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[Netleyned]

Phillnjack

You came on the forum asking for some information that was supplied by members
That is what we are here for.
We also try to abide by the rules
35 MHz is reserved for Fliers
If a flier on the same freq caused you to lose a boat
you would not be a happy bunny
I know someone who flies a large aircraft controlling it from his dads cessna
Hope he doesn't fly over your bit of the ocean

Ned

[phillnjack]

I give up with you two, you obviously cant read , or wouldnt come out with such crap




phill

[PMK]

Phil&Jack,

For arguments sake, let's assume that most all R/C transmitters have an output power of somewhere around 100 millwatts. Let's also assume that it's pretty safe to say that, in reality, most all R/C transmitters have an output power of far less (some can be as little 50mW or even lower). Making sense so far? Now, bear in mind that the characteristics of the 2.4GHz frequency is waaay different from that of, say, 27MHz or even 40MHz -- even though they may indeed have the amount of power outputs. 2.4GHz, being Ultra-high frequency is, as you rightly said, mostly line-of-sight. UHF does not penetrate or travel across water anywhere near as good as a HF signal would. For the record, 35mHz and 40MHz is just inside the VHF part of the radio spectrum, whereas 27MHz is near the upper edges of the HF spectrum. In other words, a 27MHz signal will radiate across water slightly better than than a radio operating on VHF and UHF frequencies.
In case you're wondering, the reason for all this gobbledegook is to try to answer your question of whether you will lose control of your model when it's hidden by a two-foot swell. If you are using UHF, then I would hazard a guess of "yes".... especially over a distance of several hundred feet away. Aircraft models, on the other hand, are a different kettle of fish. Being that the R/C receiver in a plane is much higher above ground level means that the UHF signal will carry a far greater didtance. If you were operating a model plane then I'd have no hesitation in recommending one of those 2.4GHz units from, say, GiantCod. But being that you are using a model boat - and under such extreme circumstances - then it might be best if you were to stay with 27MHz.
For what it's worth, there are some excellent 27MHz R/C transmitters available dirt cheap nowadays. And if you wanted to be really naughty, you could easily beef-up the output power in order to make sure that your little 100mW signal has a far greater chance of making sure that your model stays under control... even if it does hit a two-foot swell.
My only other word of advice would be to avoid 27MHz Acoms sets like the plague.

[phillnjack]

Thanks PMK you have answered my question.

as for the acoms, its funny you say that as ive never had a problem with acoms , but never used acoms apart from a lake.
Ive used an old jr beat radio on 27 am no probem on rivers and at sea, but only on flattish water.

I think ill stick with 27 am for a touch longer, and just keep my ff7 on the back burner for a while.

what do most of the offshore racers in omra use ?


phill

[PMK]

On second thoughts I'm not sure that I have answered your question.
As you know already, the FF7 is a superb radio - not to mention the excellent spectral purity of the output signal. Like JR, some of the more modern Futaba equipment is built for quality - and the main RF output board is housed inside a separate plug-in unit. So, to answer your initial question, yes - the FF7 can be converted to 2.4GHz quite easily. Very cheaply, too. Myself and at least one other Mayhem member have converted a Futaba 9C (which is just a beefed-up version of the FF7) for 2.4GHz. The new 2.4GHz board employs a similar channel-hopping system as that of Futaba - and the appropriate receivers are miles cheaper, to boot.
I didn't mean to bad-mouth Acoms equipment, but I've lost count of the number of Acoms sets which have quite a dirty output signal. i.e: nowhere near as tight nor as clean as the JR or Fut' gear.
Regarding 27MHz transmitters, you might want to consider one that uses frequency modulation (FM, as opposed to AM) - preferably one which uses a receiver with dual conversion and not single conversion... if that helps any.
Sorry I can't help with the OMRA question.

[triumphjon]

i think you will find that ALL OMRA modellers will be using the legally allocated frequency ! 35 mhz has always been , and always will be specifically for AIRCRAFT USE ONLY  model cars and boats work very well using 27 or 40 mhz to which we have been allocated , just because you choose to operate upto a couple of miles off shore dosnt excuse the fact you are operating on an illegal frequency ! the other members arent talking "rubbish " merly stating the facts i cant see any problems using a 2.4 ghz set in a 2 foot swell , ive a metre class yacht that spends quite alot of its time either on its side or with its bow under the surface of the waves , ive been doing this for best part of a year and had no problems with control .

