alt.hn

5/16/2026 at 4:49:15 PM

Kv4p HT – A homebrew 1W radio (VHF or UHF) that plugs into an Android phone

 https://www.kv4p.com/

by krupan

5/19/2026 at 12:40:06 PM

There are many cheap shanzhai android phones with walkie talkie ptt functions (around 400MHz iirc) for about a decade. We tried to convince manufactures to open up the software stack to no avail, while being bullied at local hackerspaces (“this is illegal!”). I am licensed.

by thenthenthen

5/19/2026 at 3:47:12 PM

It's mindblowing to me how modern cell phones have worse broadcast and P2P capabilities than what we had decades ago (when feature phones often featured FM receivers and could share photos via Bluetooth across manufacturers and OSes).

Airdrop was the closest thing we had, and even that has been intentionally nerfed for non-contact senders.

It's absurd that modern phones can talk to satellites hundreds of kilometers above, but not to other phones a few meters away in the same room, airplane cabin, train car etc.

by lxgr

5/19/2026 at 3:50:46 PM

P2P capabilities aren't what the providers and governments want.

The providers don't want it because they can't charge you for it. The governments don't like to see people communicate outside of their control. See how Apple caved to China making AirDrop no longer public and has followed suit in the rest of the world because other governments fear this capability too.

by wolvoleo

5/19/2026 at 7:08:34 PM

So, do phones in the "libre" genre have these features ?

by euroderf

5/19/2026 at 8:53:41 PM

No, but I think this is more because it takes them so much effort replicating the basic functionality and compatibility with e.g. android apps that they just don't have the energy for it.

Also, the hardware for good peer to peer communication is just not present in regular phones. Some libre hardware projects do have optional addons for LoRa, such as the PinePhone: https://pine64.org/documentation/Phone_Accessories/LoRa/

by wolvoleo

5/20/2026 at 10:21:45 AM

That's not at all true, phones have both WiFi and Bluetooth, both of which are perfectly capable of communicating peer to peer. Bluetooth file transfer worked 20 years ago. Wifi is physically capable but the software usually requires one phone to be the Daddy and host a hotspot, because god forbid an IP subnet exist without routable internet i.e. the mothership. There is a standard, "Wi-Fi Direct", that solves this - it's been around since 2009 and everyone implements it except Apple, so naturally nobody uses it.

Perhaps you mean p2p phone calls. Fine - although I have a hard time believing that the 900 Mhz radios capable of talking to a tower literal miles away are physically incapable of talking to each other. They're just programmed not to. In any case, the inconvenience and unreliability of sending files 3 feet, vs the streamlined experience of sending them via a corporate datacenter thousands of miles away, demonstrates that this is not about hardware. This is about software, and by extension about control.

by dTal

5/21/2026 at 8:44:03 PM

Bluetooth and WiFi on a mobile device don't have enough range for this stuff. You need to be too close to other participants.

Hence LoRa. Yes, 5G would be an option but the licensed spectrum (and firmware restriction) makes that impossible.

by wolvoleo

5/21/2026 at 7:39:51 PM

5G NR radios could also be capable of communicating peer to peer long distance if manufacturers (phone or baseband?) wanted them to. It's in the spec.

by atomicthumbs

5/20/2026 at 11:31:55 AM

Exactly: Perfectly capable in hardware, almost perfectly locked down in software.

by lxgr

5/20/2026 at 9:45:49 AM

> share photos via Bluetooth across manufacturers and OSes

You can still do that! It never went away.

by throwaway270925

5/20/2026 at 12:34:42 PM

It's never been a thing on iOS, unfortunately.

by lxgr

5/19/2026 at 8:00:37 PM

Why is it that pretty much every ham operator I've met has been a complete jackass.

by lichenwarp

5/19/2026 at 6:44:48 AM

Is it so difficult to have schematics and pcb exported as PDF so that people do not need to fire up KiCAD to view the stuff?

by s03nk3

5/19/2026 at 11:28:24 AM

I encounter this problem as well when looking at projects on Github on a near daily basis it seems.

