Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > R/C Electric Topics - General > RC Radios, Transmitters, Receivers, Servos, gyros
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

RC Radios, Transmitters, Receivers, Servos, gyros Discussion all about rc radios, transmitters, receivers, servos, etc.

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 08-17-2011, 03:02 AM   #1
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default "Poor Mans" 2.4 Ghz Spectrum Analyzer

As most RC modelers are well aware, the newer radios have gone to the 2.4 Gigahertz frequencies. This 2.4 GHz frequency band is being used by a lot of services, even including your microwave ovens at 2.450 GHz.

So, the questions comes up, is there any potential for interference to our RC 2.4 Ghz radios and outside interference making equipment?
So far, very few interference cases have been noted on our RC equipment. To counter this issue for some of those very large RC fun flies, the Spektrum radio manufacturers have come out with their DSMX system that is a combination of Spread Spectrum and Frequency Hopping.

Unless you’re attending some of these very large RC fun fly events, there is really no need to update your RC equipment to the DSMX system.
To observe the 2.4 Ghz frequency spectrum this requires an expensive “Spectrum Analyzer”, something that can cost thousands of dollars.

On this note, I found a very low cost “Spectrum Analyzer” on the internet that simply plugs into an USB port on your computer. It only costs $39.00, so one was ordered. This is a thumb sized unit with no external antenna (One with an external antenna is available for another $30.00) Check it out:
http://ubnt.com/airview

This unit has been tested with a standard Laptop, and the results have been interesting. It shows “Usage” of the various frequency bands in the 2.4 Ghz frequencies. By far the strongest signal came from the laptop itself. The laptop has wireless internet service running on 2.4 Ghz. Turning this wireless off then resulted in the second most powerful signal coming from the wireless internet “Router” that is used for communications to the laptop, my wife’s Kindle and so on.

You can also see the effect of the range check button on the DX7 transmitter with this unit. The Futaba radios as well as perhaps several other new 2.4 Ghz systems use “Frequency Hopping”. It would be interesting on just how this shows up with this Airview unit.

The laptop PC was placed on a stand in my driveway, with the Spektrum Analyzer placed about 3 feet from the computer on a USB extension cord. Then both DX7 transmitters were turned on, and both were walked away to about 500 feet distance. The little Airview2 showed reception during the entire period of time.

This unit is also available with an external antenna, but that’s another $30.00.

Next, first one, then the second DX7 transmitter was turned off, and back on.

Take a look at the waterfall view of the attached screen dump of the Airview2 screen display. From two minutes to seven minutes, Transmitter “A” has outputs on channel 1 at about 2.408 Ghz and channel 2 at about 2.448 Ghz. Transmitter “B” has outputs on channel 1 at about 2.428 Ghz and channel 2 at 2.468 Ghz. The color of this graph changes in relation to the signal strength received.

Note that the top graph shows information 7 minutes old at the top, and recent info at the bottom. It will read to about 1/2 hour total if left on long enough.

Below the two minute mark on TXA, you can see where this transmitter was turned off. And from zero to about 1.5 minutes, you can see where Transmitter “A” turned on at about 2.414 Ghz and 2.473 Ghz. And Transmitter “B” turned on at 2.404 Ghz and at 2.468 Ghz. The two transmitters were turned off for several seconds before turning them back on again. Note that transmitter “B” grabbed the one of the frequencies of Transmitter “A” on the power down and power up cycles.

This Airview2 also shows other information such as relative signal strength and a lot of other stuff.
It’s interesting how wide the bandwidth of the PC Router is, that unit splattered it self across several times more bandwidth than the two DX7 transmitters. This router was located about 40 feet from the Airview unit, in the basement of my home, NOT line of sight.

So, in conclusion, is this $39 unit worth its thirty nine bucks? Who knows. But, for me, it definitely was worth it.

It obviously does not have the sensitivity of a good quality 2.4 Ghz receiver such as the Spektrum AR7000 receivers. Maybe it would with the Airview unit with the external antenna.


Attached Thumbnails
Click image for larger version

Name:	Analyzer Screen Dump with Comments.jpg
Views:	2030
Size:	114.7 KB
ID:	151996  

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-17-2011, 03:24 PM   #2
CNY_Dave
Member
 
Join Date: Aug 2011
Location: near Cortland NY
Posts: 774
Thanked 36 Times in 35 Posts
iTrader: (0)
Friends: (1)
Default

A waterfall display on a 39 buck 2.4GHz usb spectrum analyzer- in some ways these are amazing times...


