Antenna cable loss query
 

I guess this is the age-old "what's the perfect all-band antenna plus
cable" question.

Want to install a single (or maybe two) not too large or fancy small
whip-type "all-band" antennas on the eaves of a residence and run cables
to BNC jacks inside, for scanner listening in the 25-50 MHz, 100-160
MHz, and 450-490 MHz bands, and am trying to decide between a less
desirable antenna and scanner location but with only about 3 to 4 meters
of cable run, or a more desirable location for antenna and scanner but
with maybe 7 to 10 meters (25 to 30 feet) of cable run.

Question is, if I use good 50 ohm coax how serious would the cable
losses be for 20 to 30 feet of cable in the above bands (with the
100-160 MHz band probably the one of most interest)?

Thanks for any suggestions or pointers, on cable loss or specific
antenna models.

Want to install a single (or maybe two) not too large or fancy small
whip-type "all-band" antennas on the eaves of a residence and run cables
to BNC jacks inside, for scanner listening in the 25-50 MHz, 100-160
MHz, and 450-490 MHz bands, and am trying to decide between a less
desirable antenna and scanner location but with only about 3 to 4 meters
of cable run, or a more desirable location for antenna and scanner but
with maybe 7 to 10 meters (25 to 30 feet) of cable run.

Question is, if I use good 50 ohm coax how serious would the cable
losses be for 20 to 30 feet of cable in the above bands (with the
100-160 MHz band probably the one of most interest)?

Use any cable 1/4 inch or more in diameter , YOu will not notice it up to
500 mhz for only 30 extra feet. Best bet is some rg-6 cable if you can find
some that has a copper shield or if you have a good way to make a connection
to the shield as some is aluminum. RG-8x is good for a short run. Don't
worry about the impedance of 50 vers 70 ohm cable. It will not effect your
receiver coverage.

Ralph Mowery wrote:


Want to install a single (or maybe two) not too large or fancy small
whip-type "all-band" antennas on the eaves of a residence and run cables
to BNC jacks inside, for scanner listening in the 25-50 MHz, 100-160
MHz, and 450-490 MHz bands, and am trying to decide between a less
desirable antenna and scanner location but with only about 3 to 4 meters
of cable run, or a more desirable location for antenna and scanner but
with maybe 7 to 10 meters (25 to 30 feet) of cable run.

Question is, if I use good 50 ohm coax how serious would the cable
losses be for 20 to 30 feet of cable in the above bands (with the
100-160 MHz band probably the one of most interest)?

Use any cable 1/4 inch or more in diameter , YOu will not notice it up to
500 mhz for only 30 extra feet. Best bet is some rg-6 cable if you can find
some that has a copper shield or if you have a good way to make a connection
to the shield as some is aluminum. RG-8x is good for a short run. Don't
worry about the impedance of 50 vers 70 ohm cable. It will not effect your
receiver coverage.

I will add to what Ralph said that the most likely place for "signal
loss"
will be at the connection(s) you make at each end of whatever coax you
use.
Buy some good quality pre assembled coax if at all possible. Avoid Radio
Shack junk.

I would go for the better antenna location and not worry about the added
cable length. 30 feet is nothing serious to worry about.

Al KA5JGV



"AES/newspost" wrote in message
...
I guess this is the age-old "what's the perfect all-band antenna plus
cable" question.

Want to install a single (or maybe two) not too large or fancy small
whip-type "all-band" antennas on the eaves of a residence and run cables
to BNC jacks inside, for scanner listening in the 25-50 MHz, 100-160
MHz, and 450-490 MHz bands, and am trying to decide between a less
desirable antenna and scanner location but with only about 3 to 4 meters
of cable run, or a more desirable location for antenna and scanner but
with maybe 7 to 10 meters (25 to 30 feet) of cable run.

Question is, if I use good 50 ohm coax how serious would the cable
losses be for 20 to 30 feet of cable in the above bands (with the
100-160 MHz band probably the one of most interest)?

Thanks for any suggestions or pointers, on cable loss or specific
antenna models.

In article ,
"Al - KA5JGV" wrote:

I would go for the better antenna location and not worry about the added
cable length. 30 feet is nothing serious to worry about.

Al KA5JGV

Thanks much for this and several earlier right-to-the-point replies.

Helpful people on newsgroups can be really helpful.

I will add to what Ralph said that the most likely place for "signal
loss"
will be at the connection(s) you make at each end of whatever coax you
use.
Buy some good quality pre assembled coax if at all possible. Avoid Radio
Shack junk.

That remimded me of some pix I saw of a cut away of a RS connector , maybe
it was L type where a spring or coil of wire was used. That thing acted
almost like a RF choke and had a very high loss.

In article ,
AES/newspost wrote:

I guess this is the age-old "what's the perfect all-band antenna plus
cable" question.

Want to install a single (or maybe two) not too large or fancy small
whip-type "all-band" antennas on the eaves of a residence and run
cables to BNC jacks inside, for scanner listening in the 25-50 MHz,
100-160 MHz, and 450-490 MHz bands, and am trying to decide between a
less desirable antenna and scanner location but with only about 3 to
4 meters of cable run, or a more desirable location for antenna and
scanner but with maybe 7 to 10 meters (25 to 30 feet) of cable run.

Question is, if I use good 50 ohm coax how serious would the cable
losses be for 20 to 30 feet of cable in the above bands (with the
100-160 MHz band probably the one of most interest)?

Thanks for any suggestions or pointers, on cable loss or specific
antenna models.


I went to the Radio shack site and looked up RG8 (16 AWG) and got these
numbers and calculated the loss for the rounded distance numbers:

Freq loss per foot @ 10 foot @ 30 foot
100 MHz .037 dB .37 1.11
400 MHz .080 dB .8 2.4

3 dB is half your power so over 400 MHz your higher antenna better pick
up twice the signal to make the longer run worth it. The cable loss is
fairly linier so you could plot the two points in excel sheet and figure
the loss for any frequency around these points.

--
Telamon
Ventura, California

I went to the Radio shack site and looked up RG8 (16 AWG) and got these
numbers and calculated the loss for the rounded distance numbers:

Freq loss per foot @ 10 foot @ 30 foot
100 MHz .037 dB .37 1.11
400 MHz .080 dB .8 2.4

3 dB is half your power so over 400 MHz your higher antenna better pick
up twice the signal to make the longer run worth it. The cable loss is
fairly linier so you could plot the two points in excel sheet and figure
the loss for any frequency around these points.

In radio work 3 db is not really that much for most applications. It can be
going from 1 watt to 2 watts or 500 watts to 1000 watts. Also you will not
be getting 3 db differance as to go the first 10 feet you loose .8 db, to go
20 feet more (the first 10 plus the next 20) it is only 1.6 db differance.