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Old 04-21-2014, 03:16 PM   #1
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Default 2.4GHz vs. 72MHz

I found this and thought it might make a good sticky as it answers a lot of newbie questions.


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File Type: pdf 72mhz vs 2.4 ghz.pdf (108.8 KB, 32 views)

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Old 04-21-2014, 03:54 PM   #2
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Originally Posted by FlyWheel View Post
I found this and thought it might make a good sticky as it answers a lot of newbie questions.
mmmmm bit old isn't it ... think a few items have been updated since that was written - or author used old info.

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Old 04-21-2014, 05:03 PM   #3
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Originally Posted by FlyWheel View Post
I found this and thought it might make a good sticky as it answers a lot of newbie questions.
Yes, quite good but as Nigel say's a little dated now.

To be honest though, I dont think anyone new to the hobby give a passing thought to a comparison between 72MHz with 2.4GHz. Newbies would most likely be totally unaware that 72MHz ever existed. All systems they would be looking at would be 2.4GHz of one type or another. Like it or not, 72MHz is history.
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Old 04-21-2014, 09:19 PM   #4
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2.4 and 72Mhz both have their good points and not so good points, 72Mhz will be around for a long time, because some people dont want to put up with the issues that 2.4 Have, I know I dont LOL

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Old 04-21-2014, 10:51 PM   #5
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What would those 'issues' be? No system is 100% perfect but on balance 2.4GHz is far better than 72MHz ever was. If it were not so why the total switch over to 2.4GHz by every manufacturer without exception?

Is there a 72MHz system still available that you can actually buy new? I know Futaba (whose delay in converting to 2.4GHz lost them their dominance in the RC market) still list the bottom of the range 4YF 72MHz but I'm not sure if in practice they are available to buy? I don't think any other mainstream manufacturer lists even one 72MHz system between them.

I appreciate that there are still perfectly good used 72MHz systems in circulation that work fine and some people will no doubt keep using for a while yet, but you could say the same thing for VHS video tape recorders or audio cassette players... All are inevitably on their way into the history books.
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Old 04-21-2014, 11:23 PM   #6
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Originally Posted by JetPlaneFlyer View Post
What would those 'issues' be? No system is 100% perfect but on balance 2.4GHz is far better than 72MHz ever was. If it were not so why the total switch over to 2.4GHz by every manufacturer without exception?

Is there a 72MHz system still available that you can actually buy new? I know Futaba (whose delay in converting to 2.4GHz lost them their dominance in the RC market) still list the bottom of the range 4YF 72MHz but I'm not sure if in practice they are available to buy? I don't think any other mainstream manufacturer lists even one 72MHz system between them.

I appreciate that there are still perfectly good used 72MHz systems in circulation that work fine and some people will no doubt keep using for a while yet, but you could say the same thing for VHS video tape recorders or audio cassette players... All are inevitably on their way into the history books.
Yeah
I tried googling for brand new 72 Mhz transmitters. Only place they showed up was in Ebay as used radios.

If 72 Mhz was so great, then how come so many conversion kits are available to upgrade those old transmitters to 2.4 Ghz???

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Old 04-22-2014, 12:22 AM   #7
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Originally Posted by JetPlaneFlyer View Post
I know Futaba (whose delay in converting to 2.4GHz lost them their dominance in the RC market) still list the bottom of the range 4YF 72MHz but I'm not sure if in practice they are available to buy?
Even the low cost Futaba 4YF has gone to 2.4 Ghz! That's the same price as the entry level Spektrum transmitter/receiver.

http://www.amazon.com/Futaba-2-4G-R2...A2LD5KOFCRAIEJ

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Old 04-22-2014, 12:33 AM   #8
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Originally Posted by JetPlaneFlyer View Post
What would those 'issues' be?
IMHO, most of the problems noted with the 2.4 Ghz radios was the use of inadequate receiver power supplies. It's just not a good idea to use a 2500 Mah four "AA" type Nih battery pack on these new radios. Especially on the larger models with power hungry servos.

If you want absolute secure battery power for your receiver and its servos installed in those larger model airplanes, check out a two cell A123 pack, or even a two cell LiFe pack. If your receiver and servos work with a 5 cell Nih battery pack, those A123 or LiFe batteries are a direct drop in. No regulator required.

