EMRFD Message Archive 9774

Message	Date	From	Subject
9774	2014-02-22 06:07:29	Jim Miller	Pic power meter for 630m band use?
I'm starting to play with getting on the 630m band when it is approved. I was going to use a 40db tap and the PIC power meter as a test of my output power. However I see the PIC power meter appears to be good only down to 1Mhz rather than the needed 472Khz. From the schematic it looks like the only highpass element is the 0.01uf cap at the input to the AD8307. Would changing that to a larger value be all that is needed or are there other limitations (HW/SW) that would prevent its use? Thanks jim ab3cv
9775	2014-02-22 06:41:12	Ephemeral	Re: Pic power meter for 630m band use?
The AD8307 has a DC offset cancellation loop which uses an internal filter. To extend the range below 1 MHz you can add an external capacitor. Please refer to the datasheet, particularly the section "OPERATION AT LOW FREQUENCIES".   There are other ways to measure power, e.g. do you have an oscilloscope?   Adrian
9776	2014-02-22 07:51:46	Jim Miller	Re: Pic power meter for 630m band use?
Adrian Thanks! I'll check out the AD8307 section you mentioned. I do have a nice Tek465 but I don't have it in my shack which I try to keep neat since it's upstairs. All my test equipment is in the basement where I do building and most of the testing. The PIC power meter and 40db tap would be small enough to keep up here for a bit while I'm getting going. Thanks Jim ab3cv