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Old Feb 12, 2013, 12:03 AM
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Joined Feb 2013
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72mhz FM vs 72mhz pcm vs 2.4ghz FAAST

Good day all,

Back in my old hobby. Have not been flying for 3 years now, last weekend went and tested my new Edge 540 with DLE 20cc, and also Hawk Pro 30 chopper. Everything was ok, until I had some problem with heli.

Guys worned me that there is an interference problems in my area.

My first radio was Futaba 6ch, with R127df radio. Been flying on that since 2000. No problems.

Then I got 9CAP, synthez, pcm receiver. No problems so far. But some guys say they have crashed several models in my area, all on pcm/fm

they all recommend going into the 2.4ghz system.

I'm planning to purchase TX/RX module for my 9CAP, which will transfer it to 2.4ghz system.


Any feedback on this? Just don't want to trash my pcm receivers after I go to 2.4ghz....

thanks
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Old Feb 12, 2013, 09:02 PM
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United States, CA, Clovis
Joined Mar 2004
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Before you trash anything PCM... why don't you invest in a small frequency scanner and see if there's anything going on frequency wise.

I still believe the FM links are good, mostly based on the fact that I've never had any trouble in my area.. but in this day and age, the areas are getting closer and closer together...

I don't want to even mention or question if there's any chance someone could be intentionally shooting down planes with a rogue transmitter, and odds are slim.. in any case though, Hobbico makes a smallish scanner thats about $30 I think... and there's probably other brands also... thats a ton cheaper then tossing a PCM receiver..

The one nice thing about 2.4 is there just is no chance that you can get shot down by someone else turning on thier tranny...

But it all depends really... I'm not that savvy with the techy side of radios, and just entered the 2.4 arena a few years ago myself with a Spektrum system.. I definately still use my 9CAP though... thats a tried and true radio for sure..

You might even disclose your general vicinity, as maybe someone on here has some experience there too...

I've been looking for a synthesized module for my 9C for a while myself too, and they just aren't out there.. I don't think you'd have to "trash" anything though, as you're probably well aware, that stuff would sell fast on this site.. I wish you well... hopefully a real radio "guru" will post to this..
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Old Feb 12, 2013, 09:19 PM
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United States, IN, Bloomington
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Our club of ~200 still has lots of people on 72 mhz systems. We probably average about 1-2 shoot downs during the entire summer and we don't even know for sure why radio control is lost so we can't tell for sure it is spectrum related.

Will 72Mhz work for you? If you are well outside a metropolitan area and clear of any radio towers then in all likelyhood 72 mhz wont have any issues for you. As always, range test your gear before you fly and take DGrant's suggestion and scan the spectrum at your flying site.

If you decide however you want 2.4 ghz then by all means go for it. 2.4 isn't bullet proof, but it's as close as you can get. Personally I only use 2.4. Its just nice to not have to worry. Just make sure that whatever 2.4 system you get its FHSS (frequency hopping spread spectrum) . FASST is a FHSS product and is very good. DSMX is also good, but STAY AWAY FROM DSM2. DSM2 is NOT FHSS its a different type called DSSS which isn't nearly as interference proof.
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Old Feb 12, 2013, 10:21 PM
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Thank you gents,

I'm gonna tell you one thing, and after you will definetly recommend staying on 72.

RC hobby is very very young in my area, and there are only a dozen people why fly at all. And on single the chance of 2 aircraft in the air is almost non. And we all check the radio channels.

I do have 1 frequency checker, and flip it on before I fly. No problem so ever.

The rumor here, is some guys lost few aircraft here, and the all claim that it is 72mhz has inteferance problems, and 2.4 will solve the issue. Which I strongly do not believe. I think it was technical problems, such as receiver battery was dead, servos did not pull enough etc.

I will definetly by Futaba FAAST module for my 9cap. But not now, in close future.

