LNA for ~422 MHz?

[Coto]

Hi all,

I'm looking for an LNA at around 422 MHz. I'm basically trying to detect Pulsars using a very low-cost setup, like this guy managed to do: http://neutronstar.joataman.net/sites/iw5bhy_barga_3/index.html

I'm looking to follow identical steps, but his LNA is no longer available.

Anyone knows where I can get an LNA with similar characteristics (NF & Gain) to the author's LNA of choice?

 

Thanks,

- Coto

P.S.: RTL-SDR V3 should arrive tomorrow. Hopefully connecting the Ku-Band LNB directly to the SDR should allow me to do some solar drift scans...

[Dave S]

Hi Coto

Does it need to be centred at 422Mhz?  I use Wideband LNA's which run from about 1MHz - 2GHz  They are very cheap ( I just ordered another from Amazon this evening).

I depends on whether your receiver is nice and selective or suffers from strong local interference from other frequencies.  I assume that you have a dish setup for narrow area reception and as you are pointing skyward then a wideband should be ok so long as your connecters and feerder cable are good.

I've been experimenting with software defined radio and home brew antennas to receive and decode images from the NOAA satellites.

This is the one I've just ordered.

https://www.amazon.co.uk/0-1-2000MHz-Broadband-Amplifier-Radio-Module/dp/B076631WKC/ref=sr_1_6?ie=UTF8&qid=1548625234&sr=8-6&keywords=lna

Dave...

 

[Coto]

@Dave S Hi Dave, most LNAs from ebay and similar suppliers have unreliably bad characteristics (i.e. they say the NF very low or the gain is very high which is either not true because they're lying or their testing equipment is poor). The problem with most wide-band LNAs (as far as I understand the circuit of amplifiers) is that the wider the operating frequency, the lower the gain.

Other than that issue, I could just use a  bandpass filter, so I don't mind having a wide-band LNA as long as it covers my desired band and has a low noise-figure (NF) and reasonable Gain.

 

Coto

[Dave S]

@Coto  I agree totally that a lot of cheap electronics can be less than perfect (usually a lot less)  I try to source from reliable manufacturers.  My preferred one is NooElec as I've used them on quite a few occations and find their products good quality and they have a support centre in the UK.  The LNA I chose fits the bill for my needs as I'm not looking for huge signal gain and it doesn't have to perform perfectly to justify the £12 spent.  There are Radio Amateur equipment suppliers that will stock quality LNA's in narrower bandwidths but we're now talking expense.  The bandpass filter is wise addition as my experience with the RTL-SDR dongles is that certain powerful local signals can clamp down the front end of the receiver causing a sudden drop in the signals you are monitoring.  I've been recently working 137MHz but a local pager transmitter running in the 140MHz area periodically kills the signal strength of the frequencies I'm using.  It's not a big problem as I think the Interference needs to be within a few MHz.  The RTL-SDR dongles have a bandspread of 2-3MHZ so they can continuously display that range.  That's probably too narrow for other type of interferece to be a problem.

I'm not suggesting that they will work for your needs but lo cost solutions will always have limitations in it's results but at the low cost it's well worth a try.  If you're working 432MHZ at high gain and sensitivity be aware that there's a whole host of devices operating at around 433MHz.  These include car key fobs, baby monitors, home weather stations and cursedly no licence required walky talkies.  433 is the low power unlicensed device mini band.

Please post your progress as I would love to see how it goes.

Cheers

Dave...

[Carl Reade]

G8FEK.com sells exactly what your looking for and roughly same price as the discontinued one in your link.

[Coto]

3 hours ago, Carl Reade said:

G8FEK.com sells exactly what your looking for and roughly same price as the discontinued one in your link.

The SBA430 LNA seems to be exactly what I want, and I found it at a cheaper price (80 GBP) sold by someone who no longer needs it. Hopefully he's still selling it!