MRF101AN-START kit

[g0mjw]

I have now built the 2m version and bench tested it at 50V. The linearity improved greatly with increased bias, 400mA seemed good. The image below shows some tests at 10W output, which is about the limit on 2m. Remember we have a 50W ERP limit and 7 dB antenna gain is not a particularly large array. This output requires 50V at 1A DC input, so entirely achievable with a small 48V PSU. Efficiency is 25% which is not bad for DVB-T. Not too hard to cool either.

MRF101.jpg (515.21 KiB) Viewed 3520 times

DVB-T is difficult to send cleanly, but IMPs 40dB down are possible at the 10W level. It is of course possible to get a lot more out, but the spectrum suffers. Gain is a little over 20dB at low levels and about 1W input was needed for 100W output in CW mode, which is as far as I pushed it. In DVB-S mode (66ks/s, 50W output) there is more potential, the shoulders at 10W are 50dB down which is good. At 50W they are only 30 dB down, which isn't acceptable.

Mike

[G3GJA]

My most recent NoV states 50W ERP; looks like it's been reduced.

Clive

2m NOV.png (64.74 KiB) Viewed 3503 times

[radiogareth]

Don't think it was ever 100W IIRC.
There's always feeder losses to account for ......
Gareth

[g0mjw]

I was confusing it with 4m where it is 100W. Edited to fix. Many antenna gain figures are 3 dB below what the manufacturer claims.

Mike