SDR# Coax cable v3 sdr

[rickythomaslfc]

Could someone please recommend low noise coax
for my sdr v3 dongle manly listen to air.marine etc
I at present am using rg58.thin coax.
Getting lot noise.
Antenna is a discone.
Thank you

 

[PDXh0b0]

On the cheap, rg6, I use it, no issues, you could also wind the run around something like 4in pvc to create a choke

 

[MELERIX]

please don't use RG6 for radio signals! because RG6 impedance is 75 ohms (which is designed for CATV and AIR TV).

for radio signals better use RG8 which impedance is 50 ohms.

but if you want something cheap, but better than RG58, and with similar size, then use LMR195 or LMR200.

 

[MUTNAV]

Are you sure the noise is from the coax?,,

Do you have a way of shorting the coax at the antenna end with a 50 ohm load (resistor)?

If you do, then with it shorted with a 50 ohm load you should get no noise in the receiver, if no noise, then it's something else.

I'm just having as hard time blaming the quality of the coax for lots of noise,

It seems more reasonable to investigate proper grounding of the shield., or noise on the shield-ground .

If your coax shield is grounded to a noisy ground, there could be problems.


This is assuming you've done the basics and made sure that with the coax disconnected at each end, that there is an open between the center conductor and shield. That is really the first thing that should be done.


I don't know if this helps

Thanks
Joel

 

[KevinC]

Could someone please recommend low noise coax
for my sdr v3 dongle manly listen to air.marine etc
I at present am using rg58.thin coax.
Getting lot noise.
Antenna is a discone.
Thank you

Define “noise”. Maybe it’s OOBE raising your noise floor.

 

[MUTNAV]

Define “noise”. Maybe it’s OOBE raising your noise floor.

Fair enough, I was assuming that the OP has experience with SDR dongles, which may not be the case.

In which case I assume filters would be more appropriate, it that correct?

Thanks
Joel

 

[KevinC]

Fair enough, I was assuming that the OP has experience with SDR dongles, which may not be the case.

In which case I assume filters would be more appropriate, it that correct?

Thanks
Joel

I wasn’t taking anything away from your post, just wanted some more info about this “noise”.

But yes, filters are commonly needed on SDR’s to attenuate the FM broadcast band.

 

[MUTNAV]

I wasn’t taking anything away from your post, just wanted some more info about this “noise”.

But yes, filters are commonly needed on SDR’s to attenuate the FM broadcast band.

No No.... What I meant was that just because the OP mentioned coax quality, that seems to have been the main focus... it could be lots of different things, you pointed out a possibility I hadn't considered that is a real possibility, so 'fair enough'.

Thanks
Joel

 

[boatbod]

please don't use RG6 for radio signals! because RG6 impedance is 75 ohms (which is designed for CATV and AIR TV).

for radio signals better use RG8 which impedance is 50 ohms.

but if you want something cheap, but better than RG58, and with similar size, then use LMR195 or LMR200.

There's nothing inherently wrong with RG6 per-se, but you should try to match the coax impedance to that of the antenna in order to minimize losses.

 

[popnokick]

SDR dongles work just fine with 75 ohm coax e.g. RG6

 

[PDXh0b0]

Mostly the thing to take into consideration, the rg58u coax shipped with most dongles is inherently crap. Get some adapters like F Female to sma male, they sell mixed assortments , try some rg6 you have laying around( thift store have it cheap, if you have a goodwill outlet, they sell electronics for 20ish cents per pound) than decide if you want to invest in expensive coax for dx'n

 

[smason]

please don't use RG6 for radio signals! because RG6 impedance is 75 ohms (which is designed for CATV and AIR TV).

for radio signals better use RG8 which impedance is 50 ohms.

but if you want something cheap, but better than RG58, and with similar size, then use LMR195 or LMR200.

Strongly disagree! Many people use RG6 for receive with excellent results. Any loss due to the insignificant impedance mismatch will be more than made up for by the much lower losses, and excellent shielding.

 

[MELERIX]

SDR dongles work just fine with 75 ohm coax e.g. RG6

ofc it works, just that is not recommended due it have more attenuation.

 

[MELERIX]

Strongly disagree! Many people use RG6 for receive with excellent results. Any loss due to the insignificant impedance mismatch will be more than made up for by the much lower losses, and excellent shielding.

RG8 have better shielding and proper impedance with less attenuation compared to RG6.

 

[KevinC]

Before we argue the virtues of any coax how about we wait until the OP returns and gives use more info. I highly suspect his/her choice of coax isn't the cause of the "noise".

 

[smason]

Before we argue the virtues of any coax how about we wait until the OP returns and gives use more info. I highly suspect his/her choice of coax isn't the cause of the "noise".

Good point. And the merits of RG-6 despite being 75 ohm have been argued discussed a lot on the site.