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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 10th Jul 2022, 8:11 am   #1
wd40addict
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Default Making Racal Burndept Connectors

The RA17 and friends use the completely unobtainable Burndept coax connectors. Recent acquisition of an SSB adaptor meant I needed to connect the 100kHz IF out of my RA17 to the input of the adaptor. Obviously I could change the sockets, but it's nice to leave them original. First photo shows output sockets on RA17.

What I did was as follows: take some 15mm brass plumbing pipe and cut an approx 7mm ring off it. Now take a slice out of the ring until it is the right size to fit inside the Burndept (photo 2). Now go through your collection of female Belling-Lee style TV aerial connectors until you find one whose outside diameter fits. Photo 3 shows a VHS type lead and photo 4 a typical solderable type.

That's it!
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Old 10th Jul 2022, 8:38 am   #2
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Default Re: Making Racal Burndept Connectors

Racal used BNC on the RA117. Would those square patterns of holes around the Burndepts happen to suit flanged connectors?

David
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Old 10th Jul 2022, 9:15 am   #3
Craig Sawyers
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Default Re: Making Racal Burndept Connectors

Contact Rob Filby racalrob17@yahoo.co.uk . He makes Burndept to BNC adaptors. He takes the cable gubbins off the end, and then drills and taps holes to suit a flanged 75 ohm BNC socket. So you get a Burndept to 75 ohm BNC adaptor

I forget how much he charges, but not much.

He also sells the Plessey mains plugs. Last time I was across I bought two for less than a tenner each. Wrong orientation, so I had to disassemble and adjust that so it engaged with the RA17.

Craig
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Old 10th Jul 2022, 1:21 pm   #4
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Default Re: Making Racal Burndept Connectors

Hi wd450addict,

Not completely unobtainable!

These two have the same cable entry size out of the three I have.

Yours for a fiver to cover small parcel postage.

Kind regards
Dave G0ELJ
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Old 10th Jul 2022, 2:40 pm   #5
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Default Re: Making Racal Burndept Connectors

Hi Dave, I'll take you up on your kind offer. PM on the way.
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Old 10th Jul 2022, 2:52 pm   #6
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Default Re: Making Racal Burndept Connectors

The only thing that is worth watching for is the ferrule size. Some of them are sized for 50 ohm coax, and some for 75 ohm.

Found that out by buying a reel of 75 ohm coax (I needed some anyway) and finding it would not go into the Burndept ferrules I had. Probably not a big problem to use 50ohm coax because the length of coax typically used a meter or two.

Craig
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Old 10th Jul 2022, 10:11 pm   #7
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Default Re: Making Racal Burndept Connectors

Often to be found at radio rallys. I got two for £4 at the last rally and that included 15m of RG59 co-ax between them.
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Old 10th Jul 2022, 10:23 pm   #8
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Default Re: Making Racal Burndept Connectors

That is a good bargain!

Of course the interesting thing is noone seems to know for certain what the characteristic impedance of Burndept connectors are.

However the output connection from my 1955 CT318 signal generator hernia boatanchor is Burndept, and the output impedance is 75 ohms. So maybe the characteristic impedance of the connector is close to 75 ohms?

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Old 11th Jul 2022, 8:31 am   #9
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Default Re: Making Racal Burndept Connectors

Certainly in the above case Racal are using it as a 75R connector hence my use of TV aerial cabling. Presumably sticking one on a VNA would give a definitive answer.
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Old 11th Jul 2022, 9:50 am   #10
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Default Re: Making Racal Burndept Connectors

They were the standard RF connector used on the Army Larkspur range of radios which were 75 ohms. The bargain I had was in fact a NOS Larkspur cable and being 75 ohms not a lot of use to most amateurs, hence the cheap price.
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