[RaaArtyGunner]

Phill,

As a bystander, pretty good commentary (and I see your point), even though you may not like/agree with some of the answers. 

At the end of the day the choice is yours as you don't have too heed any advice (all extremely good, knowlegable and experienced) given.

Bottom line is, if  you break the rules, doesn't matter which ones and it goes pear shape then be prepared to pay the penalty.

There is thread on the forum, about a plug in FrSky module, for converting Futaba to 2.4 also Giant cod has a Video review (favourable) of the conversion.

Some one locally,(from where you are as you have not indicated a location) might be able to provide the links.

[PMK]

"...ive a metre class yacht that spends quite alot of its time either on its side or with its bow under the surface of the waves , ive been doing this for best part of a year and had no problems with control ."

@ triumphjon:
That's comforting to know. But, just out of curiosity, are you sailing your yacht on a lake/pond, or briny sea water? And what distance is your yacht from your transmitter when its bow is under the water?
Pardon me if these Q's sound a tad cheesy, but believe it or not, these parameters (especially salty sea water) will have a certain effect upon the transmitted signal reaching the receiver in the model. If you are indeed sailing in sea water with 2.4GHz, then are you able to achieve glitch-free control over the same sort of distances as those used by Phillnjack?
Again, apologies if this sounds in any way cheesy. I'm just curious is all.

[phillnjack]

Thanks pmk, greatly apreciated info.............

Triumphjon, Now being as you have a sailing boat that cannot in any way whatsoever be compared to a powerboat
apart from they both float, radio glitches of even half a second would probably not be noticed by you.
But a boat travelling at say 50mph having a 1/2 second glitch could of veered ofcourse dramatically.

3 foot sail boat possibly 4 knots if its realy quick one, 5 foot powerboat 45 to 50 knots if a quick one.

im not knocking sailing boats, they look great on ponds, and lakes.
I personally have not seen many rc sailing boats on the sea, ive seen a couple in a sheltered harbour though.
they probably look pretty good on the salt water waves.

But you state you have had no problems with 2.4ghz even with a bow under water,
where on your sail boat is the reciever, and how high is the ariel ?




phill

[triumphjon]

my receiver is mounted inside of a baloon and about half of an inch below the deck , when operating the deck is no more than 1 1/2 inches above the water , the areil on the receiver is just over an inch in length ! as for the speed of my sail boat i feel this to be irrelevent , and as the radio has its own built in fail safe should any problems arise the radio will activate the chanel as set by the owner of the set , which can be set to whichever chanel you require and can be set to do whatever you would like the fail safe to do ! the fact that i used to race both in ic multi and off shore events , and often now operate my electric models in the solent .

[phillnjack]

reciever ariel is only  half an inch long ?  are all 2.4 meg reciever ariels only half an inch long ?

Is there any benefit in making a longer ariel to protrude outside of the hull ?
I normally have ariels that resemble scale vhf or around 1 foot in height, but if they dont need
then even better i suppose..

But half an inch, that does surprise me.

I too used to dabble with multi's a long time ago, the days of mini jaguars ,jumbo jaguars, opus 40's etc.
when the wee mccreggor radio was considered good stuff,futab only came metal cased, flexi shafts were new ideas,
and the thought of ever getting new 2 channel radio for only £50 was considered mental.
Digimac 2 was the cheapest at £79.50 = 2 weeks wages.


phill

[John W E]

Hi phillnjack
have a look at this pic ,it is the 2.4  set up i have in the surfury

hope  this helps

aye

john e

[malcolmfrary]

