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G0HZU_JMR · 25th May 2020, 9:14 pm

I had a good rummage and tidy up and found three bags of MMBTH10 transistors. These are all from Farnell and two of the bags have Farnell part number 2454030. I think these are obsolete now but I tested one in the LNA circuit. I think this part is the SMD version of the MPSH10.

http://www.farnell.com/datasheets/22...623.1571773262

If fitted straight into the circuit with no L match it managed a noise figure of 2.8dB and a gain of just over 16dB on the spectrum analyser.

With the L match fitted I could get about 17dB gain and a really good match with a VSWR less than 1.2:1 across the whole of the 88-108MHz band on the VNA and also a flat 2.5dB noise figure on the spectrum analyser. This is a good result. See below for the MMBTH10 (MPSH10) circuit with the L match added. I used 1nF ceramic caps for the dc blocking but the value isn't critical.

I think the 2SC2026 will probably manage a noise figure of 1.8dB with the L match and about 20dB gain based on the model. When used as a preamp in front of a FM receiver I'm not sure anyone would notice the improvement of the 2SC2026 over the MMBTH10 unless they used test gear to measure it on a test bench. I'd imagine that galactic band noise and man made noise would mask any difference once an antenna is fitted.

25th May 2020, 9:14 pm	#50
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: Building A VHF Amplifier For Valve Sets I had a good rummage and tidy up and found three bags of MMBTH10 transistors. These are all from Farnell and two of the bags have Farnell part number 2454030. I think these are obsolete now but I tested one in the LNA circuit. I think this part is the SMD version of the MPSH10. http://www.farnell.com/datasheets/22...623.1571773262 If fitted straight into the circuit with no L match it managed a noise figure of 2.8dB and a gain of just over 16dB on the spectrum analyser. With the L match fitted I could get about 17dB gain and a really good match with a VSWR less than 1.2:1 across the whole of the 88-108MHz band on the VNA and also a flat 2.5dB noise figure on the spectrum analyser. This is a good result. See below for the MMBTH10 (MPSH10) circuit with the L match added. I used 1nF ceramic caps for the dc blocking but the value isn't critical. I think the 2SC2026 will probably manage a noise figure of 1.8dB with the L match and about 20dB gain based on the model. When used as a preamp in front of a FM receiver I'm not sure anyone would notice the improvement of the 2SC2026 over the MMBTH10 unless they used test gear to measure it on a test bench. I'd imagine that galactic band noise and man made noise would mask any difference once an antenna is fitted. Attached Thumbnails __________________ Regards, Jeremy G0HZU Last edited by G0HZU_JMR; 25th May 2020 at 9:41 pm.