It just led me to finding this:

https://kicanvas.org/

worth a bookmark.

by mk_stjames

5/19/2026 at 2:45:25 PM

Or even a picture of the physical device! I found some on a linked sales listing: https://chelegance.com/products/kv4p-ht-plugplay-vhf-radio1-...

by Retr0id

5/19/2026 at 6:06:23 PM

Thanks! I was looking for that.

I see they use those cheapo Chinese RF modules (SA818). I've seen those also with SDR input/output, that's interesting. The underlying chip is very similar: The chip that will be used in this module is the RDA1846. This is a chip that's in most Chinese handhelds and is internally fully SDR but it decodes to analog. There's also the RDA1847 with similar pinout which offers the raw SDR stream and can thus be used for any mode, but with the added complexity of having to do the SDR decoding externally.

That means that this design could probably also be modified to do DMR. Though the SDR side might be a little bit too much to ask of an ESP32. On the other hand, it is only a very low bitrate signal.

by wolvoleo

5/19/2026 at 5:06:33 PM

Sounds like a great contribution you could make!

by oslem

5/21/2026 at 12:35:15 PM

There are like six ways to export PDFs from KiCad. Project owners choose not to.

by vitally3643

5/19/2026 at 3:48:29 PM

Nice!! I wish it could do DMR though. Analog isn't used to much anymore in these parts. Although to be more precise, HAM radio has declined a lot but DMR repeaters are linked in groups so it seems like there's a lot more activity.

by wolvoleo

5/19/2026 at 11:40:53 PM

Exactly my thought. APRS is nice but I'm just not interested in buying another otherwise analog-only radio. I know a lot of the popular digital modes are hard due to proprietary components but I'd be a lot more interested in something that supported digital voice and higher rate data modes even if it were just M17.

by wolrah

5/19/2026 at 6:58:16 AM

I used to use SDR for DAB radio in the nexus 7 in the dash of my BMW E46. It didn’t work very well but was closer to being some kind of radio receiver (not trans at least)

by bdavbdav

5/19/2026 at 7:18:20 AM

> 1 watt transmit can go miles yet sips your phone’s battery

How far can such a device reach in a typical urban environment with the longer antenna?

by landgenoot

5/19/2026 at 8:20:08 AM

VHF is effectively line-of-sight, and no antenna size can change that (although it does improve efficiency for both sending and receiving), so for two handheld radios, you are limited to about 10 km.

The only thing that really helps extend the range is elevating the antenna, and repeaters allow you to do that even between two mobile stations.

by lxgr

5/19/2026 at 3:08:00 PM

VHF doesnt need line of sight, it has excellent ability to penetrate obstructions due to its long wavelength. For example, its not difficult to receive FM radio transmissions indoors, even from tens of km away. Some obstacles will effectively block any radio signal though, such as solid earth or concrete (esp rebar reinforced concrete).

You are right that handheld radios wont get more than about 10km, but that is due to the curvature of the earth. Mountain top to mountain top, you could easily do 50-100km

by ac29

5/19/2026 at 3:41:58 PM

That's what I meant by "effectively": Reflections, diffraction, and (moderate, i.e. think doors and windows, not walls) light obstacle penetration make some indoor reception possible, but the radio horizon remains the strong limiting factor.

That's even true for the L- and S-band; otherwise you wouldn't be able to use a cell phone in a windowless room, for example. (Much of what's commonly attributed to "object penetration" is actually mostly due to reflections and diffraction around obstacles.)

by lxgr

5/19/2026 at 6:09:09 PM

I think there's other phenomena that people might be interested in such as E-skip and tropospheric ducting. Although you cant really rely on those.

by giantg2

5/19/2026 at 12:36:32 PM

Practical use, dense urban, flat, UHF is about 1km. VHF is worse.

Most radio amateurs would utilize a repeater to get over this limitation. Assuming there is a reliable repeater one is welcome to use nearby.

by souterrain

5/19/2026 at 2:23:19 PM

In dense urban environments, VHF (~144 MHz) actually performs better than UHF (~446 MHz) for a few reasons... Lower frequencies diffract better around obstacles. VHF diffracts more readily around and over buildings than UHF. VHF penetrates building materials better than UHF — lower frequency = longer wavelength = better penetration through walls. UHF suffers from higher path loss over distance compared to VHF.

by quietsegfault

5/19/2026 at 5:41:13 AM

1w seems a little limited? A cheap baofeng is 8w.

by RobotToaster

5/19/2026 at 6:26:52 AM

Those cheap baofeng's are illegal to use where I live on most of the spectrum they can operate on. Illegal to press the talk button anyway.