Dave
CNY_Dave is offline  
  Reply With Quote
Old 08-17-2011, 04:38 PM   #3
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by CNY_Dave View Post
A waterfall display on a 39 buck 2.4GHz usb spectrum analyzer- in some ways these are amazing times...


Dave
Is that the truth!!!

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-17-2011, 05:27 PM   #4
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,236
View rcers's Gallery57
Thanked 507 Times in 497 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

It would be fun to see the Futaba, Hitec, Airtronics or DSMX on that display (i.e the frequency hoppers).
rcers is offline  
  Reply With Quote
Old 08-17-2011, 05:41 PM   #5
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by rcers View Post
It would be fun to see the Futaba, Hitec, Airtronics or DSMX on that display (i.e the frequency hoppers).

That it would. Problem is, the club I belong to is 99.9% Spektrum/JR. I'm taking it to our club fun fly Aug 28, will put that info in this thread after its over. Will have to ask around, might be one person in our club has a Futaba 2.4 Ghz radio. It might be a conversion though.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-17-2011, 07:03 PM   #6
stevecooper
Super Contributor
 
stevecooper's Avatar
 
Join Date: Aug 2006
Location: Shadeville Fl,
Posts: 7,040
View stevecooper's Gallery86
Thanked 518 Times in 501 Posts
Club: Mullet Mauroders
Awards Showcase

WAA-08 Pilot  Outstanding Contributor Award 
iTrader: (2)
Friends: (88)
Default

2.4 has been a crap-shoot from the start, as with the growing pains of any thing new,, brown-out's, Lock-out's,add-on's needed to fix past prob's,Etc,
I never saw so many planes go down as in the last three SEFF's from said prob's, spectrum was there putt'in add-on "fix's" to their TX's,, I do own a spectrum that I fly ultra micro's with as 2.4 RX's are what they come with so it's the only game in town , I'm 100percent sure we'll all be 2.4 in years to come but for now give me three feet on the flightline for antenna swing!!!!bubsteve


Attached Thumbnails
Click image for larger version

Name:	155254_1652266980329_1046641667_1758404_2776567_n.jpg
Views:	791
Size:	122.7 KB
ID:	152009   Click image for larger version

Name:	150014_1652262780224_1046641667_1758385_3799317_n.jpg
Views:	782
Size:	94.1 KB
ID:	152010  

Monkey Minion'air
stevecooper is offline  
  Reply With Quote
Old 08-17-2011, 07:11 PM   #7
CNY_Dave
Member
 
Join Date: Aug 2011
Location: near Cortland NY
Posts: 774
Thanked 36 Times in 35 Posts
iTrader: (0)
Friends: (1)
Default

Originally Posted by rcers View Post
It would be fun to see the Futaba, Hitec, Airtronics or DSMX on that display (i.e the frequency hoppers).

Do they use frequency-hopping spread spectrum, or wide bandwidth sequence chipping (real spread-spectrum)?

Dave
CNY_Dave is offline  
  Reply With Quote
Old 08-17-2011, 08:03 PM   #8
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,236
View rcers's Gallery57
Thanked 507 Times in 497 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

They are frequency hopping. Hitec can be adaptive (in Scan mode) where it won't hop to the busier chunks of the spectrum.
rcers is offline  
  Reply With Quote
Old 08-18-2011, 01:52 AM   #9
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by stevecooper View Post
2.4 has been a crap-shoot from the start, as with the growing pains of any thing new,, brown-out's, Lock-out's,add-on's needed to fix past prob's,Etc,
I never saw so many planes go down as in the last three SEFF's from said prob's, spectrum was there putt'in add-on "fix's" to their TX's,, I do own a spectrum that I fly ultra micro's with as 2.4 RX's are what they come with so it's the only game in town , I'm 100percent sure we'll all be 2.4 in years to come but for now give me three feet on the flightline for antenna swing!!!!bubsteve
Interesting.

As for my club, after several seasons of flying with the 2.4 Ghz radios, primarily Spektrum or JR, there have been zero failures caused by interference or any similar issue.

