Prices

On the 19th of March I got a home battery system installed. The government has a rebate scheme so it had a list price of about $22k for a 40kWh setup and cost me about $12k. It seems that 40KWh is the minimum usable size for the amount of electricity I use, I have 84 cores running BOINC when they have nothing better to do which is 585W of TDP according to Intel. While the CPUs are certainly using less than the maximum TDP (both due to design safety limits and the fact that I have disabled hyper-threading on all systems due to it providing minimal benefits and potential security issues) given some power usage by cooling fans and some inefficiency in PSUs I think that assuming that 585W is accounted for 24*7 by CPUs is reasonable. So my home draws between 800W and 1KW when no-one is home and with an electric car and all electric cooking a reasonable amount of electricity can be used.

My bills prior to the battery installation were around $200/month which was based on charging my car only during sunny times as my electricity provider (Amber Electric) has variable rates based on wholesale prices. Also the feed in rates if my solar panels produce too much electricity in sunny times often go negative so if I don't use enough electricity. I haven't had the electric car long enough to find out what the bills might be in winter without a home battery.

Before getting the battery my daily bills according to the Amber app were usually between $5 and $10. After getting it the daily bills have almost always been below $5. The only day where it's been over $5 since the battery installation was when electricity was cheap and I fully charged the home battery and my car which used 50KWh in one day and cost $7.87 which is 16 cents per KWh. 16 cents isn't the cheapest price (sometimes it gets as low as 10 cents) but is fairly cheap, sometimes even in the cheap parts of the day it doesn't get that low (the cheapest price on the day I started writing this was 20 cents).

So it looks like this may save me $100 per month, if so there will be a 10% annual return on investment on the $12K I spent. This makes it a good investment, better than repaying a mortgage (which is generally under 6%) and almost as good as the long term results of index tracker funds. However if it cost $22K (the full price without subsidy) then it would still be ok but wouldn't be a great investment. The government subsidised batteries because the huge amount of power generated by rooftop solar systems was greater than the grid could use during the day in summer and batteries are needed to use that power when it's dark.

Android App

The battery system is from Fox ESS and the FoxCloud 2.0 Android app is a bit lacking in functionality. It has a timer for mode setting with options "Self-use" (not clearly explained), "Feed-in Priority" (not explained but testing shows feeding everything in to the grid), "Back Up", "Forced Charge", and "Forced Discharge". Currently I have "Forced Charge" setup for most sunny 5 hours of the day for a maximum charge power of 5KW. I did that because about 25KW/day is what I need to cover everything and while the system can do almost 10KW that would charge the battery fully in a few hours and then electricity would be exported to the grid which would at best pay me almost nothing and at worst bill me for supplying electricity when they don't want it. There doesn't seem to be a "never put locally generated power into the grid unless the battery is full" option. The force charge mode allows stopping at a certain percentage, but when that is reached there is no fallback to another option. It would be nice if the people who designed the configuration could take as a baseline assumption that the macro programming in office suites and functions in spreadsheets are things that regular people are capable of using when designing the configuration options. I don't think we need a Turing complete programming language in the app to control batteries (although I would use it if there was one), but I think we need clauses like "if battery is X% full then end this section".

There is no option to say "force charge until 100%" or "force charge for the next X minutes" as a one-off thing. If I came home in the afternoon with my car below 50% battery and a plan to do a lot of driving the next day then I'd want to force charge it immediately to allow charging the car overnight. But I can't do that without entering a "schedule". For Unix people imagine having to do everything via a cron job and no option to run something directly from the command-line.

It's a little annoying that they appear to have spent more development time on animations for the app than some of what should be core functionality.

Management

Amber has an option to allow my battery to be managed by them based on wholesale pries but I haven't done that as the feed-in prices are very low. So I just charge my battery when electricity is cheap and use it for the rest of the day. There is usually a factor of 2 or more price difference between the middle of the day and night time so that saves money. It also means I don't have to go out of my way to try and charge my car in the middle of the day. There is some energy lost in charging and discharging the batteries but it's not a lot. I configured the system to force charge for the 5 sunniest hours every day for 5KW as that's enough to keep it charged overnight and 5KW is greater than the amount of solar electricity produced on my house since I've been monitoring it so that forces it to all be used for the battery. In summer I might have to change that to 6KW for the sunniest 2 or 3 hours and then 4KW or 5KW surrounding that which will be a pain to manage.

