Buying custom crystals...

[eccerr0r]

Re: Buying custom crystals...

I don't take samples for one offs, seems like theft. However if I were thinking about mass producing,then I'd view samples as advertising...

Then again, maybe they should be advertising their product to me for a future design...

[Agent24]

Re: Buying custom crystals...

That's what samples are for! It's a free test. Even if you intend on mass production there's no guarantee you're going to use the same chips you prototype with. The design can always change.

And, if you successfully use their sample to mod your radio, that IS advertising - other people may want to do the same, and they may sell more chips as a result...

[eccerr0r]

Re: Buying custom crystals...

I think I got a green light on the prototype side... I think I can get this HF circuit working on a solderless breadboard after someone getting an FM transmitter (VHF) working on a a solderless breadboard

Unfortunately I'm still out locating and extracting a varactor or few.

Also after finally figuring out the dividers, kind of bummed that either I have to build a 17-bit programmable counter to get 5KHz stepping, or I could use a 16 bit for 10KHz steps for the receiver. Needless to say, 17-bit counters will be very expensive and 16-bit counters are "free."

So I plan on making the transmitter with the 5KHz step and receive 145.115- on my scanner as proof of concept that my contraption works (and hope someone's still using the NCARC 2m repeater)

[goontron]

Re: Buying custom crystals...

^Ive said before i have some boards that may have varactor caps on them. Let me check, its boards from an old 2M radio where the final (a discrete package) got blown out by a nearby lightning strike, but the rest was OK.

[eccerr0r]

Re: Buying custom crystals...

You should fix it and make a new discrete transistor final for that radio...

Anyway it doesn't matter that the parts comes from a 2m radio, I have to redesign it anyway because the LO is actually more like HF or low VHF.

[goontron]

Re: Buying custom crystals...

You should fix it and make a new discrete transistor final for that radio...

Ive looked into that. Then decided that since it didn't have CTCSS and all my attempts to add it, be it from an actual function generator or a hack job using a TRS cord and a computer to try a higher level (hotter) output, have failed. So i scrapped it.

[eccerr0r]

Re: Buying custom crystals...

Ouch... hope I don't run into that issue... That will be next...

[eccerr0r]

Re: Buying custom crystals...

BTW how did you try to hook up the tone generator? Mixed with the microphone input or after the microphone BPF? If you hooked it up at the microphone you'd need a pretty hot signal to blow over the BPF (if there is one of course --- what radio was this?)

Gosh I hope this isn't going to be that hard to get it to work..scared now. I thought the PLL was going to be a daunting challenge, if CTCSS is going to also be equally as tough... shiver in 90°F weather....

[goontron]

Re: Buying custom crystals...

^ Its a TR9000. Before the mic preamp/bandpass it would get filtered out. I tried after the BPF and using the tonepad input. They both work, but they either cause distortion or don't open up the (very old) repeater...

[eccerr0r]

Re: Buying custom crystals...

Hmm... would need to know how that input is fed into the modulator to know more, perhaps the DTMF input overblows the voice input and really need a more balanced mixer.

How did you control enabling the tone - enabled the oscillator when keyed up? I suppose if you kept it running continually, it should work minus the distortion problem.

[eccerr0r]

Re: Buying custom crystals...

GRRRRR... I hate SMT.

I bought an old, junk VCR in hopes that I could swipe the varactor from it... It was an 1986 model...

... and it had SMD

Ugh... plus the proprietary parts make it tough to figure out where the varactor is. Sigh. Might have to go buy from fleabay after all

[Agent24]

Re: Buying custom crystals...

Sorry to say it but you'll have to get used to SMD sooner or later... with the right tools its not all bad though. I used to hate SMD parts too. Now they only mildly annoy me.

I actually like them more sometimes for DIY and prototypes. No holes need to be drilled in a custom PCB. But it depends on the part. Most chip resistors, ceramics, diodes, etc are easy and fun. SMD electrolytics are silly though. Ultra fine-pitch ICs aren't necessarily joyous either.

But hey. It's where we're headed...especially in repair.

[eccerr0r]

Re: Buying custom crystals...

Well, it's not that... actually finding which device is the varactor is the problem when they're not labeled properly, no schematic, and custom parts

But yes, I hate drilling PCBs too.

[eccerr0r]

Re: Buying custom crystals...

Ugh...speaking of tariffs, I wonder what to do if I do end up needing to china import varactors.

