51–60 of 86 posts
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?
> 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.
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
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.
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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.
With a ham license the limit is 1.5kW, without one its zero
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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?
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…
Is it still worth it to mess around with older full duplex handhelds ?
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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
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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.
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…
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.)
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.
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.