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Dec 18, 2015, 07:00 PM
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5685 5760 5800 5860 5905 is Ham legal and seems to work as well.
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Dec 19, 2015, 12:42 AM
fly by night
BCSaltchucker's Avatar
Quote:
Originally Posted by Havoc256 View Post
The problem comes in play because a lot of us use the 600mw transmitters and they stop all over the 200mw transmitters. Also when we have our race events, the pilots tend to sit right next to each other. So this does become a real life issue.
yes!

we found it was even worse racing indoors. While 3 of us woudl fly freestyle outside just fine, when we go indoors barely 2 can be really flyable at a time. I never run more than 200mW, but tons of folks violating the HAm principles slamming us with 600mW. grrr

I very much look forward to everyone having 25-100mW Raceband systems. standardized, discreet, half with LHCP and half with RHCP.

admiring what the Immersion folks are doing to innovate with Raceband .. until we get affordable low latency digital links
Dec 19, 2015, 12:44 AM
fly by night
BCSaltchucker's Avatar
Quote:
Originally Posted by MultiGP View Post
5685 5760 5800 5860 5905 is Ham legal and seems to work as well.
this is important to note too.

some of those Boscam channels run into illegal frequency range that are not legal for HAM users

the legal range is 5650 MHz to 5925 MHz.

but that does not mean that 5650 and 5925 are legal. Because of bandwidth, broadcasts centred on 5925 and 5645 are not legal, only 5905 at the top end and 5665 at the bottom end of Boscam E band would be legal for a licensed HAM with appropriate equipment and procedures

though for a couple years I have enjoyed being outside the crowded IRC using my E Band equipment in casual flying. I still get stomped on when 3 or 4 or us try to race indoors.

Last edited by BCSaltchucker; Dec 19, 2015 at 12:56 AM.
Dec 19, 2015, 10:32 AM
Registered User
Thread OP
It is important to note that the 'Race Band' frequencies only solve one problem: adjacent channel interference.

They still suffer from IMD related problems because they are evenly spaced from one another.
Dec 19, 2015, 04:23 PM
fly by night
BCSaltchucker's Avatar
so they reduce it by running way lower power. typically 25mW

though I have yet to see raceband work in person as advertised, esp with 8 flyers at once.

Can be complicated by multipath from metal objects, like we saw at Drone Nationals. Or was that some IMD in the mix too?
Last edited by BCSaltchucker; Dec 19, 2015 at 04:45 PM.
Dec 19, 2015, 04:36 PM
Team AlienWarpSquad
Quote:
Originally Posted by BCSaltchucker View Post
Can be complicated by multipath from metal objects, like we saw at Drone Nationals. Or was that some IMD in the mix too?
My guess is that both multi-path and IMD were causing the issues at the Nationals.
Dec 20, 2015, 11:40 AM
Registered User
techspy's Avatar
So we have been running into similar issues when trying to race at our local league. We tested all TXs last time with an RF Explorer to verify that they were all on their center freq and we also tested them all for power output. We still had issues but we made an interesting discovery.

I powered up on my freq and immediately someone said I was causing interference. I tried 3 different quads, all 200mw on that freq and he said they all interfered. He was using the new Headplay. I powered on my goggles (Skyzone 3d) and tuned to his frequency and had no interference on his channel with my quad powered on and only a few feet away..

So, it appears that the RX is just as much of an issue as TXs (as someone pointed out here already). I wish a hi/low pass filter could be accurate enough for each channel that could be placed on the RX (and TX?) antenna.

Another note we discovered on video TX power. We have not found ANY proof that simply having a 600mw flying when a 200mw/25mw is in being used causes ANY issues. We have tested with a 600mw in the air while others have flown 200mw and no one complained. I think there is a lot more to be considered other than power output. It all comes down to the quality of that specific TX and RX.

Something else we noted was the huge amount of "spewing" emitted when power on ANY TX. We observed the RF Explorer when powering on and it was just crazy. It saturates the entire band almost.

So, we are going to try a couple things to help with this;

- We are requiring all TXs to be tested before use at an event. This will test for freq and power.
- Red and Blue pilots: We will stagger the frequencies so that every other freq is in Blue and Red groups.
- Red groups will fly for 10 min, then Blue groups with a 5 min rest between where people can power on their TX for testing etc. No powering up during the heat regardless of the group.
- We also ask everyone to turn off their WiFi on their phones.
- We are going to try different frequencies. Right now we are on the "Golden 8" but may trim it down to 5 when we try the new Red/Blue scheme.

