UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - MuTek Pre-amps for the FT290R

G0HZU_JMR · 14th Oct 2018, 5:24 pm

My FT290R mk1 has the Mutek preamp fitted and my main issue with it is (in)stability.

It goes unstable when using the whip antenna unless the whip is fully extended and is kept away from other objects. Of course, this would be normal practice but it isn't nice to hear it generating noise and birdies unless it sees an antenna load it likes. It also hoots when removing the coax fed antenna with the whip fully down.

I think the gain can be tweaked down in order to balance NF vs signal handling and I do remember turning this down slightly. I haven't bothered to adjust the front end tuned circuit but I suspect that it was tweaked (by whoever fitted it) for max gain rather than lowest noise figure. I recall that I got an overall receiver noise figure of 2.5-3.0dB with the Mutek preamp when I last played with this radio on my workbench. I suspect it can be adjusted to be better than this but I doubt there is much point because of the band noise level where I live.

14th Oct 2018, 5:24 pm	#5
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: MuTek Pre-amps for the FT290R My FT290R mk1 has the Mutek preamp fitted and my main issue with it is (in)stability. It goes unstable when using the whip antenna unless the whip is fully extended and is kept away from other objects. Of course, this would be normal practice but it isn't nice to hear it generating noise and birdies unless it sees an antenna load it likes. It also hoots when removing the coax fed antenna with the whip fully down. I think the gain can be tweaked down in order to balance NF vs signal handling and I do remember turning this down slightly. I haven't bothered to adjust the front end tuned circuit but I suspect that it was tweaked (by whoever fitted it) for max gain rather than lowest noise figure. I recall that I got an overall receiver noise figure of 2.5-3.0dB with the Mutek preamp when I last played with this radio on my workbench. I suspect it can be adjusted to be better than this but I doubt there is much point because of the band noise level where I live. __________________ Regards, Jeremy G0HZU Last edited by G0HZU_JMR; 14th Oct 2018 at 5:42 pm.