Instead of charging the car every day during sunny times I charge it once or twice a week, I have a 3.3KW charger and the car has a 40KWh battery so usually it takes me less than 10 hours to fully charge it and I get at least 5 hours of good sunlight in the process.

There are people hacking on these devices which is interesting to get direct control from computers [1], and apparently not banned from the official community for doing so. I'm not enthusiastic enough to do this, I've got plenty of other free software things to work on. But it's good that others are doing so.

• [1] https://foxesscommunity.com/viewtopic.php?t=2397

17 Apr 2026 12:58pm GMT

It started with a thought: to understand people's perspectives on life and its meaning. So I texted folks, "What is life (to you)?". Each of the following list items (-) is a response from a different individual, mostly verbatim.

- A lot

- Everyone has a few universal basic qualities, and some special qualities. To me life is pursuit of exploring world based on those qualities and maturing those qualities as one goes on about exploring world/life with those qualities.
Discovering and enhancing experiences as one goes through them.

- life is endless suffering

- my answer might change daily, but this is what I've noticed and feel recently. Life is a spectrum with two distinct ends: what we control and what we don't. At birth, the spectrum is largely tilted toward control, but throughout our lives, it gradually shifts toward the other side. Ultimately, as we approach death, we lose all control over any aspect of our existence, reaching the other end of the spectrum.
tho this isn't universal, privilege plays a huge part in what you control tho i believe it holds true for the majority
but yeah man, meaning and purpose are dynamic, it's in their nature to change i can give you a different answer this evening itself xD

- Funeral Monologue from Synecdoche, New York. https://www.youtube.com/watch?v=Z9PzSNy3xj0

- Zindagi ek nadiya hai, Aur mujhe tairna nahi aata
(translation - Life is a river, and I don't know how to swim)
On a more serious note, Life is what you make it out for yourself. The only established truth is that it will end. We can never know if there is something after or if there was something before. So try to live a life that you feel aspired by? But this question was beautifully answered by that book which you had about that dying professor
(Me - He was talking about Tuesday's with Morrie)

- My answer is 42

- One, it's living on your own terms, you define everything for yourself, success, normal, whatever. You get to curate your version of it no matter the societal norms.
It's an accumulation of experiences - friends, parents, work, activities, doing shit loads. Sab try karo- travel, zumba, art, music, workout, sports, dil kara ye karna hai karlo. (translation - If your heart wants to do it, just do it.)
Then I think relationships - all that you've nurtured, people forget maintaining people because of work. It takes efforts to keep people in your life, everyone that comes has a place in yours, how well thats stays is upto you. You also get to curate your people, who stays who don't. Family toh hai hi (translation - family is there) but everyone else that comes along can make it pretty good.
So I don't want to be 50 and be like chalo ab kuch apne liye karte hai… (translation - Come on, now let's do something for ourselves) Do whatever shit you want today. Not everything costs money, and if it does get thrifty
But do keep healthy while doing all of that

- Being alive so that my daughter can grow up and i can help raising her kids as well. Raising kids without mother is tough :P

- Definitively, I feel like Life is a by product of proteins and energy working together. But in a more personal sense, Life is a dumb joke played onto us. It's a rat race. But rats exists because of life and then it becomes a chicken-egg problem
Honestly, I don't give good answers to life questions. I'm generally the one asking
Life can be like a box of chocolates, you don't know what you're gonna get untill you experience the chocolate(assuming the chocolates are heterogenous and contains a mix of everything)
Camus once said, "Life is a revolt", and one of his students added more spice to it like "Life is a revolt against the meaninglessness of existence"
I kinda feel like Life is the pursuit of every person's search for meaning

- Imprisonment waiting for execution 😄
I have one more thought while we are on the topic , game with pre defined starting position and predefined destination , path to reach is a maze

- Life to me is to live without regrets and live with freedom.
Life is always unpredictable and this unpredictability makes it more interesting and worth it.

