NooElec RTL-SDR Antenna

[951ryan]

Diving into the world of SDR. I bought the NooElec Brand RTL-SDR from Amazon, received it the next day and am trying to learn all the ins and outs. Amazon.com: NooElec Brand RTL-SDR, FM+DAB, DVB-T USB Stick Set with RTL2832U & R820T. Great SDR for SDR#, HDSDR, and Other Popular SDR Software Packages!: Electronics

I am trying to pickup a single frequency in the 460Mhz band and it's pretty much inaudible. I understand the antenna is everything and the one that is provided with it is really crappy but the part that baffles me is I have a $60 RadioShack scanner (with stock antenna) sitting in the same area picking up the frequency just fine... this leads me to believe that maybe it's not the antenna and maybe my settings? Screenshot: http://i.imgur.com/2JsVmnd.png

I know I need to upgrade the antenna, but Im stumped on how a $40 RadioShack scanner is able to pick it up just fine. Any thoughts? Maybe my settings are all wrong.


Also, recommendations for an indoor antenna, I can't mount outside, in the attic or on the walls so has to sit in a window seal or somewhere else.

 

[xrorx]

For my HF receiver I have a wire that goes from the floor to the ceiling, along the ceiling and back down to the floor on the other side of the room and this gives me ok results on HF. So now when I got my RTL-
SDR dongle I removed the antenna from the antenna cable and attached a small alligator clip which I then clipped on to my room long wire I described. Again, this works ok for the dongle as well.

 

[jonwienke]

Screenshot is showing a nice RF spike near 460.8125, indicating a transmission on that frequency. However, you are tuned to 460.175, where the display shows no activity, and therefore aren't going to hear anything. Have you checked your frequency drift to see if your dongle tuning frequency is accurate? Some of them need a calibration adjustment so that the display frequency matched the actual tuning frequency.

 

[Spleen]

What is your gain (RF) set to? And yes, the only real use that little antenna that comes with it has is for you to be able to cut the wire close to the antenna and make yourself a pigtail for adaptation to another connector, maybe so you can hook a mag-mount scanner antenna or similar up to it.

 

[BM82557]

Spleen raises a good point, a lot of people forget to adjust the RF gain when they install SDRSharp. Click the third button from the left at the top to configure your settings.

 

[951ryan]

I made a few adjustments from what I could see within your posted screenshot. Still wondering if my settings are off. This cheap RadioShack scanner is picking up the frequency pretty descent. 460.175 is the frequency I'm trying to pickup.

 

[DK327]

951ryan: I agree with jonwienke, I think you might need to increase your ppm to compensate for the "drift" so it lines up properly. It will still drift slightly but after about 15-20 mins should stabilize as the dongle warms up. One way to figure this out would be to tune to a known NOAA frequency and adjust the drift until it's dead on, then tune back to your 460.175 and should be right on the spike.

I see a couple of spikes on that screen shot so adjust the ppm's while looking at those until they line up with the red bar in the middle, one of them (the one closer to the red bar most likely) should be your signal.

Once you're on that signal, might want to also decrease your bandwidth to something like 8000 or as wide as the signal is.

 

[majoco]

What DK327 said. Bring your bandwidth down to 5000Hz - IMHO your signal may be masked by all the noise coming through the wide filter.

 

[ab5r]

I also notice that you have VOLUME Slider MAXED out. Mu slider acts flakey some times and I have to adjust it too for sound volume. I acts like old volume pots that have gaps sometimes. Try that.

 

[rbm]

Your bandwidth is pretty wide so any recovered audio will be low.

Rich

Here's another set of sample settings:

 

[Flatliner]

2.4 mbps sample rate is really on the edge for the RTL. Backing off a little may help also.

 

[951ryan]

Thanks everyone for your help! Im now picking them up, getting close to the same quality as the scanner.

 

[951ryan]

I'm looking into buying this antenna to mount on my roof...
Amazon.com: SCANNER ANT-BASE 30-1300MHZ 50'RG6 15ELM: Electronics

It comes with 50' of coax and F-Female adapter. I want to extend it to 100'. So I need another 50' of low loss coax, the problem is I'm confused by what adapters I need to make it all come together.

