40cm dish

YES, it is

DK2ZF JO43VH

using 60cm portable or 1.40cm from home

@IW5BNL

Hi David,

Quote from David IW5BNL

Is it a realistic number with so small dish?

For my reception experiments I use a 35cm camping dish on a tripod on the ground, a TCXO modified OPTICUM LSP-02G and a NOOELEC RTL-SDR with a 10dB attenuator at the input.

I have the beacon peak at about 25dB over noise floor (see attachment).

73, Thorsten

What is the type of the camping dish ?

Tnx, Rudi - ON7CL

S/N ratio is, especially for CW, a function of detection bandwidth, or in the case of an SDR, a function of sampling rate and fft size. For a regular analogue radio with real HW filters, the CW power is (hopefully!) considerably more than the noise, so the (peak) power measurement will fairly accurately depict the carrier energy level with even quite wide detection bandwidth. For noise however, we need to consider the noise bandwidth. The broadband, filter passband-filling noise power (which should be detected in RMS by the way) will be highly dependent on the bandwidth of it, i.e. how much noise energy is being integrated into a number. Increasing the detection bandwidth from e.g. a ~300Hz CW filter to a ~3kHz SSB filter will result in 10dB more (noise) power. In other words the CW carrier S/N ratio will appear 10dB worse with a 3kHz filter than a 300Hz filter

The point is, to make any kind of S/N ratio comparison, we need to know the modulation (CW is very different from 400BPS PSK) and we need to know the detection bandwidth. And in the case of SDR it is important to know the sample rate and FFT size (bin count). Only in this way can we compare apples with apples or make orange/apple conversion calculations to make comparison possible.

And for really meaningful S/N measurements, peak detection should be used for the (CW) carrier (S) and RMS detection for the noise (N).

It does not hurt to realize that the noise factor (N) is often noise + interference (I) and that a more accurate measurement would be S/(N+I), but fortunately for us, due to it's very high linearity, the QO-100 transponder noise floor has been and is pretty much random noise. In AO-7, AO-40 and the like, this was not so simple as HELAPS and other high efficiency RF amplification and other linearization and non-linearity processes resulted in noise-sounding (N+I.)

The result of all this is that 9dB SNR can easily be the same this as a 25 dB SNR. Only the measurement conditions are different.

73 - Michael, oh2aue

iw5bny What is the elevation Angle of your QTH antenna?

Quote from ON7CL

What is the type of the camping dish ?

Tnx, Rudi - ON7CL

Question addressed to me?

A Megasat offset camping dish (35/40cm)...

I will use one for my portable operation with helix feed 5 turns

Hi, 40cm camping dish will be here this week

Hi,

whats the gain of a 40cm dish at 2.4 GHz and how many power do you need for upload with a good signal ?

Thanks

Uli DF5SF

Yesterday we tested the portable uplink for the Es'hail / QO100 Satellite, with the 40cm dish, the Helix with 5 turns, 5 watts was enough to reach the Satellite 😀😀

Ciao David,

Yes like you see it we used it with the helix.

The radio is a Yaesu FT818 using 0.5w, into SGlabs transverter + amplifier. Output 5w

73 - Rudi - ON7CL

As the 40cm dish has a F/D of 0.5 a poty is performing better then a helix, and more compact

15-20w is needed to be at the beacon level

A 40cm dish has 18 dB gain at 2.4 GHz. Another potential portable uplink antenna is a standard loop yagi which would need to be about 1m long. Potentially easier to fit in travel baggage if it splits into smaller lengths. For RX you still need the dish though so a dualband feed might be the best answer.