scanner coax length
 

Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal).

Maybe not as much, but it does impact reception, especially in the 800+MHz
frequencies.

Keeping the antenna inside, has advantages. No corrosion, no wind damage,
no sun's UV rays breaking down your cable insulation. If the insulation in
your attic has the aluminized paper backing, it could be a problem however.

50 feet would not be excessive, if you use good quality coax.

Bill Crocker


wrote in message
oups.com...
Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal).

the higher the better.
extended coax length will ofcourse increase coax losses but they will be far
lower than the gain you will get by sticking it up high, and outside.

mike

wrote in message
oups.com...
Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal).

"mikeFNB" moc.dlrowltn@FNB7G-ekim wrote in message
...
the higher the better.
extended coax length will ofcourse increase coax losses but they will be
far
lower than the gain you will get by sticking it up high, and outside.

mike

wrote in message
oups.com...
Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal).




I hope I'm not posting twice (The first one vanished for no good reason)!

The best thing you can do is mount a bullet amp at the antenna. Even the
best quality coax has a large loss at microwave frequencies. Use the type
of amp meant for satellite television. Since you aren't transmitting you'll
get by cheap. This will also allow you to use cheaper RG6.

wrote in message
oups.com...
Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal). At 20 feet
you get about 4.4 miles times about 1.3 for about 5.8 miles to the radio
horizon. At 30 feet you get 5.4 times 1.3 for 7.1 miles. YOu will have to
do the same to the other station's antenna and add the two numbers to find
the total distance. So as you can see the height is important. Five watts
will go over 100 miles if the antennas can see each other so power or loss
in coax is not too important(within reason) if you can gain height.


Go for the heigth. You will loose some signal, but you will still have more
than you need if you use atleast rg-6 coax or beter. On vhf and higher you
take the square root of the height multiplied by a "fudge factor" to find
the distance.

Loss is loss. If you lose 3db in your feed line, that's 1/2 your signal
gone, whether you're transmitting it or receiving does not matter.



Ralph Mowery wrote:
wrote in message
oups.com...

Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal). At 20 feet

you get about 4.4 miles times about 1.3 for about 5.8 miles to the radio
horizon. At 30 feet you get 5.4 times 1.3 for 7.1 miles. YOu will have to
do the same to the other station's antenna and add the two numbers to find
the total distance. So as you can see the height is important. Five watts
will go over 100 miles if the antennas can see each other so power or loss
in coax is not too important(within reason) if you can gain height.


Go for the heigth. You will loose some signal, but you will still have more
than you need if you use atleast rg-6 coax or beter. On vhf and higher you
take the square root of the height multiplied by a "fudge factor" to find
the distance.

not quite, but never mind.

mike
"bob" wrote in message
...
Loss is loss. If you lose 3db in your feed line, that's 1/2 your signal
gone, whether you're transmitting it or receiving does not matter.



Ralph Mowery wrote:
wrote in message
oups.com...

Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal). At 20
feet

you get about 4.4 miles times about 1.3 for about 5.8 miles to the radio
horizon. At 30 feet you get 5.4 times 1.3 for 7.1 miles. YOu will have
to
do the same to the other station's antenna and add the two numbers to
find
the total distance. So as you can see the height is important. Five
watts
will go over 100 miles if the antennas can see each other so power or
loss
in coax is not too important(within reason) if you can gain height.


Go for the heigth. You will loose some signal, but you will still have
more
than you need if you use atleast rg-6 coax or beter. On vhf and higher
you
take the square root of the height multiplied by a "fudge factor" to
find
the distance.

Careful, though...if you have a sensitive receiver, adding the amp could
actually reduce performance by overloading your receiver and possibly
introduce intermodulation distortion depending on what stations are nearby.
Since he won't be monitoring microwave frequencies, there are several
choices of coax that would work quite well for a 50' run. In reality, there
is some point where the advantage you gain with altitude is cancelled out by
the loss in the coax. For a 50' run, you may be getting close to a wash,
especially for UHF, unless you use better coax. It's difficult to make
comparative measurements because you don't have antennas in both locations
at once, but it sure would be nice to be able to do that.

- Doug


"Jim" wrote in message
...
The best thing you can do is mount a bullet amp at the antenna. Even the
best quality coax has a large loss at microwave frequencies. Use the
type of amp meant for satellite television. Since you aren't transmitting
you'll get by cheap. This will also allow you to use cheaper RG6.

"bob" wrote in message
...
Loss is loss. If you lose 3db in your feed line, that's 1/2 your signal
gone, whether you're transmitting it or receiving does not matter.



Ralph Mowery wrote:
wrote in message
oups.com...

Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal). At 20
feet

you get about 4.4 miles times about 1.3 for about 5.8 miles to the radio
horizon. At 30 feet you get 5.4 times 1.3 for 7.1 miles. YOu will have
to
do the same to the other station's antenna and add the two numbers to
find
the total distance. So as you can see the height is important. Five
watts
will go over 100 miles if the antennas can see each other so power or
loss
in coax is not too important(within reason) if you can gain height.


Go for the heigth. You will loose some signal, but you will still have
more
than you need if you use atleast rg-6 coax or beter. On vhf and higher
you
take the square root of the height multiplied by a "fudge factor" to find
the distance.


That's not the point. A 6 db gain amp at the antenna overcomes that 3 db
lose in the cable.