Antenna w/F-Female -> ?? 50' Low Loss Coax ?? -> F Female to MCX Male Right Angle

The part I'm stumped on is for the Coax extension to be added what type of connectors do I need on each side?

 

[popnokick]

Both adapters are available from Amazon in multiple version choices. You'll need an F female to MCX adapter for the connection to the SDR stick to the coax, and an F female-to-female to couple the additional 50' of coax to the 50' that comes with the antenna. Be sure to use a good quality, low loss RG-6 or other 75 ohm cable. The Antennacraft ST-2 is a widely used and respected antenna... good choice. But also try a 75 ohm preamp inline with the cable. If it doesn't work or increases the noise/interference, you can remove it. 100' is a long run of coax for the ST-2 and the inline amp (also multiple types available on Amazon) may help overcome the loss of the additional cable.

 

[951ryan]

Thanks popnokick....

So will these 3 combo items work together then...

Amazon.com: Premiertek 8-Meter Low Loss RP-SMA Male to RP-SMA Female RG58/U Coaxial Cable (PT-SMA-EXT-8): Computers & Accessories
Amazon.com: 2pcs SMA Female to MCX Male Right Angle Pigital Cable 30cm: Computers & Accessories
Amazon.com: SCANNER ANT-BASE 30-1300MHZ 50'RG6 15ELM: Electronics

 

[popnokick]

Welll.... that's not 75 ohm cable. The ST-2 antenna comes with 75 ohm cable and rather than mismatch 75 and 50 ohm cable... since you're buying new anyway... you should probably stay with 75 ohm cable throughout. It may not be significant from a loss perspective, but why risk it? Order RG-6 quad shield cable (same stuff you can buy locally at any place that sells TV accessories, hardware, etc.). It will come with F-connectors on both ends (or put on your own). Then the adapters I noted in my other message in this thread will work to provide the 50' extension and connection to the SDR dongle. And you won't need the SMA adapters.
Regarding the amp - because I have two scanners running on one antenna (an Off-Center Fed Dipole) I use this 2-port amp. It works fine... yes there is some loss but I cannot hear it or detect it on my signal strength meters... whether via my SDR stick or the scanners:
http://www.amazon.com/Bi-Directiona...&qid=1411670726&sr=1-3&keywords=pct+amplifier

 

[rbm]

Thanks popnokick....

So will these 3 combo items work together then...

Amazon.com: Premiertek 8-Meter Low Loss RP-SMA Male to RP-SMA Female RG58/U Coaxial Cable (PT-SMA-EXT-8): Computers & Accessories
Amazon.com: 2pcs SMA Female to MCX Male Right Angle Pigital Cable 30cm: Computers & Accessories
Amazon.com: SCANNER ANT-BASE 30-1300MHZ 50'RG6 15ELM: Electronics

That first item, the coax is not needed and that particular cable/connector combination will NOT work.

The connectors on that cable, are 'Reverse Polarity' (RP)

Therefore, there would be no connection to the center conductor for your setup.

The RG6 cable that comes with that antenna will work just fine. (With the proper adapters)

Rich

Other options for your USB dongle to coax may save you hunting down adapters.

 

[951ryan]

Thank you guys! Seriously you guys are a ton of help!

So I got the ANT-BASE going to a Female to Female F-Type Adapter then to 50ft RG6 75ohm, Quad Shield, CL2 Coaxial Cable with F Type Connector then to a MCX Male to F Female Video Adapter.

Sound better?

 

[rbm]

And two examples of what the dongle can do with the ST2 antenna. Like that in your last link.

I have five of them and just one of them feeds 32 radios. Including the dongle used to create the following videos.

Rich

Milsat Satcom Satellite SDRSharp with Eztv668 SDR dongle e4000 chip - YouTube

and

Dripping water on SatCom, using USB DVB-T Dongle and SDR#, ST2 antenna with LNA-1000 preamp - YouTube

And, if you want to spend less than $30 to build prcguy's X-Wing antenna for MilSats, you can do this:

http://www.youtube.com/watch?v=GzQWGPzs1r8

 

[Spleen]

I just re-read that. 100' cable run? You're going to need somewhat better cable unless you're not planning on listening to anything far away or much above 500MHz. You said you couldn't mount outside, where is the other end of the 100' run going to end up? And what/whose systems do you plan on monitoring?