Quote:
Originally Posted by Username1
dtvmcdonald; where can I find good antenna design stuff so I can make myself a better yagi for those trouble stations....? Thanks.
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In an old ARRL handbook, like 60s or so, or, better, in one of the
old special ones the made for antennas and transmission lines. Let
me search eBay ... search for ARRL ANTENNA. They are there, cheap.
For the plain Antenna book, 60s or 70s or early 80s should have
what you need. There is also a current "classic" one that might.
In any case ... what I used was a very basic multielement Yagi
for 432 Mhz simply scaled to the frequency I wanted. The only
problem is the coax attachment. I STRONGLY suggest a driven
element that works like the old twin-lead antennas, a 4:1 step
UP in impedance ... the natural impedance is about 25 ohms.
For balun use the kind that attaches the coax directly to the two
elements, and has a 1/4 wave piece of 1/2" copper tubing
attached to the shield of the coax 1/4 wave plus 1/2 inch
down.
I can email you a design scanned from an ancient book. These
things are NOT CRITICAL ... they just work, and put commercial
ones in their rear view mirror. For indoor use or reachable outdoor,
you can make the boom out of 3/8 in copper, steel, or brass rod or tube and
the elements out of 1/8 inch copper rod or tuning, soldered on.
Equally important is the preamp. I suggest the best, the difference really does matter:
http://www.advancedreceiver.com/page12.html
near the bottom, the 0.6 dB one for TV, its GaAsFET and not cheap. Made for
specific channel, but rather wide, see the Amateur or Commercial pages
for price, its same as nearby standard ones. Really ... the difference between
this and a wideband one is just what the specs say. For digital 1 dB is a
really huge difference if its on the edge. Really.