Hi Cinaed, Yes, dB is a ratio. However, it is commonly referenced to a mW or a W, which does then give a value. What I was saying is that 30dBm (referenced to one milliwatt) is equivalent to one Watt (1000mW). I did not change the reference. To go from 30dBm to 40dBm, an increase of 10dB is an increase of ten times the power, from 1W to 10W in this case. A further 3dB increase doubles the power to 20W. I did not change the reference. As I said before, I suggest that you read up on dB. By the way, it is incorrect to say dBm = dBW, 0dBW is actually 30dBm. Best regards Roy
> On 9Mar, 2016, at 15:27, Cinaed Simson <[email protected]> wrote: > > On 03/08/2016 05:42 PM, Roy Harcup wrote: >> Hi Cinaed, >> >> You really need to read up on dB’s. >> >> 0dBm = 1mW as you have stated; >> 30dBm = 1W; >> 40dBm = 10W; >> 43dBm = 20W, one more dBm will take that to somewhere around 22W (I haven’t >> done the calculation, I’m working from memory). > > dB is a ratio - ratios have no units. > > That is the ratio of 44mW/1mW = 44W/1W, so > > 10*log_10(44mW/1mW) = 10*log_10(44W/1W) > dBm = dBW = 44 dB. > > If you want to change the reference power in the definition of dBm from > 1 mW to 1 W, then that's a different ballgame. > >> >> If you ’smoke’ the RF stage on the HackRF I doubt that you would see >> anything usable on the output, indeed you could end up with a really bad >> source of interference. >> > > You're probably right - I am trying to do everything I can to keep from > smoking it. > >> Best regards >> Roy >> Formerly G4GGS >> >> >>> On 9Mar, 2016, at 09:18, Cinaed Simson <[email protected]> wrote: >>> >>> Hi - I'd like to increase the TX power of the HackRF to 50 mW. >>> >>> First, I disable TX. >>> >>> Since the dBm=0, this implies the power output will be on the order of 1 >>> mW. >>> >>> Then I add an external LNA with a gain of 44 dB on the RF band I'm >>> transmitting on which raises the TX power of the HackRF to 44 mW. >>> >>> The antenna has a gain of 6 dB - the cable and connector losses are on >>> the order of 1 dB, so the maximum effective power is 49 mW. >>> >>> I'm assuming this independent of the IF gain. >>> >>> So I could smoke the TX amplifier on HackRF and still be able to use the >>> HackRF to TX at roughly 17 dBm :). >>> >>> -- Cinaed >>> >>> _______________________________________________ >>> HackRF-dev mailing list >>> [email protected] >>> https://pairlist9.pair.net/mailman/listinfo/hackrf-dev >> >> . >> > > _______________________________________________ > HackRF-dev mailing list > [email protected] <mailto:[email protected]> > https://pairlist9.pair.net/mailman/listinfo/hackrf-dev > <https://pairlist9.pair.net/mailman/listinfo/hackrf-dev>
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