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Re: Help listening to Shortwave

Posted: Thu Apr 19, 2018 1:10 pm
by HobbyMan
Your LNA could be out of range. check to see if any higher frequency signals are amplified., like FM broadcast.

Re: Help listening to Shortwave

Posted: Thu Apr 19, 2018 6:16 pm
by illllm
maybe voltage. I am only feeding it 6V. Reviews say best perf is at 9v.

All in all , I now have about $175 invested in this :o :shock: :roll:

Should have just bought a nice Sangean or Tecsun radio at that price :D

But the tinker in me would not be happy with that I guess :lol:

Waiting for my connectors and other misc wires to come from Amazon. They lost my package :cry:

Re: Help listening to Shortwave

Posted: Thu Apr 19, 2018 6:19 pm
by HobbyMan
You should probably supply it 9v then. But do you know what the freq range of the amplifier is?

Re: Help listening to Shortwave

Posted: Fri Apr 20, 2018 1:29 am
by illllm
Operating frequency: 0.1-2000MHz
Amplifier gain: as shown below
F = 0.1 MHz, gain = 32 dB
F = 500Mhz gain = 31dB
F = 1000MHz gain = 29dB
F = 1500Mhz gain = 25dB
F = 2000 MHz gain = 20 dB
Maximum output power: + 10dBm (10mW) @ 1dB compression point
Noise figure: 1.9dB (refer to the main view picture)
Supply voltage: 6 - 12VDC

Re: Help listening to Shortwave

Posted: Fri Apr 20, 2018 4:57 am
by rtlsdrblog
illllm wrote:
Thu Apr 19, 2018 1:48 am
I figured it out finally. I am getting a few AM and SW stations but noise is a problem through the entire spectrum. Tried with LNA, with ferrite UNUN, monopole , wire antenna.....test showed no change between just a direct wire and all the other gadgets.

I wonder if the LNA is working ?

Should I enable bias T when using the LNA ? The LNA has a 6volt Power supply of its own.
No need to enable the biasT if it's already got it's own power.

You might be giving the dongle it too much gain though with the LNA. If you have an attenuator or HF filters, try adding those into the chain.

Re: Help listening to Shortwave

Posted: Fri Apr 20, 2018 7:26 pm
by illllm
So Amazon lost my package. Then I had to reorder all my stuff again and they sent it same day delivery for free.

I did some tests with the LNA with 9 Volts and this time I see a definite increase in signal strength. Noise also goes up a but, but a marked increase in signal strength.

My purpose was shortwave radio, but I guess in the daytime, I will not be able to receive much of the good stuff on SW :|

Also, a long with antenna was not much of a help. I coiled about 20 meters on a 1 yard stick and placed it perpendicular on a grounded aluminium foil and i did pick up many more SW stations.

I will test it some more....

Re: Help listening to Shortwave

Posted: Fri May 25, 2018 1:37 am
by radiowaz
As a final ,, try HDSDR, I could never get SDR# to work,, and trust me I tried everything.. Also use GQRX on Linus on a Raspberry Pi (works great and lots of fun) Increasing your voltage is not the problem.. mine, V-3 , at 6 volts works just great.
I can hear everything form 500Hrz to 1.7 Ghz with several dipoles.. try the HDSDR its free and see if its the program or the dongle.

Re: Help listening to Shortwave

Posted: Fri Jul 06, 2018 6:29 pm
by W1ABA
I hope this thread is still active.

I am new to RTL-SDR, but know my way around communications technology. I expected to hear some signals with an indoor quarter wave vertical (on VHF). What I found is that the computer makes so much wideband noise that any antenna located within a few feet of the computer makes the RTL-SDR deaf as a post-this is not an exaggeration.

I hope you aren't using a random wire inside your house for reception on the AM broadcast band. For AM broadcast band, the LNA/rf preamp is not needed. There is so much nature made noise on the AM broadcast band that an attenuator would probably help. To the best of my knowledge, all RTL-SDR's have a severe mismatch with regard to the input impedance. Classic/typical input (and output) rf impedances are in the 12 ohm to 300 ohm range, most use 50 or 75 ohm systems. However, the RTL-SDR has a 3000 ohm input impedance. The 9 to 1 balun you wound doesn't even start to address this mismatch. The loss in ability to hear weaker signals due to this problem is devastating!

Get your antenna away from the computer, and you should see a massive improvement in your ability to hear AM broadcast band signals.

Keep in mind that modern switching supplies generate massive amounts of interference on the AM broadcast band. Depending on your location, the best AM band receiver only hears buzzing.

For AM band antennas, I suggest a tuned loop, fed to the RTL-SDR with open wire line (balanced) with the use of the 9 to 1 balun you already built. Having the feedline balanced is important, it strongly rejects noise generated close to the computer....coax is expensive and conducts noise into the receiver because of rf that travels on the braid. Some have used ferrites to decouple the noise that would be sent to the receiver on the braid of coax.

Hope this helps.