Perils of Patch Leads
Posted: Fri Nov 24, 2017 1:47 pm
Here's a lesson that I've learnt the hard way.
I tweeted https://twitter.com/DavidHo34732663/sta ... 1202585600 at the beginning of November
My Portsdown was working on my 50th birthday fine. A few days later I uploaded the week's sensational software updates and checked that it was running again using the same M0HMO power meter. Nowt came out . Oh dear. There's a lot hanging on this device working. Dave G8GKQ wrote me a note asking what was the matter and took me through a series of tests. What a very decent man. These concluded with "send the oscillator board to me for testing on a known good set up". Meantime I took some filters to our club in Wolverhampton for spectrum analysis and alignment. SMA patch leads were borrowed from my kit and nothing worked. Ron M0RNW scratched his head a great deal and suddenly announced "there's an open circuit and I think it's your patch leads". Sure enough Reverse SMA patch leads had wriggled into my kit. (The leads that we did use afterwards came from Dr Frankenstein's lab! Nice W1GHZ comb line BPF for 437MHz but I think the 6dB insertion loss would go on a modern instrument with normalised leads) . I don't remember ordering reverse SMA leads so I must have picked them up from a for sale table at Telford or Finningley. I thought about all the tests that had gone poorly of late and concluded reverse SMA test leads had done for my Portsdown power measurement. I wrote to Dave, apologised and owned up to incompetence. Curiously enough there was nothing wrong with the oscillator board. The Portsdown is back together and working fine.
So if like me you've never seen reverse SMA connections, complete with a receptacle hole where a pin ought to be, take care when you suddenly have a duff bit of kit which worked a few days before. Have a look what's inside one of the gold mounting nuts and beware of the Perils of Patch Leads.
73
David M0YDH
I tweeted https://twitter.com/DavidHo34732663/sta ... 1202585600 at the beginning of November
My Portsdown was working on my 50th birthday fine. A few days later I uploaded the week's sensational software updates and checked that it was running again using the same M0HMO power meter. Nowt came out . Oh dear. There's a lot hanging on this device working. Dave G8GKQ wrote me a note asking what was the matter and took me through a series of tests. What a very decent man. These concluded with "send the oscillator board to me for testing on a known good set up". Meantime I took some filters to our club in Wolverhampton for spectrum analysis and alignment. SMA patch leads were borrowed from my kit and nothing worked. Ron M0RNW scratched his head a great deal and suddenly announced "there's an open circuit and I think it's your patch leads". Sure enough Reverse SMA patch leads had wriggled into my kit. (The leads that we did use afterwards came from Dr Frankenstein's lab! Nice W1GHZ comb line BPF for 437MHz but I think the 6dB insertion loss would go on a modern instrument with normalised leads) . I don't remember ordering reverse SMA leads so I must have picked them up from a for sale table at Telford or Finningley. I thought about all the tests that had gone poorly of late and concluded reverse SMA test leads had done for my Portsdown power measurement. I wrote to Dave, apologised and owned up to incompetence. Curiously enough there was nothing wrong with the oscillator board. The Portsdown is back together and working fine.
So if like me you've never seen reverse SMA connections, complete with a receptacle hole where a pin ought to be, take care when you suddenly have a duff bit of kit which worked a few days before. Have a look what's inside one of the gold mounting nuts and beware of the Perils of Patch Leads.
73
David M0YDH
