Wire Random wire antenna with RTL-SDR (V4)

[mcatis]

First of all: I'm a complete beginner
I want to listen to the shortwave bands with my RTL-SDR dongle (V4). I only want to receive - not transmit. The simplest setup is supposed to be a long wire antenna. I wanted to order a few meters of copper wire for this.

Now I have a few questions:

1. What's the best way to get the wire to my RTL-SRD stick? The output of my dongle is an SMA female. My idea would be to screw an adapter onto it -> SMA Male to BNC female. Then connect an adapter with 2 pole terminals to the BNC female (see setup pic below) to which connect the copper wire. Is that okay, or are there better solutions?
2. I wanted to let the copper wire hang a few meters (3-4 meters?) out of the window, or tie it to a tree 15 meters away. Do I have to pay attention to anything at the end of the wire? Should I connect a ferrite core? Do I need to ground something?
3. What cross-section should I use for the copper wire? Is 0.14mm² fine?

Could this setup work to receive in the HF range?

It would be nice, if you could keep the answers as simple as possible and explain to me the simplest possible setup. Thx!

 

[KQ4ZVY]

That setup would probably work! And if you already have the BNC posts, then use what you have. The antenna you have at hand is always better at putting signal in your ears than the one on the catalog page. But, you might find it simpler to use a unit with the right cable connections to start with instead of a converter. NooElec makes a neat little unit well suited for receive antennas. You could hook your antenna wires up to something like this, then run one cable with SMA connections to your dongle.

As far as wire gauge, installation, and grounding, I will leave that to people with more experience. I'm not knowledgeable enough on the topic to give advice.

 

[merlin]

My setup like that goes up to the roof and across. 88 foot. I just soldered the wire to the center of a PL259 and used an adapter to SMA.
Works very good, even upconverting from 200 KHz. Got a couple beacons way down there but problems.
Not only was the noise from the other side of hell, but the conveter introduced even more birdies.
A good VLF, LF, MF preselector is in order.

 

[ka3jjz]

Well maybe...

On that dual plug you show the black side should be grounded. In fact I would consider putting in a 9:1 balun. If memory serves there is one that is compatible with the RTL-SDR and it's quite inexpensive. Using this it looks like you don't need that dual plug that you show in your diagram

https://tinyurl.com/26mrr56p

I would also caution about putting too much wire on the hot side of that dual plug. These little sticks will overload rather easily, especially if you have AM or FM stations that are close to you

Mike

 

[devicelab]

Your setup will work fine but it'll be noisy as heck. Any un-un would help greatly with a random wire antenna. You can use normal speaker wire if you want. Keep it under 50ft.

With the SDR, don't use the RTL or Tuner for gain control. Just set it to 25-40db gain on the slider. Any more and you'll likely get images unless you live in a rural area.

If you know you want to listen to HF (and you have a decent noise floor) then you may want to consider a receive-only loop antenna.

W6LVP Amplified Receive-Only Magnetic Loop Antenna – With Power Inserter | W6LVP

www.w6lvp.com

If you plan to listen to the entire RF spectrum then a quality discone antenna would work too. My Diamond D3000N works just fine on HF. It's not perfect but it works fairly well down to 2 Mhz. I have other antennas for HF anyway.

DIAMOND D130J

25 - 1300 MHz Super Discone Antenna - No Coax - UHF Connector

www.hamradio.com

Feed it with quality coax like LMR240 or LMR400 coax. I prefer name brand but if you are on a budget then this will work:

https://a.co/d/1Usx6Lj

 

[vagrant]

Here is what I would do:
1. Computer
2. SDR USB dongle
3. RG6 coax, or whatever you may already have. LMR240 or LMR400 is not necessary for RX on HF. Especially since it appears your coax run will not be that long.
4. Flamingo+ AM filter version 2 ( You probably have an AM broadcast tower or two somewhere nearby that needs to be filtered )
5. 9:1 transformer
6. No more than 50 feet (15 meters) of 14 AWG stranded wire. I would not use a lower gauge as it will be thicker and unnecessarily heavier. 14-18 gauge is fine. You could go smaller, but you don't want the wire to break/fail over time due to sun/snow/ice/wind.
7. At the end of the wire you could simply put an insulator ( piece of plastic/PVC ). Then connect a string to the other end of the insulator and a slight weight that hangs over a tree branch. This will keep the wire reasonably taught yet adjust when windy. Some use a pulley with the string, or even a loop of whatever to allow the string and counterbalance to do its job and slide back and forth.
8. You will probably need some adapters as well for the coax ends unless you can find a short run of coax with SMA connectors.
* 9. You may or may not need to use ferrite beads. If your noise floor is low you're probably fine. Otherwise six (6) mix 31 snap on ferrite beads on the coax may help. Place them near the antenna end of the coax.

The above is an inexpensive way to start for HF receiving. If you want to RX above 100 MHz, this same setup will work for strong signals. Still, you may want to consider an improved solution (separate antenna system) like a discone antenna mounted above your roofline, improved coaxial cable, an FM broadcast filter inline on that coax and whatever adapters from the dongle to the coax, filter and antenna.

I actually have a small RX kit that closely mirrors steps 1-8. I use it when camping/traveling. For step #9 I have a 1:1 choke balun I can put inline on the coax if needed.