Those A123 cells will burn up the servo wiring if the servo should ever short out. I've seen it happen twice.

The first failure was with a servo that was pushed way beyond its ratings in a giant scale model. The servo wires were melted from the shorted out servo clear back to the receiver. The second was a kyleservicetech screw up where the battery charge connector connection on a switch harness was accidentally shorted out. Instant smoke everywhere. It welded the switch contacts together in the switch harness. But, that two cell 2300 Mah A123 pack wasn't even close to its rated maximum current output capability.

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Old 04-22-2014, 12:42 AM   #9
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Originally Posted by FlyWheel View Post
I found this and thought it might make a good sticky as it answers a lot of newbie questions.
If you have an interest in these radios, I put together a PDF file a few years back on this subject. This file also has a few notes on those 2.4 Ghz radios, and what's involved with them.

How it Works Our Remote Controlled Radio Systems
http://www.wattflyer.com/forums/showthread.php?t=45173

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Old 04-22-2014, 12:47 AM   #10
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I Totally Agree with Dave Horvath, yes this Discussion may be a little old, but it still holds true, Yea, I know all the die hard 2.4 fans dont like to hear the truth, they think 2.4 is the greatest thing since CokaCola LOL,

http://www.modelairplanenews.com/blo...he-discussion/

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Old 04-22-2014, 02:01 AM   #11
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I still fire up some 72mhz junk everyonce in a while. noone else at the flying feild does. my kids got a small 28mhz toy plane i bought him. even after he broke the antenna off i haven't had any range issues for the 30 seconds I've been able to get him to fly it .

It sure is nice to fly with 10-15 other people/planes and not worry about interferance or model memory stuff.

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Old 04-22-2014, 02:23 AM   #12
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Originally Posted by CHELLIE View Post
I Totally Agree with Dave Horvath, yes this Discussion may be a little old, but it still holds true, Yea, I know all the die hard 2.4 fans dont like to hear the truth, they think 2.4 is the greatest thing since CokaCola LOL,

http://www.modelairplanenews.com/blo...he-discussion/

Die hard 72Mhz Fan for ever
Yeah
I've read that article before. There are a lot of half-truths in it, along with stuff that simply doesn't apply to our RC models, such as that Freznal effect. Plus, perhaps a little BS. This Freznal effect applies when the range is such that the curvature of the earth has to be considered.

Here are some other comments about that David Horvath article.
http://www.rcgroups.com/forums/showt...8#post19743277

Several of my club members have gone to those giant RC flyins, such as Joe Nall, where hundreds of transmitters may all be turned on at the same time. And, zero interference problems were noted.

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Old 04-22-2014, 04:39 AM   #13
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Originally Posted by hayofstacks View Post
I still fire up some 72mhz junk everyonce in a while. noone else at the flying feild does. my kids got a small 28mhz toy plane i bought him. even after he broke the antenna off i haven't had any range issues for the 30 seconds I've been able to get him to fly it .

It sure is nice to fly with 10-15 other people/planes and not worry about interferance or model memory stuff.
Use Berg Receivers with 72Mhz, the other Receivers dont have the RF filtering that a berg receiver does, Hitec receivers are good too, those are the only 2 receivers I will use with 72 Mhz With E Power.

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Old 04-22-2014, 06:13 AM   #14
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Originally Posted by CHELLIE View Post
I Totally Agree with Dave Horvath, yes this Discussion may be a little old, but it still holds true, Yea, I know all the die hard 2.4 fans dont like to hear the truth, they think 2.4 is the greatest thing since CokaCola LOL,
Chellie,

You might have been on the 72MHz side in 'the war'.. But face facts, like it or not, the war is over, 2.4GHz won. 72MHz has been replaced by 2.4GHz not because the manufactures wanted to change but because the vast majority of users prefer 2.4GHz for all the advantages it brings, and that's what they want to buy.

As noted, that article you keep referring to is half truths wrapped in BS. None of the 'issues' highlighted are problems in real life. If they were why do 95+% of RC flyers use 2.4GHz and every manufacturer has already completely converted their production to 2.4GHz?.
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Old 04-22-2014, 06:28 AM   #15
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Originally Posted by kyleservicetech View Post
Yeah
I tried googling for brand new 72 Mhz transmitters. Only place they showed up was in Ebay as used radios.

