DIY radio update

So it looks like you are good to go, once you solve any nagging little technical details.

Currently, the RC Mfrs each have a unique take on how to implement

2.4Ghz frequency diversity. The end result is that you have to have a TX & RX that work using the same scheme(s).

As to once upon a time "they were all DIY"-- I remember the early 1960's days when rubber band driven escapements and DIY or kit single button tube transmitters were the norm, with tone transmitters and receiver reed relays just coming out to play. The 27Mhz (CB) band was in use. We got very unhappy, due to some sort if interference from an unknown source, possibly industrial or even early remote traffic signal control. The strange part of the problem was that the flying field was a few miles away from known RF sources, and the other side of town from heavy industry.

The cure at the time was to use a CB mobile unit, with an adapter cable that picked up the tone signal from the RC transmitter and fed it into the mike input of the CB unit. The 2 Watt output of the CB unit and a mobile antenna produced a strong enough signal to overcome the problem. Receivers were fairly simple, and not really capable of much in the way of rejection of unwanted signals.

About a year ago, Corona (China web site) had several 2.4Ghz modules that looked interesting. Since no mention was made of FCC approval, I totally ignored them.

Besides that, working with such things as ball grid arrays and surface mount components is not my cup of tea. (old, tired eyes, etc.)

On Tue, 16 Nov 2010 00:08:21 GMT, Skywise wrote in :

OK, this confirms my view. But I'm impressed with the work you did to get it from the horse's mouth.

Well done!

Much appreciated.

Marty

Chuck wrote in news:_skEo.26146$ snipped-for-privacy@newsfe04.iad:

And getting the yay/nay from the FCC. Although it's possible I've misunderstood something, I have found further documents on the FCC website that seem to very clearly support my effort. But I'm looking for the "final word" just to be sure.

The modules I'm interested in are transceivers. That is, each one is a transmitter AND receiver, and two of them will talk to each other when configured to do so.

Oh, those must have been the days. Sounds like it was fun.

As I progress in my ham radio education, I recently learned that there are a lot of 10-meter radios being imported that are known to the FCC as not being compliant.

I know what you mean. Prototyping will be DIP, using development modules from the manufacturers. Final version, though, will have to be SMT because at least one chip ONLY comes in SMT, which I can handle if I take my time. When I was an electronics tech I used to have to replace the occasional SMT widget with about 140 pins without just a plain vanilla soldering iron, one - pin - at - a - time. Actually, removing is much harder than putting on. Fortunately, the chips I'm looking at are only about 48 pins or so. What will be new to me is I want to try photo-etching my boards. Not done that before, but it doesn't look all that difficult from what I've read.

Brian

On Tue, 16 Nov 2010 03:52:50 GMT, Skywise wrote in :

The College electronics club did some photo-etching last year.

I happened by as they were looking at some of their first boards.

They didn't know that some copiers automatically reduce by 2% or so. Their circuits were just a little bit off as a consequence. I don't know whether they were able to salvage them or had to start over.

The moral of the story is to provide some witness marks in both the X and Y axis so that you can verify that you've got a good mask before using it to etch a board.

Marty

The ARRL says "Never ask the FCC for permission to do something -- they'll just say 'no', and make a rule". But then they say "ask us instead" -- and they probably don't care about any cruddy license-free band.