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.