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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

#41

Post by souterrain »

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?

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.

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

#42

Post by mystraline »

asdff wrote: post #26
fodmap wrote: post #18

Earlier quoted context omitted.

Most of the time they get a complaint, and they investigate. https://www.fcc.gov/reports-research/guides/fcc-enforcement-...

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.

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

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

#43

Post by thenthenthen »

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.

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

#45

Post by jimnotgym »

FabCH wrote: post #8
alexwwang wrote: post #7

Earlier quoted context omitted.

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

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…

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

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

#46

Post by souterrain »

mystraline wrote: post #40

[flagged]

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.

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

#47

Post by souterrain »

Kaliboy wrote: post #5
RobotToaster wrote: post #2

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

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.

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.

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

#49

Post by souterrain »

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?

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.

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

#50

Post by quietsegfault »

souterrain wrote: post #41
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?

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.

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.
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