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

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

#61

Post by gh02t »

sfmike wrote: post #24
alexwwang wrote: post #7

Earlier quoted context omitted.

Agree. We need a compact short wave transceiver device actually.

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

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.

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

#62

Post by wolvoleo »

lxgr wrote: post #59
thenthenthen wrote: post #43

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.

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 a…

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.

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

#63

Post by jonah »

alexwwang wrote: post #7
Crunchified wrote: post #6

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.

Agree. We need a compact short wave transceiver device actually.

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

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

#64

Post by Bender »

gh02t wrote: post #55
Bender wrote: post #35

Earlier quoted context omitted.

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 usua…

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 ve…

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

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

#65

Post by lovelearning »

Crunchified wrote: post #22
lovelearning wrote: post #16

Earlier quoted context omitted.

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…

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 tha…

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

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

#67

Post by topspin »

iberator wrote: post #39
topspin wrote: post #20

Earlier quoted context omitted.

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

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

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.

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

#68

Post by wolvoleo »

Retr0id wrote: post #51
s03nk3 wrote: post #10

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?

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-...

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.

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

#69

Post by giantg2 »

lxgr wrote: post #23
landgenoot wrote: post #13

> 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?

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.

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.

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

#70

Post by euroderf »

wolvoleo wrote: post #62
lxgr wrote: post #59

Earlier quoted context omitted.

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 a…

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.

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