- As of now, for the state of mind that I am in , I think for me life is about subtle struggle, subtle inconveniences and yet moving forward cause that's all I know.
I am not sure if any of this has any meaning, but sometimes I feel I was born of a purpose and that the universe has my back.
For me it's about raising my consciousness, understanding people to their depths, gaining moderate material success and helping people to some extend.
I have tried to seek a grander meaning but I have failed.
Life for me is what I make out it.
In my times of great success i rarely think about life for I am busy enjoying it, whatever you may call that state of mind.

- For me its the little things that you enjoy with YOUR people

- Life to me is about living and loving, and doing it in a way that sustains. It's the people who shape you, the work you get absorbed in, the quiet moments in between. There's also the wanting, the drive to figure out what's worth going after and how to get there, but that's just one part of it, not the point of it. And none of it happens in a vacuum. I'm aware of the privileges that let me live this way, and I try to hold on to that gratitude. In the end, life has both a material and a non-material side, and a lot of what we do is chasing material things in an attempt to satisfy something non-material within us

- Mere liye (translation - for me) life is staying at my home and studying random economics papers. That's when I enjoy myself the most.

- Very complicated
Some days I wish this life never ended and some time I feel it would be better if it stopped at that moment.
It all depends on the events that happen in the so called "life".
So life to me is a string of events that happen anyway and you get to make some decisions which can turn it in any direction and then you wonder how did that happen.

- not forgetting to breathe, learn, eat, game, take a good shit, love, sleep.

- To be honest it changed with time! At 19 it was about freedom, wasn't sure what freedom meant but i wanted that! To be free from everything, maybe because parents still controlled a part of my life. Then came 22-24 where i was working, trying to figure out what i want, the meaning changed from freedom to living for myself. To earn more, to be greedy about myself and pursue whatever would help me gain more steps in my career.
Came my mba life, switched my life from doing for myself to trying everything out to have no regrets. Life meaning was just about living with no regrets, invested, gambled, did everything to earn that tag of "yeah, have tried that". Now it has all switched to, it was all just a fake facade. Life turned to having a meaningful life rather than finding meaning in what i am doing. Living for people around me, chhoti chhoti cheezo m khushi (translation - happiness in small things(?)) isn't really a topic of conversation but more of happy thing for me. So it changed, and m quite happy to be honest. Life did show me a lot of failures, but was privileged enough to face those failures. Gained a lot of learnings if not money😂
Hopeful for more learnings and change meaning of life with time

- A task.

- You have different answers at different times You learn different meanings at different times When you are studying, basically it is about job, finding a partner then it becomes, house, car other things based on your income in between, there can be passion too
Free Software was a passion, electoral politics too, but both kind of faded and I want cooperative and user driven development now (prav - something that motivates me every day) and these days learning Chinese and watching Cdrama takes a huge part of my leisure time it is heavily subjective and also influences by previous experiences people around you, how much influence they have on you
it also depends on if they had to struggle in their life or not, for some life did not give much troubles and trouble itself can be relative people who never had to struggle may find even smallest challenges as troubles like if you own a car, your worry is finding a parking slot

- I am too young to think about lyfe

- A ticket to see the show on earth, I guess 😀
I guess life is different depending on the mood. It is a very broad question.
(Me - What is it in this present mood?)
Learning stuff (like I am learning a new language) and being happy but also to regulate emotions in a world where being optimistic is getting harder each day.
Life is also having a unique set of glasses you wear. Both in terms of looking from your eyeballs and your psychological perspective. Both are unique and cannot be replicated.
It is interesting what people on their deathbed think of life. If I know I am dying, my perspective would change a whole lot.
Life is finishing reading books while we are alive 😉
Life is sleeping after a good XMPP chat 😉

- Dukh dard peeda (translation - surrow pain suffering)

- uhh to word it? life is just like a journey from A to somewhere and its all about what paths you take and what line you get on to me, just a series of short adventures that all connect to a larger sequence until you can't have any more adventures-
(Me - eee, THE END. drop dead, like a coin)
yeaaaah- I am not really for spirituality of an afterlife, to me life just ends at some point, after which point there fails to remain a discernable you, and some X time after which, you will be last remembered, try to make that last time a good one I guess?
(Me - no soul?)
uhhh not in the way most people think of it i guess?
theres just a lot of yous, theres the physical you, there is the idea of you, there is the expectation of you, and one of the undefinable you I would label as the soul maybe? like the part thats not physically you, but also certainly you
(Me - can't say I understood part, but I get you in this sense)
mhm- well its about just questioning who you are more so questioning what life is-, I have sadly spent way too much time trying to figure that out

- Making the best of the time you have

- living a full range of experiences and embracing the good ones, seeing all that the world has to offer. In the end we were always just stardust. Might as well enjoy it when we are stardust with a consciousness of our own.

