#garfield Logs

Apr 15 2023

12:10 AM rue_mohr: weather might be good enough for my to try a casting again
12:21 AM rue_mohr: need the pulley blanks for the cnc
11:56 AM WormFood: polprog, I have a *LOT* of experience working on CB radios, as I used to repair them professionally for several years. If you need any information, let me know.
11:57 AM polprog: WormFood: oh, awesome! Thank you, I will pick your mind if i need to
11:57 AM polprog: I'll see if the guy lets me buy his radios for $10 each
11:57 AM WormFood: One trick some systems use, to not need more crystals, is to take the 10.240 MHz xtal, divide it by 2, to 5.12, the multiply it by 3, to get 15.36 Mhz, which is then mixed with the VCO output, to get 27 Mhz.
11:57 AM polprog: they are not worth much because of the 5/0 issue
11:58 AM polprog: Yeah i saw this trick with the HD42853
11:58 AM WormFood: making them shift by 5 kc is not hard. I used to do that all the time, and put it on a switch, for some truck drivers, that run on odd frequencies.
11:59 AM polprog: Which has the PLL's dividers fixed to generate the channels in the fives only
11:59 AM WormFood: I have a vintage President Jackson, which I want to modify. I want to take out the PLL and VCO, and replace it with a DDS module, so I can dial it into whatever frequency I want.
11:59 AM polprog: hm, i have a President Harry somewhere
11:59 AM polprog: sounds like a cool project
12:00 PM WormFood: by fives, you mean ending on 5kc, like 27.195?
12:00 PM polprog: yeah
12:00 PM polprog: and Poland uses zeros, ie 27.190
12:00 PM WormFood: That shouldn't be too hard to get, but of course, depends on the design of the PLL circuit.
12:01 PM WormFood: Well, I mean, it depends on the pll, and how they're doing their xtals.
12:01 PM polprog: That particular radio seems to use it similarly to how the example schematic in the datasheet does it
12:01 PM WormFood: You have a single xtal in the radio, or is there also another xtal like 10-15 MHz somewhere else?
12:01 PM polprog: There's a single 10.24 xtal in the radio
12:02 PM WormFood: Many, many radios use the exact same design.
12:02 PM WormFood: Everything is being generated by that one xtal, if you shift it, you'll shift *everything* in the radio.
12:02 PM WormFood: You'll need to build an xtal osc, and inject the proper signal to shift it by 5kc
12:02 PM polprog: Yes, thats why i will not be touching the PLL part
12:02 PM polprog: thats what i figured out
12:02 PM polprog: :)
12:03 PM polprog: if i shift the XTAL the PLL goes completely off the channels
12:03 PM WormFood: Take for example, that 15.36 MHz signal, could be replaced by another osc
12:03 PM WormFood: If you shift the 10.240 xtal, then your channel spacing won't be 10kc, but it should be so little, it wouldn't matter.
12:04 PM polprog: I figured out I need to replace the 10.24 that goes into first converter (RX) and the final mixer (TX) to shift both RX and TX by 5kc
12:04 PM polprog: I want to do it properly
12:04 PM WormFood: When I was cleaning up yesterday, I came across several of the boards you need. These were specifically designed, to do what you want. Of course, it's just a regular osc, but it was sold for modifying the frequency range of CBs.
12:05 PM polprog: I think i will put something together quickly. need the oscillators, i will buy them tomorrow
12:05 PM WormFood: If you want to do it "properly", then just build a small osc with an xtal, and inject the signal into the right place. You need to replace a signal, not change it.
12:06 PM polprog: I figured it all out yesterday doodling on the chips datasheet
12:06 PM polprog: This is exactly how i want to do it
12:07 PM WormFood: I have a radio, where I replaced the 10.240 MHz xtal, with a 5.12 MHz xtal, because in that radio, that xtal is ONLY used for the PLL, and it's channel spacings, so I got my radio to work in 5 Kc steps, instead of the original 10 Kc steps.
12:08 PM WormFood: There is most likely a pin, on the PLL, that is toggled from tx to rx. I'm sure your PLL does this, even if your radio does use that feature. But it will shift everything by 455 KHz.
12:08 PM WormFood: What is the model of PLL in your radio?
