View Full Version : ham scanner??

02-03-2007, 07:05 PM
Any ham radio experts out there? I have a cb base that has the board pictured below, can I use a POT and the prop to replace the crystal board on this base to make it a scanner?

02-03-2007, 10:45 PM
There are 4 wires going from the board, what should I look for on my osciliscope to determine the frequency (carrier) wires, there should only be 2, right? maybe 2 are for the transmit. (the 2 white wres you see are just the lamp)

Mike Green
02-03-2007, 11:03 PM
I can't tell anything from the picture other than there are lots of crystal cans and a rotary switch. Presumably, the switch selects a pair of crystals and the 4 wires are just 2 pairs, each for a selected crystal. Usually one is for transmit and the other for receive (offset from the channel by the IF frequency). Frankly, to make a scanner, I'd suggest doing a mechanical fix, removing the detents and springs from the rotary switch and hooking a servo to it or a small geared stepper. You're going to need a schematic if you want to substitute some other oscillator (to find the best place to inject the signal). If you want to use the Propeller for the frequency source, you're going to have to clean up its output signal a lot to eliminate noise, harmonics, etc. There's an article in this month's QST magazine on a digital VFO. That may give you some ideas.

02-03-2007, 11:25 PM
I would like to get it in the 2 meter range, I am sure replacing the crystals would do that, but I wanted to go digital with more fine tuning, a DSS chip may be the answer.

Mike Green
02-03-2007, 11:30 PM
I thought you were talking about a CB scanner. You're not going to be able to use the unit for anything else (other than maybe 10 meters). It's got all kinds of tuned circuits in it designed for 26-28MHz. 2 meters is a whole 'nother thing.

02-03-2007, 11:35 PM
hmm, thanks, thats why I asked for the expert opinion, as I am not a RF expert. I just thought that the 28-28mhz limitation was just in the crystal board. Thanks for clearing that up. What do you think the hackable ranges are then, 20mhz to 30 etc. is there any ham activity in that range besides CB channells that would be interesting to listen to? I guess I can answer that myself if I can find my ICOM RC1 in the garage.

02-04-2007, 12:41 AM
Looks like there is some activity in that range that is not CB channels so this might be a cool thing to do to this unit (I just like to play with stuff) , as I despise listening to the weird cb channel "talk"
I took a look at this thread and got some good idea's:


also heres a 555 timer oscilator... I might use a 100k pot and a3300pf cap to adjust the frequency, the use the prop to display it????


And it appears that it I should be able to do this with the prop alone, the audio will not be nearly as clean as my Icom scanner is, but I suspect it will be clean enough to listen to. So I still want to do it just for the sake of doing it. Ill stick with 20 to 28mhz range on the prop just to test out the theory with .05 khz steps . Then see how far I can go, I doubt ill smoke the base.....

I paid $2.00 for the base at a garage sale, so its no biggie if I smoke it, Ill still have some good crystals and knobs etc.

Post Edited (bassmaster) : 2/3/2007 10:04:10 PM GMT

Graham Stabler
02-04-2007, 03:54 AM
My Dad converted several PMR (public mobile radio, a bit like CB) rigs to 2m. I thought that generally the filters are at some fixed IF frequency and the cystals are used to mix the RF down to that IF. Of course there are general band pass filters as well.

In any case I'd look up conversions in general and then when you know what a standard conversion entails and requires you will be better placed to find out if the prop fits the bill. Even if it doesn't I'm sure it would make a great controller for lots of ham applications.


02-04-2007, 04:47 AM
Graham, that is cool. I got lucky at radio shack one day, they had this big box with $1.00 liqudation items in it, it had tons of junk but tons of great stuff like hundreds of led's, relays coils, ic's, solar panels, breadboards, solder and about 15 variuos project boxes + resistors and much more, it probably weighed 40lbs,I asked if he would sell the whole box for 20 bucks and he took it! the largest sack they had doubled was so big it barely fit in my passenger seat 3feet long. One big box I added a one of my $3.99 serial displays to it and am ready to make something cool like a ham reciever. But have little experience in rf. thanks for your and mikes suggestions.

02-04-2007, 11:11 AM

I just found this website. should be able to make a nice scanner with the i2c interface....

Post Edited (bassmaster) : 2/4/2007 3:39:27 PM GMT