There have been a number of problems caused by using to small of a receiver battery, or depending on the BEC of the ESC to power a four servo receiver from a 4 cell LiPo. That is not the receivers fault, that's the result of not using the proper equipment. Same would happen on 72 Mhz, 27 Mhz, or what ever they might use next.

One of the current magazines points out that Spektrum was updating their radios with the DSMX software that does both DSSS and frequency hopping. That allows 100 transmitters to be on at the same time, with no interference between them.

Current DSSS only allows about 50 transmitters on at the same time. Between people in the pits turning on their transmitters and people at the flightline turning on their transmitters, who knows???

I was at a large electric fun fly in the East Coast in 1999, where the people in charge were allowing 15 planes in the air at the same time. Nobody was flying any sort of a pattern. My giant scale 10 foot wingspan Piper Cub got hit by a high powered biplane AFTER my Piper cub had landed. took the entire tail off of my Piper, took two weeks to repair the damage. The guy didn't even apologize. His son who was spotting was busy watching girls. Never went back.

Its interesting, frequency hopping design goes back to the middle of the 1900's, over 50 years ago, DSSS is a pretty recent design. Take a look:
http://en.wikipedia.org/wiki/Direct-...pread_spectrum

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-18-2011, 02:03 AM   #10
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,236
View rcers's Gallery57
Thanked 507 Times in 497 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

Yea the switch for me has never been a crap shoot. It has been the most reliable RF link I have used in years in the hobby.

Our club is 95% 2.4GHz. The last fly-in event I attended there were 67 pilots and 3 72MHz boxes. Two on the same channel. And yes one of those guys shot down the other one.

I don't miss 72 one tiny bit.

Mike
rcers is offline  
  Reply With Quote
Old 08-18-2011, 02:08 AM   #11
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by rcers View Post
Two on the same channel. And yes one of those guys shot down the other one.

I don't miss 72 one tiny bit.

Mike
Talk about a little black cloud over those two modelers head!!!

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-18-2011, 02:35 AM   #12
stevecooper
Super Contributor
 
stevecooper's Avatar
 
Join Date: Aug 2006
Location: Shadeville Fl,
Posts: 7,040
View stevecooper's Gallery86
Thanked 518 Times in 501 Posts
Club: Mullet Mauroders
Awards Showcase

WAA-08 Pilot  Outstanding Contributor Award 
iTrader: (2)
Friends: (88)
Default

It took me a while to get over changing from AM!but like I said before were all changing over in the next few years anyway,,,Crap-shoot may have rattled some chains,,,sorry,, MustangMan and myself were fly'in and sharing our planes a few years back,,we were swapping Tx's back and forth, I handed over his (2.4)to fly and he gave me mine(FM),,,,,,I forgot the ant, was down,,,,50' down the field GLITCH,,,,,I got it up before she whet in, I guess it's easy to get used to those stub ant,,,,,bubsteve


Attached Thumbnails
Click image for larger version

Name:	155980_1652332341963_1046641667_1758502_6525381_n.jpg
Views:	646
Size:	103.1 KB
ID:	152020  

Monkey Minion'air
stevecooper is offline  
  Reply With Quote
Old 08-26-2011, 02:56 AM   #13
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by rcers View Post
It would be fun to see the Futaba, Hitec, Airtronics or DSMX on that display (i.e the frequency hoppers).
OK
One of my club members loaned me his Futaba 2.4 Ghz transmitter for check outs. (He was not happy with this transmitter. It went dead in flight and caused the crash and total loss of a $6000 wet turbine model. Sent it into Futaba, they found nothing wrong with the transmitter, receiver or battery. Put it into another acrobatic model, the transmitter again went dead, and crashed another model.)

So, I turned on this transmitter, and watched the Analyzer fill up the screen. It's apparent this unit is "hopping" all over the 2.4 Ghz band. It was interesting that when I turned on a Spektrum DX7, the Futaba transmitter continued to broadcast on all previous frequencies, including the DX7 frequencies. Same when I turned on the DX7 first, then the Futaba, the Futaba continued to broadcast over the DX7 signals.

The analyzer shows that the Futaba 2.4 Ghz signal is very narrow band, as compared to the Spektrum DX7 signals.

Take a look at the attached, and compare them to the DX7 signals. As a matter of information, the top of the first screen dump shows the analyzer recording for about 8 minutes. That horizontal "Blank space" in the middle of the top screen view is where I turned off the Futaba transmitter for a few seconds to see what would show up. The second screen dump shows the recorder for about 15 seconds.


