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The RF Workbench / New here, and my journey building a SW xmtr
« on: September 20, 2018, 1907 UTC »
Hello everyone, I'm new here on the board but definitely not new to radio experimentation, broadcasting, and electronics work.
I have plenty of experience on AM and FM with legal power levels, i.e. Part 15 and squeezing as much range as possible out of such systems. Recently though I've gotten interested in SW broadcasting. After doing a lot of research I've decided as a first project to try to build an AM modulated Michigan Mighty Mite, as described here: https://makerf.com/posts/so_you_want_to_be_a_shortwave_pirate
Half a watt ought to be plenty for me to mess around with for now. I don't want to go overboard. Don't have the resources to deal with the possible repercussions of yet higher power levels...
Plus on SW it's much easier to make an efficient antenna on a small scale. Quarter wave at 7000 kc is 34.5 feet... not out of reach for hanging on a tree or something, just for giggles. Much better than Part 15 AM where your antenna efficiency is probably 5% or less even with the very best systems. Even 1/8 wave would probably be pretty good, right?
So I ordered up some parts from Mouser. As many crystals for different frequencies within the usual pirate bands I could find that they had in stock, plus any parts I didn't already have to make the circuit.
My question here is, anyone have suggestions for building this circuit and for SW broadcasts in general? I'm not looking for "MMM sucks, build {some other xmtr}". Any other projects can come later. Right now I'm just doing this because it's small and easy and all I have the resources and time for.
One of my specific questions I'm wondering about is whether I can put a potentiometer somewhere in the MMM circuit to vary the power output level. Ideally I'd have a mark somewhere on that dial for "legal" power with a certain antenna setup, so I could use it for micro-power broadcasts when I just want to send something to a radio in the house for fun. Unfortunately I don't have a field strength meter so it would be difficult to determine the actual legality, but I guess I could approximate by just walking around with radio.
Thanks!
I have plenty of experience on AM and FM with legal power levels, i.e. Part 15 and squeezing as much range as possible out of such systems. Recently though I've gotten interested in SW broadcasting. After doing a lot of research I've decided as a first project to try to build an AM modulated Michigan Mighty Mite, as described here: https://makerf.com/posts/so_you_want_to_be_a_shortwave_pirate
Half a watt ought to be plenty for me to mess around with for now. I don't want to go overboard. Don't have the resources to deal with the possible repercussions of yet higher power levels...
Plus on SW it's much easier to make an efficient antenna on a small scale. Quarter wave at 7000 kc is 34.5 feet... not out of reach for hanging on a tree or something, just for giggles. Much better than Part 15 AM where your antenna efficiency is probably 5% or less even with the very best systems. Even 1/8 wave would probably be pretty good, right?
So I ordered up some parts from Mouser. As many crystals for different frequencies within the usual pirate bands I could find that they had in stock, plus any parts I didn't already have to make the circuit.
My question here is, anyone have suggestions for building this circuit and for SW broadcasts in general? I'm not looking for "MMM sucks, build {some other xmtr}". Any other projects can come later. Right now I'm just doing this because it's small and easy and all I have the resources and time for.
One of my specific questions I'm wondering about is whether I can put a potentiometer somewhere in the MMM circuit to vary the power output level. Ideally I'd have a mark somewhere on that dial for "legal" power with a certain antenna setup, so I could use it for micro-power broadcasts when I just want to send something to a radio in the house for fun. Unfortunately I don't have a field strength meter so it would be difficult to determine the actual legality, but I guess I could approximate by just walking around with radio.
Thanks!
