Did I do this TV antenna right for 665mhz?
 

Trying to pull in TV channel 46 for an afternoon superbowl viewing.
To make a temporary antenna, Here's what I did:

1. figured that Channel 46 is roughly 665mhz
2. Divided 496 by 665 and came up with 8 3/8 inch length
3. Screwed TWO 8 3/8" pieces of electric fence wire to a 2x1x1/2 wood
block
3.5. (Made the wires face away from each other as straight as
possible)
3.6. (The distance between the screws is approx 1/4 inch)
4. Ran 50 feet of 300 ohm coax attached with one pole wire to each
lead
5. stuck a cork in the end of 12 foot electric conduit pipe
6. fixed the assemply to the cork by running a screw through the
middle of the 300 ohm insulation about one inch below the wood block.
7. Attached the pole to the chimeney with a bungee
8. Spun the antenna for best reception (seems to point at repeater)

Noted that reception is marginally better than using a Radio Shack UHF
antenna inside the house. Reception seems to be sensitive to
placement of the 300 ohm coax.

Anything I could have done better? Tips hints?

Thanks all.

If you want to use 300 Ohm twinlead, you should make a folded dipole out of
300 Ohm twinlead, not a straight dipole out of single conductor wire. You
are using 300 Ohm transmission line with a 75 Ohm antenna and losing some
signal.

When using twinlead, you need to keep it away from all metal ( at least a
couple of inches), and twist it about one twist per foot.Do not tape it to,
or run it inside a metal pipe.

Tam/WB2TT
"Caezaar" wrote in message
om...
Trying to pull in TV channel 46 for an afternoon superbowl viewing.
To make a temporary antenna, Here's what I did:

1. figured that Channel 46 is roughly 665mhz
2. Divided 496 by 665 and came up with 8 3/8 inch length
3. Screwed TWO 8 3/8" pieces of electric fence wire to a 2x1x1/2 wood
block
3.5. (Made the wires face away from each other as straight as
possible)
3.6. (The distance between the screws is approx 1/4 inch)
4. Ran 50 feet of 300 ohm coax attached with one pole wire to each
lead
5. stuck a cork in the end of 12 foot electric conduit pipe
6. fixed the assemply to the cork by running a screw through the
middle of the 300 ohm insulation about one inch below the wood block.
7. Attached the pole to the chimeney with a bungee
8. Spun the antenna for best reception (seems to point at repeater)

Noted that reception is marginally better than using a Radio Shack UHF
antenna inside the house. Reception seems to be sensitive to
placement of the 300 ohm coax.

Anything I could have done better? Tips hints?

Thanks all.

If I understand, you made the antenna twice as long as necessary. See
below.


"Caezaar" wrote in message
om...
Trying to pull in TV channel 46 for an afternoon superbowl viewing.
To make a temporary antenna, Here's what I did:

1. figured that Channel 46 is roughly 665mhz
2. Divided 496 by 665 and came up with 8 3/8 inch length

496 (I thought it is 486, but close enough) gives the length of a
dipole's total length, not each half of a dipole.


3. Screwed TWO 8 3/8" pieces of electric fence wire to a 2x1x1/2 wood
block

This is now TWO half waves.


3.5. (Made the wires face away from each other as straight as
possible)

Not sure what "face away from each other "means?? I can only guess that
you mean "end-to-end". That is, the two wires are both in a single line
with two ends close together (at the two screws).


3.6. (The distance between the screws is approx 1/4 inch)
4. Ran 50 feet of 300 ohm coax attached with one pole wire to each
lead [...mechanical details ... snip...]
8. Spun the antenna for best reception (seems to point at repeater)

Not sure what you mean "Point at". I assume you mean the TV repeater.

The folded dipole suggestion made in the other post would be good. Take a
piece of 300 ohm twinlead and make it 8-3/8 long with both ends shorted
together. Yes, twist together about 1/2 inch of each of the two 300 ohm
wires at each end (solder optional). Precisely in the middle, cut only one
of the twinlead wires and connect the feed line to the two loose ends you
just created.
--
Steve N, K,9;d, c. i My email has no u's.

"Steve Nosko" wrote in message
...
If I understand, you made the antenna twice as long as necessary. See
below.

I missed that.

Tam/WB2TT