sbright33:
I understand that it is my responsibility to build it and test it. But I'm traveling right now and I need to estimate costs for the project so I'm asking for help. I need to order the needed parts, so far none. Not for someone to verify it. Just your thoughts. Will it work at all for my application? If I need more sensitivity an LM358 will be more than enough? Thanks for your help so far!
Well as cell phone use microwave frequencies I would at a minimum try and find a suitable diode and transistor rated for such frequency, as I'm sure those shown are just not very effective at cell phone frequency. Note also that such 'field strength' meters are not frequency selective without additional front end filtering so will respond just as energetically to cordless telephones, garage door openers, and other common consumer RF generators.
Lefty