Sunday, 8 June 2014

10Ghz part 2

I temporarily put the 10GHz transverter on the mast this afternoon. I was surprised at how little the 144MHz receiver noise level increased when it was powered up. On further investigation I found that the locked 106.5MHz LO from the shack was delivering only around -5dBm at the transverter LO port. From previous measurements the DB6NT G2 needs typically +6dBm. The loss of signal turned out to be in the 20m of RG58 coax from the shack to masthead. What is more the second cable carrying the 144Mhz IF had even more loss! Those rodents again?

I think both cables need to be replaced although the high loss of the LO cable has, for now, been overcome by adding a PGA Amp in the LO box in the shack. That delivers +20dBm to the RG58 coax and +9dBm to the transverter. This is not ideal practice, but will do for the moment.
It certainly explains why the 3cm system had become progressively more deaf until I took it out of service two years ago.
I think I will replace the IF RG58 with LMR400 as the IF signal has to be routed on to the indoor shack. Even more loss!
Progress at last and maybe QRV on 3cm from mid week!
Sam


2 comments:

  1. time to train the cat Sam or it should pack its bags...hi

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  2. Having checked the cable it would appear it is just that it has been sitting in water in the duct. A new cable has been pulled in. The GB3PKT beacon near Clacton is quite strong.
    Sam

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