- Life is being fucked by everything and you just have to figure out and try to stick to the things worth being fucked for

Note: Following was transcribed from a audio message.

- There are five conditions to become a life to survive in the environment. I think there's five conditions by the biological definitions and reproduction is one of the factor virus is not considered a life form because it cannot reproduce on its own but technically it's kind of a life because it reproduces using the DNA ability this is the biological definition. Do you want a philosophical definition?
My definition is kind of the same except that you get life experiences along with it as a human. Extra benefits is that you are not an NPC. All other organisms are NPCs. But humans can interpret the world and change it to their liking. That is life in the case of a human. But then many humans are mostly NPCs. But they still can change the life. Okay, fuck this. Where is this even going?
A human is an exception in the case of life, because human is not an NPC. Human can interrupt the world, human can change it to its liking, which is why we are such a successful organism on this planet. That is life to me. That's a human. But all of this is kind of meaningless, because the biological impurity of a human being still exists, so you still have the urges to reproduce, which kind of makes it like just another organism. But then, humans are yet to evolve to overcome that biological imperative.

I'm grateful for all the replies, outlooks, and subsequent conversations I got to have after this question with everyone. After all, it was a deeply personal question. It does fit in nicely with my definition of life:
"Life is all about experiences and all the transient relationships one gets to have with folks we meet on the way."

PS - I would love you hear you on this. Feel free to text or email on sahil AT sahilister.in

16 Apr 2026 5:59pm GMT

It's true - processing data from software defined radios can be a bit complex 👈😏👈 - which tends to keep all but the most grizzled experts and bravest souls from playing with it. While I wouldn't describe myself as either, I will say that I've stuck with it for longer than most would have expected of me. One of the biggest takeaways I have from my adventures with software defined radio is that there's a lot of cool crossover opportunity between RF and nearly every other field of engineering.

Fairly early on, I decided on a very light metadata scheme to track SDR captures, called rfcap. rfcap has withstood my test of time, and I can go back to even my earliest captures and still make sense of what they are - IQ format, capture frequencies, sample rates, etc. A huge part of this was the simplicity of the scheme (fixed-lengh header, byte-aligned to supported capture formats), which made it roughly as easy to work with as a raw file of IQ samples.

However, rfcap has a number of downsides. It's only a single, fixed-length header. If the frequency of operation changed during the capture, that change is not represented in the capture information. It's not possible to easily represent mulit-channel coherent IQ streams, and additional metadata is condemned to adjacent text files.

ARF (Archive of RF)

A few years ago, I needed to finally solve some of these shortcomings and tried to see if a new format would stick. I sat down and wrote out my design goals before I started figuring out what it looked like.

First, whatever I come up with must be capable of being streamed and processed while being streamed. This includes streaming across the network or merely written to disk as it's being created. No post-processing required. This is mostly an artifact of how I've built all my tools and how I intereact with my SDRs. I use them extensively over the network (both locally, as well as remotely by friends across my wider lan). This decision sometimes even prompts me to do some crazy things from time to time.

I need actual, real support for multiple IQ channels from my multi-channel SDRs (Ettus, Kerberos/Kracken SDR, etc) for playing with things like beamforming. My new format must be capable of storing multiple streams in a single capture file, rather than a pile of files in a directory (and hope they're aligned).

Finally, metadata must be capable of being stored in-band. The initial set of metadata I needed to formalize in-stream were Frequency Changes and Discontinuities. Since then, ARF has grown a few more.

After getting all that down, I opted to start at what I thought the simplest container would look like, TLV (tag-length-value) encoded packets. This is a fairly well trodden path, and used by a bunch of existing protocols we all know and love. Each ARF file (or stream) was a set of encoded "packets" (sometimes called data units in other specs). This means that unknown packet types may be skipped (since the length is included) and additional data can be added after the existing fields without breaking existing decoders.

