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I am looking for more range and fewer dropouts.

I am currently using a falsweb 2.4ghs 500mw system and a 10db circ flat antenna. with resonable results but still getting dropouts at 400yds or less.

I have seen amplifiers mentioned a number of times in varioius threads as one way to increase range. These seem to take the form of either really small ic's that are surface mounted somewhere in the RX antenna line, or prebuilt amps.

Any imput from users of these systems? I also see by directional wifi amps on ebay with recieve gains of 11-21 db. Will these work in recieve only mode for video?

http://www.minikits.com.au/kits2.html

Sells a number of preamp kits, anyone use one of these to extend range?

Any amp will also amplify any noise, so will these really help much, in a mixed suburban environment?

I am also looking at the diversity receiver as another option. It's pretty expensive, but seems to really help those dropouts.

Any help????

Thanks!

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dropouts at 400yds or less.

That is a bit of a worry, are you flying near buildings ? Are you flying aerobatics ?

If either of these a diversity system may well help, also remember your TX aerial needs a clear path to the RX aerial, no bits of the plane in the way and needs to be as side on as you can get.

A preamp won't help much at this range. It will be worth you checking all your connections to the aerials as this seems likely if your total range is very poor.

I had the top half of my aerial on the plane break inside the heatshrink and it kept me guessing for a while.

Terry

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Lupy excuse my question but.

Where did you buy your receiver and transmitter from?

Did you buy the TX and RX from the same place, or each one came from different place ?

Where do you have your Rx anntena placed at?

I have a routine flying at 1000 feet high and 1/2 mile with 2.4ghz 500mw and I have no problems with video drops,

Make sure about few things:

- Patch antennas needs to pointed towards the transmitter

- The closer to the ground you fly, the worse video you get.

- Bad coax cable, plane gear ( i.e. motor, ESC. ), bad wire connectors would cause problem as well.

I strong believe that, you will not have any improviments with amplifiers, unless you find out what is causing the drops.

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The xmitter and receiver are a Falsweb set. I am using the DIY groundplane antenna as described here:

http://www.yb2normal.com/antenna3.html

I have tried several others, but none seem to work any better. The Falsweb unit comes with no connectors, so the antenna is soldered directly to the xmitter and runs through a short length of coax. As I said, I have tried several different antennas and lengths of coax, and I am currently using the best I have seen. I also have several of the Airwave xmitters, and have found the falsweb to have a slight advantage, it also draws more current. I am using a separate battery with a 5v non switching reg.

I am flying a seaplane, as I live on a lake. My current plane is a Donald, which has a glass fuse, so I have had the antenna mounted in the nose of the fuse, pointing down. I supose the thin glass fuse could be killing the xmitter, but I would think hanging it from under a wing would be even worse, since at times the signal would have to pass through all of the plane. I have a spare canopy, so I can try putting the tip of the antenna through a small hole in the canopy, But then the signal is going more up than down.

I am running a axi 2212-26 with a CC25 esc. I get no difference with motor run.

I am using a luxul 10db circ patch antenna, which was an improvment over the GPP I was using. It is directional, but even when pointed directly at the plane, I am getting dropouts.

I realise that 2.4ghz isn't ideal around water, and I have thought about going to 900mhz, but I have heard so many problems with the various 900mhz systems, that I am a little gun shy at this point. The 2.4 seems to have the benifit of a much larger knowledge base, and the latest technology.

Light at a high angle will bounce off of water, is there any chance I am getting 2.4ghz reflections off the water that cause multi path?

I'm going to have to wait untill the ice melts before doing much. I am in the Seattle area, and it's been unusually cold these last few weeks.

Thanks for the pointers, it's hard to tell what I should be getting.

Ken

Edited by Lupy

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I believe that water can cause mulit path problems. You might try varying the height of the rx above the water to see if you can reduce it.

god luck.

B.

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2 things. can you post a pic of your plane/tx aerial. can you test fly over land ?

Terry

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Here are a couple of pics. I have tried several antennas and placements, but all have been within 5ft or so of the water. I can try mounting it higher, but with a patch, adjusting direction is more of a problem.

I will see if there is somewhere I can fly that isn't over water. but I will have to change the settup. The Donald isn't really set up to land on land, as it's a glass fuse. I supose there might be some tall grass somewhere.

I am re-thinking my 900mhz opinions, the videos on:

http://www.rcdon.com/html/video_cub_high_flight.html

Show a flight to ~8000ft, there is some interferance in rolls and loops, but it is so much better than my results.

A .5watt system as he used can be had for about $165 less camera. So it's a lot cheaper than a diversity system.

I just don't understand why some others have had so many problems with these 900mhz systems.

post-2-1170379200_thumb.jpg

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I just don't understand why some others have had so many problems with these 900mhz systems.

I see that rcdon used the Supercircuits 900Mhz video system. The one I used was a Supercircuits model and it worked fine for me. So, if you go to 900Mhz, I suggest the Supercircuits system since it is a known entity.

Have you tried your Tx GP antenna on top of the model, far away from all the wiring and metal parts in the model? This will probably mean the Tx must move too, but for a test that should not be too nasty to try.

BTW, your poor results could just be due to a poor performing video Tx or Rx. Sometimes these sort of things are born that way. Too bad you don't have a known working Lawmate system to drop in for a comparison.

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The tx aerial position is far from ideal, the fus/hull when wet will mess up the signal. I would mount the aerial on a servo swivel so it can be deployed like landing gear below the fus/hul.

Mr RC-CAM's idea to put the aerial high will be better than what you have now but you will still get parts of the aircraft blanking the signal at times.

And as he says you may just have a bad componant !