If 72 Mhz was so great, then how come so many conversion kits are available to upgrade those old transmitters to 2.4 Ghz???
Hey c'mon guys and gals ... the only REAL reason people go for 2.4Ghz - is the lack of need for Freq control and peg-boards.
Turn up at site .. switch on and go ... no more need to check board and see if a peg is available for your slot.

The rest is just add-on ..

Personally - if I have a working 35Mhz set - I'm happy to use subject to making sure no other is on my 'number'.

AND there are New FM sets around ... check out RTF boxes .. there are still quite a few that sell FM and even AM 27 .... and I am not just talking the Toy market .. my Lanyu ME109 was 35Mhz ... and still is available with 35 ...

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Old 04-22-2014, 06:32 AM   #16
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Originally Posted by kyleservicetech View Post
IMHO, most of the problems noted with the 2.4 Ghz radios was the use of inadequate receiver power supplies. It's just not a good idea to use a 2500 Mah four "AA" type Nih battery pack on these new radios. Especially on the larger models with power hungry servos.

If you want absolute secure battery power for your receiver and its servos installed in those larger model airplanes, check out a two cell A123 pack, or even a two cell LiFe pack. If your receiver and servos work with a 5 cell Nih battery pack, those A123 or LiFe batteries are a direct drop in. No regulator required.

Those A123 cells will burn up the servo wiring if the servo should ever short out. I've seen it happen twice.

The first failure was with a servo that was pushed way beyond its ratings in a giant scale model. The servo wires were melted from the shorted out servo clear back to the receiver. The second was a kyleservicetech screw up where the battery charge connector connection on a switch harness was accidentally shorted out. Instant smoke everywhere. It welded the switch contacts together in the switch harness. But, that two cell 2300 Mah A123 pack wasn't even close to its rated maximum current output capability.
And of course - the old FM sets would not 'drop out' ... they just kept working down into the depths of voltage !!

Bit like Digital Broadcast radio vs the old ... old would keep playing but interference and white noise would increase ... digital shut of when signal was at a certain level.


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Old 04-22-2014, 06:52 AM   #17
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Evidence suggests that a large portion of the time FM system owners were screaming "I got hit" the RX did a quick reset making the servos jump...

We've proven that the servo loads we were used to imposing on our RX power supplies were driving voltage WAY down. The infamous "brown out" and subsequent reset sequence was that proof.
If you don't drop the voltage below 3.85 at the RX then the Spektrum RX doesn't "brown out"
The Spektrum RX isn't demanding more current than the old FM units did... So the low voltage was ALREADY an issue. You were just getting away with it.

Some of us found out about the low RX voltage due to inadequate power source earlier than others.
I started installing a stand alone failsafe between RX and the throttle servo that sent throttle to idle or shut down a couple of years before the Spektrum systems hit the market.
Interestingly my favorite failsafe device would take over at 3.85v.
It prevented takeoff a couple of times and I didn't complain about the failsafe. I found the reason I had an indication of low RX voltage and fixed it.
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Old 04-22-2014, 07:06 AM   #18
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I do not dispute that we may have had low voltage issues in the past and we got away with it because FM Rx's were not 'linked / bound' to a particular signal ... they would pick up instantly a signal was heard.

The 'infamous' Glitch ... I can remember often ... "Hey guys - just had a glitch..."

BUT fact is that radios such as my JR Propo 35Mhz ... would still operate at very low voltage to Rx ... it did not 'brown-out' as Digital 2.4 does. I proved it on bench years ago ...

There was a big discussion in one club about glitches and the subject of voltage was raised ...as now. At home after I powered a Rx via a variable voltage supply and connected a whole bunch of servos ... this is over 30yrs ago and I seem to remember I connected 5 standard what would be 40 - 50gr equivalents now ... they were JR 4001, 1001, 5001 servos. Lowering the voltage and waggling sticks ... those servos kept going till voltage was so low I just couldn't believe any Rx could go .. it never lost lock or action. Of course the servos were losing ability to move surfaces ... but what I'm getting at - the 3.85V ... 3V or whatever people talk about now - in that example shows it's a modern day matter ... todays Rx's drop out whereas yesterdays didn't .. well at least my JR Propo's didn't and my Futaba M's didn't. Even my 27Mhz AM Acoms didn't ... At least the drop out was at so low a voltage as to be totally impractical

It might be interesting to see if Chellie would do similar with her 72Mhz ... BUT we need a non-synth Rx as that may have drop-out similar to a 2.4 digital.
I may even redo the test with my 35Mhz gear on return home - if someone reminds me ..

