On 01/29/2019 03:16 PM, Albin Stigö
wrote:
Loss will be proportional to the length of coax,
type of coax, impedenace match and frequency. Higher frequency,
higher loss. For example at 10MHz the loss in in 100m RG58 would
be around 3.7dB, at 1000MHz 48dB, a factor 27000 difference.
It's normally best practice to put the
receiver/transmitter as close to the antenna as possible.
--Albin
That's quite true, however the higher and more in the clear outdoors
you can put it will improve the signal considerably. For coax, you
should use a 50 ohm cable, preferably the Times Microwave
types LMR-240 or, better, LMR-400. You can look up the specs on
these cables on the Internet and calculate cable loss versus length
from the information found there. You will need to adapt the
cable connectors to the small ones on your radio. Commercial
adapters are available for all combinations of interface. I suggest
terminating either of the cables I recommend in type N male.
Doug, WA2SAY, retired RF Engineer
Hi
If
you want to go “cheap” use coax intended for satellite
TV reception. Be carefull about 75ohm, as the Hack RF
is a 50 ohm system, you can use RG58U not to costly,
don’t expect good performance above 1.2 GHz. Not sure
what you want to intercept, if it VHF UHF you will be
ok, else you could try RG213 but that ½ inch thich and
you will have to adapt.
The
thinner coax RG179 /178 will be fairly lossy.
I
suggest personaly start with RG58 its cost effective
and maybe an LNA near the antenna
Regards
Zr1tR
From: Discuss-gnuradio [mailto:discuss-gnuradio-bounces+tarquin.roode=address@hidden] On
Behalf Of david vanhorn
Sent: Tuesday, January 29, 2019 9:52 PM
To: cliff palmer
Cc: address@hidden
Subject: Re: [Discuss-gnuradio] Moving my
antenna
Coax loss can be a big issue.
Given the low power levels you
will suffer less loss on a long run using 75 ohm
coax cable which is designed for low loss, even
assuming you do nothing about the mismatch at the
ends of the run. All that is good up to about 1ghz
where more specialized coax is needed for minimum
loss.
The antenna is a significant part
of the equation and you are well advised to use an
antenna suited for the frequency of interest.
Broadband antennas like discones have very low gain,
and they pull in other strong signals you don't
want.
I have a HackrfOne with an
Ant500 antenna connected to my workstation in my
basement (where the internet connection lives). I
need to move the antenna out of the basement to
improve reception, so I thought I would use coax
to connect the antenna from upstairs to the
HackrfOne.
I'm too new to SDR to be
confident about just moving the antenna and
using a spare length of cable coax. Please
provide some help on selecting, sizing and
connecting coax between the HackrfOne and the
Ant500.
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