So maybe the 1w is also a regulatory issue.

by Kaliboy

5/19/2026 at 1:15:44 PM

In the US all transmitting at 1W with these radios is contrary to regulations.

That said, no one is going to stop you from squatting on 146.580 MHz for example, a frequency commonly used by outdoors folks, rules notwithstanding.

by souterrain

5/19/2026 at 3:13:33 PM

> In the US all transmitting at 1W with these radios is contrary to regulations.

With a ham license the limit is 1.5kW, without one its zero

by ac29

5/19/2026 at 7:39:58 AM

How does the FCC enforce this sort of thing? Are they listening in to certain frequencies nationally with the ability to triangulate a handheld down to actually identifying someone?

by asdff

5/19/2026 at 10:24:07 AM

They mostly don't. They send scary letters and maybe eventually fine someone. They have a handful of triangulation vans for the entire US. The barely respond to complaints that are revenue impacting and generally don't respond to complaints from hams that a non ham is using their equipment. Once a quarter they make an example of someone so that it appears they enforce things. The people they make examples of are usually trying really hard to troll them or doing something highly disruptive and these will end up on a few websites and magazines.

People tinkering and staying away from ham bands will generally be fine and for the cheap ham gear that made easy by design usually by doing a factory reset or worst case having to clip a diode to widen their frequency ranges. Most ham gear is designed to be highly hackable.

by Bender

5/19/2026 at 3:29:17 PM

You only really get attention from the FCC if you interfere with some other service, especially broadcast or emergency communications frequencies. Grumpy Hams will also hunt you down sometimes, but only if you're persistent. Otherwise yeah, the FCC can't practically enforce every rule everywhere and doesn't really try. Still, get a license and be a good citizen if you want to play with this kind of thing, it's not very difficult.

by gh02t

5/19/2026 at 4:49:58 PM

Agreed. One youtuber [1] calls them Sad Hams. That has stuck with me. Linked video is the FCC's recent enforcement actions. I personally find some ham gear to be slightly less sloppy 11 meter rigs and a number of others agree.

[1] - https://www.youtube.com/watch?v=QeMjMlHpus8

by Bender

5/19/2026 at 8:03:16 AM

Most of the time they get a complaint, and they investigate.

https://www.fcc.gov/reports-research/guides/fcc-enforcement-...

by fodmap

5/19/2026 at 8:26:51 AM

Wow, you mail them the complaint? No reason to worry about accidentally hitting the talk button I guess. Probably nothing happening unless you spam the frequency for weeks I'd guess.

by asdff

5/19/2026 at 12:37:38 PM

Yes, weeks if its cell or GPS. Months or never otherwise.

by mystraline

5/19/2026 at 7:58:15 AM

Someone complained, they send someone to check and triangulate, verify that the operator doesn't have the license, then issue a warning or fine.

by martheen

5/19/2026 at 8:39:04 AM

I wonder how close they can triangulate? I'd guess they are SOL if I am in an apartment building with 200 other units.

by asdff

5/19/2026 at 9:44:17 AM

I mean, if you're deliberately being a dick about it, they will ask for a warrant and have the LEO accompanying them while triangulating, they can easily figure out which unit and even room you're in by walking around in the building with directional receiver.

But in general, yeah, unless you do it regularly, living near sensitive facilities (airport, military base, hospital, factories, research labs etc) or deliberately transmitting at/near emergency frequencies (police, paramedic etc) at most you'll get yelled by a pissed off operator (at that point, stop, they could be already coordinating with someone else to triangulate you)

by martheen

5/19/2026 at 9:53:05 AM

Unless you're going out of your way to force them to react, they do not.

by l23k4

5/19/2026 at 5:48:04 AM

Only on the paper, the real power is around 3/3.5W

by lormayna

5/19/2026 at 6:20:44 AM

1w is usually okay and using 8w from a phone is probably way too much power demand

by takipsizad

5/19/2026 at 8:51:46 AM

Is it still worth it to mess around with older full duplex handhelds ?