Frequency and ideal aerial length are closely related.  At low frequencies such as 27MHz, a few centimetres either way on what is probably a piece of wire set to about 1/16th the resonant length doesn't make a huge difference, not really enough to notice.  However, the odd millimetre out on something tuned to 100,000 times the frequency is going to be critical, and will probably prevent reception by effectively tuning the entire thing out of band.  Real digital signals are tremendously robust - they can produce a good result even after a great deal of mangling, but when they go beyond limits, they GO.  Very suddenly.
The big advantage of the lower frequencies in your situation is that you can fit a longer aerial, and you can mount it vertically.  This way, there is less likelihood of it being hidden behind a wave enough to lose the signal.  Bear in mind that signal strength does drop with range, and a partially hidden aerial will be less effective than one in full view.  Also my previous comment about digital systems - none of the pre-2.4 systems are fully digital, they are analogue transmission systems that use the RX to create a digital signal.  The RX can take a weak, possibly badly distorted, signal and produce a viable digital signal to work the servo, right up to the time when the limit is exceeded.  Sensitivity will probably improve - selectivity will suffer (open the window further, more flies come in) but in your situation, this should not be a problem.
Most model boating happens at less than 400 yards range - we like to see the boat.  On most venues the transmitter will be a good few feet above the water surface (and the bank usually doesn't go up and down by itself), so the very short aerials associated with 2.4, although very near the water level, are very rarely obscured.  Many have two aerials, and take a vote on which is working, with a bias to doing something, which accounts for them continuing to work even in quite lumpy conditions.  A long swell on open sea will be very different, not least because your boat will at some time be in a trough at the same time as the model.

[John W E]

Hi all, I have bided my time to see if anyone has picked up yet on the 2 photographs and about interference on 2.4s (blind spots if you want to call them that) .  When I first tested the Surfury out on 2.4 I had a problem with the planet 5; when I switched the set on - it would swap modes.   It was originally set up throttle on left hand stick and rudder on right hand stick. This would just happen for no reason at all - instantly swap over - pretty dangerous.

The other thing, when I had the Surfury in the pool in the garage, if I lay the transmitter on the ground whilst I was adjusting the motor, even though the transmitter was only feet away from the model, it would lose signal.  I am not sure if this is just 'one of those things' but, until I get it sorted, I myself have been reluctant to run this model on an open lake - you see gone are the days for me when I could run after a model if it goes astray - so I am considering going back to 40 mghz.

Just some food for thought there.

I know there are a lot of off shore lads use 2.4 and swear by it, but, I have yet to be fully convinced.

aye
johne
bluebird

[HS93 (RIP)]

the better sets have built in Failsafe, also has the aerial been painted, and could you not get any more of it it in to free space so it has a chance to work ?

HS93

[unbuiltnautilus]

Interesting thread, and the type I swore not to get involved in... However, rather than using an illegal frequency set on a model boat, and painting all boat modellers as irresponsible, why not spend a little bit of cash on a 40mhz set of similar spec, power boating isnt a cheap side of the hobby, why be a cheap skate about it and use an aircraft set to operate yuor model??
We run models with pyrotechnic effects fitted so can stand on our own soapbox about how the lesser modellers "wouldn't understand". We don't though..
Suggest running a couple of extra miles off shore into international waters or better still a bit closer to France, I'm not sure but they may use the 35mhz frequency for all sorts of nefarious RC activity!!!!

[triumphjon]

as ive been told the ariel on the receiver is actually a small coax type wire , therfore lengthening it isnt possible ! however ive been using a planet t5 set since last march and havent experienced any problems with range or loss of signal , its pssible to change the sets from mode 1 to mode 2 as there is a selection switch inside the back of the set , there is also the fail safe switches inside the set . considering this set costd just £50 i consider it well worth the money ! having considered the idea earlier in the year about converting a hitec tx that i had , somebody offered me a good deal on it so ive bought another planet 2.4 transmitter , the new 6 chanel with 8 model memory for £55 minus the rx !

[Stavros]

Having been using the futaba 2.4 system for 18mnths and have NEVER had an issue with range with a 1mtr yacht,sailing with the deck awash reciever on the blind side,in other words 2ins down in the hull and under water at ranges in excess of 400 yds,yes I know it's a tiny speck,never failed to resonse.had trouble in the past with both 40 and 27hz even though areal was above water .Strange but true

stavros

[triumphjon]

funny that stavros , the comment i had earlier was that due to the fact i had a yacht in similar conditions its not as quick as a nitro powered race boat ! i dont think speed is of the issue , more the fact that WE still have control of our models !

