LNA spf5189z issue

[HighPrecision]

Hi radiolistener,
see this document from MiniCircuits:
https://www.minicircuits.com/app/AN60-034.pdf

This maybe help on your problem of burning SPF5189Z, in paragraph 4 there are some suggestions to mitigate this issue.

MiniCircuits PGA-103+ is declared as a direct replacement of SPF5189Z in datasheet.

Beware that these devices are NOT UNconditionally stable below 100MHz, maybe a good idea to place a filter for FM broadcasters and other signals in <100MHz band. This issue is described here:
https://www.minicircuits.com/app/AN60-064.pdf

[Max.Bz]

Also got a large number of fake LNA SPF5189Z (visually easy to distinguish by the shape of GND pin in the original it is shorter and skewed) in terms of parameters, this is far from LNA, but nevertheless they do not fail , since they had to use them in an amount of several thousand pieces, gain was 13-15dB, @~1GHz

[virtualparticles]

You normally cannot hang an LNA directly on an antenna. Various noisy bits in the air will eventually conspire to overload the input of the device. Put some sort of bandpass filter in front of it. I speak from 15 years experience designing Tower Top Amplifiers for Land Mobile Radio. I definitely know how to burn out LNA's. 

Best,

Brian

[cdev]

What do you think about built in ESD protection?

Some MMICs  ( like Mini Circuits PSA4-5043+) build in a moderate level of ESD protection.
But it seems that even with the manufacturers basic ESD protection, they often get taken out by ESD from sources like lightning.

An ungrounded conductive path (like a quarter wave monopole) going straight into the LNA, even if you have a DC blocking capacitor on the input (which can be awfully small) seems like its asking for trouble..

Even so, unless one has both lower and higher out of band frequencies attenuated in many tower settings especially, unless one if far away from other RF sources strong out of band signals seem likely to "steal dynamic range" from the desired application.

So a band pass filter and DC block as well as a DC path to ground seem like common sense, maybe almost mandatory?

[radiolistener]

What do you think about built in ESD protection?

I'm using two antiparallel diodes and 47 nF capacitor for DC block on the input

[A.Z.]

What do you think about built in ESD protection?

I'm using two antiparallel diodes and 47 nF capacitor for DC block on the input

two may suffice, but may also cause signal clipping

http://www.kk5jy.net/rf-clipper/

[cdev]

Mini circuits PSA4-5043+ has quite decent ESD protection (ive never lost one from ESD) and its just a three terminal device so its as simple as it gets for an LNA. Basically, you can make an LNA out of a little chunk of 50 ohm trace in just a couple of minutes. They cost around $2.75 each.

They are probably better than these Chinese bootleg spf5189 LNAs. I have both so if you want me to compare the two I'd be happy to.

[cdev]

WA5VJB also makes a small LNA PCB well suited for a mini circuits mmic or bias tee and sells them for very little. Maybe $1. Its an easy, half hour LNA with generic pads which would support all kinds of parts..

[genugeo85]

In order to limit the current to this mmic it is necessary to introduce a negative voltage of approximately -0.6--1V on the circuit input (similar to the supply of GaAs and HEMT transistors). The current will be reduced to 50-90mA.

[Gerhard_dk4xp]

No, it is not. Read the data sheet, it says clearly "single supply".
The chip is end of life, Mouser has no stock, nothing new to arrive.

Mini Circuits PGA103 works nicely, even less noise.

[radiolistener]

I also hear that adding bias offset on the input can help to improve performance for this fake/counterfeit Chinese chip. But didn't tried it

[genugeo85]

What the Chinese say in the datasheet is one thing, the reality is another ...
I also burned a few pieces until I injected a voltage of -0.8V at the input. At that time I measured a consumption of about 60mA.
I speak from my own experience ...

[genugeo85]

Some photos with the behavior of my modified amplifier ...

[cdev]

Some LNA  MMICs have built in ESD protection. I have used it in quite a few PSA4-5043+ devices. (just that device, no others)

At least ten were successful and the failures were not caused by ESD. On one I accidentally pulled a leg off.. (oversoldering)  . Oh, and I lost one in the messy area beneath my desk. Because they are very very small.

But none have had to sit up on a tower directly connected to a monopole..A high static risk situation. I bet a high value resistor to bleed off ESD to ground or any antenna with a DC path to ground would protect it.

Datasheet for  PSA4-5043+ attached.

Mini Circuits claims
*Class 1B HBM ESD rating (500V)

It seems like it would make a lot of sense to buy 20 and use it to retrofit each of your various cases with a simple, new LNA.

[m3vuv]

I have just got one of these lna moduals from aliexpress for my si 47xx homebrew radio,ive a couple of questions,1 are these ok for hf ,and 2 will these run from an 18650 cell?,are they ok for 2 meters as well?,ok 3 questions lol. TIA.

