Rigol DSA815 - VSWR-Bridge tear down...

[seahood]

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

[KJDS]

It's almost certainly a wheatstone bridge autotester, some intro reading here

http://www.anritsu.com/en-US/Products-Solutions/Solution/Understanding-directivity.aspx

[seahood]

Nice ! I ask me how hard it is to build such a device... studying details... --> No Details about the inner organs of the device...

[babysitter]

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 connectors

I 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.

[seahood]

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

[babysitter]

Olektron, my fault. Available on e-Gay sometimes, or at the german surplus dealer "Helmut Singer".

[seahood]

There is a difference between a directional coupler and an VSWR bridge !

[KJDS]

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.

[iDevice]

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

The 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$

[seahood]

If i search by eBay i will found only bridgets for 500$, i dont see any bridge for 150$ anywhere.

[Rory]

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=item1c3bbc0f83

Here'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

[iDevice]

If i search by eBay i will found only bridgets for 500$, i dont see any bridge for 150$ anywhere.

I guess you didn't read my post...

[hammy]

Get a "Mini Circuits ZFDC-20-5+" Coupler. Works fine.

[seahood]

@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 -->