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Feb 25, 2017, 08:04 AM
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Hi

I'm new to the 1.3/1.2 game. Just treated my self too this lot. Looking forward to trying a dirty ground test on distance. I've got a filter to on the RX as you can see. I've seen a few with what looks alike a filter on the VTX. Anyone shead any light
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Feb 25, 2017, 02:41 PM
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Quote:
Originally Posted by Daemon View Post
Good luck with that unit. The standard digital display 1.3Ghz VRXs are generally considered
to be junk (they directly pick up 433Mhz LRS control signals as noise). This has been
discussed many times earlier in this thread. Nobody has ever found a fix
other than to pretty much replace the entire guts of the VRX with new components,
and even then the old Racewood style Rxs (4ch tan box) are still better at rejecting interference.
When I order FOX800 VTXs direct from Sunsky, they come with the same digital display VRX, and I
*literally* throw them in the trash.

Also you might be interested in the history of uuustore.
Start here (where they changed their name) and work back to their origins as rc4y
https://www.rcgroups.com/forums/show...n-answer/page8
They are spammers and scammers and literally started their business by
cloning another RC website (stocking none of the items they listed themselves).


That may be right, but I was able to achieve crystal clear video at 10KM range with that VRX and 433MHz system on 1240MHz with only the SAW filter mod.


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Feb 25, 2017, 02:43 PM
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Quote:
Originally Posted by changosurf View Post
thanks man.

The PIC MCU's in these things aren't programmable AFAIK.

If really necessary, a drop-in/spliced-in mini arduino will easily tune it to 1258 .

I can provide a schematic & sketch if needed.



I've basically given up on 1258, and am sticking exclusively to 1280 (for antenna builds & stuff).

It's a hassle having to deal with finding VRX & VTX gear that tunes to 1258.

Plus, I've still got that stupid FPV1000 DVR that nukes 1258, and I'd still like to try to get my money's worth from it, so 1258 is out if I still wanna use the DVR.


Were you able to retrieve the code from the MCU?

If so we could modify the code and use a programmable PIC with similar layout to tune the VRX.


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Feb 26, 2017, 03:15 AM
Quote:
Originally Posted by Roish View Post
Were you able to retrieve the code from the MCU?

If so we could modify the code and use a programmable PIC with similar layout to tune the VRX.


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From what I gathered when I looked into it, the PIC's in the 'Digital Display' units are not programmable; They're write-once ROM burned by the manufacturer. I was never able to find a pin-compatible replacement.

I don't know what type of MCU is in the racewood VRX's, but I'm assuming that it's going to be a similar problem.

The easiest solution is to simply bypass the PIC and tune the comtech tuner manually with an arduino via i2c. It's pretty simple to do. At a bare minimum, you'd need to wire up 4 wires: VCC to the 5V regulator within the VRX, GND, and two wires from a couple of digital pins on the arduino to the i2c pins on the comtech (i2c done via bit-banging). If you need to change channels, you could include some kind of push-button or switch connected to the arduino & mounted on the VRX case (or left hanging on a wire lead) that can be used to cycle through the desired channels.
Mar 05, 2017, 01:41 PM
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Abc
Last edited by bladexxl; Mar 06, 2017 at 02:31 PM.
Mar 19, 2017, 03:18 PM
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lkrustev's Avatar
Quote:
Originally Posted by artemen View Post
Hey, does anyone have experience/heared something about this 1w vtx?
http://www.ebay.com/itm/1-2GHZ-1W-10...cAAOSwEANXHLgh
Attachment 9787486

Thanks!
Those are good - I have several. All work well. Does not get too hot. Real power 600-800 mW
Mar 19, 2017, 04:03 PM
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I just got my tan RX from dpcav. Can't wait to test it out. Thinking about ways to mount it on my face with my goggles lol
Mar 20, 2017, 03:06 AM
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lkrustev's Avatar
Quote:
Originally Posted by elmtree View Post
I just got my tan RX from dpcav. Can't wait to test it out. Thinking about ways to mount it on my face with my goggles lol
Make a biquad, put the receiver directly connected on the back of it with L shape sma connector. Hang it on your neck.
Mar 20, 2017, 03:19 AM
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lkrustev's Avatar
Quote:
Originally Posted by Pete Wright View Post
Hi

I'm new to the 1.3/1.2 game. Just treated my self too this lot. Looking forward to trying a dirty ground test on distance. I've got a filter to on the RX as you can see. I've seen a few with what looks alike a filter on the VTX. Anyone shead any light
There are two cases in which you could need lowpass filters. Please, note that you may not need it if you pick the right channel.

