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Old Aug 03, 2011, 02:35 AM
Living in the south of France
paulinfrance's Avatar
Joined Aug 2011
442 Posts
Can anyone help me please

Hi,
logging in on your site for the first time, 59 years young, all forms of modeling, from Free flight, control line etc,,,, up tu a turbine Rafale, passing by Helicopters,,,, but at the moment i am having some trouble with my new FPV set, i have been flying FPV on and off for the last 9 years on 2.4 giga, but with my club flying mostly on 2.4 giga i had to find a new frequency for my setup, i bought this,
http://www.bevrc.com/bev-13g-400mw-p-242.html
having some serious distance and quality problems till it was suggested i tried the channel 'H', which solved the problems with the 400 mw set but now my problem is that i have 'twiddled' with most of the Dip switches on this
http://www.bevrc.com/bev-12ghz-200mw...-fpv-p-42.html
and i still cannot find a 'good' one to fly on, has anyone out there the plan for these switches so that i can set them up ?, or any other suggestions ?, i don't mind a 'rubber duck antenna but after flying the last 9 years with a patch which means that you have to keep your head in the direction of the plane which is very annoying.
I have also an axe to grind with Futaba, do i whinge here ? elsewhere ? after a few more 'posts' ? or just shut up ?.
thanks Paul.
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Old Aug 03, 2011, 02:50 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
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You should be able to get 1km or more FPV video with stock dipole antennas on 400mw.

Both antennas vertical, and the receiver/antenna mounted up off the ground on a plastic pole.

The antennas that come with that are the good dipole kind that are fat at the bottom and skinny at the top ( as long as they are actually the correct frequency).

As to which frequency, the best is the legal ones. Really. It is best to use just the ones that are legal in your country.

FPV transmitters can reduce the range of RC.

1.2g fpv or 1.3 fpv is very close to half of 2.4g RC. If you are flying 2.4g RC with 1.2 or 1.3, you need an antenna low pass filter to keep the FPV transmitter from transmitting on the 2.4g harmonic.

If you are not flying 2.4g RC, you should have a dual conversion receiver. The cheap Corona RP8D1 receiver is known to work well with 1.2 and 1.3 FPV transmitters. One of my planes has a 72mhz Corona with 1280mhz FPV.

Of course, you still must mount the FPV antenna far away from the RC receiver and antenna.

Cliff
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Last edited by theothercliff; Aug 03, 2011 at 02:59 AM.
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Old Aug 03, 2011, 06:09 AM
Living in the south of France
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Joined Aug 2011
442 Posts
Quote;
with 1.2 or 1.3, you need an antenna low pass filter to keep the FPV transmitter from transmitting on the 2.4g harmonic.

Whats that ?.

I have found the frequences on the 200 mw TX,
http://www.bevrc.com/bev-12ghz-200mw...-fpv-p-42.html
D dip switch down U = up.
DDDU channel 4 = 1.080 mhz
DDUD = 5 = 1.120mhz
DUDD =6 = 1.160
UDDD =7 = 1.200
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Old Aug 03, 2011, 07:11 AM
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Quote:
Originally Posted by theothercliff View Post
. If you are flying 2.4g RC with 1.2 or 1.3, you need an antenna low pass filter to keep the FPV transmitter from transmitting on the 2.4g harmonic.

Cliff
That's incorrect - you don't NEED a low pass filter. They make such a small difference it's almost not worth it.
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Old Aug 03, 2011, 10:58 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
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Quote:
Originally Posted by AP_OZ View Post
Quote:
Originally Posted by theothercliff View Post
If you are flying 2.4g RC with 1.2 or 1.3, you need an antenna low pass filter to keep the FPV transmitter from transmitting on the 2.4g harmonic.
That's incorrect - you don't NEED a low pass filter. They make such a small difference it's almost not worth it.
I don't fly 2.4g RC, but if I take an average of what people say about it, I find that most say the RC range is reduced without a low pass filter; with smaller airplanes and closer spaced components being affected worse. OMM and Rusty even designed a dual notch filter to keep from splattering on both 2.4g RC and GPS.