12:08 PM polprog: HD42853
12:08 PM polprog: It has a tx/rx switch but the radio keeps it connected to ground or 5V, i dont remember
12:08 PM WormFood: Yeah, that's a standard PLL
12:09 PM polprog: I have the schematic somewhere
12:09 PM polprog: I dont have the radio yet
12:09 PM polprog: I didnt buy it yet :P
12:09 PM polprog: But yeah. I will make the 10.235 oscillator and test it, then install it in the radio
12:09 PM polprog: then test it on the comms analyzer
12:10 PM WormFood: The PLL was designed to internally have 5 kc steps, then they use a ROM between the channel selector and the PLL, so that it will throw the right codes at the PLL for your given channel.
12:11 PM WormFood: You can no dick around with that xtal, and still expect your radio to work. It's just impossible, because they use that xtal to generate so many other frequencies. That's why you have to inject a new frequency.
12:12 PM WormFood: Remember, your LO comes off that xtal too, so change that, and you literally change *everything*.
12:12 PM polprog: i know this
12:12 PM polprog: :)
12:12 PM WormFood: I'd be happy to send you the parts you need, if shipping isn't stupidly expensive. I'm not sure I have the right freq xtal, but there is a good chance I do.
12:13 PM polprog: i have 5 pages of notes where i figured out what traces to cut to inject my new signal
12:13 PM polprog: That would be very kind of you! But i will check if i can get them tomorrow
12:13 PM WormFood: You don't need to figure it out on your own. This stuff has been documented before.
12:13 PM polprog: I dont have much experience with "traditional" radio
12:13 PM polprog: and i kinda wanted to figure it out mysely
12:13 PM polprog: myself*
12:15 PM WormFood: It can be fun, and is a great learning experience. However, I recommend you figure it out on your own, and before you do anything, check what you figured out, against what other people figured out, and see if you got it "right".
12:15 PM polprog: This is a good idea
12:15 PM polprog: so i have one thing im not sure about
12:15 PM WormFood: Would I be correct in assuming this is just a normal AM radio?
12:15 PM polprog: Yes, FM is "illegal" on CB in here
12:15 PM WormFood: Or does it also do SSB too?
12:15 PM WormFood: Not in all countries.
12:15 PM polprog: In Poland you can only talk on AM
12:16 PM WormFood: I took a normal CB (legal), and I gave it FM support. :D
12:17 PM WormFood: It was really weird, because the radio was based on an export design. They changed the traces in the power output, so you couldn't use dual finals, like the export version does, but oddly, they didn't remove the circuits for FM.
12:17 PM WormFood: So, the legal radio, had traces on the board, for FM support....so I found all the parts I needed, and added them to the radio, and made it work on FM. I don't have the tools to set the deviation on it properly, but it did work.
12:18 PM polprog: If you look at that chips datasheet there's the RX chain on top of the schematic on page 1, originally the 10.24MHz signal goes into the 2nd converter.. I need to change that signal to 10.235 to RX on the -0 channels, but that will mean that the signal in first converter's output is going to be at 10.690 rather than 10.695, which means i "should" retune the filters between 1st and second converter
12:19 PM polprog: or do they have enough bandwidth? I figured that since 5kc is half the channel bandwidth their passband would be similar width and i should retune them
12:19 PM WormFood: It's really easy to make an AM radio xmit FM. Just reroute the audio, to the PLL's VCO. As you speak, you create a voltage, that changes the frequency with your voice. Also, listening to an FM signal on an AM radio isn't hard either, as long as you can adjust the frequency it receives on.
12:19 PM polprog: a lot of people here transmit on FM either knowingly or not (they flipped the AM/FM switch) and you can still hear them
12:20 PM WormFood: I hate to tell you this, but your idea isn't going to work well.
12:20 PM WormFood: Do you know why you can still hear people on FM?
12:21 PM polprog: which idea?
12:21 PM WormFood: to change the 10.240 MHz frequency.
12:21 PM polprog: I dont want to change the 10.24 frequency
12:22 PM polprog: I know it will screw up the PLLs output, therefore i will not be touching it
12:22 PM polprog: I will be adding a new frequency
12:22 PM polprog: I will leave the entire PLL part as is and only change the mixer's input and the 2nd converter LO
12:22 PM WormFood: You do realize, you can completely replace the whole PLL circuit, right, and make it do whatever you want?
12:23 PM polprog: Yes, but i want to do it as simple as possible, i dont want to design a retrofit PLL board
12:23 PM WormFood: Of course. In that case, build yourself an xtal osc.
12:23 PM polprog: thats what i will be doing
12:24 PM polprog: as for why you can hear FM on AM the answer is obvious as soon as you look at the emission spectrum of both
12:24 PM WormFood: well, normally an FM radio needs special circuits to decode the audio signal.
