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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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2nd Oct 2016, 3:02 pm | #1 |
Octode
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,795
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RF Power meter (AD8307)
Hi Peeps. While building my SSB exciter and PA... I realised I had no method of checking the RF Power output, or "Relative" power. Thus I started a search on the tinternet and came across various projects and modules using the AD8307 device. I purchased a module from the far east, and also a number of chips only, to make my own, using a circuit by FOXDELTA. Being a canny yorkshire person with lots of spare time, I made my own pcb, bought the 16F876 PIC which I programmed from the files published. The original file date was 2002, but a recent 2008 file was also downloaded.
The main thrust of my query is this.. The Power meter uses 2 X AD8307, one for RF measurement and the other for Reverse voltage in a SWR meter bridge. However both have an input resistive divider of 3 x parallel 100R in series with the input and 3 X parallel 100R to ground, thus giving an input R of 33R. Now you and I know that most circuits chose or use 50R as the terminal impedance. I looked at the complete module and that has a 50R input impedance. I can only assume that the software writer used an "odd" lookup table for 33R instead of 50R. Has anyone "out there" either bought a module or tried the FoxDelta module and what conclusions were made. I am quite impressed with the display data, and I am loathed to start again. See attached photo's
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Should get out more. Regards Wendy G8BZY |
2nd Oct 2016, 4:44 pm | #2 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: RF Power meter (AD8307)
Ignoring the amplifiers input impedance I make it approx 66 Ohms?
Lawrence. |
2nd Oct 2016, 10:03 pm | #3 |
Octode
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,795
|
Re: RF Power meter (AD8307)
Ooops how clumsy of me..... grrrr Thanks Lawrence....
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Should get out more. Regards Wendy G8BZY |