[cdev]

I have used two metods to stop oscillation.

1, inserting lossy elements in parallel with inductors in the power chain, for example, adding low value resistors to reduce the Q of the bias tee inductors,

2.) using flexible RF loss antistatic foam, you can attach it to copper tape (on its back) and then put a thin piece of cellophane wrap right on top of the circuit and press the antistatic form over that. Apply some pressure right on the device. This will introduce loss.

3.) make sure that both the input and output to the LNA go through a short length of decent 50 ohm transmission line, ideally where the shielding is well grounded. Ferrites around these two short lengths of transmission line may help too, all my gain stages are festooned with as many ferrites as I can reasonably fit on them. This may look funny but my experience is that it pays off in signal integrity.

4) Make sure the grounding on the MMC is top quality. It should be immediately under the MMIC, for example, place your vias right at its legs. Make sure the impedance of the vias is low. Grounding is the most important thing with newer 50 ohm LNA devices. They are super easy to use if you give them what they want.

[m3vuv]

I have used two metods to stop oscillation.

1, inserting lossy elements in parallel with inductors in the power chain, for example, adding low value resistors to reduce the Q of the bias tee inductors,

2.) using flexible RF loss antistatic foam, you can attach it to copper tape (on its back) and then put a thin piece of cellophane wrap right on top of the circuit and press the antistatic form over that. Apply some pressure right on the device. This will introduce loss.

3.) make sure that both the input and output to the LNA go through a short length of decent 50 ohm transmission line, ideally where the shielding is well grounded. Ferrites around these two short lengths of transmission line may help too, all my gain stages are festooned with as many ferrites as I can reasonably fit on them. This may look funny but my experience is that it pays off in signal integrity.

4) Make sure the grounding on the MMC is top quality. It should be immediately under the MMIC, for example, place your vias right at its legs. Make sure the impedance of the vias is low. Grounding is the most important thing with newer 50 ohm LNA devices. They are super easy to use if you give them what they want.

well looks like my question is unanswered!

[cdev]

The simple example of the Chnese copycat LNA that I have is still working, but my guess is that the noise figure is higher than the original. (which is specced at less than 1 db, [pretty good) Maybe 4 db or more is what it seems like to be just judged on how it performs with local sigansl here in the NYC suburbs. I can receie lots of signals down the Jersey SHore and even signals from NASA at Wallops Island.. (they lauch lots of satellites from there. So I find the copycat LNA  to be crap, it doesnt really make sense to use it say with an RTLSR which already has around a 4 dbm noise figure. The really weak signals from south of here and along the Long Island Sound, do come in better with the minicircuits LNA.

So whats the point?  Transmit, I dont know. I only receive. An 18650 fully charged might give you a day or two of enhanced reception. As stated, its not such a great LNA. Also, as radiolistener has pointed out they tend to die from ESD. So arent so great.

[cdev]

Not so great for below 50 MHz. They dont specify because the OEM specs end at 50 MHz. So they dont have to.

Lots of people find they die from ESD fairly young. My LNA4all has, in contast lasted me now more than eight years, getting used a lot in all that time..

But I have never used it outdoors.. Its never had to deal with ESD from an outdoor monopole.. Just lots of planar disk antennas, discones. etc.

The easy indoor life.

[Costas07]

Hi,
Bought one of these Chinese LNA supposedly based on SPF5189. It consumes ~ 160mA from 1 Li-Ion cell 18650 size (4.2V fully charged).
Based on the specs this is too much. Also the gain is lower and barely gets to 15dB contrary to datasheet. To me it seems these are not original MMICs.

[spider_provider]

Hey all,

I think there's two variations available on eBay etc: on the shield, the SPF5189z label is either in black text, or black outlined text.

From my experiments, the ones with outlined text want 120-160mA, and the one with solid black text wants 60mA. (Voltage ~5V, tested 3x outline and 1x solid variants)

So I'm guessing the solid black text ones are real. Only going off current, they both work the same to me, I don't have any spectrotron professor farnsworth stuff like you guys

Edit: Adding side-by-side. That's a pair of antiparallel 1N1418's under the heatshrink, and no I am not sorry about my soldering job.

[biastee]

When a device oscillates, its current will typically increase above normal. So, it is worthwhile to check for oscillation whenever the current is abnormal.

But none have had to sit up on a tower directly connected to a monopole..A high static risk situation. I bet a high value resistor to bleed off ESD to ground or any antenna with a DC path to ground would protect it.

Why suspect static only and NOT consider indirect lightning strikes? Another way the designer can protect the LNA is to choose a high pass L-network as the input match. This network has a shunt L that can bleed static & transients.