One thing is interesting for me, 2.4 transmitters are only 0.1W output power, where 72 is full 1W, 10 times more powerful. So range is sacrificed on 2.4?
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Old Feb 12, 2013, 11:02 PM
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USA, CA, Oceanside
Joined Jul 2008
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I still fly 72 regularly here in San Diego and have not ever had one hit or shoot down.
That being said I do also own 2.4

I believe that most Spek issues have more to do with the right thumb of the pilot than anything related to the technology we use.
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Old Feb 12, 2013, 11:18 PM
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United States, IN, Bloomington
Joined Sep 2012
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Quote:
Originally Posted by jeka616 View Post
Thank you gents,

I'm gonna tell you one thing, and after you will definetly recommend staying on 72.

RC hobby is very very young in my area, and there are only a dozen people why fly at all. And on single the chance of 2 aircraft in the air is almost non. And we all check the radio channels.

I do have 1 frequency checker, and flip it on before I fly. No problem so ever.

The rumor here, is some guys lost few aircraft here, and the all claim that it is 72mhz has inteferance problems, and 2.4 will solve the issue. Which I strongly do not believe. I think it was technical problems, such as receiver battery was dead, servos did not pull enough etc.

I will definetly by Futaba FAAST module for my 9cap. But not now, in close future.

One thing is interesting for me, 2.4 transmitters are only 0.1W output power, where 72 is full 1W, 10 times more powerful. So range is sacrificed on 2.4?
Yes 2.4 definitely doesn't have the range of 72 mhz.

With 2.4 you MUST have and unobstructed line of sight to the model. The best range i've seen on stock 2.4 setups is about 2.5 km. So well out of sight but unless your an fpv pilot then it wont matter to you.
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Old Feb 13, 2013, 09:44 AM
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United States, WI, Slinger
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Originally Posted by btown2 View Post
but STAY AWAY FROM DSM2. DSM2 is NOT FHSS its a different type called DSSS which isn't nearly as interference proof.
Any proof to back up that claim or is it just because you fly Futaba? I've been flying Spektrum radios since the day they came out starting with the DX6 Bought the DX7 the day it came out. I've flown everything from airplanes to helicopter, gas, glow and electric and I've never had a single issue and I don't know of anyone in my club that has.

Mike
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Old Feb 13, 2013, 12:37 PM
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United States, IN, Bloomington
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http://www.rcmodelreviews.com/fhss_vs_dsss.shtml

I have no problem with DSMX which is spektrum. I wouldn't hesitate to use it. But DSM2 is a completely different animal and I would'nt willingly fly it.
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Old Feb 13, 2013, 01:39 PM
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Canada, BC, Langley
Joined Nov 2007
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Originally Posted by jeka616 View Post
Good day all,

I'm planning to purchase TX/RX module for my 9CAP, which will transfer it to 2.4ghz system.


Any feedback on this? Just don't want to trash my pcm receivers after I go to 2.4ghz....

thanks
I am using a Futaba TM8 module in my 9CAP with no problems now for two seasons. One caveat, if you are switching between 72MHz and 2.4GHz. REMEMBER TO PUT YOUR ANTENNA UP when flying your 72MHz stuff. I have had an occasion to take off with a 72MHz systen and forgot to pull the antena up. Fortunately I made a turn into the circuit before my plane got out of range and managed to pull the antenna up before I lost total control. Another thing that you should be careful of is that plugging and unplugging the module often is not recommended as the pins may become intermittent and cause problems. I have several transmitters so I do not change the 2.4GHz module in my 9CAP but use another transmitter for my 72MHz stuff.
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Old Feb 15, 2013, 01:41 AM
TigreJohn
United States, CA, Corona
Joined Aug 2008
996 Posts
Jeka616: Would advise that your source that says that a 2.4 transmitter has one full watt of power is full of doo-doo. An ancient FCC tech spec (when we were on 27mhz Am) and still in effect limits us to 100 milliwatts (0.1 watt) in an attempt to limit us to a usable range of 1/4 mile. Of course, with the additional frequencies and much improved receiver sensitivity we can exceed that distance.
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Old Feb 15, 2013, 03:09 AM
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Joined Dec 2005
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I use 72 mhz at times, at fields that the locals swear certain channels will not work. No problems for me. I think it is often setup issues, and equipement quality issues. Do have to watch out for harmonic interference from certain channel combinations. I stay away from certain channels that are more likely to get into harmonics. But would have to look up a chart. It has been so long since I have thought about that, since usually I'm the only one with a 72 mhz. Tv broadcasts used to be a problem on certain frequencies, but most Tv stations have switched now, so not sure if that is a problem anymore.
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Old Feb 15, 2013, 05:56 AM
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United States, WI, Slinger
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Originally Posted by btown2 View Post
http://www.rcmodelreviews.com/fhss_vs_dsss.shtml