Ahh... you did say almost not worth it.

Cliff
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Old Aug 03, 2011, 11:23 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
3,132 Posts
Quote:
Originally Posted by paulinfrance View Post
Quote;
with 1.2 or 1.3, you need an antenna low pass filter to keep the FPV transmitter from transmitting on the 2.4g harmonic.

Whats that ?.

I have found the frequences on the 200 mw TX,
http://www.bevrc.com/bev-12ghz-200mw...-fpv-p-42.html
D dip switch down U = up.
DDDU channel 4 = 1.080 mhz
DDUD = 5 = 1.120mhz
DUDD =6 = 1.160
UDDD =7 = 1.200
Just like a guitar string at 440hz will also produce sound at 880hz and 1320Hz and ..., the FPV on 1150mhz to 1300mhz will produce output on 2300mhz to 2600mhz which is close enough to the 2.4g RC (on 2400 to 2500) to cause problems. A 1300mhz low pass filter will allow frequencies at or below 1300mhz to pass to the antenna, but block the higher harmonics around 2450mhz from getting to the transmitting antenna. A dual notch filter shorts two frequencies to ground to keep from transmitting them. Those frequencies are 2450mhz and 1575mhz. 1575mhz is a GPS frequency.

In the USA, those frequencies for the 200mw unit are used for full sized airplane radio-navigation. I believe that they are also used that way internationally.

The best thing is to look up and use the legal frequencies for your country.

Cliff
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Old Aug 03, 2011, 07:53 PM
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Quote:
Originally Posted by theothercliff View Post
I don't fly 2.4g RC, but if I take an average of what people say about it, I find that most say the RC range is reduced without a low pass filter; with smaller airplanes and closer spaced components being affected worse. OMM and Rusty even designed a dual notch filter to keep from splattering on both 2.4g RC and GPS.

Ahh... you did say almost not worth it.

Cliff
I did extensive practical testing with low pass filters on the 900mhz & 1.2ghz bands and found very little reward in using them. The range differences were generally around 5%-10% which is negligible in my opinion considering most of my aircraft are quite quick and that extra 5m to 10m per 100m just isnt worth it particularly when you shouldnt really be pushing out to you maximum range for safety reasons.

This is just another case of the text book data and practical data being different.

Just my opinion..
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Old Aug 03, 2011, 10:21 PM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
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Quote:
Originally Posted by AP_OZ View Post
I did extensive practical testing with low pass filters on the 900mhz & 1.2ghz bands and found very little reward in using them. The range differences were generally around 5%-10% which is negligible in my opinion considering most of my aircraft are quite quick and that extra 5m to 10m per 100m just isnt worth it particularly when you shouldnt really be pushing out to you maximum range for safety reasons.

This is just another case of the text book data and practical data being different.

Just my opinion..
And if your 1280mhz FPV antenna had been closer to your 2.4g RC antennas you would have seen a larger difference in range.

This discussion has all been about the effects of FPV transmitters on 2.4g RC. I just want to reiterate that. Harmonics from 900mhz and 1.2g (the common definition for 1.2g being 980 to 1200) aren't as close as the harmonics from 1.3g (1240 to 1360).

For the common case of 2.4g RC and 1280mhz FPV perhaps the reader should take away from this discussion that they need to do their own RC ground range testing (and GPS testing) with the FPV transmitter on vs. off, and consider an FPV antenna filter if the range decreases too much with the FPV transmitter on.

Cliff
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Old Aug 04, 2011, 06:27 AM
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Quote:
Originally Posted by AP_OZ View Post
I did extensive practical testing with low pass filters on the 900mhz & 1.2ghz bands and found very little reward in using them. The range differences were generally around 5%-10% which is negligible in my opinion considering most of my aircraft are quite quick and that extra 5m to 10m per 100m just isnt worth it particularly when you shouldnt really be pushing out to you maximum range for safety reasons.

This is just another case of the text book data and practical data being different.

