End of summer

Well, I had all kinds of plans for what I wanted to get done over the summer, but most of it didn't happen. What else is new? Most of the time I was just too busy. A couple of times I wanted to get out to the garage and work, but it was just so hot that I couldn't bring myself to go out there. A couple other times I said "heck with it" and went out there anyways - dripping sweat on my work.

I did get a few things done though. I completed the transmitter (which I've already talked about) though I do want to work on some dial-lighting so that I can know when it's on. I completed the battery eliminator for my Silvertone farm radio, and I finally got to play with the scroll saw.

Here's what the transmitter looks like:


While I'm pretty proud about how this project turned out, I do see the limitations of the one-tube design. It does have fairly high distortion at peak volume. I have tried a few different software packages that are supposed to do some of the compression and limiting that professional radio stations use, in order to get a "louder" and more consistent sound with less distortion, but I either I haven't figured out how to properly use them (likely) or they just don't work well. Some day I may try a more elaborate transmitter to see if I can get cleaner sound. This design is also kind of drifty - it does not stay on frequency. Not a big deal if you're using an old radio, but if you try to tune it on a digital radio you find that one day it's on 1200 khz, the next day it's on 1204, or maybe 1202. Even so - it was reasonably easy for this beginner to build, and it does work quite well, considering the simplicity of design - which is more than you can say for the $15 kit that I bought from Electronics Goldmine.

In truth, I'm probably the only one around here who even notices the distortion. I would like to get better range though. At the moment it barely covers my property. A better antenna would probably help, but the other big problem is that we're only a half-block away from an AM station. During the daytime when they're running 50Kw, they really interfere with my transmitter. It's somewhat better at night when they drop to 20Kw. So I probably can't expect very much from any home-brew design - at least not in this neighborhood.

Next on the list is the battery eliminator. This works really well, and fit right into the small priority mail box that I dressed up with a design from Billy Richardson on ARF. You'll notice that I did modify his design to say "A/B" battery instead of just "B". Other than that, it's stock. He did a great job with the artwork. Now that I think about it, I suppose I should have changed it to say 1.5v/90v, but oh well. I'm not going to mess with this one any more.


So back to the Philco 70. I finally got out to the garage a couple of weeks ago to play with the scroll saw. I sketched the pattern from what was left of my original front panel directly onto a piece of masonite. I needed some masonite for another project, and they only sell it in 4 x 8 sheets, so I had them cut it down so that I could use it to practice on. Here's my first try:


Yes, I cut the bottom holes way too large - I forgot that the veneer had smaller holes than the plywood, and traced these holes from the plywood. Next time I'll just drill them with a drill bit. While I think it looks pretty decent for a first-try, I still need more practice. It also looks a lot better in the picture than it does in person. The other thing is that masonite can't really be sanded, so the end-result when cut from plywood, and later sanded to nice smooth curves, should come out pretty nice. I just have to remember to stay INSIDE the lines when cutting. You can always go back over it with sandpaper, but you can never put missing wood back.

I'm going to order the veneer for my 70 soon, and try to get started on the real panel. I'm ordering 2 pieces of the front-panel veneer - just in case.

So I'm making slow progress to be sure, but it's still progress.

Oh yeah, I forgot to mention one more thing. I finally got around to trying out the Philco 89. I plugged it in through my dim-bulb tester, and it actually works pretty well. I think I'll do a recap though before I start trying to use it very much. It also needs a good cleaning and lubing of all of the switches and contacts. The dial is pretty dirty too, but I need to be careful about that. The 70 is first in line right now, and after that I'll look at the 89.