Shop our Airplanes Products Drone Products Sales
Thread Tools
Jun 15, 2017, 06:42 PM
Registered User
Daemon's Avatar
Besides just not being legal, what happens depends on where you are.
The channels below 1258 overlap 100% with the 80 control channels for the MLS DME/P system.
That is radar ranging for full scale commercial aircraft flying in inclement weather.
They generally use GPS as primary guidance, and MLS as secondary but when they're active
you'd see pulses on your video, and there is the potential to interfere with their signals.
Usually it's only used when they're descending through thick clouds but can be affected
up to 30-50 miles away from the airport.

The channels above 1280 overlap with L2 ground based radar for detecting aircraft at long
range. These signals can be extremely powerful, and in some cases their signal will splash
over and step on 1280Mhz (as it does here near Denver). Here, the radar signal seems to
be centered right around 1300 so 1360 is actually cleaner than 1280.
Sign up now
to remove ads between posts
Jun 15, 2017, 09:18 PM
Registered User
Quote:
Originally Posted by Daemon
Besides just not being legal, what happens depends on where you are.
The channels below 1258 overlap 100% with the 80 control channels for the MLS DME/P system.
That is radar ranging for full scale commercial aircraft flying in inclement weather.
They generally use GPS as primary guidance, and MLS as secondary but when they're active
you'd see pulses on your video, and there is the potential to interfere with their signals.
Usually it's only used when they're descending through thick clouds but can be affected
up to 30-50 miles away from the airport.

The channels above 1280 overlap with L2 ground based radar for detecting aircraft at long
range. These signals can be extremely powerful, and in some cases their signal will splash
over and step on 1280Mhz (as it does here near Denver). Here, the radar signal seems to
be centered right around 1300 so 1360 is actually cleaner than 1280.
Thanks Daemon,
I am enlightened!
Not that I would ever transmit on those other channels..
Just wanted to know what else was on them.
Jun 15, 2017, 11:38 PM
g0t rabb1t?
ABLomas's Avatar
Quote:
Originally Posted by Daemon
The channels below 1258 overlap 100% with the 80 control channels for the MLS DME/P system.
That is radar ranging for full scale commercial aircraft flying in inclement weather.
While checking why entire 1.2-1.28G range is legal here (with HAM licence) i found some interesting comments about MLS:
Code:
<...>MLS employs 5 GHz transmitters at the landing place<...>
<...>In the United States, the FAA suspended the MLS program in 1994 in favor of the GPS (Wide Area Augmentation System WAAS). The FAA's inventory of instrument flight procedures no longer includes any MLS locations;[2] the last two were eliminated in 2008.<...>
<...>However, in reality the only major installation was London Heathrow Airport, which was decommissioned on the 31st of May 2017.<...>
src
While prob. not legal at your location - should be free, smth like RF explorer or SDR with antennas/preamp is your friend =)
Jun 15, 2017, 11:46 PM
Registered User
Daemon's Avatar
The 5Ghz signal is probably the radar ranging signal itself. The 1.0-1.2 Ghz signals were
for control. Basically a ping and response. I definitely saw it thrash my video some years ago,
but may have been before 2008. Even if MLS is gone, I kinda doubt they'd just abandon
that frequency band.
Jun 18, 2017, 06:19 AM
Registered User
Mariete's Avatar
Quote:
Originally Posted by changosurf
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.
Hi Changosurf.

Please, can you share your sketch for frequency change in the Partom VTX via i2c with me?

I have a nuked Partom (I just removed if from the case) and would like to experiment with it. My goal is to control frequencies from the Arduino so I can read SWR at different frequencies automatically to create antenna charts.

Thank you.

Edit: I just learned, by diving into the datasheet, that it's not a i2c protocol but a bit-bang protocol. Some what more difficult to do by myself. I will be very thankfully if you can share your code with me.
Last edited by Mariete; Jun 20, 2017 at 01:01 AM.
Jun 20, 2017, 07:59 AM
Registered User
Mariete's Avatar
Quote:
Originally Posted by changosurf
FYI, for anyone interested...
Here's the math for the partom PLL frequency tuner chip:

Fout=12*[(64*N)+A]/R

(12 being 12MHz, the clock speed of the 'can' xtal inside of the vtx)

So, for partom's channel '9', 1280.1MHz, the values are:
N=1000
A=5
R=600
so, Fout=12*64005/600=1280.1MHz
- This is apparently what the partom vtx actually tunes to, 1280.1, and not precisely 1280. I got these values from sniffing the i2c bus.

