp: February 05, 2014, 09:43:59 am
content: Hello Seahood,you can expect either a wheatstone bridge with some details for RF around (a kind of transformer), googling for "return loss bridge" will shed light on this.The other possibility is that it is a "directional coupler", just google for it. This is composed normally of 2 transmission lines close to each other and some impedance magic.Lots of literature about it in ham radio websites and fora available, also "DIY" manuals.Expect to get some Ferrite parts, thin semi rigid line, "tuner box" enclosures and devastating results when you go for BNC or PL connectorsI was willing to measure VSWR too, but I decided for a Oletron RK1413 directional coupler. Good enough for amateur radio use.~$30 in germany is quite good compared to the rigol thingy and is a good match to the not-too-perfect DSA815.

author: seahood
author_rank: Newbie
timestamp: February 05, 2014, 09:49:51 am
content: Ok, things are now clearer. But why does this things coast 500$ ? I cannot find any information about the "Oletron RK1413" via an internet recherche.http://www.ve2azx.net/technical/RLBridges.pdf

author: babysitter
author_rank: Frequent Contributor
timestamp: February 05, 2014, 10:46:22 am
content: Olektron, my fault. Available on e-Gaysometimes, or at the german surplus dealer "Helmut Singer".

author: seahood
author_rank: Newbie
timestamp: February 05, 2014, 11:31:22 am
content: There is a difference between a directional coupler and an VSWR bridge !

author: KJDS
author_rank: Super Contributor
timestamp: February 05, 2014, 11:58:33 am
content: A directional coupler is inherently a narrowband device and it's hard work to make it broadband.A bridge is inherently a broadband device but it's hard work to make it work well at UHF and beyond.

author: iDevice
author_rank: Regular Contributor
timestamp: February 05, 2014, 08:43:59 pm
content: Quote from: seahood on February 05, 2014, 09:49:51 amThe bridge costs only 150$.500$ is only for the license and once licensed the DSA815-TG can use any VSWR bridge.But Rigol sells a package with both the license and the bridge for 650$ which places the bridge at 150$

author: seahood
author_rank: Newbie
timestamp: February 05, 2014, 08:45:33 pm
content: If i search by eBay i will found only bridgets for 500$, i dont see any bridge for 150$ anywhere.

author: Rory
author_rank: Frequent Contributor
timestamp: February 05, 2014, 09:04:34 pm
content: Try using 'return loss bridge' as your ebay search term.On ebay USA, there were lots of hits.Here's a $289 one.http://www.ebay.com/itm/Return-Loss-Bridge-Amtronix-SW2012N-NEW-SWR-Bridge-with-1-yr-warranty-/121261264771?pt=LH_DefaultDomain_0&hash=item1c3bbc0f83Here's a $45 one, 75 ohms is why it's so cheap:http://www.ebay.com/itm/WAVETEK-FB40-75-RETURN-LOSS-BRIDGE-Reduced-price-/290961472148?pt=LH_DefaultDomain_0&hash=item43bea7ba94

author: iDevice
author_rank: Regular Contributor
timestamp: February 05, 2014, 09:55:58 pm
content: Quote from: seahood on February 05, 2014, 08:45:33 pmI guess you didn't read my post...

author: hammy
author_rank: Unknown
timestamp: February 05, 2014, 10:05:13 pm
content: Get a "Mini Circuits ZFDC-20-5+" Coupler. Works fine.

author: seahood
author_rank: Newbie
timestamp: February 05, 2014, 10:10:25 pm
content: @iDevice --> Sorry, i searched for VSWR bridges on eBay instead for return loss briges.i have fist to study the background... i will try it out. Here is a Video for the proposed configuration -->