by Melatonic

5/19/2026 at 3:35:07 PM

Analog handhelds are still abundant, they've gotten smaller and more efficient but older ones are still basically just as good as new. IMO digital handhelds are superior, but digital protocols are much more fragmented so analog remains king as a common denominator (practically every digital handheld can do analog, too).

by gh02t

5/19/2026 at 8:42:49 AM

I loved it, amazing work, thanks for sharing it!

by tamimio

5/19/2026 at 6:27:10 AM

This doesn't turn your phone into a ham transceiver at all. It turns your phone into a transceiver controller. Given that a cell phone is a transceiver, this headline is rather disappointing clickbait.

by Crunchified

5/21/2026 at 5:16:45 AM

Arguably, that's still a viable thing.

I've used a few handheld transcievers and they tend towards clunky user interfaces-- tiny, fiddly displays, highly modal keys, and basically needing to memorize the manual to use it.

Even worse-- there's not a strong correlation between the quality of the RF unit and the user-interface. The Yaesu FT-60 is a reliable, high-quality radio, with all the user friendliness of a live porcupine.

But with a 6-inch pocketable touchscreen you could solve most of the UI problems, and focus on the radio problems.

Keeping the division also gives you flexibility-- you could design a 25-watt tabletop unit, or modules for different bands, that shared the same basic control software and UI

by hakfoo

5/19/2026 at 6:29:30 AM

Agree.

We need a compact short wave transceiver device actually.

by alexwwang

5/19/2026 at 3:52:12 PM

QRP is the keyword you may be looking for. 9W, battery powered, SDR shortwave transceivers. There are inexpensive and expensive versions.

by jonah

5/21/2026 at 1:53:48 AM

The antenna is the most critical part in this system. The transceiver is the second part, as to me at least.

by alexwwang

5/19/2026 at 6:32:53 AM

Baofeng is 20 dollars? How much cheaper and compact do you need?

And I know, I know, Baofengs are notorious for going over the allowed noise limits… but still…

by FabCH

5/19/2026 at 6:36:07 AM

Baofeng's are not shortwave radios afaik

by takipsizad

5/21/2026 at 2:03:54 AM

yes. it's a good choice for light use in UHF/VHF scenarios even communicating to satellites if you have a Yagi antenna.

by alexwwang

5/19/2026 at 1:02:50 PM

Baofengs also have terrible receive filtering. It is perfectly possible to hear no stations because you are being overloaded by something on another frequency. I tried my first SOTA activation with a Boafeng. A transmitter on another hill meant I received nothing, although stains could hear me. By a Yaesu, still cheap

by jimnotgym

5/19/2026 at 7:30:19 AM

Yaesu FTW

by NordStreamYacht

5/21/2026 at 2:02:12 AM

yeap if you utilize "moneiability".

by alexwwang

5/19/2026 at 8:24:13 AM

Is this prevented by physics or cost or just no one has the motivation?

by sfmike

5/19/2026 at 3:49:59 PM

Compact HF/shortwave radios with transmit capability exist, but they're pretty expensive and are generally definitely portable but not quite handheld. The biggest user of such equipment is the military, so a lot of the tech is engineered for that with civilian/amateur use as an afterthought. ICOM, Yaesu, and Xiegu are probably the best known makers, and you're looking at ~$1000 as table stakes for a modern one, though there are some slightly cheaper options.

Handheld CB radios do exist and are cheap, but I've never really used them.

by gh02t

5/19/2026 at 1:25:33 PM

There are a number of compact shortwave (radio amateurs prefer the term "high frequency" or HF, in contrast to VHF, UHF) transceivers. The impracticality is from the size of an efficient antenna.

I have personally made voice (single-sideband or SSB, which is analog like AM without wasting energy transmitting a carrier or redundant sideband) contacts with a 5 watt portable (Elecraft KX2) between countries in Europe, using a meter-long whip antenna and a trailing counterpoise wire.

These radios are incredibly complex weak-signal equipment, and that is reflected in the price.

That said, it is fun. Using morse code to do the same is even more fun.

