Chinese Solder - An update

After months of using different solders I have updated my findings. Only 2 of the Chinese sourced solders I tested are a realistic alternative to the comparatively expensive Multicore solder. Thoughts? Opinions? Comments welcome.

73's

23cm Amplifier Test Boards are almost here

As many readers will know, the current Covid19 pandemic has significantly increased the time it takes for air freight to be received. But the test boards have all been made and are presently in Singapore.

New Part - VHF Low Noise Amplifier MXDLN02C

So I was browsing for a high speed op amp and I came across this wrongly catalogued part at LCSC.COM. I am now testing it for a commercial project but it could have uses in ham projects.

But there are some caveats that go with a US$0.05 part:

1. The datasheet could be better
2. This is not a strong signal handling part
3. No details exist on how best NF is obtained

The MXDLN02C is meant to be used as a pre-amp for FM broadcast receivers. The datasheet suggests the noise figure is under 1.5dB and gain is above 20dB from 50MHz to 150MHz with good stability. I wrote to Maxscend as part of the commercial project requesting the S parameters in a table format. The response suggests Maxscend will never be one of my preferred suppliers.

So, in Ham spirit because this is a really cheap part, I simply hooked up the input to the nanoVNA and measured S11. Now I don't claim the nanoVNA is the last word in measurement, or that my test board was perfect. But the results I got suggest Maxscend was way off the mark.

From the Datasheet (2.85V) :

From measurement (also 50-150MHz) (3.3V):

I'm not dwelling on the possible reasons why there is such a disparity. What is important that based on my measured S parameters matching networks were easily calculated in RFSiim99. So, a few minutes of tweaking and I had a return loss of -30dB on the input at 6m and about 20dB of gain.

A similar story on the output port.

Summary:

It's ridiculously cheap.

Useful for 6m and 2m in non-demanding front-ends, still has +13dB of gain at 70cm.

This is not a MMIC so matching to 50 ohms, while easy, will be required

Like a MMIC no biasing calculations needed

Stability concerns limit HF applications

I always advocate using what is in your junkbox. But if you had to buy a device for low level amplification at 6m or 2m then this is what I would suggest.

73's