23CM 500mW Amplifier AH101

 I have not determined why the SXB4089Z input matching was out. After lots of maths and component substitution I suspect the mmic itself is damaged. I will swap it out soon to confirm this.

In the meantime I tested an AH101 device. This was made awkward because the test board was set out with matching networks for the AH1, which are quite different. With some hacking I got it to work. Input return loss was initially 17db but I was able to tune that to under 30dB with a little foil gimmick capacitor. Output return loss was 17db. Gain was 13dB.

 

73's

23cm 500mW Amplifier SXB4089Z

 After calming down over JLPCB's appalling process for dealing with their errors, which is to deny everything and obfuscate to the point I gave up, I populated one of the test boards for the SXB4089Z. My earlier posts here, here and here set out the steps I took to end up with the following:

 

Expected Results

My results did not quite match this. Using the nanoVNA to measure the input and output ports, adjust for the attenuation used and then combining everything into a single file for RFSIM99 to read showed that the output matching was nearly spot on (I will need to change the 1.2pF output capacitor to 1.0pF) but the input matching was all over the place. I repeated the measurements and got the same result.

Actual Results

I am confident that once the input reflections are resolved that it will only take a small tweak to get this working well.

73's

Richard

New part - SMA3109 MMIC

Something different....

I stumble across new parts from time to time that set a price / performance benchmark. So I thought it would be worth alerting readers to these parts. Here is the inaugural post on this subject.

The new benchmark in my shack for general purpose mmics is the SMA3109. It happens to be the cheapest mmic that LCSC stock. I had wanted to use this commercially but the initial lack of S parameters meant I passed it over in favor of another device. That decision might get revisited.

Despite the low price the SMA3109 offers outstanding performance from VHF through to 4GHz. Compare it with other low cost mmics such as the BGM1013 and you will see why I rate it so highly.

When I evaluate a MMIC I consider:

1. stability
2. input and output return loss
3. noise figure at intended frequency
4. gain
5. ease of hand soldering
   

This device is ticking all my boxes but the NF of 4dB rules out demanding low noise applications.

I suspect it is useful outside these ranges but the S parameters kindly supplied by Onsemi technical only cover 100MHz to 4GHz.

Band	Gain	S11	S22
2m	23dB	-28dB	-13dB
70cm	24dB	-24dB	-16dB
23cm	24dB	-38dB	-16dB
13cm	23dB	-15dB	-14dB
9cm	21dB	-11dB	-17dB

The input match on 23cm is outstanding and I will definitely use this device in my 23cm projects where filters are connected to the input. For driving filters I would consider at least a 3-6dB pad to provide a better source termination. Being very stable across the entire frequency range matching if needed is straightforward.

Where linearity is important I would budget to get around 0dBm out of the device.

My hunch is that the feedback within the device makes it useful below 100MHz except for the output becoming a poor match to 50 ohms.

The device appears to be very useful from 2m through to 9cm and represents terrific value for signal outputs up to the Po(1dB) level of +4dBm. Definitely worth a look at US 11cents each!

73's