Unlike a "traditional" TLV structure, I opted to add "flags" to the top-level packet. This gives me a bit of wiggle room down the line, and gives me a feature that I like from ASN.1 - a "critical" bit. The critical bit indicates that the packet must be understood fully by implementers, which allows future backward incompatible changes by marking a new packet type as critical. This would only really be done if something meaningfully changed the interpretation of the backwards compatible data to follow.

Within each Packet is a tag field. This tag indicates how the contents of the value field should be interpreted.

In order to help with checking the basic parsing and encoding of this format, the following is an example packet which should parse without error.

 00, // tag (0; no subpacket is 0 yet)
 00, // flags (0; no flags)
 00, 00 // length (0; no data)
 // data would go here, but there is none

Additionally, throughout the rest of the subpackets, there are a few unique and shared datatypes. I document them all more clearly in the draft, but to quickly run through them here too:

UUID

This field represents a globally unique idenfifer, as defined by RFC 9562, as 16 raw bytes.

Frequency

Data encoded in a Frequency field is stored as microhz (1 Hz is stored as 1000000, 2 Hz is stored as 2000000) as an unsigned 64 bit integer. This has a minimum value of 0 Hz, and a maximum value of 18446744073709551615 uHz, or just above 18.4 THz. This is a bit of a tradeoff, but it's a set of issues that I would gladly contend with rather than deal with the related issues with storing frequency data as a floating point value downstream. Not a huge factor, but as an aside, this is also how my current generation SDR processing code (sparky) stores Frequency data internally, which makes conversion between the two natural.

IQ samples

ARF supports IQ samples in a number of different formats. Part of the idea here is I want it to be easy for capturing programs to encode ARF for a specific radio without mandating a single iq format representation. For IQ types with a scalar value which takes more than a single byte, this is always paired with a Byte Order field, to indicate if the IQ scalar values are little or big endian.

Header

Each ARF file must start with a specific Header packet. The header contains information about the ARF stream writ large to follow. Header packets are always marked as "critical".

In order to help with checking the basic parsing and encoding of this format, the following is an example header subpacket (when encoded or decoded this will be found inside an ARF packet as described above) which should parse without error, with known values.

00, 00, 00, fa, de, dc, ab, 1e, // magic
00, 00, 00, 00, 00, 00, 00, 00, // flags
18, 27, a6, c0, b5, 3b, 06, 07, // start time (1740543127)

// guid (fb47f2f0-957f-4545-94b3-75bc4018dd4b)
fb, 47, f2, f0, 95, 7f, 45, 45,
94, b3, 75, bc, 40, 18, dd, 4b,

// site_id (ba07c5ce-352b-4b20-a8ac-782628e805ca)
ba, 07, c5, ce, 35, 2b, 4b, 20,
a8, ac, 78, 26, 28, e8, 05, ca

Stream Header

Immediately after the arf Header, some number of Stream Headers follow. There must be exactly the same number of Stream Header packets as are indicated by the num streams field of the Header. This has the nice effect of enabling clients to read all the stream headers without requiring buffering of "unread" packets from the stream.

In order to help with checking the basic parsing and encoding of this format, the following is an example stream header subpacket (when encoded or decoded this will be found inside an ARF packet as described above) which should parse without error, with known values.

00, 01, // id (1)
00, 00, 00, 00, 00, 00, 00, 00, // flags
01, // format (float32)
01, // byte order (Little Endian)
00, 00, 01, d1, a9, 4a, 20, 00, // rate (2 MHz)
00, 00, 5a, f3, 10, 7a, 40, 00, // frequency (100 MHz)

// guid (7b98019d-694e-417a-8f18-167e2052be4d)
7b, 98, 01, 9d, 69, 4e, 41, 7a,
8f, 18, 16, 7e, 20, 52, be, 4d,

// site_id (98c98dc7-c3c6-47fe-bc05-05fb37b2e0db)
98, c9, 8d, c7, c3, c6, 47, fe,
bc, 05, 05, fb, 37, b2, e0, db,

Samples

Block of IQ samples in the format indicated by this stream's format and byte_order field sent in the related Stream Header.

