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Suitable Low Noise Amplifier

Posted: Mon May 09, 2016 8:05 pm
by harayz
Can someone tell me if this RF LNA can improve the signal performance but if not, how can i make it useful? I bought it by mistake a while back for my WiFi dongle which doesnt do anything to it. However, it would be awesome if it could work with RTL-SDR and i just need to purchase the MCX-SMA adapter to hook it up to my antenna. Please advice, thank you~

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http://www.aliexpress.com/item/NEW-RF-r ... 4.2.hdpd0Z

Product Info:
Broadband radio frequency small signal receiving amplifier, suitable for all kinds of wireless applications, part of the short-wave frequency, VHF, UHF, radios, and small signal receiving antenna, such as digital radio, minimum signal input to 60 DBM, maximum output signal + 19 DBM, 3 v power supply, broadband work 20 MHZ to 2400 MHZ can be used!


Product performance:

(1) working frequency: 20 MHZ, 2400 MHZ
(2) the minimum input power: - 90 DBM, nava is 1
(3) the maximum output power: 19 DBM, which is about 80 mw
(4) the frequency of different gain size will have different (the following is only, for example, does not represent the real gain size)

For example:
20 MHZ gain size 12 DBM
100 MHZ gain size 18 DBM
500 MHZ gain size 20 DBM
1000 MHZ gain size 21 DBM
1500 MHZ gain size 18 DBM

(4) : working voltage 3 v
(5) working current: 0.02 A

Re: Suitable Low Noise Amplifier

Posted: Tue May 10, 2016 2:11 am
by rtlsdrblog
Yes you can use that LNA. Though not much useful information is given about that one, in particular no noise figure measurement. But it should be good enough for most purposes anyway.

Place it are close to the antenna as possible. It won't help that much if it's placed right next to the dongle when compared to placing it next to the antenna. http://www.rtl-sdr.com/tutorial-on-prop ... io-system/

Also don't forget to power it.

Re: Suitable Low Noise Amplifier

Posted: Wed May 11, 2016 12:35 pm
by harayz
AWESOME! Thank you for responding. In addition to the LNA, i just bought Nooelec 1:9 balun and another DVB-T dongle. Would it be better to use it separately or together as pictured down here?

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Re: Suitable Low Noise Amplifier

Posted: Sun May 15, 2016 6:01 am
by rtlsdrblog
Wait, I think you are making a mistake here.

Do you have an upconverter? The balun 1:9 is designed for connecting a "long wire" or "random wire" antenna (basically just a stretch of wire as long as you can get it), and this type of antenna is normally used for HF signals (0 - 30 MHz). These frequencies aren't covered by a normal RTL-SDR, and so you will need an upconverter. Nooelec sell their ham-it-up upconverter, and I also highly recommend the SpyVerter upconverter from the Airspy folks.

Also, the amp you are using is rated from 20Mhz and above, so I don't think it would work very well, if at all on HF frequencies. Anyway, an amp isn't critically needed for HF frequencies, though it can sometimes help a little. For HF, you might want to consider something like the 'LNA4HF' by 9A4QV - Google for it.

If you are just wanting to use the RTL-SDR on VHF-UHF, then you won't need the balun 1:9, and using the balun 1:9 would degrade your signal since it becomes quite lossy above 100 MHz.

Re: Suitable Low Noise Amplifier

Posted: Wed May 18, 2016 4:53 pm
by harayz
Unfortunately no i do not own an upconverter but i plan to get one as soon as i have enough fubds. My main goal is to listen to 30MHz VHF-Low frequency in my area. Do you think that this configuration will be able to achieve this and how would you do it in absence of upconverter? Also, i have a few attenuators given to me and a bunch of ferrite beads + rings salvaged from old PCBs that can be used for this purpose.

Suitable Low Noise Amplifier

Posted: Fri May 20, 2016 4:35 am
by Adriannito
Hello everyone

Im using a class D amp from Sparkfun through which I want to play some audio files. I have a RC filter with 10kohms r and 30 nF cap. From the output of the amplifier I hear a very noisy sound. I hear the audio but with it is a lot of high frequency sound. How do I reduce the noise?

When I attach the speaker directly to pin 9 there is no noise but its just not loud enough..any suggestions please Really need help here

Re: Suitable Low Noise Amplifier

Posted: Fri May 20, 2016 6:17 am
by rtlsdrblog
harayz wrote:Unfortunately no i do not own an upconverter but i plan to get one as soon as i have enough fubds. My main goal is to listen to 30MHz VHF-Low frequency in my area. Do you think that this configuration will be able to achieve this and how would you do it in absence of upconverter? Also, i have a few attenuators given to me and a bunch of ferrite beads + rings salvaged from old PCBs that can be used for this purpose.
A standard R820T2 can usually go down to 24 - 25 MHz, so it should be okay, though to be fair, reception performance that low usually isn't great. Probably still no need for the balun at those frequencies though.

Re: Suitable Low Noise Amplifier

Posted: Fri May 27, 2016 12:03 pm
by harayz
understood. thank you for that. one last question - when using the 1:9 balun, what would be the range of frequencies good to listen to? Would it allow me to listen to 1090Mhz for ADS-B better - compare to not using the balun? I'm just curious to know how and what is the best spectrum can i see/listen to with the existing parts.

Re: Suitable Low Noise Amplifier

Posted: Fri May 27, 2016 1:00 pm
by rtlsdrblog
The balun is for use with a "long wire"/"random wire" antenna, and mainly for HF 0 - 20 MHz where a long wire antenna is most useful. It might also help between 20 - 30 MHz, and since you already have it you can experiment.

It will only make things much worse for ADS-B. Above 30 MHz don't use the balun.

Re: Suitable Low Noise Amplifier

Posted: Mon May 30, 2016 6:27 pm
by harayz
does that include nfc reader as well? i know this might be a tad far fetched but if i have an NFC (13.56MHz) reader/writer with SMA connector (no, i have not seen one anywhere) will the balun be able to make it perform better? i wonder if the balun can increase the range/distance of operations.