[phillnjack]

well im suprised the sail boats do so well with their decks underwater ?

The sub boys who have wanted 2.4 have been very dissapointed and told it dont work.
The makers of the radios say it dont work,
The people who sell the radios say it dont work.

Yet here we have sailing boats that have had their recievers deliberatley placed below waterline getting
fantastic results even when the decks of the boats have been covered by water  !!!

Maybe everyone is lying about how bad the water is against 2.4 i dont realy know, i aint got 2.4ghz.

but id do understand the difference of losing control at certain speeds.
A fast model powerboat can be travelling at 90 feet per second by the way.
a rc sail boat  travels at around 6 feet per second.


phill

[RaaArtyGunner]

well im suprised the sail boats do so well with their decks underwater ?

The sub boys who have wanted 2.4 have been very dissapointed and told it dont work.
The makers of the radios say it dont work,
The people who sell the radios say it dont work.

Yet here we have sailing boats that have had their recievers deliberatley placed below waterline getting
fantastic results even when the decks of the boats have been covered by water  !!!

Maybe everyone is lying about how bad the water is against 2.4 i dont realy know, i aint got 2.4ghz.

but id do understand the difference of losing control at certain speeds.
A fast model powerboat can be travelling at 90 feet per second by the way.
a rc sail boat  travels at around 6 feet per second.


phill

Phil,

 I also don't have 2.4Ghz plus I don't think we are on the same boat.

What I am understanding that is being said is, that decks awash, not submerged, can be handled by 2.4Ghz. Perhaps because there is only a momentary loss/disrution of signal if any.
Whereas submerged, that is a submarine which is under the water the 2.4Ghz signal is degraded, particularly in salt water.

So as not to labour the point if you do a search of the forum relating to 2.4Ghz it will bring all this to the fore. 

[HS93 (RIP)]

The offshore chaps seem to have no problems racing in OMRA a properly installed 2.4 is normally no problem in big waves, it is used extensively in the UK and USA in big boats that run in rough water.

HS93

[triumphjon]

i too cannot see a problem in a swell , the radio waves must be bouncing over the waves ? im told the frequency is the same as used by our moblie phones , which still work when we travel up or down hills or behind buildings , having bought now my second 2.4 ghz radio ive not experienced any issues with its signal or range , and i doubt that many of us can see to the point of the radio being beyond its operating range anyhow ?

[malcolmfrary]

i too cannot see a problem in a swell , the radio waves must be bouncing over the waves ? im told the frequency is the same as used by our moblie phones , which still work when we travel up or down hills or behind buildings , having bought now my second 2.4 ghz radio ive not experienced any issues with its signal or range , and i doubt that many of us can see to the point of the radio being beyond its operating range anyhow ?

The radio waves bounce off surfaces.  The only way they can go from the sea surface is up, and having bounced, carry on upwards.  Cellphones work in most places because there are a great many transmitters, and the cell phone picks from a selection the one it likes best, and has the ability to change on the fly.  There are still dead spots even so.  In model use, there is just the one transmitter.  The scenario here is not extreme range, but a transmitter going up and down because the boat that the operator is on is going up and down, as is the boat under control.  There will come a time when both are is a trough at the same time with possibly a lot of sea and several waves in between.  Wave swells tend to have a gentle slope, and reflect.  Steep waves will absorb, and after going more than a few inches into the water, the signal will have all but vanished.  This is the same problem as the submarines have.  The model could have its aerial out of communication for long enough to give trouble.  A temporary loss of power would not be a problem (assuming a fail safe) but a loss of steering could be.

[phillnjack]

Thankyou malcolmfrary .
you have explained it perfectly.

Now ill just use 27am for a while , and maybe get 2.4 for when i want lakes and rivers.

and i think ill get my futaba converted to 2.4 then i know i have a good set, rather than cheapo.

If the cheap ones are that good i cannot see why futaba and likes havnt gone bust yet,like mccreggor did when
futaba made cheaper sets.

Thanks everyone for all your input on this subject, im now off to look at prices for conversion stuff on tinterweb.

happy new year to you all


phill