Just my opinion..
Most people will notice zero gain of any type with a low pass filter. The reason the filter does not increase range is that generally the noise floor is well above the sensitivity level of the RX so increasing it's sensitivity does not yield any real gain. Of course if You have a poorly tuned antenna and an unusually noisy RX, the low pass filter will certainly help.

-Alex
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Old Aug 04, 2011, 10:05 AM
FPV Browncoat
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United States, CO, Parker
Joined Mar 2011
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Hmm, that's interesting. I was under the impression a low pass filter was absolutely essential to fly 1.2ghz video and 2.4ghz RC control. Did I just waste $30 buying one for the FPV system I'm assembling?
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Old Aug 05, 2011, 01:14 AM
John
United States, WA, Mason
Joined Apr 2011
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After destroying my "Skywalker", I am testing my electronics to put back into a new plane. Most everything seems to be OK other than I can't get a picture out of my Vrx. I know the GoPro is putting out live feed. I assume since nothing really happened to the Vrx that it is probably OK. That leaves the OSD or the Vtx. Since the Vtx broke off the antenna and layed on the ground for an hour with battery still hooked up, does that pretty well mean that would ruin it for sure? Is there an easy way to test it? -- thanks, JOHN
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Old Aug 06, 2011, 01:47 AM
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Are you saying this that it would increase the range of the video link or rc link? Isn't the purpose of getting a low pass filter to increase rc range? And you are saying it doesn't increase it?

Here is a clear example of rc range being severly reduced if no filter was used:

http://www.rcgroups.com/forums/showp...&postcount=148

http://www.rcgroups.com/forums/showp...&postcount=151



Quote:
Originally Posted by IBCrazy View Post
Most people will notice zero gain of any type with a low pass filter. The reason the filter does not increase range is that generally the noise floor is well above the sensitivity level of the RX so increasing it's sensitivity does not yield any real gain. Of course if You have a poorly tuned antenna and an unusually noisy RX, the low pass filter will certainly help.

-Alex
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Old Aug 06, 2011, 10:01 AM
Engineer for Christ
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A low pass filter removes the harmonics of a system. At 1.3GHz, the second order harmonic is 2560MHz, which is well outside the 2.4GHz band. Also, this harmonic is typically very small. The third order harmonic is the killer. Luckily, we have no control systems on that band. Now if you are flying 1200 or 1240 MHz, the filter will help you.

This also assumes that you use adequate separation. All the filtering in the world will not help you if you place your components right on top of each other.

-Alex
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Old Aug 07, 2011, 03:34 AM
Living in the south of France
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Joined Aug 2011
442 Posts
filter

Thanks for the feedback, my 1.2 ghz RX ant antenna are on my head ( avatar)
and my radio on 41.100 mhz and 2.4 ghz is at waist height will the 'filter' help ?.
Below is the comment that i put on the "bevrs" site to get some feedback on the 200 mw system that is giving more problems than it is worth, sometimes loosing the picture on 'finals' less than 30 meters away !.




Hi, After having problems with the club fliers on 2.4 ghz i decided to change my old system from 2.4 ghz to 1.2 ghz, i first ordered the 400mw system but i had a lot of problems on distance and quality on the system but the only one that gave me a good image feedback is the channel 'H' which with the standard antenna gives over 600 meters, (at 200 meters high) switching to my 200 mw system all i managed was 60 to 80 meters and lousy distorted images, i fiddled with the 'dip' switches for hours as there are NO instructions on the site, No feedback and No answers from bevrs 'customer service' (mails), i found at least 5 positions that gave me an good image on the channel 4 but flying was a disaster !, i eventually flew on channel 6 which gave me an acceptable picture but only below a distance of 100 meters does anyone have a plan for the frequencies ?, and any suggestions for another antenna (NOT a patch ) ?, thanks Paul.
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Old Aug 07, 2011, 02:13 PM
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Someone please help!

It has been nearly two months since RangeVideo recieved the package I sent concerning the problem with my FPV- they will not answer e-mail, phone, and God knows where this thing is! How can I contact them and does anybody know them I am so frusterated!!! There was almost $300 worth of stuff in there!
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