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Old 04-22-2014, 07:12 AM   #19
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Evidence suggests that a large portion of the time FM system owners were screaming "I got hit" the RX did a quick reset making the servos jump...
FM sets Rx's never 'reset' ... they didn't 'set' at any time. They responded to a signal on that freq. number / colour irrespective of source. Reset implies a bound or link between two specific as in 2.4.

One club I was in - did a relay flight across water .. switching on another Tx when another switched of ... flew the model about 8 miles if I remember correctly. Took some organising with Walkie Talkies etc. and a very stable trainer plane - but it worked.... 35Mhz.

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Old 04-22-2014, 07:26 AM   #20
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Originally Posted by solentlife View Post
I do not dispute that we may have had low voltage issues in the past and we got away with it because FM Rx's were not 'linked / bound' to a particular signal ... they would pick up instantly a signal was heard.

The 'infamous' Glitch ... I can remember often ... "Hey guys - just had a glitch..."

BUT fact is that radios such as my JR Propo 35Mhz ... would still operate at very low voltage to Rx ... it did not 'brown-out' as Digital 2.4 does. I proved it on bench years ago ...

There was a big discussion in one club about glitches and the subject of voltage was raised ...as now. At home after I powered a Rx via a variable voltage supply and connected a whole bunch of servos ... this is over 30yrs ago and I seem to remember I connected 5 standard what would be 40 - 50gr equivalents now ... they were JR 4001, 1001, 5001 servos. Lowering the voltage and waggling sticks ... those servos kept going till voltage was so low I just couldn't believe any Rx could go .. it never lost lock or action. Of course the servos were losing ability to move surfaces ... but what I'm getting at - the 3.85V ... 3V or whatever people talk about now - in that example shows it's a modern day matter ... todays Rx's drop out whereas yesterdays didn't .. well at least my JR Propo's didn't and my Futaba M's didn't. Even my 27Mhz AM Acoms didn't ... At least the drop out was at so low a voltage as to be totally impractical

It might be interesting to see if Chellie would do similar with her 72Mhz ... BUT we need a non-synth Rx as that may have drop-out similar to a 2.4 digital.
I may even redo the test with my 35Mhz gear on return home - if someone reminds me ..

Nigel
Hi Nigel After switching to Berg Receivers, I never had a glitch, I used to get glitches with JR receivers, they just did not have the filtering for E Power, they worked great with nitro, I have had 0 issues with 72 Mhz and Berg receivers, I learned about 2.4 the hard way, i lost a plane due to a brown out, and at that time I was not aware of 2.4 low voltage problems and brown out issues, as i am sure a lot of newby Rc Pilots are not aware of low voltage and masking issues, Then the Quality control issues of the Spectrum 1st generation Transmitters was really a turn off for me, 2.4 has flooded the market, thats the only reason 72 Mhz is dyeing out, just goes to prove if a MFG Hypes up a Transmitter Market, everyone will buy it just Goes to show you can sell anything to anybody and it does not necessarily have to be good or better, Oh well, I have 0 Low voltage problems, 0 Masking problems and 0 Range Problems, That Alone says Alot, Can anyone with a 2.4 Radio System say they have 0 low voltage problems, 0 masking Problems and 0 Range problems If they say they dont, they are Fibbing IMHO Take care and have fun, Chellie

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 04-22-2014, 07:40 AM   #21
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I would have no hesitation to use 35Mhz again .. we have a couple of guys I fly with who still use 35.

But what I would miss is the programming that has come about with digital computer systems. It is far more extensive than we ever had with FM ..

But saying that - my JR Propo was quite versatile in the mixing dept. even though it was mechanical pots etc. In fact simpler to understand than todays programming ... but yes - not so extensive.