We are still trying to figure out a good way to test each RX. I wish they had an analog dial that you could use to tune it in perfectly for your TX

Man I wish digital video was available now! (low latency, cheap and small that is!)
Dec 20, 2015, 04:07 PM
Team AlienWarpSquad
Yes on all.

When these vTXs are powered on their Oscillators and PLL frequency multipliers "SWEEP" the band until the PLL's "lock in' on the set frequency. My local group sees this all the time.
A better design would have the OUTPUT power Amp disabled until the PLL frequency Lock in acquired.

The vRXs have very POOR front ends which is where the IMD issues start. From doing Ham Radio contesting with a well know VHF club, if the First MIXER uses a very low level LO then Other strong In Band frequencies cause IMD products.
This is also True of the LNA before the Mixer, If the Bias current is low or the Design is Poor then IMD products are more easily produced which will cause interference in the De-modulation stage.

This has Nothing to do with the Frequency TUNING of the vRX so a analog Dial will NOT help.

There are many tests that can be done on a RX. IMD or 3rd Order intercept is one of these and is related to RX Dynamic Range:
http://www.arrl.org/files/file/Techn...0708qex046.pdf

Goggle Search RX testing and look at the web sites on Ham Radio RX testing.
Last edited by waltr; Dec 20, 2015 at 04:49 PM.
Dec 20, 2015, 10:46 PM
fly by night
BCSaltchucker's Avatar
certainly I have had much better results using the Rx built into my older Boscam goggles than with my Dominators+TBS 32ch Rx module (on E band usually). Even better than with the RC305. Sticking with that and only E band has kept my video pretty clean with all the new guys showing up with IRC 600mW units. But this is outdoors where we have a lot less trouble than indoor racing.
Dec 21, 2015, 11:39 AM
Registered User
Thread OP
Quote:
Originally Posted by MultiGP View Post
5685 5760 5800 5860 5905 is Ham legal and seems to work as well.
Those are pretty good combos, I think it will work.

However, I ran them, and there are 4 IMD products that come close and could cause some problems. Maybe Rob can chime in and check my work.

Generally, we have tried to make sure IMD products are >= 20MHz away from any desired frequency. Three combos in your frequiences fall below that, but it still may work fine.

The IMD products are in yellow, with potential problems in orange: (EDIT: 5915 should also be highlighted as a potential problem)



Making some of the antennas LH polarization will help, too.
Last edited by Jon h2; Dec 21, 2015 at 12:28 PM.
Dec 21, 2015, 12:34 PM
Registered User
Thread OP
For comparison, if I run our numbers 5645 5740 5820 5860 5945, which do technically fall out of the HAM band, I get this:



There are two IMD products by my count that are within 15 MHz, but pretty good otherwise.
Feb 16, 2016, 09:24 PM
Registered User
Our racing squad owns:
  • 8 ImmersionRC Raceband 5.8GHz 25mW
  • 8 ImmersionRC Duo 5800 v4.1Race Edition
  • Alternating left and right mini patch antennas

What is the best we can do to improve video clarity indoors for racing 8 pilots at the same time?
Using bandpass filters on receivers ?
Feb 17, 2016, 10:06 AM
Team AlienWarpSquad
Quote:
Originally Posted by lilopiglet View Post
Our racing squad owns:
  • 8 ImmersionRC Raceband 5.8GHz 25mW
  • 8 ImmersionRC Duo 5800 v4.1Race Edition
  • Alternating left and right mini patch antennas

What is the best we can do to improve video clarity indoors for racing 8 pilots at the same time?
Using bandpass filters on receivers ?
there are NO RX filter available that would help.
Just follow the guildelines in this post and the Channel combinations recommended by MultiGP race league.
Feb 17, 2016, 12:55 PM
Registered User
Quote:
Originally Posted by waltr View Post
there are NO RX filter available that would help.
Just follow the guildelines in this post and the Channel combinations recommended by MultiGP race league.
  • 5645 5740 5820 5860 5945 are MultiGP suggested ones
  • 5685 5760 5800 5860 5905 are Jon H2 suggested ones
So according to this it means that we can only fly 5 pilots at the same time and immersionRC raceband equipment that we just purchased is useless for indor purposes ?
Last edited by lilopiglet; Feb 17, 2016 at 01:20 PM.
Feb 17, 2016, 01:56 PM
Team AlienWarpSquad
You can TRY flying more at the same time.
Low power and alternating RH/LH CP antennas will help but there are limits from the Physics and cheap RF equipment.


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