Attached Thumbnails
Click image for larger version

Name:	08-25-2011 Rogers Futaba VI.jpg
Views:	985
Size:	162.8 KB
ID:	152293   Click image for larger version

Name:	08-25-2011 Rogers Futaba VII.jpg
Views:	522
Size:	128.1 KB
ID:	152294   Click image for larger version

Name:	Analyzer Screen Dump with Comments.jpg
Views:	455
Size:	114.7 KB
ID:	152295  

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-26-2011, 03:35 PM   #14
CNY_Dave
Member
 
Join Date: Aug 2011
Location: near Cortland NY
Posts: 774
Thanked 36 Times in 35 Posts
iTrader: (0)
Friends: (1)
Default

Mental note: if ever flying an expensive plane, spend 40 fricken' bucks to test the transmitter!
Not lomng ago, that would be about impossible. Nowadays...

Holy cow, are futaba's supposed to do that? I can't wait to see what another one looks like, I'm sure this guy is going to want to see what a properly-working output looks like, then cram the data up futaba's hindquarters.

Dave
CNY_Dave is offline  
  Reply With Quote
Old 08-26-2011, 03:58 PM   #15
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,236
View rcers's Gallery57
Thanked 507 Times in 497 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

Originally Posted by CNY_Dave View Post
Mental note: if ever flying an expensive plane, spend 40 fricken' bucks to test the transmitter!
Not lomng ago, that would be about impossible. Nowadays...

Holy cow, are futaba's supposed to do that? I can't wait to see what another one looks like, I'm sure this guy is going to want to see what a properly-working output looks like, then cram the data up futaba's hindquarters.

Dave
You bet they can do that. 2.4GHz standards say you have to accept all interference with other devices. Remember they are "on" that channel for a tiny fraction of a second.

Spektrum was in fact the "odd ball" only transmitting on 2 channels. It would at least scan and pick open areas to do that on. By the way it works fine! By the way odd ball does not mean bad or wrong. Video cams and other items also just use one channel.

Hitec, Futaba, Airtronics JR (newer stuff) and Spektrum (DSMX protocol) all hop around very quickly.

Hitec systems can actually adapt (scan mode). So when it sees a user on a specific sections (channels) of the spectrum it starts to move traffic off those channels. Pretty slick eh?

Read up:
http://en.wikipedia.org/wiki/Frequen...pread_spectrum

No reason to go nuts it is all working as designed. You can however see why when 100 TX's on at the same time things get very interesting in a hurry.

Mike
rcers is offline  
  Reply With Quote
Old 08-26-2011, 04:43 PM   #16
CNY_Dave
Member
 
Join Date: Aug 2011
Location: near Cortland NY
Posts: 774
Thanked 36 Times in 35 Posts
iTrader: (0)
Friends: (1)
Default

What I'm saying is, if another futaba does not look the same, that's a smoking gun.

If I wasn't trying to rub nickels together to make quarters, I'd snag one of these analyzers for when I start putting $200 of hardware up in the air.


Dave
CNY_Dave is offline  
  Reply With Quote
Old 08-26-2011, 05:04 PM   #17
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,236
View rcers's Gallery57
Thanked 507 Times in 497 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

Originally Posted by CNY_Dave View Post
What I'm saying is, if another futaba does not look the same, that's a smoking gun.

Dave
I guess I don't follow. The Futaba uses FHSS as do other systems. All the major systems are all a bit different but 2.4GHz allows for that.

So I am
rcers is offline  
  Reply With Quote
Old 08-26-2011, 06:19 PM   #18
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by rcers View Post
I guess I don't follow. The Futaba uses FHSS as do other systems. All the major systems are all a bit different but 2.4GHz allows for that.

So I am
I'm trying to understand why our club member absolutely refused to use this transmitter again (After loosing that turbine model)

Well, last night, this transmitter was sitting there, turned on, working just fine. Battery showed 60% capacity on the display. Then after about 5 minutes, it just shut off. Dead. Nothing. And no RF output either. Turned it off, turned it back on, worked fine.

Out of curiosity, left it on for awhile, battery showed 55% capacity. Then after about 10 minutes, it just shut off. Again.

Agreed, this is just one transmitter failure out of many Futaba 2.4 Ghz units that are out there.

