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Hackrf one - increase RX-TX

Posted: Thu Jan 31, 2019 7:19 pm
by Eagle72
Anyone know if it possible to increase the Rx & Tx signals for hackrf one, its really weak , especially rx is like 3 times weaker than my rtl-sdr, i dont understand how its possible a dongle for 20 usb have much more powerfull rx than 250usd device!

Is there any part i can replace to make it stronger? or to buy amp , if so what is recomended one?

I have also acess to lots of old satelite tv ampliers but mosly are 12 volt ... please anyone who know let me know.

Re: Hackrf one - increase RX-TX

Posted: Wed Feb 06, 2019 2:48 am
by aurgathor
Unless you really know what you are doing, you probably don't want to mod your board. But to get an "increased RX", there a number of different LNAs available from various sources. However, normally you would also want a band pass filter or two to go with it. Also, remember that antennas can make a very big difference.

You need to understand the trade offs between the various SDRs -- all have different cons and pros, and you want to pick the "right ones" for your needs. If you want relatively sensitive receive only SDR and you don't need the higher frequencies, the Airspy HF+ is a very good one.

Re: Hackrf one - increase RX-TX

Posted: Wed Feb 06, 2019 9:16 pm
by Eagle72
Thanks for answer so it is possible , and i can tell you i dont know what im doing when it comes to modify hardware thats why i asked if anyone did something, otherwise i know how a bit basics of electronics...

When you say LNA ampfilers can u tell any site who sell them? and regarding to bandpass filer i only got 88-120mhz fm bandpass block filter, is this what u speak about? if i want to do 433 ism band and increase rx/tx do i need a specific bandpass filter for ism band ? will it not block the incomming signals?

Re: Hackrf one - increase RX-TX

Posted: Thu Feb 07, 2019 6:18 am
by Airwind
You need a specific band-pass filter for every frequency range you're interested in. For 433MHz you need a 433 MHz band-pass filter. This will filter out strong signals that may even be outside your receiving range, but can still damage your RF hardware. And when receiving be sure to wire the filter in between the antenna and LNA, not between the LNA and HackRF.

Re: Hackrf one - increase RX-TX

Posted: Thu Feb 14, 2019 7:40 pm
by aurgathor
If something is available anywhere, the first 2 places to go to look for them are eBay and Amazon. :!:

Using the search terms of "LNA 433 MHz" I got 16 hits on eBay for 2 - 3 different types of LNAs.
Looks to me one type ($40+) comes with a SAW filter, the others (under $20) probably don't.

Note well, the LNA is for receive (RX) only!!

Also, I got 378 results for "antenna 433mhz" and over 40 for "filter 433mhz".

Re: Hackrf one - increase RX-TX

Posted: Tue Feb 19, 2019 1:40 pm
by Airwind
aurgathor wrote:
Thu Feb 14, 2019 7:40 pm
Note well, the LNA is for receive (RX) only!!
Oh? Citations? I believe a LNA can also be used for TX (provided that you will only transmit through this channel) by swapping the input/output ports so that the output now faces the antenna and the input is oriented towards the SDR TX port. Be careful though as there are legal limitations on which frequencies and power levels you are allowed to transmit.

~aw

Re: Hackrf one - increase RX-TX

Posted: Wed Feb 20, 2019 8:07 pm
by aurgathor
LOL. ;)

You can most certainly argue that an amplifier is an amplifier and you can use an LNA in both places, but what you normally want to use for TX is an RF power amplifier. https://en.wikipedia.org/wiki/RF_power_amplifier

While *in theory* one can certainly make an amplifier that could work in both places; for real life use, they aren't interchangeable as far as I know.

Can you show an RF amplifier [complete module with in and out connectors] that would work for either RX or TX without modification?

Re: Hackrf one - increase RX-TX

Posted: Wed Feb 27, 2019 6:55 am
by Airwind
aurgathor wrote:
Wed Feb 20, 2019 8:07 pm
Can you show an RF amplifier [complete module with in and out connectors] that would work for either RX or TX without modification?
Not for both ways (who uses that anyway?) or without modification, but scroll down to the HackRF TX mod here: http://lna4all.blogspot.com/
That's a LNA mod for TX only, the default schematics works for RX.