12:26 PM WormFood: But if you tune a poor quality AM radio, to be slightly off frequency, so that the middle of the FM transmission, is in the middle of your filter's skirt, then you can create a slope detector. This won't work on high quality radios, because the skirts on their filters are too steep.
12:27 PM WormFood: anyways, it's a neat little trick
12:28 PM polprog: oh
12:31 PM polprog: Last year i took a microwave eng 101 course
12:31 PM WormFood: that sounds cool
12:31 PM polprog: they told me all about mxiers and plls, transmission lines and all
12:31 PM WormFood: microwaves are some freaky stuff.
12:31 PM polprog: I dont have a ham licence and i never did ham radio, so i dont have all that part, but i learn quickly
12:32 PM WormFood: Have you seen the 42851 PLL?
12:33 PM polprog: no, but my gut says its similar to 42853 but programmed for -0 channels?
12:33 PM WormFood: Since there are multiple models of PLLs that really are the same, you might be able to find another PLL, that will do what you need, as a drop in replacement.
12:33 PM WormFood: Then you'd be wrong.
12:33 PM WormFood: It's actually programmable. It can do both 10kc and 5kc steps.
12:33 PM polprog: yeah, it looks a bit different
12:34 PM WormFood: it does 100 channels
12:34 PM polprog: neeat :o
12:34 PM WormFood: I don't know, but it seems to me, that it would be likely, that they'd reuse the same designs, and just modify them to that particular market.
12:36 PM WormFood: Like there is a PLL, that is used with a 455 kc shift for rx, but all the SSB radios that use them, don't use that feature. So they made a version of the chip, without that 455 khz rx shift. But if you just swap the PLL, you can toggle that pin, and make the radio give you 80 channels.
12:36 PM polprog: yeah, if i had a shortform databook or a general databook it would be neat
12:36 PM polprog: i need to get some databook for radio chips
12:37 PM WormFood: There is a book called The PLL Databook (I have a copy), but you can find this online. If you have problems, let me know, and I'll find it for you.
12:38 PM WormFood: However, it is targeted towards the american market, BUT, we get a lot of export radios here, so the information covers everything you're likely to encounter in a CB radio's PLL circuit.
12:40 PM WormFood: Did you notice the CB channel vs frequency gets weird between channels 22 and 26?
12:40 PM polprog: you mean the -A channels?
12:40 PM WormFood: no
12:41 PM polprog: I found the book, thanks!
12:41 PM WormFood: if you go by freq, an assign them to channels, it would go 22, 24, 25, 23, 26
12:42 PM WormFood: There are 5 A channels, every 5 channels, between 3A and 19A
12:42 PM polprog: heh, this order is how polish wikipedia lists it
12:42 PM polprog: whats up with it?
12:42 PM WormFood: They were originally intended for radio controlled models, but nobody uses them for that anymore.
12:43 PM WormFood: Well, they took their band plan from usa, and originally we only had 23 channel radios, and there were 2 gaps between 22 and 23. So, when they went to 40 channels, they put 24 and 25 between 22 and 23, and then continued up to 40, with no gaps.
12:44 PM polprog: interesting
12:44 PM WormFood: But what is really weird, to me anyways, is the fact that countries like New Zealand, use the same channel layout, but on totally different frequencies, that don't overlap anything else in use.
12:45 PM WormFood: Anyways, based on what I've seen so far, I feel it is very likely, that if you find the right PLL, that you can simply replace that, to get the features you want.
12:46 PM WormFood: And I'm basing that, on the datasheet for the 42851 PLL, and seeing what features they have, and how they're switchable, leads me to believe this should be fairly straight forward. Of course, I could be totally wrong, but I feel it's worth investigating.
12:47 PM polprog: i will look for a pin compatible pll that is just set to -0 channels
12:47 PM polprog: which would be the easiest way
12:49 PM WormFood: I agree. That would be the "best" way
12:50 PM WormFood: And I think there is a very good chance of that too.
12:52 PM polprog: i will have to look for it
12:52 PM polprog: i gotta do some spice simulations now
12:53 PM WormFood: Alright. Have fun. I need to do some work outside (replacing most of my water pump system (except the actual pump itself))
12:53 PM polprog: Good luck!