Looks like I should have targeted AM radios, alas, AM radios with varactors somewhat uncommon to be garbage unlike VCRs... AM radios without varactors are frequently garbage, however.

[eccerr0r]

Re: Buying custom crystals...

I SEE YOU, LITTLE BUGGER!!! STOP HIDING! (though I don't know about all the SMD on the other side of the board...)

Anyway, thank you silkscreen!

Unfortunately it still is an unmarked. Hopefully I can get its capacitance and it falls into the range I need...

[eccerr0r]

Re: Buying custom crystals...

OOhhh..this is annoying. I found another one, hooked them up inverse parallel, and was able to get a voltage adjustable capacitor according to my Sencore! Was getting 15pF to 30pF or so. It's a start!

However, building this into a Colpitts isn't working Can't seem to get it to oscillate Perhaps the ESR of the varactors are too high to oscillate with the coil I was playing with... I suppose I also need to carefully take into account the extra picofarads that are lying around in the solderless breadboard as it introduces random capacitance every which where, which may break the circuit.

Should do a bit more due diligence on calculating expected frequency, currently tossing random devices to see what it would do...if it would do anything at all. I might still need to buy off the shell varactors anyway, this 30pF is a bit small. I don't think I need all the way to 300-400pF but perhaps having it that high is helpful.

Sometimes amazing thinking about the difference between a 1000uF SMPS output cap and a 40pF varactor... Many orders of magnitude here!

[goontron]

Re: Buying custom crystals...

RF anything....solderless breadboard

[eccerr0r]

Re: Buying custom crystals...

http://sci-toys.com/scitoys/scitoys/...readboard.html
https://www.youtube.com/watch?v=fwOvI_cqZoQ
http://www.qsl.net/jh5esm/homebrew/7tr1015bb.html

It's all about managing parasitics.

Oh BTW, first rev of this circuit shall be ~7MHz only, I've done 10MHz stuff just fine, so it should be okay... well except an extra 2pF capacitance on 30pF is a huge 7% - will need to more carefully place.

Might actually be a wiring problem though.

[eccerr0r]

Re: Buying custom crystals...

YES... well sorta YES! I hit checkpoint 3!

Checkpoint 1 was: basic design, digital and analog section top level planning.
Checkpoint 2 was: Varactor diode validation - verified I can adjust capacitance with voltage.
Checkpoint 3: ~6.25MHz oscillation sustained on a solderless breadboard that's variable by voltage!

Well, I didn't completely pass the checkpoint but close. Problems I see is that the adjustment range is not what I want, I have some bad noise on the waveform despite being on batteries, and the waveform is jittery at certain voltage points (VERY BAD).

My calculated oscillation frequency is not quite the measured frequency, though it's expected on a breadboard; and I have too much inductance in places which is probably the source of strange artifacts on the waveform.

I'm using my 20MHz 'scope (calculated frequency from interpolating the calibration marks). Eventually I should view this on the 300MHz Teks, but this should be sufficient for now.

Note my target frequency needs to be a somewhat higher than 8MHz (because 8MHz * 18 is 144MHz: low end of the 2m amateur band) so I still need need to tweak this.

Progress brings hope, hope is needed for success!

[eccerr0r]

Re: Buying custom crystals...

FAIL! Well, expected fail. Haha!

Well, the whole loop is now complete and assembled on the solderless breadboard. It's time for debug

I guess I got lucky on one thing: I got my LCD routines working first try YAY! Well I had swiped my known working routine from another project, but I needed to reroute one pin due to needing the resource on the microcontroller... Anyway, fast 4-bit LCD updates is working with a random HD44780 LCD I grabbed. Luckily this particular LCD actually works, I have never seen it working until now. Also shows gcc-7.3 is capable of generating working AVR binaries, and I was able to get it to shrink the code down so I have plenty of space left.

Now problem is, my phase comparator hit one of the rails...heh. I will need to tune my inductor and caps to see if it's even possible for it to get into range (no clue what the inductance is after I discovered a second slug -- and rotated it out to speed things up...

... or if I'm using the CD4046's phase comparator properly, could have been dumb and it's currently pumping up when it's supposed to pump down. Shame shame didn't read the datasheet clearly (was assuming its onchip VCO behaved the same way as my VCO, though usually higher voltage denotes higher frequency.)

Anyway, full steam ahead!