MiniTiouner Power Level Indication
As with any receiver, the MiniTiouner needs the input signal strength to be within a defined range to achieve best results. As the MiniTiouner must always be used with an external preamp or LNB, this means putting the right amount of gain between the aerial and the MiniTiouner input. I had not found any documentation on the correct input level and wanted to implement some indication on the Portsdown, so did some tests.
Summary of Results
My conclusions were:
- For the MiniTiouner to operate at its best and be as sensitive as possible, the RF Power indicated on the MiniTioune software with no incoming signal should be above -70 dBm. No advantage was observed with higher indicated RF Powers.
- The indicated RF Power on MiniTioune is useless as a means of peaking weak RB-TV signals for maximum signal strength, as the power is measured across about 10 MHz of bandwidth (3dB) and the noise power in this bandwidth swamps any marginal increase in signal power.
- It is very difficult to measure the RF Power using a digital tuner and the indications on MiniTioune are neither absolute (labelling as dBm is misleading) or very linear. Having said that, the indication is very useful - thanks to F6DZP!
Detailed Analysis
Measurements of the received power indication were made using MiniTioune Version v0.9beta8_9 while receiving the QO-100 beacon. A line amplifier and a switched attenuator were used to accurately input a wide range of power levels. Using the same test set-up similar measurements were made using modified LongMynd software to support developement of input level indication on the Portsdown.
The results are tabulated below.
| Input Lev (dB) | MT Indication | LM AGC1 Val | Portsdown Indication | Remarks |
|---|---|---|---|---|
| -60 | -89 | 0 | < -70 | Reduced MER |
| -59 | -88 | 0 | < -70 | Reduced MER |
| -58 | -87 | 0 | < -70 | Reduced MER |
| -57 | -86 | 0 | < -70 | Reduced MER |
| -56 | -85 | 0 | < -70 | Reduced MER |
| -55 | -84 | 0 | < -70 | Reduced MER |
| -54 | -83 | 0 | < -70 | Reduced MER |
| -53 | -82 | 0 | < -70 | Reduced MER |
| -52 | -81 | 0 | < -70 | Reduced MER |
| -51 | -80 | 0 | < -70 | Reduced MER |
| -50 | -79 | 0 | < -70 | Reduced MER |
| -49 | -78 | 0 | < -70 | Reduced MER |
| -48 | -76 | 0 | < -70 | Reduced MER |
| -47 | -75 | 0 | < -70 | Reduced MER |
| -46 | -74 | 0 | < -70 | Reduced MER |
| -45 | -73 | 0 | < -70 | Reduced MER |
| -44 | -72 | 0 | < -70 | Reduced MER |
| -43 | -71 | 0 | < -70 | Reduced MER |
| -44 | -71 | 0 | < -70 | Reduced MER |
| -43 | -71 | 0 | < -70 | Reduced MER |
| -42 | -71 | 0 | < -70 | Reduced MER |
| -41 | -71 | 0 | < -70 | Reduced MER |
| -40 | -71 | 1 | -70 | Best MER |
| -39 | -71 | 10 | -69 | Best MER |
| -38 | -70 | 21800 | -68 | Best MER |
| -37 | -68 | 25100 | -67 | Best MER |
| -36 | -66 | 27100 | -66 | Best MER |
| -35 | -64 | 28100 | -65 | Best MER |
| -34 | -62 | 28900 | -64 | Best MER |
| -33 | -60 | 29600 | -63 | Best MER |
| -32 | -59 | 30100 | -62 | Best MER |
| -31 | -57 | 30550 | -61 | Best MER |
| -30 | -55 | 31000 | -60 | Best MER |
| -29 | -54 | 31350 | -59 | Best MER |
| -28 | -53 | 31700 | -58 | Best MER |
| -27 | -52 | 32050 | -57 | Best MER |
| -26 | -50 | 32400 | -56 | Best MER |
| -25 | -49 | 32700 | -55 | Best MER |
| -24 | -47 | 33000 | -54 | Best MER |
| -23 | -45 | 33300 | -53 | Best MER |
| -22 | -44 | 33600 | -52 | Best MER |
| -21 | -43 | 33900 | -51 | Best MER |
| -20 | -42 | 34200 | -50 | Best MER |
| -19 | -40 | 34500 | -49 | Best MER |
| -18 | -39 | 34750 | -48 | Best MER |
| -17 | -38 | 35000 | -47 | Best MER |
| -16 | -37 | 35250 | -46 | Best MER |
| -15 | -36 | 35500 | -45 | Best MER |
| -14 | -35 | 35750 | -44 | Best MER |
| -13 | -33 | 36000 | -43 | Best MER |
| -12 | -32 | 36200 | -42 | Best MER |
| -11 | -31 | 36400 | -41 | Best MER |
| -10 | -30 | 36600 | -40 | Best MER |
| -9 | -30 | 36800 | -39 | Best MER |
| -8 | -29 | 37000 | -38 | Best MER |
| -7 | -28 | 37200 | -37 | Best MER |
| -6 | -27 | 37400 | -36 | Best MER |
| -5 | -26 | 37600 | -35 | Best MER |
| -4 | -26 | 37700 | > -35 | LNA Gain reduces to 12.3 |
| -3 | -26 | 37700 | > -35 | LNA Gain reduces to 11.2 |
| -2 | -26 | 37700 | > -35 | LNA Gain reduces to 10.1 |
| -1 | -26 | 37700 | > -35 | LNA Gain reduces to 9.1 |
| 0 | -26 | 37700 | > -35 | LNA Gain reduces to 7.9 |