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Comment by tecleandor | Hacker News Reader

An additional radio would raise the price of your phone for at least another 200 or 300 dollars. Try to enable VoLTE if available for your operator. That makes the phone use the LTE connection for voice and don't drop the Internet connection while you talk.

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Dual SIM Dual Active phones are under £100 in the UK, I imagine under $100 in the US.

Dual SIM Dual Standby (two or more SIMs, one radio) is cheaper, less battery, less space, and usually good enough. It's literally a few dollars, not 200-300.

Seems like I forgot to specify "5G" (those radios tend to be expensive) as the original poster was asking for an additional 4G/5G radio.

DSDA in 5G is rare, and I can't reliably find a phone that can do it in EU or US (I can find higher end chipsets that can do it, but phone vendors don't seem to follow through with it). Usually it's 4G+5G or 4G+4G.

You can get an additional phone with a screen, 5g radio, ram and everything for $150. An additional radio should not raise the price for another 300.

I assume for something like a phone these things are non-linear. going from 2 PCIe lanes (nand, radios) to 3 (another radio) may cause an SOC to jump from entry-level to mid-level, larger PCB and increased layer count, more antenna for simultaneous use, etc. so its not just the cost of the chip but all the secondary effects.

In many phones, some of the radio hardware is integrated into the SoC. Adding a second, independent radio is a larger engineering task.

A non-linear cost for a small fraction of the phone. A slightly larger PCB with two more layers is about twice the price for the PCB, more antennas is a couple dollars, a one lane PCIe switch is a few dollars if that's cheaper than upgrading your SOC. And if it shrinks your battery 10% you save money on that part.

I blame niche-ness far more than the actual design and production costs.

Edit: fixed the pcb wording

> PCIe switch is a few dollars if that's cheaper than upgrading your SOC

perhaps you're more familiar with these options than I am, but I see 4 lane PCIe switches are 10x10 mm and maybe they are a few dollars but take more board space, new/larger power supplies, etc so it seems that the costs are more than just a few dollar PCIe switch chip. not sure how many phone PCBs can handle additional 100 mm2 but definitely looking forward to learning more.

[1] https://www.diodes.com/products/connectivity/pcie-packet-swi...

add to the antennas are likely based on best/cheapest efficiency for the available area, then additional antenna would reduce the area for each and require more effort/cost.

> not sure how many phone PCBs can handle additional 100 mm2

You are clearly out of your league. Get some 20 y/o flip Motorola, disassemble it and think, think hard.

No, 'PCIe switches' has nothing to do with the smartphones at all - so their PCB real estate do not indicate anything.

It won't, but the pre-made platform solution you pick and the prompt you send to Chinese ODM who do all the hard work must specify it has to be (DSDA|DSDV|DSDS|DSSS), or otherwise it'll default to DSDS.

The chips cost under $100 even for top tier modems from Qualcomm.

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