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Sunday, October 8, 2017

A Direct Conversion iPhone!


Well, really a DC receiver in an iPhone box.

I think the Apple iPhone boxes have great potential as project enclosures.  They are cardboard, but they are very rigid and solid.   I decided to use them for a Direct Conversion receiver project I've had in mind.  


This is a 40 meter DC receiver.  No chips.  Ceramic resonator VXO tuned by a varactor diode. 9V battery as the power source.  Ear buds as the transducer.  Passive, two diode, singly balanced detector.  It sounds great -- so great that I may have to add a gain control. 

The nice fit is no coincidence -- I cut the board so it would fit in the iPhone box.  


Take a look at that top cover.  It is all, well, empty.   I could put another board in there, right?  Maybe a balanced modulator,  a mic amp and an RF amplifier.  Then this thing would be a Double Sideband transceiver.  We could even make use of the little microphone that comes with most of the ear buds.  


I'm thinking that this might be the kind of project that people would like to take on this winter.  Build the VXO first.  Then the AF amp.  Then the product detector and front end. At that point you've built a receiver.  For extra credit you could go on to the transmitter.  No need to use Apple boxes (but they are cool...)  I will try to get the schematic done soon.  My nephew John Henry will test the prototype. 



4 comments:

  1. Nicely done Bill. I have a similar iPhone box here for a future project but last week I rebuilt the rx part of my ZL2BMI DSB tx/rx with an NE602 as the mixer and as I wanted to put it on 40m I used my (boxed up with display) AD9850. I had to add a BPF to get rid of broadcast interference at night and now it works great. However, it needed some shielding so I've put it in a sweet tin which is about 10x10x3 inches. Listening to cw on a DC rx with no filtering certainly helps sharpen up my receiving skills!

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  2. Bill, I am building Pete's Simpleceiver Plus DCR, are you planning to compete with that? Put up Youtube videos, and have a community vote? Pete's has lots of volume from the LM380, and I think that helps...

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  3. I could never compete with Pete Juliano: I wouldn't do it, and if I did, I'd lose. These are different projects based on our different preferences. 73 Bill

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  4. Bill, cool packaging. But, "Yet another 40M rig??" ;) I'm trying to decide whether to build for 30 or 60M. Two less-crowded bands. What do you think? 73, Jason W6IEE

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