Hi,
Due to strong local interference I probably need to update my broadband LNA (Mini-BB from SHF Elektronik) with filtered LNAs, one for VHF and one for UHF. RX only.
Where can I find good filtered LNAs? Not the most expensive but not the cheapest either…
/Lars SM0TGU
Take a look …
https://store.uputronics.com/index.php?route=product/category&path=59
73’s de EA5WA Juan Carlos
Thank you Juan Carlos.
Anyone else has some more recommendations?
/Lars
I use the MiniKits masthead preamps on my station:
2m: https://www.minikits.com.au/electronic-kits/rf-amplifiers/rf-preamplifiers/eme220-2m
70cm: https://www.minikits.com.au/electronic-kits/rf-amplifiers/rf-preamplifiers/eme221-70cm
These have bypass relays, which is important as I use the station for transmit too.
Try cavity filter between antenna and LNA.
Putting a cavity filter up on a mast isn’t going to be a viable solution for most people…
Also unless you go build one yourself, they are pretty expensive.
The filtered preamp solutions listed above are a somewhat more practical approach than strapping a large metal can to your mast.
Thank you for answers. I have done some googling and also found this brand:
https://www.antennas-amplifiers.com/low-noise-amplifier
They are a little bit more expensive but have N connectors and several different versions.
Hi Lars,
just my humble opinion…
before investing a lot of money into another LNA, please also consider replacing your RTL-SDR with a more sophisticated SDR…
I also started with an RTL-SDR and was totally disappointed because of huge interference from in- and (nearby) outband signals…
I than replaced the RTL-SDR by an Airspy R2 SDR and had much less interference and even better performance.
Than again I compared the AirSpy R2 with the Airspy HF+ Discovery SDR and was more than surprised to even see more improvements and almost interference free reception on VHF…
Indeed, if you want to skip 137 MHz and APT satellites, a special filter narrow-band filter for 145 MHz may work well for you too.
But make sure you look carefully at the data sheet, this for example is a very good one and you can get it for 60€ without housing… it’s used by EME operators and was published in DUBUS magazine…
http://ha8et.hu/VLNA-144/index.htm
best regards
Peter
Sorry, but I don’t necessarily agree with this advice.
The Airspy R2 has the exact same frontend as the RTLSDR v3 - the Rafael Micro R820T. This chip sets the noise figure of the unit, and as such, the sensitivity of the RTLSDR v3 and the Airspy R2 are pretty much the same, with about 6dB best-case Noise Figure. Both units will require a LNA for further improvement.
Yes, the Airspy has more ADC bits, which will mean somewhat better dynamic range, but the RTLSDRs can perform just as well with appropriate filtering.
Peter, thank you for your advice. I have actually been using the old version of HA8ET LNAs in my large Yagi setup before switching to relay LNAs from SHF Elektronik (as I’m using my large setup for TX). But the new HA8ET version should be suitable for my RX only SatNOGS.
I have done some tests with Airspy Mini and I can visually see some better results then with RTL-SDR v3, but it’s difficult for me to say which one is the best. You can also do a lot of tweaking with the gain settings to make it better. I have not had enough time to play with the gain settings so I can be better.
On the other hand, the price different between Airspy Mini and RTL-SDR v3 is not so much today.
Well, I can only say that I’ve spent days/weeks to find the optimum settings of all three (four) SDRs and with biggest distance the best so far (for me!) is the Airspy HF+ Discovery (VHF only). I did used various tools to see the spectrum and effects of gain setting in realtime and also tested various settings with SatNOGS and CubicSDR etc or with SDR-Console, GQRX etc… not only in the Waterfall visible, but also in the number of decoded packets etc…
I will soon try RSP1A.
We also use the Airspy HF+ Discovery for our APT station and VHF-Omni in Bochum and the Airspy R2 for UHF: https://network.satnogs.org/users/dk0sb/
Indeed I use good LNA’s on all antennas, thus the noise figure is given by the LNA and the noise figure of what’s-ever SDR is insignificant…
73 Peter
I have done a series of tests during a week and this is my results:
)Thank you all for your comments in this thread, it has been a huge help for me.
//Lars SM0TGU
Hi Lars
I agree with Peter. The first step should be the SDR. In addition you can use a “FM filter” (filter for 80-109 MHz), or LTE filter - if a strong transmitter is nearby
Talking about LNA or pre-Amp´s. I have very good results with products from this little company:
https://www.tgn-technology-online.com/en/EME-TROPO---Satellite-33/
https://www.tgn-technology-online.com/en/HAM-RADIO-Preamplifier/
Best regards
Alex DL4EEC
Thank you Alex for info about TGN Technology. Are these LNAs filtered? Price a little bit high compared to others…
BR /Lars
Hi
Yes they are. Well I compare them with the other well known company from Germany 
I´ll try a 0.3dB noise factor version the next days. Actually it´s raining all the time…
This looks promising? https://www.antennas.us/lnau-0436-648-uhf-amateur-radio-satellite-amplifier-lna-and-filter.html
This looks promising?
not at all… compare technical specification like IP3, gain and noise figure with these:
http://ha8et.hu/VLNA-432/vlna-432.htm
just a few examples…
I ordered few from there:
https://vhfdesign.com/clients/kits
LNA-70cm-EME-SAV541-SAW-N-female, aluminium case, based on SAV-541+, SAW filter. Gain > 18 dB, NF < 0.3 dB at 432 MHz, OIP3 = 33 dBm, BW (-3dB) < 20 MHz
LNA-70cm-ATF531-SAW-N-female, aluminium case, based on ATF-53189. Gain > 22 dB, NF < 0.4 dB at 432 MHz, BW (-3dB) < 20 MHz, OIP3 = 37 dBm, P input = 24 dBm (max)
Specs are good for the money, schematics and PCB documented with measurement results, well made and at least the noise figure is according to the specs.
On saturday I have got the TWIN-Notch Filter (88-108 MHz & 170-230 MHz) from TGN-technology.
Today I have seen for the first time a twin-band preamp (TWIN270 from TGN…). I think I should order one