"hf fuse" for sg output protection
 

Hello, I am looking for the external N-plug with a built in fuse that HP and Marconi used at the output of their signalgenerators for attenuator protection. Does anybody know where the plugs and fuses can be bought today?
73 de SM6FBY Bengt
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Re: "hf fuse" for sg output protection
 

Well, the plug assemblies sometimes appear on eBay, which is where I bought mine from. Sadly the cartridge fuses to go inside seem to be unobtainable.

Re: "hf fuse" for sg output protection
 

That would be nice on my 8555 18GHz spectrum Analyser plugin on HP141T.

Though would the fuse blow faster than the mixer on the 1mW range :( ?

Re: "hf fuse" for sg output protection
 

Hello, an easier/more reliable alternative may be a 20dB or 30dB 1GHz (or suitable freq) power attenuator, rated at say 25W. May be worth considering?
I used to use a 20dB 25W (N type) attenuator permanently attached to my sig gen output. It was accurate (in dB) and many times paid for itself in protecting the sig gen. In fact, testing 25W VHF transceivers, I would often repeatably toggle between tx and rx whilst looking for intermittant antenna relay faults!
Like a previous post, the fuses (Littlefuse?) were hard to find.
73, Robin

Re: "hf fuse" for sg output protection
 

Actually, these seem easier to find than I thought. There's an example of the N connector version (TM5753) on eBay UK at the moment and there's examples of both the BNC connector version (TM9884) and an HP N connector equivalent (all with spare fuses!) here.

The fuses are 1/16A (62.5mA) produced by littelfuse, though my bit of paper with the type number on seems to have been mislaid. However short, fat fuses (1"-ish long but same diameter as 1.25" fuses iirc) rated at 62.5mA, as Robin says, aren't easy to find!

Having said that, I also agree with robin's point about using an attenuator.

Hugh

Re: "hf fuse" for sg output protection
 

Aren't 20mm 63mA fuses readily sourced? A simple adaptor (or just a bit of spring) should take care of the fitting........

Re: "hf fuse" for sg output protection
 

Indeed they are, thank you for reminding me.

Unfortunately, because of the way the fuse is mounted, replacing the 25x6.3mm original with a 20x5mm fuse needs a little bit more than a spring as the fuse "ends" need to be increased in both length and girth. The photos below illustrate what I mean.

Still, it's clearly not impossible and I've been toying with the idea of drilling a 5mm hole through the middle of an old (metal) pot spindle. One day I might actually get round to doing something about it!