LNA4ALL pre-amp

I recently got an LNA4ALL pre-amp which I have used to replace the satellite amp I was previously using. The satellite amp claims 13dB-20dB gain between 950MHz and 2GHz. The gain for 1090MHz is probably closer to the lower figure. The LNA4ALL has a gain of 18dB for ADS-B.

The satellite amp has a noise figure of around 4-5 dB, whereas the LNA4ALL is below 1dB.

I have the amp connected directly under the antenna with a few metres of coax running to the Flightaware filter and the dongle. After a day, it’s clear that the LNA4ALL has much better performance. The raw message rate is a bit higher, but as I was already getting levels that appear to be at the limit the dongle is capable of (1500-1600 messages/sec) I wasn’t expecting to see much difference there. What has improved is the number of aircraft tracked, and the range. The antenna is mounted in the loft at the moment.

Today I saw a peak of 250 aircraft tracked, and the total number of aircraft tracked has been consistently above 200. With the satellite amp, I saw peaks of about 220 aircraft with 160-180 being more typical throughout the day. The number of MLAT positions has also increased significantly.

Satellite amp:


LNA4ALL


Aircaft:


Range

You are correct on the satellite amp spec. The 13-20 db gain spec for 950-2000 means that it is 13 at 950 and 20 at 2000. A good sat amp will be " slope compensated" for the increased losses at higher frequencies. The end result they want is a constant gain of about 13 at the receiver over the complete range (950-2000 in your case).

I’d guess the low noise on the new one is what makes it superior.

Let us conduct a cost comparison… cost of LNA4ALL + all of it’s accesories vs cost of Satellite Amp + all of its accessories???

All accessories = power supply + power inserter (bias tee) + casing if any + connectors & pigtails etc etc.

I also think that the low noise figure is what is providing most of the improvement. It’s mostly signals at range that I’m seeing more of, but closer tracks are more reliable with less gaps.

As far as cost goes, the satellite amp was about £5 from memory. The LNA4ALL is 18 Euros or 23 if you want it ready to use with a bias-t, but you could modify it yourself by adding the appropriate inductor on the board.

The adaptors for the LNA4ALL were one from N connector to SMA, and then SMA to F connector. At the other end they are the same for both as I’m using the same bias-t with a different power supply. I haven’t changed the coax over as the loss from using 75Ohm is pretty small for an amplified system.

The power supplies were ones I had previously - a 13.8V I used to use for powering radio gear for the satellite amp, and a small 500mA selectable voltage regulated transformer for the LNA4ALL, so there was no additional cost there. You could use a dongle like the RTL-SDR blog one with built in bias-t to feed the amp and remove the power supply and external bias-t altogether. That would reduce the number of connectors so reduce losses and costs if you were starting from scratch. I have one on order because I wanted another dongle for something else, so I’ll probably use that one for ads-b and the current one for other stuff.

The satellite amp does provide pretty decent value, but I don’t think the LNA4ALL is prohibitively expensive considering the improvement in performance.

Similar findings for my LAN4ALL, it’s a pretty decent pre-amp that can be positioned near to the antenna, which is ideally where any pre-amp should be and then feed the receiver/dongle which can be some distance away (if needed). Adjust the dongle gain settings to get the optimal signal levels.
The cost is negligible really, especially when compared to what I have invested in some of my other radio gear, it’s not even the cost of a decent N type connector.

You pays your money and takes your choice

lna4all.blogspot.co.uk/

Nigel.