"MICHEL SAMSON" wrote to "PHIL MARLOWE" (03 Jul 03  17:32:00)
 --- on the topic of "TV reception"

 MS> It didn't cost me much:  a pre-amplifier i got from someone who
 MS> had switched to cable and a variable indoor amplifier plus some wiring;
 MS> the antenna was so rudimentary i feel ashamed to tell you what it was!
 MS> I'll do violence to myself and confess it all:  i attached a spare
 MS> ~UHF~ loop to the pre-amplifier which itself was screwed to top of a
 MS> wooden stick i scavenged from an old mop, this antenna wasn't efficient
 MS> for lower ~VHF~ frequencies but since i had so much trouble with being
 MS> close to channel- 2 and 6 the configuration happened to suit my needs
 MS> just fine i'd say...
 MS> %-)

Sometimes the simpler solution will trump a thousand dollar project.
The UHF loop has a gain of about 1db over the dipole when vertical and
about -3db when horizontal. You could have made a folded dipole using
some 300ohm line in front of a reflector element for a not so negligible
gain of about 5db. The R/S table top UHF dual bowtie we discussed has
about 7db gain. This is nearly the gain of a small 10db preamp.
Realize that the big advantage of antenna gain over preamp gain is that
antenna gain doesn't have amplified circuit noise.

A couple of antennas have fascinated me but don't seem practical to
build. One type has no metal elements at all and is simply a solid
dielectric block forming a lens of sorts extending from a waveguide for a
gain of 14db. The dielectric block has a length of 18.5 feet at 200Mhz!

Another is a type which uses metal strips embedded in a dielectric form.
I suppose it uses some type of Fresnel effect to achieve an astounding
34db. The dimensions are the real challenge about 120 feet square by 100
feet long at 200Mhz! Both are not table top projects...

But one which might is intriguing in its simplicity. However I don't
know if the book has a typo or something. It says this "longwire"
consists of a piece of #10 solid copper wire mounted horizontally
broadside (bidirectional) at the transmitter.

A "5-1/4 wavelength" (25.8 feet?) or "29.5 inches" (1/2
wave?) is stated
at "4.5db gain at 200Mhz". It feeds into a grounded 72 ohm transmission
line. Not exactly something difficult to try but it may poke an eye out
so stick a small rubber ball on the end! But like I said I don't know if
it's 25.8 feet or "29.5 inches" as this old cook book says two things.
Well, 29.5 inches is easy enough to try, where's my coax...!

Another intriguing comment about indoor antennas is that signal strength
inside a room may sometimes be stronger than outdoors because of
resonnant cavity effects of the metal structures around the room. In
other words if the room behaves as a resonnant tank at a desired
frequency and there is an opening for the energy to get in then the
signal will be naturally amplified!

 Mike
 ****

... Is that line-noise or is that a C program-listing?
--- Blue Wave/DOS v2.30