2w transmitters

[powerlord]

http://www.uuustore.com/boscame-58-ghz-2000mw-video-tx-rx-transmitter-receiver-58g-2w-p-9.html


Not that I am suggesting they should be used in the UK...  Cough.

Be interested to know of any real world tests though...

Stu

Sent from my HTC One using Tapatalk 4

[QuadBod]

If I';ve got my sums right they should give you twice the distance of a 200mW transmitter, and about 4.5 times the distance of a UK legal (for unlicensed use) 25mW transmitter.

Power is nothing, antennas are everything!*

(*Okay, not really, but power and distance are in no way proportional. Inverse square if anyone cares!  https://en.wikipedia.org/wiki/Inverse-square_law)

[powerlord]

Yup that is true of course.  But more is still more....

Sent from my HTC One using Tapatalk 4

[teslahed]

The problem is it will also draw more power, generate more heat and quite possibly produce more noise to effect other electrical items and radio systems on the quadcopter. You get twice the range of 200mW but 10 x the power draw / interference issues etc. More is more - but more of the bad as well as more of the good.

I would suggest spending the money on a better receiver, possibly with diversity, and some good antennas. If you want long range then mixing direction and omni directional with a diversity receiver will give you good results.

[powerlord]

I';m not buying one!  I just posted the link for interest as I hadn';t see 2w ones before.  I';m happy with my setup. Not sure your calculations are right though?  You double the range each time you multiply the tx power by 4. So I make that over 8x distance of 25mw.  (which would be 1600)

Sent from my HTC One using Tapatalk 4

[kilby]

The essentially inverse square requires to square the values not simply multiply by 4 (you also have to pull Pi into it as spherical areas are usually involved)

It produces a very rapid rise in transmission power required.

clipped from http://www.mpoweruk.com/radio.htm

Radiation and the Inverse Square Law
The rate at which energy emanating from a fixed, constant source of electromagnetic radiation passes through a surface at a distance d from the source is proportional to 1/d2. This is known as the Inverse Square Law. It arises simply because the surface enclosing the source is a sphere, centred on the source, through which all the energy must pass and the surface area of this sphere increases as the square of the distance d from the source. Thus the energy flow (measured in Watts per square metre (W/m2)) falls off rapidly as the distance from the source increases.

/clipped


Watts (along with decibels) are another one that can casue issues at times, the time I have spent (read wasted) with guitarists that can';t get their heads around that a 100W amp is only around twice as loud as their practice amp

[powerlord]

http://en.wikipedia.org/wiki/Inverse-square_law

makes it clear with some diagrams.

I still think I';m correct - I think Quadbod just ';squared the square'; by mistake.

Same law applies to light after all (you need a light 4x as bright at source to double the brightness at a particular distance)

So back to our video transmission:

to get the same signal strength twice as far away needs 4x the power (2^2)
to get the same signal strength  4x as far away needs 16x the power (4^2)
to get the same signal strength 8x far away needs 64x the power (8^2)
to get the same signal strength 9x far away needs 81x the power (9^2)

81x25 = 2025 - so more than we';ve got
64x25 = 1600

So we can say that we will get more than 8x the range with 2000mw over 25mw.

Of course, hte nature of 5.8ghz means no matter what the power a few trees will block the signal however strong it is, but there u go.

64 TIMES the power to get 8x the distance is still a lot of power, just not as much as QuadBods calculation, which would have led to 8x the distance needing 8W.

stu

[KeithW]

have led to 8x the distance needing 8W.

It';s not all about power levels...path loss is very important at microwave frequencies.What pays off in all cases where extended range is required are efficient antennas.

[kilby]

In the real world you always require more than a multiplier of 4 to double the distance.

Frequency and antenna design (and quality) can make absolutely massive improvements

[QuadBod]

In the real world you always require more than a multiplier of 4 to double the distance.

Yes, I got my figures from a table that was supposed to show ';real-world'; ratios, but the power figures were not exactly the same as those we typically come across for FPV, so my ';calculations'; were more a bit of mental fudge to adjust accordingly.

The truth of the pudding is in the flying of course, but the point still stands that an 80x increase in power isn';t an 80x increase in distance, and as teslahed says, unless (and possibly even if) you have a very high quality transmitter, it';s going to bleed all over your RC TX, so the only thing you';ll see over FPV is your beloved multi-rotor disappearing into the distance! 

[powerlord]

You started at 100 though. 

1.3 x2 = 1.7. (ie less than the 2x theoretical I had).  Apart from that,  same formula.  Start with a nominal 1km at 25mw, end up with 4.8km at 1600mw. (say 5 for 2k)

So 5X actual increase in distance for 64X more more, rather than the theoretical 8x (CHECK: 8/1.7 = 4.7ish so it all matches up)

Yup I';ve read Bruce';s stuff before on his blog.  Unfortunately nothing seems to have happened on there for a while -  I was watching for his diversity design circuits, but no updates it a year.... :-(

[powerlord]

ah - just had a google hunt again for the blog, but came up with someone else posting schematics - looks pretty straight forward.

http://www.rcgroups.com/forums/showthread.php?t=1661980

Be an interesting project - really no need for quad flying I suppose - who flies their quad 10km away ??, but would be interesting none the less. I was thinking it would be useful for a space flight - i.e. helium balloon job to 130K I';d still like to try at some time.

stu

[QuadBod]

Looks like a fair amount of work when you can by di / tri / quad -versity receivers off-the-shelf.

So I';m curious, what';s the greatest distance with acceptable picture quality you can realistically achieve with a 25mW transmitter and suitable receiver antenna combo (that doesn';t have such a narrow field of view as to restrict flying).

[powerlord]

Yup.  10 quid vs 100 quid though. 

Sent from my HTC One using Tapatalk 4

[QuadBod]

Not quite, because you still need two receivers, and then there';s the opportunity cost of the time spent building it.

Of course if you already have two receivers, and fancy the challenge, then it may be worth it, but I suspect by the time you add the case, fan and connectors, circuit board and components,  the build cost is way more than £10.

I';m all for a good DIY project though!

[powerlord]

Not quite, because you still need two receivers, and then there';s the opportunity cost of the time spent building it.

Of course if you already have two receivers, and fancy the challenge, then it may be worth it, but I suspect by the time you add the case, fan and connectors, circuit board and components,  the build cost is way more than £10.

I';m all for a good DIY project though!

True.  As you say,  I have all the spare kit lying around so hadn';t considered costs of starting from scratch and needing RX etc. But for the base thing it really is just pennies.  A arduino mini pro is 3 quid.  Rest of components are less than a quid total.

Sent from my HTC One using Tapatalk 4