02:10 PM polprog: awesome, all 3 bucks work
02:10 PM polprog: the 10 to -24 takes >100ms to stabilize but i will fix that
02:10 PM polprog: i simulated all 3 of them
02:10 PM polprog: so far the most complicated spice simulations ive done
02:13 PM polprog: time to crack open a beer and watch a movie
03:32 PM rue_mohr: buck converters?
05:55 PM rue_shop5: rue_mohr, buy more usb to ttl convertesr
07:55 PM Tom_L: fiddling with the mill a bit while cleaning it up from the last job... found i was getting 240ipm rapids now
10:34 PM rue_mohr: :)
10:36 PM Tom_L: i had it throttled back on most of the settings to 210 but realized it would do better
10:36 PM Tom_L: Z is slower
10:37 PM Tom_L: done anything interesting lately?
10:37 PM rue_mohr: no I'm kinda frustrated
10:53 PM Tom_L: about?
11:19 PM rue_mohr: not getting much of anything doen today
11:20 PM Tom_L: well me either
11:23 PM rue_mohr: I need to build something or I'm gonna go insane
11:23 PM rue_mohr: mechanical
11:23 PM rue_mohr: short project
11:23 PM rue_mohr: https://dyna.kokoroyukuma.de/protogen/#
11:23 PM rue_mohr: protoboard generator, thats cool
11:24 PM Tom_L: yeah
11:25 PM rue_mohr: if I put two powered wheels on a platform (again)
11:27 PM rue_mohr: the problem I always end up at is self-charging
11:28 PM rue_mohr: I need a team of small bots to drag little brushes around the floor of the house
11:28 PM rue_mohr: keep dust bunnies on the run
11:28 PM Tom_L: called a rumba
11:28 PM rue_mohr: no
11:28 PM rue_mohr: small and not dust collecting
11:28 PM rue_mohr: just push it around
11:28 PM rue_mohr: it'll gather somewhere, can be sure of that
11:29 PM rue_mohr: but an army of them
11:29 PM rue_mohr: like 6-12
11:29 PM rue_mohr: little dust pushers
11:29 PM rue_mohr: self charging
11:29 PM rue_mohr: ditto with the lawn
11:29 PM rue_mohr: lots of small mowing bots
11:30 PM rue_mohr: like 4 or 5 of them
11:30 PM rue_mohr: "where did #5 go?"
11:31 PM Tom_L: swarm
11:32 PM rue_shop5: yep
11:32 PM Tom_L: like the arial quad copter led shows
11:32 PM rue_shop5: cause with the cnc machines and 3d printers, its not that hard anymore
11:32 PM rue_shop5: but
11:32 PM rue_shop5: self-charging
11:32 PM rue_shop5: I suppose I could start without that
11:32 PM Tom_L: need light or nuke etc for that
11:33 PM rue_shop5: collect them all up after a while of being out and charge them all up at once
11:33 PM rue_shop5: nuke?
11:33 PM Tom_L: charger
11:33 PM rue_shop5: nuke?
11:33 PM Tom_L: nuclear
11:33 PM rue_shop5: hmm
11:33 PM rue_shop5: haha
11:33 PM rue_shop5: pico-reactors
11:33 PM Tom_L: would be compact
11:34 PM rue_shop5: "I lost one, get the gieger"
11:34 PM Tom_L: follow the mushroom cloud
11:36 PM rue_shop5: I have a _huge_ collection of smart phone battieries
11:36 PM Tom_L: do those have heat sensors in them?
11:36 PM rue_shop5: yea, they have the protection pcb's
11:38 PM rue_shop5: build one, build improved design, repeat
11:38 PM rue_shop5: it just becoems an army
11:38 PM rue_shop5: I have some ESP8266 I can use
11:39 PM rue_shop5: just bumper bots
11:39 PM rue_shop5: 2 wheels and a cloth dragbar
11:39 PM rue_shop5: its not what I should be doing,but it might help me get going
11:40 PM rue_shop5: I need to use up stuff
11:40 PM Tom_L: yeah, you've collected long enough
11:40 PM rue_shop5: I got a one-way warehouse going on here
11:44 PM Tom_L: how do you find out if the pc is 32 or 64bit linux?
11:45 PM Tom_L: cat something?
11:46 PM Tom_L: cat /etc/debian_version gives that but not 32/64bit
11:46 PM Tom_L: ahh i see.. arch64
11:47 PM rue_shop5: k, I looked it up once, but dont remember
11:48 PM rue_shop5: what kinda machine can I make with like 200 stepper mtoors?
11:49 PM Tom_L: didn't know which 11 was
11:49 PM Tom_L: a power hungry one?