Out of curiosity, this transmitter was connected to my variable power supply. With the LCD display backlight on, this unit pulls 0.73 Amps out of that 2200 Mah Lithium battery. It drops to about 0.4 Amps after that display backlight turns it self off.

Interesting.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-26-2011, 06:24 PM   #19
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by rcers View Post
I guess I don't follow. The Futaba uses FHSS as do other systems. All the major systems are all a bit different but 2.4GHz allows for that.

So I am
Take a look at the FHSS per below:
http://en.wikipedia.org/wiki/Direct-...pread_spectrum

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-26-2011, 06:28 PM   #20
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by rcers View Post
I guess I don't follow. The Futaba uses FHSS as do other systems. All the major systems are all a bit different but 2.4GHz allows for that.

So I am
For what it's worth, FHSS (Frequency Hopping) goes back to around World War II. IMHO, doesn't mean its worse, or better than FSSS.

Any radio that allows take offs, flying, landing repeatedly with zero concerns about it working properly, or getting interference problems is a good radio!

On the other hand, if a certain radio system has a lot of complaints against it in the Internet forums, that is another concern.

(But I do like the Spektrum/JR feature where it is not possible to take off with the wrong model programmed in the transmitter!)

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 08-26-2011, 06:44 PM   #21
CNY_Dave
Member
 
Join Date: Aug 2011
Location: near Cortland NY
Posts: 774
Thanked 36 Times in 35 Posts
iTrader: (0)
Friends: (1)
Default

Originally Posted by rcers View Post
I guess I don't follow. The Futaba uses FHSS as do other systems. All the major systems are all a bit different but 2.4GHz allows for that.

So I am

I was speculating the problem he had with the transmitter might show up when compared to another of the same type on the waterfall display.


Dave
CNY_Dave is offline  
  Reply With Quote
Old 09-02-2011, 07:07 AM   #22
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default Racine Radio Control Club Field Scan

Just took this Spectrum Analyzer to our club field at 1:30 PM Wednesday afternoon for a scanning of what's out there. As it turned out, not much. A weak signal shows up at 2.447 Ghz, plus a few scattered "Blips" here and there. That's it.

Our field is located about 1/4 mile from a very large corporate central warehouse plant. Apparently those blips came from there.

Take a look at the attached. Most signals are down in the -95 Dbm range, very low values.


Attached Thumbnails
Click image for larger version

Name:	RRCC Field Scan - WF.jpg
Views:	270
Size:	107.3 KB
ID:	152484  

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 06-07-2012, 08:56 PM   #23
CNY_Dave
Member
 
Join Date: Aug 2011
Location: near Cortland NY
Posts: 774
Thanked 36 Times in 35 Posts
iTrader: (0)
Friends: (1)
Default

I suspect I had an interference problem, am going to snag one of these critters as soon as I save up the scratch... I wonder of the external antenna unit is much more sensitive than the internal-antenna unit? ($59 vs $39)

http://www.flyteccomputers.com/detai...AirView2&wre=1

http://www.flyteccomputers.com/detai...b=Airview2-EXT
CNY_Dave is offline  
  Reply With Quote
Old 06-08-2012, 01:11 AM   #24
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,221
Thanked 704 Times in 686 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by CNY_Dave View Post
I suspect I had an interference problem, am going to snag one of these critters as soon as I save up the scratch... I wonder of the external antenna unit is much more sensitive than the internal-antenna unit? ($59 vs $39)

http://www.flyteccomputers.com/detai...AirView2&wre=1

http://www.flyteccomputers.com/detai...b=Airview2-EXT

Yeah
I suspect the external antenna version will pick up much lower level signals. Kind of wish I'd gone the external antenna version.

At any rate, my unit without an external antenna had no problem picking up a transmitter located about a block away, running full power on the transmitter.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 06-30-2012, 08:06 AM   #25
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 6,201
View solentlife's Gallery47
Thanked 266 Times in 263 Posts
Club: Founder Member Ventspils RC Club. Ex Waltham Chase and Meon Valley Soaring.
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Outstanding Contributor Award  125mph Speed Demon 
iTrader: (0)
Friends: (15)
Default

Originally Posted by kyleservicetech View Post
.........
So, I turned on this transmitter, and watched the Analyzer fill up the screen. It's apparent this unit is "hopping" all over the 2.4 Ghz band. It was interesting that when I turned on a Spektrum DX7, the Futaba transmitter continued to broadcast on all previous frequencies, including the DX7 frequencies. Same when I turned on the DX7 first, then the Futaba, the Futaba continued to broadcast over the DX7 signals.
...........
Hi Denny ... sorry to drag out an old post ...