Case 1: You are using 2.4 GHZ RC control, so you may need to use lowpass filter on the video TX to filter the 1.2 ghz first harmonic whic is right about the 2.4 GHZ band.

Case 2: You are using 433 MHz UHF RC control, so you may need lowpass filter on the UHF TX to minimise the interference with your 1.2 video receiver.

"I've got a filter to on the RX" - probably this is not the case, because you do not want to put anything on the RX input ... if it is not some highpass filter ... but anyway even if it is a highpass filter I wouldn't use it. If the receiver is good it should have a good SAW filter inside which should filter the UHF noise in a more efficient way. As I see your receiver should have a Comtech tuner with upgraded SAW filter, so forget about puting this thing on the RX.
Last edited by lkrustev; Mar 20, 2017 at 03:42 AM.
Mar 20, 2017, 06:07 PM
Registered User
Seems like the truerc singularity antennas are causing renewed interest in 1.3. With the fatshark receiver module it's now on par with 5.8 for lightweight use. There's even the 250mw fatshark vtx. Every time I go away for a few months the technology advances again
Mar 20, 2017, 11:40 PM
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Daemon's Avatar
FWIW the Singularity antenna is not lighter, and it has more total solid cross sectional area than
a simple cloverleaf. The only real advantage is that it sticks out less and *may* not not
get caught up up in the props of a small quad in a crash. You might be able to half bury it
in a thick aircraft wing, but can do the same with a cloverleaf and cut the drag by about half.

It's a solution to a pretty narrow problem. I haven't yet been able to evaluate it's
ultimate performance (range, and ability to minimize multipathing).
Last edited by Daemon; Mar 20, 2017 at 11:50 PM.
Mar 21, 2017, 01:27 AM
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Quote:
Originally Posted by Daemon View Post
FWIW the Singularity antenna is not lighter, and it has more total solid cross sectional area than
a simple cloverleaf. The only real advantage is that it sticks out less and *may* not not
get caught up up in the props of a small quad in a crash. You might be able to half bury it
in a thick aircraft wing, but can do the same with a cloverleaf and cut the drag by about half.

It's a solution to a pretty narrow problem. I haven't yet been able to evaluate it's
ultimate performance (range, and ability to minimize multipathing).
It's 14g, the same or only marginally more as a lot of 5.8 antennas. It's hardly any larger than a 5.8 antenna, so why not fly 1.3? There wasn't a problem to be solved, peopel just want the size of 5.8 but the range of 1.3. This antenna provides that. It won't likely take a hardcore 5.8 guy and make him switch, but people on the fence should be sold.

The barriers towards getting into long range FPV slowly fade away
Mar 21, 2017, 02:14 AM
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lkrustev's Avatar
1.2 GHz is ment for long range and the multipath interference is hard to be noticed at this frequency. All my experience shows that you do not need at all to bother with goofy, expensive and fragile antennas.
Mar 21, 2017, 02:44 AM
Registered User
What does it mean when my ~25mw 1.2 transmitter works really well when I hold the ground element of the dipole, but turns to static/rolling picture when I let go? Also seems to work well when I wrap the same ground element around the carbon leg of my quad.

I'm thinking the antenna length is not correct for the frequency of the tx?
Mar 21, 2017, 08:10 AM
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lkrustev's Avatar
Quote:
Originally Posted by Dr. |2udie View Post
What does it mean when my ~25mw 1.2 transmitter works really well when I hold the ground element of the dipole, but turns to static/rolling picture when I let go? Also seems to work well when I wrap the same ground element around the carbon leg of my quad.

I'm thinking the antenna length is not correct for the frequency of the tx?
This is strange. What is the lenght and the construction of the antenna? Probably the impendance of the antenna does not match, so when you hold the grond you are acting like a huge groundplane. As well your transmitter could be just not working properly.


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