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Monday, 30 September 2013

So, What's happened to the bridge then?

Well,

You may recall my musings from my build of a Return Loss Bridge back here:

http://g0mgx.blogspot.co.uk/2013/09/where-does-it-lead-bridge-to-nowhere.html

And I was rather disappointed with the directivity I was achieving when measured using my dummy load and digital 'scope.

Well, I've got myself a Huber-Suhner low power dummy load (I am told they are quite good quality) and have attached this to the RLB using a Female N-Type to PL259 then a SO-239 to BNC adaptors stacked together. Anyhow, I have measured the RLB from my previous post again and am getting these results now:


And that is certainly much better, now, I tried to make a new RLB today using a different balun arrangement as I described here:

http://g0mgx.blogspot.co.uk/2013/09/time-time-time.html

and it looks like this in a die-cast box (it's a complete mess thanks to my metalwork capabilities):


In the photo above you can see the Huber-Suhner load and also there is a 50R terminator visible in the bottom of the picture. Rather than having a "known" 50R inside the RLB, this one has a fourth socket so you can attach the "known" impedance - meaning that you could use this device at impedances other than 50R.


If you look closely above you can see that this is more of a plumbing job than soldering.

Now, I nearly put this straight in the bin when I got it all wonky in the box and generally made a mess of the whole thing, but then I thought I would just see how it worked. Here's the directivity I am measuring:



So, this looks quite good - I think...

Confusing egh?

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