RFBay LNA stopped working?

[Napalm]

Alright. I remember someone on here said the RFbay amps are susceptible to voltage spikes and they replaced the amplifier chip a few times.

I have an RF bay LNA-300 that has served me well for years (since 2008) but I just plugged it in after my house move and nada.

It has voltage in and out of the voltage regulator, and all the way to the amplifier stages but that's as far as my technical knowledge goes without a circuit diagram.

Prcguy - I know it wasn't you but it was someone else who hangs around this sub-forum but do you have any insight?

 

[Ubbe]

I have two RF-Bay LNA, I think they are LNA-450, that have failed and I replaced the amplifier in one of them but it failed again and I switched to PGA103+ based LNA's that have much better specifications and over the years I only had to replace the amplifier in one, out of four. That LNA where on my table connected to a splitter when it got hot and stopped working, so could had been a bad component from the start.

/Ubbe

 

[Napalm]

I have two RF-Bay LNA, I think they are LNA-450, that have failed and I replaced the amplifier in one of them but it failed again and I switched to PGA103+ based LNA's that have much better specifications and over the years I only had to replace the amplifier in one, out of four. That LNA where on my table connected to a splitter when it got hot and stopped working, so could had been a bad component from the start.

/Ubbe

I'm definitely not confident in replacing an SMD amplifier so I guess this is going to get put in the junk drawer 🤣

Just for the heck of it a threw a Nooelec LANA in it's place. That thing is hot garbage even with input filters there's so much compression taking place.

What amps do you currently use? I like RFBay for the price to performance specs - I'd happily buy another LNA-300 from them but if there's something better I'm all ears.

 

[Ubbe]

Any PGA103+ amplifier will have this spec:



The LNA-300 looks like this:



The Nooelec LNA doesn't have any IP3 spec but compression P1 are +18dBm and the SPF5189Z its using, that I believe are what also Stridsberg uses, has a IP3 of 38dBm.

All values of P1 and IP3 are stated at the output so to get a real comparison you have to subtract the gain from those figures to see what their input levels are. But for these three LNA's they all have a more or less 25dB gain at 200MHz.

Data seems to be pretty much the same for all LNA's but real life use might be different, when a huge amount of signals are present at their input and not only a single test signal. It's the sum of all RF signals that matters, including broadcast and cellular transmitters and what else that goes thru any filters in use.

/Ubbe

 

[nickwilson159]

What amps do you currently use? I like RFBay for the price to performance specs - I'd happily buy another LNA-300 from them but if there's something better I'm all ears.

This is the question I have as well. I am using an Advanced Receiver Research GaAsFET preamp on an audio feed and it works well, but they're not cheap. And it seems like whenever they're mentioned in these forums, folks suggest other alternatives that are both better and cheaper.

This Mini-Circuits preamp is mentioned now and then, could very well have that same PGA103+ at its core based on the part number:

Connectorized SMA, Low Noise, Medium Power, Linear Amplifier, 50 MHz to 3000 MHz, 50Ω | ZX60-P103LN+ | Mini-Circuits

The high end stuff from companies like Telewave are prohibitively expensive (>$1,000).

Stridberg's look to be in the same price range as ARR, but with a worse noise figure.

I noticed that Sinclair uses RichardsonRFPD preamps in their multicouplers, but again, with a slightly higher noise figure:

https://shop.richardsonrfpd.com/Products/Product/RLAC0102A

 

[Napalm]

I use RFBays LNA-800(?) via a bunch of cheap resistive dividers to feed my Kraken SDR for my calls feeds. It has about 20dB gain and a decent noise figure.

I have that mini circuits amp on order for the other radios in the shack but I had planned on making a distribution amp for milair with my old LNA-300.

I had the Nooelec amp here for something else I'm making and as soon as I connected it to the discone it just folded up, even with a broadcast filter and a 225-400 filter in line. It's not designed for "big" antennas high up in the clear. It might work for a short whip as an active antenna for people with limited space or out in the middle of nowhere but in my location it's useless.

 

[Ubbe]

as soon as I connected it to the discone it just folded up, even with a broadcast filter and a 225-400 filter in line.

There isn't even any power transmitters in the 225-400MHz band. Either filter isn't good or the Nooelec have been damaged?

/Ubbe

 

[Napalm]

There isn't even any power transmitters in the 225-400MHz band. Either filter isn't good or the Nooelec have been damaged?

/Ubbe

Exactly my point. It's being swamped even after the filter. And the filter is good. The Nooelec is just junk when connected to anything but a wet noodle.

 

[dave3825]

I have this NooElec and it does quite well. I do attenuate the signal 10 db and my noise floor is low. Possible that particular one has an issue?

https://a.co/d/fBdPSpW