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Old 04-22-2014, 07:47 AM   #22
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Originally Posted by CHELLIE View Post
Can anyone with a 2.4 Radio System say they have 0 low voltage problems, 0 masking Problems and 0 Range problems If they say they dont, they are Fibbing IMHO Take care and have fun, Chellie
Yep, I can say it. I have never once had any of those issues (or any issues at all) with 2.4GHz, and no, I'm not 'fibbing'.

With 2.4GHz I've also never been 'shot down' by someone else turning on on my frequency, which I have experienced with 35/72Mhz technology.

The only loss of control I've had with a 2.4GHz system was when an aileron servo burned out in flight shorting out the BEC and causing it to shut down. Any radio system would have failed under those circumstances, no radio system will work without power. I was lucky, the plane landed with mininal damage in 'freeflight' mode

2.4GHz didnt 'flood the market'.. They supplied demand. If it were not so then how come Spektrum who introduced the technology has gone from none existant to far and away the biggest player in the buisiness in a relativly few years? And how come Futaba who carried on making 35/72MHz systems and were relativly slow to convert lost so much market share? Your arguments just dont hold water, no business bacame a success by flooding the market with products no one wanted. If there was a demand for 35/72MHz systems them manufacturers would still be making them.

Have you even used a modern 2.4GHz system (with a reliable switching BEC).. if not are you even qualified to compare?
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Old 04-22-2014, 07:57 AM   #23
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We can all quote incidents ... we can all see or hear about others whatever the gear.

The end result is that nothing is perfect. If it was - Humans especially would not be around !

Everything has it's faults or failures.

I was told something by an old Science teacher years ago :

"When you think it's perfect a fool or child will prove its not".

Nigel

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Old 04-22-2014, 06:33 PM   #24
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Originally Posted by fhhuber View Post
Evidence suggests that a large portion of the time FM system owners were screaming "I got hit" the RX did a quick reset making the servos jump...

We've proven that the servo loads we were used to imposing on our RX power supplies were driving voltage WAY down. The infamous "brown out" and subsequent reset sequence was that proof.
If you don't drop the voltage below 3.85 at the RX then the Spektrum RX doesn't "brown out"
The Spektrum RX isn't demanding more current than the old FM units did... So the low voltage was ALREADY an issue. You were just getting away with it.

Some of us found out about the low RX voltage due to inadequate power source earlier than others.
I started installing a stand alone failsafe between RX and the throttle servo that sent throttle to idle or shut down a couple of years before the Spektrum systems hit the market.
Interestingly my favorite failsafe device would take over at 3.85v.
It prevented takeoff a couple of times and I didn't complain about the failsafe. I found the reason I had an indication of low RX voltage and fixed it.
Yup
The Spektrum AR7000 receiver uses the CRY6936 microwave transceiver chip for communications. The specs for this chip indicate that it is to be used on voltages between 2.4 VDC and 3.6 VDC.

Since the AR7000 receiver (and most all 2.4 Ghz Receivers) operate on voltages up to about 6.5 VDC, the circuit design must use a voltage regulator. These voltage regulators will require about 3/4 volt "Headroom" above the minimum 2.4 Volts DC. I've checked a number of my Spektrum receivers. They all reboot at 3.2 Volts DC, plus or minus a few percent.

It's interesting on this chip, its rated for minus 55C to plus 125C while in operation. How things in this electronic stuff has changed.

http://www.cypress.com/?docID=28606

DennyV
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Old 05-27-2014, 05:23 PM   #25
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HI all Well I have been using 72 for a very long time been hit only once and never figured out why because we were at a private field.
BUT For people like me that have allot of money invested in high end radios and receivers what can we do I have three PCM type JR's and Futaba. took me a ton of time to save for a 1500 dollars for the 10x system JR System alone and it never has failed and I know there is Plug in for JR on conversion But The cost a new receiver is insane I need only the best for my Heli worth four Thousand with a the stuff you need.
to fly it and just the Model itself.
Why does it seem so many say it is better besides not having to look at the peg board and even if some dummy turns on there stuff with failsafe I think I was hit once and it hovered till my copilot fond the pilot and then all was right.
And to be honest I am a real new when it comes to 2.4 and all extensions IE Fast Dsm Dsm x Spectrum What ever the have Even SLT. So it is a new and very interesting and with the hopping technology.
So I do not believe 72 is dead but when using PCM it works great yet I know 2.4 is the future just do not understand the bashing on 72.
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