Re: D4D not working

Fuqua, Bill L
 

Both thermocouple and themistor type power meters measure True Power. Rather than indirectly measuring the power by measuring voltage and using a meter calibrated assuming a sinusoidal waveform.
73
Bill wa4lav


From: Fuqua, William <wlfuqu00@...>
Sent: Wednesday, October 16, 2019 3:44 PM
To: crkits@groups.io <crkits@groups.io>
Subject: Re: [crkits] D4D not working
 
This is a double sideband signal.
Remember, there are two signals and being generated and only one is being received unless the receiver on the distant end is a phase locked DSB receiver.
The calculation assumes a single sinusoidal waveform. Since the peak voltage is twice that of that for either sideband the power for the sideband which the distant station is receiving is 1/4 that calculated, or just a under 175 mW. If a thermocouple type of power meter was used. You would divide by the result by 2. Naturally if it was a single sideband signal the results would be the same and as calculated.

73
Bill wa4lav


From: crkits@groups.io <crkits@groups.io> on behalf of Dr. Pedro E. Colla (LU7DID) via Groups.Io <lu7did@...>
Sent: Wednesday, October 16, 2019 9:47 AM
To: crkits@groups.io <crkits@groups.io>
Subject: Re: [crkits] D4D not working
 
Thank you Adam by the suggestion, this is the way I meassure the power output of my WSPR/FT8 beacon (Vpp*0,35)^2/RL in this case ((17V*0,35)^2)/50 would yield 700 mW approx.

The initial testing has been very much satisfactory, in reception as reported in pskreporter.info the greatest distance reported so far is some well over 19K Km (JA), on TX I was able to work a couple of PY stations (some 2000 Km away) when the band wasn't quite opened yet; what else can a small device like this be asked (attached is the pskreporter.info logbook over the past day or so, reports to my station is of the permanent beacon I have, not the D4D).

I'd shared in my blog some of the experiences in building the kit, the blog is in Spanish but Google translate will yield a half decent translation give or take a couple of words. Thank you for the very good support while building the kit.

73 de Pedro, LU7DID 

Join crkits@groups.io to automatically receive all group messages.