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Re: [Discuss-gnuradio] Moving my antenna


From: Doug
Subject: Re: [Discuss-gnuradio] Moving my antenna
Date: Tue, 29 Jan 2019 16:06:58 -0500
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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

On Tue, Jan 29, 2019, 21:07 Tarquin <address@hidden wrote:

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.

 

On Tue, Jan 29, 2019, 12:40 PM cliff palmer <address@hidden wrote:

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.

Thanks

 

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