NIVIS is intended to be used between actual mountains. You know, these kilometer tall things of rock. There’s a hundred-kilometer reflector dish above you, courtesy of the home planet. An urban canyon will only protect you from direction finding, it won’t prevent you from being heard 200 km away. At a distance of 10 km or 20 km, you don’t even want to be heard, and NVIS makes it conveniently hard to hear you at close range.
this is just a really extravagant heater
Which of them? The Swedish guy’s copper tape antenna? Maybe, but it seems to receive nicely.
for your contrived below noise communications scheme, you need more bandwidth that is physically possible on hf,
I know that communicating at the noise floor is not suitable for HF. I did not intend to give that impression. Same for balloons. When you have a line of sight, you choose higher frequencies, isn’t that logical without telling?
with what power source?
High altitude pseudosatellites (I advise to look up the term, they’re fun) almost unexceptionally use battery and solar. I don’t propose carrying a steam engine. :) A LiPo cell will output 100 amps and more. You wait and charge, then work, then wait again. No need to run at 100% duty cycle.
better study for and get your license
For what? To make drones find their way home better? I’m not a radio amateur and I don’t need or intend to be. I build stuff that flies, uses gigahertz frequencies and navigates using radio when fiber runs out and snaps. I admit I know little of HF, but I know the basics acceptably. No need to assume a holier than thou attitude.
5500kbps in extremely favourable conditions is your peak attainable speed
Well, some people write: “In [112] we find measurements on a MIL-STD-188-110C [113] link over distances of up to 160 km, providing the users with bit rates up to 9.6 kbps in 6–9 kHz RF bandwidth.”
Maybe they’re wrong, maybe I read them lazily. Regardless, you can send SMS, teletype or something comparable just as nicely with 5 kilobits per second as you can with 9 kilobits. But as I said, I haven’t tested and don’t intend to test. I approximately know what HF does and how it propagates, but don’t use that band in practise.
By the way, the same people write:
In [5] a car-mounted vertical half loop antenna is described, using capacitance loading to achieve an NVIS antenna gain between −12 and −10 dBi from 3 to 8 MHz.
So yes, a car roof antenna definitely is a heater. Probably much more of a heater than the ones I linked to. You need much power to make it radiate. Now let’s grab a presumably representative example of such a heater, and its real world performance:
Seller self-promotion (grain of salt advised): “As the 2018 predominantly radiates RF energy towards the ionosphere as a vehicle mounted NVIS (Near Vertical Incidence Sky wave) antenna, it is effective in overcoming the skip zone common in whip based antenna systems providing superior operation in the range of 30 to 150 kms. For the same reason the 2018 antenna is highly effective for communication in mountainous areas.”
Maybe you should refresh your information about ionosphere-using comms. I have refreshed mine recently. Not for a practical reason but curiosity. You absolutely don’t need an crazy big antenna. One person can carry all that’s required. Bur of course, not in a pocket, but a backpack.
A PDF I can recommend is here. It also proposes “tent antennas” (inverted V antennas) that are portable, but need putting a pole in ground.
and stop embarrassing yourself
I’m not embarrassed. I am not qualified to teach radio to a radio amateur, even if it seems that I should. I just pass on some tips. I also remind: holier than thou will get you two word answers from most people. I don’t need your goodwill. I don’t need to give a **** or be patient. I reply because I think you are missing out on some methods of communication that some people actually like. From what I’ve heard, ionosphere bounces are fun and practical.
NIVIS is intended to be used between actual mountains. You know, these kilometer tall things of rock. There’s a hundred-kilometer reflector dish above you, courtesy of the home planet. An urban canyon will only protect you from direction finding, it won’t prevent you from being heard 200 km away. At a distance of 10 km or 20 km, you don’t even want to be heard, and NVIS makes it conveniently hard to hear you at close range.
Which of them? The Swedish guy’s copper tape antenna? Maybe, but it seems to receive nicely.
I know that communicating at the noise floor is not suitable for HF. I did not intend to give that impression. Same for balloons. When you have a line of sight, you choose higher frequencies, isn’t that logical without telling?
High altitude pseudosatellites (I advise to look up the term, they’re fun) almost unexceptionally use battery and solar. I don’t propose carrying a steam engine. :) A LiPo cell will output 100 amps and more. You wait and charge, then work, then wait again. No need to run at 100% duty cycle.
For what? To make drones find their way home better? I’m not a radio amateur and I don’t need or intend to be. I build stuff that flies, uses gigahertz frequencies and navigates using radio when fiber runs out and snaps. I admit I know little of HF, but I know the basics acceptably. No need to assume a holier than thou attitude.
Well, some people write: “In [112] we find measurements on a MIL-STD-188-110C [113] link over distances of up to 160 km, providing the users with bit rates up to 9.6 kbps in 6–9 kHz RF bandwidth.”
Maybe they’re wrong, maybe I read them lazily. Regardless, you can send SMS, teletype or something comparable just as nicely with 5 kilobits per second as you can with 9 kilobits. But as I said, I haven’t tested and don’t intend to test. I approximately know what HF does and how it propagates, but don’t use that band in practise.
By the way, the same people write:
So yes, a car roof antenna definitely is a heater. Probably much more of a heater than the ones I linked to. You need much power to make it radiate. Now let’s grab a presumably representative example of such a heater, and its real world performance:
https://airadio.com/hf-ssb-commercial/barrett-communications/2018-mobile-magnetic-loop-hf-antenna
Seller self-promotion (grain of salt advised): “As the 2018 predominantly radiates RF energy towards the ionosphere as a vehicle mounted NVIS (Near Vertical Incidence Sky wave) antenna, it is effective in overcoming the skip zone common in whip based antenna systems providing superior operation in the range of 30 to 150 kms. For the same reason the 2018 antenna is highly effective for communication in mountainous areas.”
Maybe you should refresh your information about ionosphere-using comms. I have refreshed mine recently. Not for a practical reason but curiosity. You absolutely don’t need an crazy big antenna. One person can carry all that’s required. Bur of course, not in a pocket, but a backpack.
A PDF I can recommend is here. It also proposes “tent antennas” (inverted V antennas) that are portable, but need putting a pole in ground.
I’m not embarrassed. I am not qualified to teach radio to a radio amateur, even if it seems that I should. I just pass on some tips. I also remind: holier than thou will get you two word answers from most people. I don’t need your goodwill. I don’t need to give a **** or be patient. I reply because I think you are missing out on some methods of communication that some people actually like. From what I’ve heard, ionosphere bounces are fun and practical.
End of communications.