[600MRG] Amazon/eBay special remote vector swr meter

[Dave Riley]

Ben,

Congratulations and this is outstanding... Present day hands on guy!!  
Amazing in my mind...

73s from DaveR aa1a


On 2/28/2018 2:12 PM, Ben Gelb wrote:
> Amazing what you can piece together for $25 these days!
>
> I wanted to monitor the vector impedance of my 630m antenna / matching 
> network to better track how it moves over time / weather / start 
> alignment etc.
>
> I cobbled together an AD8302 gain/phase detector with a small ADC and 
> ESP8266 microcontroller. The ESP8266 is intended for IoT applications, 
> so it has wifi capability.
>
> This can be connected to a directional coupler (you have to raid your 
> junkbox for this) and then can report return loss, vswr, complex load 
> impedance etc.
>
> See this URL (note data is garbage while I'm not transmitting, though 
> annoying reports close to 1:1 swr due to my choice of attenuators in 
> front of the AD8302):
>
> http://gw.gelbnet.com:8100
>
> Picture: https://photos.app.goo.gl/yjh61n3nZPMSH1Wj1
>
> Here's the shopping list:
>
> AD8302 Module: 
> https://www.ebay.com/itm/AD8302-NEU-Amplitude-Phase-RF-Detector-Modul-IF-2-7GHz-Phase-Detection-New/172995156780 
>
> ADS1115 Module: 
> https://www.amazon.com/gp/product/B01DLHKMO2/ref=oh_aui_detailpage_o08_s00
> ESP8266 Module: 
> https://www.amazon.com/MakerFocus-NodeMcu-Development-Compatible-Arduino/dp/B076RM8MYW
>
> I had to replace the 1nF coupling caps on the AD8302 board w/ larger 
> ones (I had 0.33uF on hand so i used that) in order to get it to work 
> at 475kHz. But after that seems to have usable accuracy out of the box 
> (1-3dB error) and a little bit better with some simple 
> spreadsheet-based calibration. I haven't tried to measure the phase 
> accuracy, though at least the 0 point seems in the right place (473.2kHz).
>
> Since its wifi, you could locate this at the antenna instead of the 
> transmitter... if you wish (only a short run of coax away in my case 
> though).
>
> Happy to share more details with those interested.
>
> 73,
> Ben (N1VF)
>
>
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