I would never rely on this for off-the-grid communication, though.

by souterrain

5/19/2026 at 3:09:47 PM

There's the trusdx or the QMX.

by _whiteCaps_

5/19/2026 at 7:14:29 AM

A compact CB transceiver would be fun.

by RobotToaster

5/19/2026 at 8:11:35 AM

Fun, but short range. A quarter wave CB antenna is about 2.7 meters long. Without that, you're making more heat than radio.

by topspin

5/19/2026 at 11:55:31 AM

wspr is known to work at 7mhz band with just cloth hanger as antenna. i think its totally possible to use headphones as shitty longwave antenna too

by iberator

5/19/2026 at 5:15:49 PM

Someone already pointed out how the WSPR anecdotes fail for CB. The longwave reception argument is fallacy as well. There, you receive powerful signals with a poor, receive-only antenna; the typical asymmetric model of commercial broadcast radio (and cellular, for that matter.) With CB, both sides are low power. Legally, that is. And neither antenna is on a huge tower.

Several handheld CB radios exist, with little loaded whip antennas. You can go buy one. You'll see. They work for talking between two tractors in a field or whatnot. Past that, not so much. Today, you're better off with license free UHF handhelds for that use case.

by topspin

5/19/2026 at 3:35:33 PM

Wspr is very optimised for weak signals, though. You wouldn't actually hear anything but noise.

by jimnotgym

5/21/2026 at 9:11:58 AM

jt8 would work. designed for ultra low db reception. We are talking here -20 dbm and chattable

by iberator

5/19/2026 at 7:52:09 AM

I don't see it as clickbait since the realities of the Android ecosystem is a shared context.

Most people know that just about every Android phone has a restricted hardware design, not an expandable one.

So, "turn your phone into X" is bound to automatically evoke images of another device that plugs into the phone via common connectors like USB or the audio jack and an app on the phone to control that device. That's what the phrase means to most people in the context of Android.

"Turn your phone into a ham radio transceiver controller" is neither needed nor entirely accurate, because then people will assume it can control _any_ ham radio transceiver.

by lovelearning

5/19/2026 at 8:17:06 AM

The article is chiefly about a radio circuit you can "build", plus some controller software that happens to run on an Android phone. Meanwhile the headline is 100% focused on describing something that your phone can be made to do (which you have admitted that it can't).

The two don't add up, and your apologetic analysis doesn't convince me otherwise. It's still clickbait. An Android cell phone has radio guts, and that headline is just gutless.

by Crunchified

5/19/2026 at 4:58:54 PM

It's not "apologetic" and it wasn't meant to convince you but to refute your pointless pedantic nitpicking for other readers.

by lovelearning

5/19/2026 at 8:12:36 AM

"Turn your phone into a nuclear reactor (by plugging it into a wall outlet served by a nuclear power plant)"

by lxgr

5/19/2026 at 9:56:36 AM

Why do some people get so hung up about minor things in life. The OP has done a fantastic job, not just building it, but both the delivery and mechanics.

by developer786

5/19/2026 at 10:22:59 AM

I agree, it is a fantastic job!

The title is still misleading to me. Not terribly so – hence my not quite serious reply – but I was expecting something like https://timestation.pages.dev/, which actually transmits using included hardware only.

by lxgr

5/19/2026 at 11:35:28 AM

Very funny.

However, your analogy is not equivalent to, nor an example for, what I said. There's a difference between a phone's own USB/audiojack interfaces and a wall outlet.

by lovelearning

5/19/2026 at 11:11:11 AM

[flagged]

by mashijian

5/19/2026 at 12:36:02 PM

[flagged]

by mystraline

5/19/2026 at 1:08:05 PM

Practically, this take emphasizes my point on repeaters. Each open active repeater develops its own subculture. (That said, the overwhelming majority of repeaters in the US are idle.)

You may not be welcome on any given repeater.

by souterrain

5/19/2026 at 12:57:24 PM

The only hams I ever enjoyed talking to were SOTA chasers when I was the activator. Bit of an all day job, and therefore something I don't really have time to do.

by jimnotgym

5/19/2026 at 1:25:06 PM

"Ham radio is like Chatroulette in that you don't know which old man at the other end of the ionosphere you're going to end up talking with."

by kotaKat