Hi Ron, I bought the unit from a ham, who finds pleasure and has the equipment to calibrate. And he did it to the unit and the sensors. This is all documented and well done. So I could measure my wspr output of 500 uW were I reached the 1 Mio km per Watt goal. But I had the troubles described above, so although I hate tinkering I will change my profession and will become a box maker ;-) and will report ... after I have done my homework.
73 de Hajo Am 26.10.2015 8:52 nachm. schrieb "Ron D'Eau Claire" <[email protected]>: > Hajo: > > A power meter based on the AD8307, such as the PM2 uses, can be very > accurate and sensitive but requires calibration. The AD3807 takes RF in and > produces a dc output proportional to the logarithm of the input signal > amplitude. > > I have a homebrew version based on a design by W7ZOI that works FB down to > below -90 dbM. That's the native sensitivity of the AD8307. You are quite > right that shielding is needed otherwise any local source of RF can upset > the readings. I presume the PM2 has an input attenuator but any RF getting > to the AD8307 chip can cause errors. If you have a steady source of RF > nearby (i.e. a broadcast station) it can introduce a fixed error in > addition > to the jigger you saw from the RS232 bus. That will depend upon how they > have terminated the input to the AD8307. > > I suggested a solution that is not dependent upon specialized test > equipment > most Hams don't have handy or depending upon the manufacturer's calibration > data. If that is not an issue, by all means the PM2 is suitable. > > 73 and have fun! > > Ron AC7AC > > > -----Original Message----- > From: Elecraft [mailto:[email protected]] On Behalf Of Hajo > Dezelski > Sent: Monday, October 26, 2015 11:47 AM > To: [email protected] > Subject: Re: [Elecraft] Accuracy of Wattmeter W2 under 2 Watt > > Hello, > > Thanks for your suggestions. It seems that the owners of the W2 use it for > higher power settings than qrpp. So it is natural that nobody could answer > my questions. > > So I will continue to use my Pm2 http://www.foxdelta.com/products/pm2.htm > . > But in a private discussion I was pointed to a solution of the irritating > numbers shown on the display. I have no cabinet and the cable from the > RS232 was too long and not shielded. So there was some hf going direct into > the circuits. So I will build a box and take some ferrits and hopefully > will > be happy. > > Thanks for the advice and your time. > > 73 de Hajo DL1SDZ > > Gruss > Hajo > > --- > Cela est bien dit, ...,mais il fault cultiver notre jardin. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