In order to help with checking the basic parsing and encoding of this format, the following is an samples subpacket (when encoded or decoded this will be found inside an ARF packet as described above). The IQ values here are notional (and are either 2 8 bit samples, or 1 16 bit sample, depending on what the related Stream Header was).

01, // id
ab, cd, ab, cd, // iq samples

Frequency Change

The center frequency of the IQ stream has changed since the Stream Header or last Frequency Change has been sent. This is useful to capture IQ streams that are jumping around in frequency during the duration of the capture, rather than starting and stopping them.

In order to help with checking the basic parsing and encoding of this format, the following is a frequency change subpacket (when encoded or decoded this will be found inside an ARF packet as described above).

01, // id
00, 00, b5, e6, 20, f4, 80, 00 // frequency (200 MHz)

Discontinuity

Since the last Samples packet for this stream, samples have been dropped or not encoded to this stream. This can be used for a stream that has dropped samples for some reason, a large gap (radio was needed for something else), or communicating "iq snippits".

In order to help with checking the basic parsing and encoding of this format, the following is a discontinuity subpacket (when encoded or decoded this will be found inside an ARF packet as described above).

01, // id

Location

Up-to-date location as of this moment of the IQ stream, usually from a GPS. This allows for in-band geospatial information to be marked in the IQ stream. This can be used for all sorts of things (detected IQ packet snippits aligned with a time and location or a survey of rf noise in an area)

The sys field indicates the Geodetic system to be used for the provided latitude, longitude and elevation fields. The full list of supported geodetic systems is currently just WGS84, but in case something meaningfully changes in the future, it'd be nice to migrate forward.

Unfortunately, being a bit of a coward here, the accuracy field is a bit of a cop-out. I'd really rather it be what we see out of kinematic state estimation tools like a kalman filter, or at minimum, some sort of ellipsoid. This is neither of those - it's a perfect sphere of error where we pick the largest error in any direction and use that. Truthfully, I can't be bothered to model this accurately, and I don't want to contort myself into half-assing something I know I will half-ass just because I know better.

In order to help with checking the basic parsing and encoding of this format, the following is a location subpacket (when encoded or decoded this will be found inside an ARF packet as described above).

00, 00, 00, 00, 00, 00, 00, 00, // flags
01, // system (wgs84)
3f, f3, be, 76, c8, b4, 39, 58, // latitude (1.234)
40, 02, c2, 8f, 5c, 28, f5, c3, // longitude (2.345)
40, 59, 00, 00, 00, 00, 00, 00, // elevation (100)
40, 24, 00, 00, 00, 00, 00, 00 // accuracy (10)

Vendor Extension

In addition to the fields I put in the spec, I expect that I may need custom packet types I can't think of now. There's all sorts of useful data that could be encoded into the stream, so I'd rather there be an officially sanctioned mechanism that allows future work on the spec without constraining myself.

Just an example, I've used a custom subpacket to create test vectors, the data is encoded into a Vendor Extension, followed by the IQ for the modulated packet. If the demodulated data and in-band original data don't match, we've regressed. You could imagine in-band speech-to-text, antenna rotator azimuth information, or demodulated digital sideband data (like FM HDR data) too. Or even things I can't even think of!

In order to help with checking the basic parsing and encoding of this format, the following is a vendor extension subpacket (when encoded or decoded this will be found inside an ARF packet as described above).

// extension id (b24305f6-ff73-4b7a-ae99-7a6b37a5d5cd)
b2, 43, 05, f6, ff, 73, 4b, 7a,
ae, 99, 7a, 6b, 37, a5, d5, cd,

// data (0x01, 0x02, 0x03, 0x04, 0x05)
01, 02, 03, 04, 05

Tradeoffs

The biggest tradeoff that I'm not entirely happy with is limiting the length of a packet to u16 - 65535 bytes. Given the u8 sample header, this limits us to 8191 32 bit sample pairs at a time. I wound up believing that the overhead in terms of additional packet framing is worth it - because always encoding 4 byte lengths felt like overkill, and a dynamic length scheme ballooned codepaths in the decoder that I was trying to keep as easy to change as possible as I worked with the format.

15 Apr 2026 3:43pm GMT