The PLL chip on the partoms is the MB15E07L. Here's the d-sheet:
http://www.fujitsu.com/downloads/MIC...l/MB15E07L.pdf

The data is sent in two parts, an 18 bit sequence & a 19-bit sequence. The data is latched in/stored by setting the 'LE' pin high on the PLL chip. Here are the two bit sequences that I got for channel '9' (MSB first):
18-bit
010000010010110001
19-bit
0111110100000001010
The bit patterns are explained in the data sheet, so you can extract the values from there.

So, the hard part is done. Now, I can simply remove the PIC, solder some jumper wires, plug up an external arduino mini, and write a control sketch for the vtx.

The only somewhat tricky part now is finding a way to automate the math so that you can easily define the 3 values (N,A, and R) needed for a given frequency. It's not so straightforward as simply incrementing a single value sequentially.

example:
given the values that I listed above as a starting point...

- increasing the value of the A term by one increments the frequency by 0.02MHz, with a max increase of 2.54Mhz (bit range is limited from 0-127)

-increasing the value of the N term by one increments the frequency by 1.28MHz, with a max increase of 1340.16MHz (that would put it up in the 2.6GHz range using the above values, waaaay too far off frequency)

-increasing the R term while keeping the others constant changes the value by ~2.13MHz (I would probably try to keep this value constant, as the math would probably get messy)

At this point, I'm having to somewhat guess at it in order to figure out which values I need for a given frequency. If anyone has a good idea on how to come up with an easy algorithm to work with that formula, please let me know.

EDIT:
looking at it again, it looks like I might just be able to increment the A value up until 63 & then increment N and reset A back to zero, will need to test & make sure it works.
example:
N=1000, A=0-63: Fout=1280->1281.26
N=1001,A=0-63: Fout=1281.28->1282.54
N=1002,A=0-63: Fout=1282.56->1283.82
etc....


What I'll probably just end up doing is creating a big list of frequencies that I can hard-code into the AVR, in addition to being able to enter arbitrary values for A-N-R over serial (that's my plan anyway).
I'm trying to implement the protocol by myself but I'm having some issues and my findings aren't the same.

This is my Partom's VTX (looks identical to your photos) communication when selecting channel 9:



N and A are the same but for R I get 620 instead of 600

If I calculate the frequency with 620 it results in 1263 Mhz. Nonsense...

I don't know what I'm doing wrong...

I attach some more captures (on different channels for reference).
Jun 21, 2017, 05:31 AM
Registered User
Mariete's Avatar

1.2-1.3Ghz Tx/Rx All infos on one page - updated: 27/10/2013


Quote:
Originally Posted by changosurf
FYI, for anyone interested...

Here's the math for the partom PLL frequency tuner chip:



Fout=12*[(64*N)+A]/R



(12 being 12MHz, the clock speed of the 'can' xtal inside of the vtx)



So, for partom's channel '9', 1280.1MHz, the values are:

N=1000

A=5

R=600

so, Fout=12*64005/600=1280.1MHz

- This is apparently what the partom vtx actually tunes to, 1280.1, and not precisely 1280. I got these values from sniffing the i2c bus.



The PLL chip on the partoms is the MB15E07L. Here's the d-sheet:

http://www.fujitsu.com/downloads/MIC...l/MB15E07L.pdf



The data is sent in two parts, an 18 bit sequence & a 19-bit sequence. The data is latched in/stored by setting the 'LE' pin high on the PLL chip. Here are the two bit sequences that I got for channel '9' (MSB first):

18-bit

010000010010110001

19-bit

0111110100000001010

The bit patterns are explained in the data sheet, so you can extract the values from there.



So, the hard part is done. Now, I can simply remove the PIC, solder some jumper wires, plug up an external arduino mini, and write a control sketch for the vtx.



The only somewhat tricky part now is finding a way to automate the math so that you can easily define the 3 values (N,A, and R) needed for a given frequency. It's not so straightforward as simply incrementing a single value sequentially.



example:

given the values that I listed above as a starting point...