But surely the only item that knows another Tx is sending out on same freq. is the Rx and that only accepts the signal with the relevant ID code. If it doesn't hear the code on that freq. it accepts the same code on other freqs the Tx is hopping around.

Tx's are dumb ass machines in reality - they send out on freqs designed and don't care about anothers ..... Ok - I see you talk about Hitec learning ... but surely its limited by economics as to how good it is at it ?

I read somewhere that depending on how the Tx signal is set up - there are different power levels allowed. As I understood from the article 'limited' freq hopping / allocation allowed a radio to be higher powered, but general bandwidth hopping was seriously limited in power. Maybe this is part of the reason that the Futaba signal appears tighter ? It's not unusual for radio signals to have side lobes / splatter as the power is increased or lesser quality components used ?

Interesting that another has mentioned the "crapshoot" ..... I also tend to this view. 20 - 30yrs ago with 27mHz and 35mHz in UK .... basically most models were not shot down by freq. interference or other Tx on same freq. but by installation faults, myself - I lost a beautiful Royal P51 Mustang due to a JR Rx pack solder joint braeking free - , or outside influence such as boosted CB's etc.

I know of only one instance of shoot down in all the years I flew FM ... and that's when Kenny Binks, UK Aerobatics Champ, switched on his Helicopter while I was flying mine - I had the freq control peg and was the 'legal' flyer on that crystal .. not him !
But since returning to the hobby and to 2.4Ghz .... I have seen more crashes of models in a matter of days than in years of FM time ! Including my own !

I find it interesting that in days of 35Mhz FM ..... JR went their own route with FMSSSSS - using a different intermediate freq in their Tx / Rx's .... so it meant you could only use JR crystals. Rest of the RC was using another. later JR amended their gear to join the general world and have same intermediate .... isn't it strange that 2.4Ghz seems to have done similar - in fact even worse as each manufacturer / brand seems to have it's own version of freq control / allocation.
Will we see a coming together of 2.4Ghz in future to a single system format ? I hope so ... It was so simple in the old days .... a pendant and number on your Tx ... a peg from the control board .... go fly. No peg - No fly. Today ? Who knows what the hell is going on up there in the ether ....

Last comment : Occasionally where I fly we have strange crashes ... and sometimes we note a bit of military or SAR activity nearby ..... mmmmmmmm
One day in fact .... we were flying at our field, about 1km away is a small radar hut ..... no-ones really sure if it's civil or military .... a security car drove up and asked if we were overflying it at all .... the answer was yes occasionally one model may get deep away over that way ... but generally no. Turns out that they had a call from "someone" that UFO returns were showing up on the radar ... that the intruder alarms were set off ... etc.
No it is NOT an old Soviet relic left-over. This is relatively new installation EXTRA to the one at Ventspils Airport.

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
- Subscribe my Youtube: "solentlifeuk"
solentlife is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > R/C Electric Topics - General > RC Radios, Transmitters, Receivers, Servos, gyros

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
ESKY 2.4 ghz sticky aileron/elevator gimble zep77 RC Radios, Transmitters, Receivers, Servos, gyros 3 06-09-2011 11:28 PM
For Sale wing dragon and erc micro 2.4 ghz p51 dr rc Airplanes - Electric For Sale & WTB 0 05-07-2011 05:59 AM
For Sale Spektrum AR6100 and 6100E DSM2 2.4 Ghz Compatible Receivers, Guaranteed to bind! RacerPaul Radio Equipment For Sale & WTB 18 04-05-2011 11:37 PM
For Sale Spektrum AR6100E & MX DSM2 2.4 Ghz Compatible Receivers! oakleyjp Radio Equipment For Sale & WTB 2 04-02-2011 04:37 AM
Gravity Hobby 2.4 GHZ RTF DX-220 Glider RTF Now $69 Shipped phillipmorris Indoor & Micro Electric Planes 6 02-25-2011 10:56 AM


All times are GMT +1. The time now is 07:57 AM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.97795 seconds with 77 queries