danr
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My Ham Radio Blog
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May 6 18:54 UTC 2004 |
I've been doing a ham radio blog for about a year and a half now. It's
been fun. I've even been mentioned in a "Surfin'" column on the ARRL
website. The URL for my blog is http://www.w8pgw.org/blog/1. Below are a
couple sample entries.
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Simple Keyers [01 May 2004|04:22pm]
After working Paul AA1LL recently, I e-mailed him to follow up on a
couple of things we'd discussed in our QSO. It turns out that Paul is an
afficionado of simple keyer circuits, i.e. ones that do not use a
microprocessor. Without a processor, you don't get any memory, but the
circuits are very simple to build.
N1HFX Simple Electronic Keyer (http://www.rason.
org/Projects/cwkeyer/cwkeyer.htm). This keyer uses just two ICs, but is
not iambic. This may seem like a disadvantage, but that makes it ideal
for use with a single lever paddle, such as my VibroKeyer or a homebrew
sideswiper.
PA2OHH Simple Iambic Keyer (http://www.geocities.com/pa2ohh/iambic.htm).
This iambic keyer uses two ICs and has built-in paddles made from PCB
material. Each paddle is connected to a transistor circuit that is
supposed to sense the change in capacitance when you touch the paddle.
It should be easy enough to modify the circuit for use with conventional
paddles, but you'll have to add another IC.
Iambic Keyer Using 4000 Series CMOS (http://www.luna.co.
uk/~jbryant/pages/iambic.jpg). This circuit uses three ICs, but is more
complicated than the PA2OHH. My first impression, formed by looking at
the two circuits, is that the PA2OHH circuit is the way to go if you
want iambic capability.
If you build one of these circuits, you might want to add a sidetone
oscillator. That will add another IC to the circuit, but then you could
use the keyer to send code practice.
Thanks, Paul!
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AAAAAAARRRRRRGGGGGGGHHHHHHH!!!!!!!!!!! [25 Apr 2004|11:40am]
A friend of mine recently got me interested in building the C-Pole
antenna as described in the April 2004 QST. It's a variation on the
vertical dipole, and needs no radials, even though the vertical length
is less than a quarter wavelength. One drawback, though, is that it
needs a balun.
The author experiemented with two different types of baluns. The first
type--33 feet of RG-58 coax on a 2-in diameter PVC pipe--seems
cumbersome and lossy (14%). The second option--14 turns of RG-174
coax--on a ferrite core seems the better choice, except that I don't
have any RG-174. Nor do I have the ferrite cores the author suggests--an
FT-240-61 for the 20m antenna and an FT-240-67 for the 17, 15, 12, and
10 m antennas.
No problem, I think, I'll just buy a couple of them. Well, for whatever
reason, neither Universal Radio or alltronics.com carries the FT-240-67,
although they have a great selection of other types. They do have the
FT-240-61, but it costs ten bucks.
So, I start thinking about alternatives. Well, it just so happens that a
long time ago I bought an Amidon balun kit (which consists of a T-200-2
core and 12 feet of #14 enamel wire). "Perfect, I think,"this thing's
been languishing in my junk box for at least 15 years. Now I can use it.
"
The balun is just a 1:1 balun, I reason, so why don't I just wind it up
and see how it works? I'm actually getting a little excited about this,
thinking to myself that this will be a pretty cool learning experience.
I go down to the shack, cut the wires, and then reach for the core on
the workbench. Unfortunately, it slips from my fingers, and when it hits
the cold, concrete floor, it snaps in two. AAAAAAARRRRRRGGGGGGGHHHHHHH!!
!!!!!!!!!
It was certainly a learning experience, although not the one I wanted to
learn. I learned that ferrite cores are very brittle, and to be more
careful next time.
Tomorrow, I'll have wander down to local radio shop and see if they
happen to have another core. I think I've seen the balun kits in there,
but am not sure if he will have just the core. In the meantime, I've
e-mailed the author of the antenna article to see what he thinks about
using this balun kit instead of one of his designs. In the article, he
hints that he thinks using closely-spaced 14-ga. wire on a ferrite core
should be less lossy than the coax version, but that he hadn't tried it.
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