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:
- stability
- input and output return loss
- noise figure at intended frequency
- gain
- 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
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