- increasing the value of the A term by one increments the frequency by 0.02MHz, with a max increase of 2.54Mhz (bit range is limited from 0-127)



-increasing the value of the N term by one increments the frequency by 1.28MHz, with a max increase of 1340.16MHz (that would put it up in the 2.6GHz range using the above values, waaaay too far off frequency)



-increasing the R term while keeping the others constant changes the value by ~2.13MHz (I would probably try to keep this value constant, as the math would probably get messy)



At this point, I'm having to somewhat guess at it in order to figure out which values I need for a given frequency. If anyone has a good idea on how to come up with an easy algorithm to work with that formula, please let me know.



EDIT:

looking at it again, it looks like I might just be able to increment the A value up until 63 & then increment N and reset A back to zero, will need to test & make sure it works.

example:

N=1000, A=0-63: Fout=1280->1281.26

N=1001,A=0-63: Fout=1281.28->1282.54

N=1002,A=0-63: Fout=1282.56->1283.82

etc....





What I'll probably just end up doing is creating a big list of frequencies that I can hard-code into the AVR, in addition to being able to enter arbitrary values for A-N-R over serial (that's my plan anyway).


I managed to make it work finally, but something is different to your findings.

In my case, instead of the "010000010010110001" (600) in the 18bit registry I had to put "010000001100100001" (620). Don't know why this difference (may be a mistake in your original message?)

Anyway, I published my messy code to Github, just in case anybody is interested or needs it:

https://github.com/melkati/VTX_Parton_Test



Last edited by Mariete; Jun 21, 2017 at 05:50 AM.
Jun 23, 2017, 12:19 AM
Wandering IT geek
ronin4740's Avatar
any idea what the current draw on this VRX is?

https://www.foxtechfpv.com/foxtech-1...er-p-1001.html

trying to decide what capacity 3S Lipo to power it and a 25mW 5.8GHz VTX with.
Jun 23, 2017, 03:49 AM
.
NutBag's Avatar
Quote:
Originally Posted by ronin4740
any idea what the current draw on this VRX is?

https://www.foxtechfpv.com/foxtech-1...er-p-1001.html

trying to decide what capacity 3S Lipo to power it and a 25mW 5.8GHz VTX with.
They don't draw a lot, maybe 500mah at the most.
I've not used that exact one but the readymade units and lawmates I have can't draw much more.
I power my goggles and rx off a 3S 4000 and regularly have it on for 4-5 hrs+.
Jun 23, 2017, 09:41 AM
Wandering IT geek
ronin4740's Avatar
Thanks. I have a couple of 3S 2100'mAh packs which are old but will hold a charge. I'll put together a parallel harness and run two of them to power the VRX and VTX.
Jun 23, 2017, 02:22 PM
Registered User
lkrustev's Avatar
Quote:
Originally Posted by ronin4740
any idea what the current draw on this VRX is?

https://www.foxtechfpv.com/foxtech-1...er-p-1001.html

trying to decide what capacity 3S Lipo to power it and a 25mW 5.8GHz VTX with.
250-300 ma
Jun 23, 2017, 04:46 PM
Wandering IT geek
ronin4740's Avatar
Thanks. So, if they both draw in the 300mAh range and I have a 2100mAh pack which I want to reserve 25% for safety I should be able to safely power the 1.2GHz VRX and 5.8GHz VTX for about 2.6 hours, correct?


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Lawmate vs BOB Fox 700 Tx/rx combo which one has the 1160? iacei FPV Talk 24 Jul 22, 2010 08:49 AM
Discussion 1.2Ghz Tx Only: Where to buy a cheap one iacei FPV Talk 9 Jun 07, 2010 02:03 AM
Question esc all one, can i change to different tx/rx? Fossy313 Beginner Training Area (Aircraft-Electric) 4 Jan 30, 2010 04:07 AM
Discussion 1.2Ghz 800mw video TX/RX on Ebay for $2.98 Euro _Spud_ FPV Talk 1 May 23, 2008 12:31 PM
Are 1.2ghz Tx and Rx any good. JustFly Aerial Photography 3 Apr 22, 2005 11:46 AM