I have no problem with DSMX which is spektrum. I wouldn't hesitate to use it. But DSM2 is a completely different animal and I would'nt willingly fly it.
All I know is I've flown my DX6 (DSM) and later DX7 (DSM2) since the day came out, for thousands of flights, and have NEVER had so much as a glitch. And as I said I have a lot of flying buddies who fly Spektrum and none of them have ever reported any problems so I have to wonder where your paranoia comes from.


Mike
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Old Feb 15, 2013, 06:09 AM
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Originally Posted by MikeCr View Post
All I know is I've flown my DX6 (DSM) and later DX7 (DSM2) since the day came out, for thousands of flights, and have NEVER had so much as a glitch. And as I said I have a lot of flying buddies who fly Spektrum and none of them have ever reported any problems so I have to wonder where your paranoia comes from.
Mike
I have seen DSM2 brownout in the early days with 4.8v, but rock solid with the use of a 6v-6.6v battery. The only issues I've had have been either the ubiquitous AR500 (exchanged by Hobby Services for an AR600 after it tested bad with multiple frame drops) or a battery shorting inflight. Beyond that I've never had a glitch with DX6, DX8 or JR 783 on a 2.4 DSM2 module. I fly electric indoor and out, and glow with my radios.

Hogflyer
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Old Feb 15, 2013, 07:12 AM
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United States, WI, Slinger
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I have seen DSM2 brownout in the early days with 4.8v, but rock solid with the use of a 6v-6.6v battery. The only issues I've had have been either the ubiquitous AR500 (exchanged by Hobby Services for an AR600 after it tested bad with multiple frame drops) or a battery shorting inflight. Beyond that I've never had a glitch with DX6, DX8 or JR 783 on a 2.4 DSM2 module. I fly electric indoor and out, and glow with my radios.

Hogflyer
That's good to know. I'll have to check my inventory of receivers to see if I have an AR500, not sure. If so i have not had an issue but I'll need to do take action. In any case your experience seems to mirror mine as far as the reliability of DSM2 in general. An individual receiver problem does not warrant a statement that all DSM2 systems are unreliable.


Mike
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Old Feb 15, 2013, 09:00 AM
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United States, IN, Bloomington
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Originally Posted by MikeCr View Post
All I know is I've flown my DX6 (DSM) and later DX7 (DSM2) since the day came out, for thousands of flights, and have NEVER had so much as a glitch. And as I said I have a lot of flying buddies who fly Spektrum and none of them have ever reported any problems so I have to wonder where your paranoia comes from.


Mike
Mike I have several planes on spektrum equipment. I have a DSMX DX6i with several DSMX receivers running on them. I am certainly not out to badmouth Spektrum. I am just trying to say that if the OP were to invest in a new 2.4 system and wants to go with Spektrum; then he should choose DSMX products over DSM2.

My reasoning is simple here... DSM2 uses two frequencies and switches between them. If you are out away from 2.4 noise then you are perfectly fine as you have seen in your own observations. However I live in a very 2.4 noisy apt complex and fly my UM DSM2 models at our basketball court. I have glitches constantly. Because every single wireless router is constantly shifting trying to find ca clear spot on the band to use. So I am often interfered with.

DSMX is frequency agile which means it is constantly shifting and thus never stays on a congested part of the band for very long. I have never had an issue with my DSMX models while I have issues all the time with DSM2.

If however you have a good quiet spot and have had good results from DSM2 then by all means keep at. But for a person buying a first time 2.4 system there is no reason not to buy the more interference resistant DSMX.
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