WHITE NOISE STRANGE GOINGS ON

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WHITE NOISE STRANGE GOINGS ON

Postby Warbo » Fri Nov 03, 2017 11:12 am

So ever since i started scanning and using various antenna i get a lot of hiss/noise listening to airband, i thought it was normal.
I have built a j pole (plan off intnet, plenty flying about) with a balun coil in the coax by the connecting point and using this almost
all the noise has gone?? even on weak signals. strong is as clear as a bell!.
I tried similar balun on my 127mhz cut di pole but still noisy. same with the w881 top mount hiss/white noise in every
signal. Dipole and Jpole both mounted on separate poles in garden and cables are identical coax approx 25 feet long, both running into man-cave :thumbup:
so any external interference/ influences should be the same?
Any thoughts why the j pole is so clear?
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Re: WHITE NOISE STRANGE GOINGS ON

Postby m0lsx » Fri Nov 03, 2017 5:45 pm

Warbo wrote:So ever since i started scanning and using various antenna i get a lot of hiss/noise listening to airband, i thought it was normal.
I have built a j pole (plan off intnet, plenty flying about) with a balun coil in the coax by the connecting point and using this almost all the noise has gone??


The Hiss is normal & on AM, which is what Air Band uses, it can be especially harsh if you are not use to it.
The so called balun you describe is actually an RF choke. It stops unwanted RF on the coax during transmissions from your station, thus it does nothing during RX & it is not a balun, despite being called one. It is just referred to as one.
Some antennas have a better noise to signal ratio than others. That is you get more signal, less noise.
The whole area of baluns is a minefield. We refer to some things as baluns or un/un's when we know they are not & even when we do get it right & they are a balun, we do not normally specify what type of balun they are & thus the term balun is as good as useless from a accuracy point of view.
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Re: WHITE NOISE STRANGE GOINGS ON

Postby Warbo » Fri Nov 03, 2017 7:13 pm

:thumbup: thanks for the info
m0lsx wrote:
Warbo wrote:So ever since i started scanning and using various antenna i get a lot of hiss/noise listening to airband, i thought it was normal.
I have built a j pole (plan off intnet, plenty flying about) with a balun coil in the coax by the connecting point and using this almost all the noise has gone??


The Hiss is normal & on AM, which is what Air Band uses, it can be especially harsh if you are not use to it.
The so called balun you describe is actually an RF choke. It stops unwanted RF on the coax during transmissions from your station, thus it does nothing during RX & it is not a balun, despite being called one. It is just referred to as one.
Some antennas have a better noise to signal ratio than others. That is you get more signal, less noise.
The whole area of baluns is a minefield. We refer to some things as baluns or un/un's when we know they are not & even when we do get it right & they are a balun, we do not normally specify what type of balun they are & thus the term balun is as good as useless from a accuracy point of view.
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Re: WHITE NOISE STRANGE GOINGS ON

Postby barrylewis1234 » Sun May 27, 2018 9:50 am

The J pole antenna is DC shorted so has a much lower noise floor. Its effecticly earthed and shorts out (but not at rf) so you may be picking up switch mode noise or some kind of interferance.

run a cable down from yourr j pole and bang a rod into the ground, give it its own earth, this well help.

If your using an RTL SDR card try giving it its own power supply (non switch mode). I will post up some pics how to do this. Then you can move the RTL SDR card to right below your antenna and avoid all the noise caused by your PC computer
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