which type of crystal

[Antennae]

There are different kinds of crystals out there.  I have an HC-49 crystal. It got hot 3 times for about a minute each time when it was working. (Like say-"ouch"-out-loud-hot with the fingerometer.)   I'm pretty sure it broke.  I have it in a Michigan Mighty Mite transmitter.  Its metal casing is small compared to RC car crystals.

Does the small case mean its a wimpy crystal type? I wonder if I was misusing it. What kind of crystal should I be looking for to replace it? 

[redhat]

If the crystal is running hot, it means your drive level is, well, excessive.  You could also have some DC present that shouldn't be there.  You can order crystals in different packages, HC-49 and HC-6 are the most common.

Taking a look at the circuit, it appears this transmitter is a power oscillator coupled to an antenna.  The crystal is either not suited for this purpose (microprocessor crystals usually aren't happy in these kind of circuits) or you may have the coil the wrong way around, driving the crystal too hard.

+-RH

[ff]

Yeah the HC49U/S micro xtals are the worst.  They are VERY easily overdriven.  As redhat said, in a MOPA circuit (like the Mighty Mike), there's too much current running through the xtal branch for a small rock.  Also, the smaller the rock, the more susceptible they are to frequency change due to capacitance.  In your situation the best xtals to use are physically large rocks like Butch (HC6) and Sluggo (FT243). HC18s are also usable, but will need a bit more care to keep from overdriving.  I often use HC49s but only in chip oscillator circuits like those built around an HCU04 unbuffered inverter or a 7400 NAND gate.  These circuits are easily found in a zillion places online and probably could be used to drive your transmitter.  The smaller the rock, the smaller the power level it can tolerate.

[Antennae]

Oh man, I learned the hard way! It was $19 for that thing shipping included.  Thanks, I'll look for a Butch or Sluggo chunk of crystal.
  
 I realize I didn't mention that when it was working, it ran hot when the transmitter's capacitor wasn't tuned.  Otherwise it wasn't hot. Another thing, after the failure, I found I shouldn't have connected the antenna's ground to the oscillator circuit ground.   I wonder if that helped it die.  

Regarding the coil winding, I made sure L1  and L2 were wound the same direction. I can't find anything else on how to wind L1 on this diagram. L1 has 21 turns total and its tapped at 7 turns.  My question is if it matters where the 7 turns and 14 turns go. Like should the 7 turns section go toward the top of the diagram or the bottom? Refer to the attachment. I wrote notes in green to aid in my question.  

[paranoid dxer]

i put the tap at the bottom   for a short lead through the circuit board
ft243 easy to grind up to freq you want   and can be had fairly reasonable on ebay

[ff]

should the 7 turns section go toward the top of the diagram or the bottom? 

Definitely towards the bottom.  Another thing - the entire 21 turns resonates on freq and your 4 turn secondary should be wound over nearly the entire length for best results.  You might already be building your Mighty Mike from Make RF's website but if not, check it out:

http://makerf.com/posts/mighty_simple_shortwave_transmitter

He has an excellent site for newbie transmitter builders - lots of good stuff!  Once you get your unit working his Altoids can Low Pass Filter is a highly recommended add-on.

[ff]

One more thing Antennae - your xtal might still be good BUT your transistor is possibly blown.  Energizing it without the antenna ground connected might have zorched the transistor, however mebbe not.  It's hard to tell considering the low power level of the Mighty Mike.  I mention it only to alert you to the possibility.  Ain't transmitter building FUNNNNN?  Now you know why its a "Black Art"...

[Antennae]

Its a fun experiment for the 40meter ham band. I can't wait to make some contacts with it.

-Yup, its from makerf.com.  He's a great resource!
-Whew, thats how my coil ended up with the 7 on the bottom. And thanks for specifying to spread the secondary over the whole thing. That was another question.  I did that because I was able to see it like that on makerf's pictures.
-It even worked on the breadboard with a coil made from enamel wire from an old RC motor.  It was all lumpy so I got some new wire for my purdy version.
-Zorched transistor eh?  I hope not, I tried it with another one I had and it still wouldn't work.  If I had an extra variable capacitor I could do a test on the crystal and make certain what the problem is.  

I can't help it, take a look at my baby!

[Antennae]

Oh yeah, I had the antenna and antenna's ground connected with a 50ohm load...mostly.   BUT I had the antenna ground connected to the ground of the Mighty Mite circuit when it shouldn't be. 

[Antennae]

It was the crystal that was busted. I installed a big honkin' FT 243 crystal and it works again, yay. 

[ff]

It was the crystal that was busted. I installed a big honkin' FT 243 crystal and it works again, yay. 

Hooray for Sluggo!

[Antennae]

I made a long 30 below blog post of my building experience with pictures. I had no intention of making it today but it just burst out of me. I hope it helps other newbies!
http://hfunderground.com/blog/?p=369

[ff]

An excellent article Antennae!  Reading it brought back memories from 30+ years ago of my plumbing mysterious radio circuitry in similar fashion.  Congratulations on your successful build and welcome to the fraternity.  As your knowledge and experience grows, may your signal always look "siney" and your curiosity never fade... 73!

ff

[Antennae]

UPDATE:
I got a ham license (hooray!) and tried the transmitter on air and it doesn't go across the street! It doesn't move the dial on my antenna tuner either. I used 2 different antennas. Full update is on the bottom of the article:
http://hfunderground.com/blog/?p=369

[OMCS]

These guys have been around for years.

http://jancrystals.com/