Terry

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Indeed, if we add that quite a few here have had bad performing Felsweb RXs. Mine gave at least 1/3rd of the range I'd get with another RX, I already had lots of dropouts at 500m...

Edited by Kilrah

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I tried with several differents coax and always get lot of video dropout. The sma connector is weld directly to the case, don`t use coax cable with Felweb tx/rx

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I will try putting a sma connector on my rx. and see if that improves things. Do you have a pic of your sma connector on your Falsweb RX? I also have a couple of Airwave Tx and RX units, so I may try with them first.

Thanks for all the help. It would be nice if i could get this system would work, but I am very tempted to just ditch it and start over.

Terry, the idea of a retractable antenna is interesting, but I think it would get wet on take off.

The 900mhz systems seem to be a lot more tolerant of antenna placement. I also have a very nice all weather ground plane antenna from an engenius 900mhz cordles phone. Sticking with 2.4ghz is tempting though, given the bigger knowledge base.

I will do an across the lake test tomorrow with the antenna in the fuse and then facing up. That should at least give me something to go on.

Thanks for the ideas

Ken

post-2-1170467024_thumb.jpg

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the sma is weld to the case and the antenna is plug in the connector. I never use any coax cable between antenna and tx or rx.

post-2-1170471396_thumb.jpg

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Good luck with the testing Ken, I will be interested to hear your results.

Terry

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I ordered some parts off ebay, I will try them and report back.

I looked at the description of installing the sma connector. MR. cam, what is the purpose of cutting the case? Wouldn't it be easier to just shorten the 4 lugs and solder directly to the case? Also, is there a critical distance between the base of the sma connector and the tin case? It looks like about .175" on the one in the pic

Thanks

Ken

Edited by Lupy

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what is the purpose of cutting the case?

It allows the SMA to get a very rigid mount on the tin case.

is there a critical distance between the base of the sma connector and the tin case?

The SMA distance on the Airwave installation is due to the PCB that extends outside its case.

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if receiver is not good, low sencitivity, adding a preamp LNA low noice Amplifier will increase the range, adding 10dB gain with no noice added, will be the same as adding 10db to the transmitter, example to go from 500mW to 5W

adding 10dB will trible your range.

The latest receivers are quite good, but I am sure 10dB extra could be achived,

I will make a super LNA next week at work, and see if it does what I predict.

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That's one of the reasons I was looking at the preamps. of course, if the signal is getting lost in general background noise, then the preamp won't help, as the background will be amplified too. I asume that a notch filter somewhere might help too. though I'm not sure how to go about putting one in.

http://www.minikits.com.au/kits2.html#eme157

I was looking at the eme103 kitD, 1.6dB NF & 24.5dB gain @ 2400MHz.

I read about a rocketry project that used one though, and he reported no better range.

I am awaiting the last of my connectors, then I can give the sma connectors a go

Ken

Edited by Lupy

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if the signal is getting lost in general background noise, then the preamp won't help, as the background will be amplified too

Yes, that is the purpose of your receiving aerial, it's job is to increase the wanted signal more that the background noise. It dose not amplify the signal as such it just moves the capture area.

adding a preamp LNA low noice Amplifier will increase the range, adding 10dB gain with no noice added

I'm sorry to say noise will always be added, thats what the NF is.

will be the same as adding 10db to the transmitter, example to go from 500mW to 5W

adding 10dB will trible your range.

Due to the Noise Figure this dose not work out in practice. The improvment seen will depend on all the other parts of the receiving system.

Back in 1998 when I first started using 2.4Ghz video the receivers availible were very poor compared to today, I was luck to get 100ft with my 10mW TX. Today a RX module with the same aerial will give me 1/4 mile, the Noise Figure is the answer why. Back then I added a pre-amp with 0.3NF HERE and the system was transformed giving over 1/4 mile. If I add the same preamp to a modern RX it still gives an improvment but only a little. You only need the GAIN of a pre-amp if there is a loss ( if you are using co-ax from aerial to RX ) .

I asume that a notch filter somewhere might help too

Yes it may well, I have thought about this to knock out the broardband wireless router noise I am getting. If used it should be fitted between the pre-amp and RX. However I have not found one suitable yet. :(

I hope this makes things more clear for you, let us know how your testing goes. :)

Terry

Edited by Terry

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Hi Terry,

-91 secitivity measured the other day on a brand new 8ch rc from black widow,

is not impressive.

and yes 0.3 to 0.5NF is possible today, then I still say it must be possible to get 10dB extra on the link budget = longer range or much better marging within the range you use = less dropouts.

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Hi Thomas, I agree not all RX's today are great, I've had differing performance from the 4 modules on my 4 way diversity system and for sure it could be improved with pre-amps but 4 of them would blow my budget. I switch to another aerial when over 1/4 mile anyway so its not justified.

I may be wrong but 10db with a pre-amp = 500mW to 5W dose not sound right to me, anyone ?

If I use an aerial with 10db more gain than the one I use before I get far more range than if I increase the TX to 5W from 500mW.

Anyway the bottom line is that it is very complicated and depends on all the componants in the system, you can't predict the same results of changing one thing on systems that are not identical.

I'm happy to be proved wrong if you can prove it in practice, I've been on a steep learning curve since 1998 and its still climbing :P

All the best, Terry

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10db with a pre-amp = 500mW to 5W dose not sound right to me, anyone ?

3dB = 2x more power. 9dB = 2x2x2x more power = 8x more power, so 10dB =~10x more power =~3x more range. (Was too lazy to fetch the calculator ;) )

-91 seems pretty good, video RXs I've actually seen specs for were never better than ~-85dBm.

We have to keep in mind it's not a low bandwidth digital signal where -100 to -105 is common, but a high bandwidth analog signal...

Edited by Kilrah

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