Hi everyone, I built Hans' 30M beacon kit and it is now on the air, about 100mW into a quarter wave vertical at around 14.140.030. What a fun little kit! I haven't seen it on any grabber yet, so please let me know if you hear me :)
For those of you building the kit, I put together some construction notes, and a few ideas for when/if I get around to trying to homebrew my own...
First, there are a few typographical errors in the text. Probably no big deal for most of you:
- On page 2, The yellow toroids are 'T37-6'.
- On page 3, building the xtal osc/buffer, there are many many typos: Missing C1, C3 listed twice, missing C9 & C10, missing R7. Also C5 & C6 (part of the LPF) should not be included in this step. If you just stuff all the parts for the top half of the board, you will have built the appropriate section.
Be careful, after installing the microcontroller, when instructed to listen to your headphones. My tones were pretty loud.
I like to cut my wire to length when winding the toroids. For 1" lead lengths, you can estimate the wire needed by the following formula: wire-length(in) = (#turns/2)+2. For instance, 20 turns on a T37 toroid would require (20/2)+2 = 12 inches of wire. If you wind all of the toroids in one step, be careful that you label which one is which. The 19 and 20 turn toroids look pretty much the same...
When building the driver/PA, the holes for the pot were spaced too closely together. Hans mentioned this at FDIM. You can cut the pins, solder some wire leads into the holes, then solder the pot to the leads.
The other issue for me was measuring power output. I don't have any sophisticated equipment in my shack, but I do have a 'scope. Doing the math, 100 mW into 50 ohms should generate a 6.3V peak to peak signal. By the way, Power (mW) = 2.5 * Vpp^2. I adjusted the pot until I got this voltage. Adjusting much higher made the 7000 get hot. For those like me who don't use a scope much, a 10x probe means that you should be looking for 0.63V, not 6.3V.
While stuffing parts, I wondered if the power & RF holes could be spaced on 0.1" centers, so that header pins could be used. This would allow you to easily change the power source and antenna. I've also seen these arranged as 3 pins (GND,+5,GND) or (GND,RF,GND) so that, no matter which you attach your jumper, it will be correctly oriented. The other place 0.1" pins would be nice is for the speed setting jumpers. Then you could use those little removable jumper shunts to quickly change speeds.
Some other ideas I thought about.
- An onboard voltage regulator (or zener), to protect the microcontroller, allow 12V input, and possibly improve osc. stability.
- NPO caps in the oscillator.
- Are the unconnected inputs to the microcontroller OK? Do they reliabily float low?
When listening on a receiver, what settings do you recommend? I just set the VFO at 10.140 MHz and listened in CW mode with a pitch of around 600 Hz, but wondering what others are using. And at what filter width? 1 KHz width should be enough, but is narrower or wider better?
My beacon seems to be shifting down 5Hz, rather than up 5Hz, when sending data. I haven't figured out the reason for this yet. I thought perhaps I had set my rx for 'Rev-CW' mode by accident, but this isn't the case. Any ideas?
Bruce - W8BH
