Serious 2.4Ghz Problem arising.

[Steve W-O]

Posted by tom wright 2 on 26/02/2011 14:36:57:

Based on the information so far it occurs to me that a conventionally equipped model would have to get very close to an illegal TX , before it became a problem,talk of 5w or even 10w transmissions ,smacks more of malicious intent,rather than accidental interference.

Steve i posted this before i saw your previous post sorry.

TW2.

 

Edited By tom wright 2 on 26/02/2011 14:45:17

 

 

Yes, I agree it seems more likely it was from another sauce switch, maybe malicious.

 

Line you shed with metal, take the door off a microwave and bypass the safety switch, cut a hole in you shed lining to fit the microwave with no door, and you have maybe 1kW of 2.4 energy going towards the flying field.

 

A high power wifi booster with a Yagi antenna pointed at the model would have a similar effect.

 

Your right, there is probably little to worry about from FPV

[Steve W-O]

Just out of interest, I just put the laptop with a small SA next to the microwave and turned it on.

 

There are spikes all over the 2.4 band, some of them stronger than my RC TX

 

 

An leakage from a microwave is much more than I have, it's about 1W

 

 

So don't use a microwave at the field

[GONZO]

Quite so SW-O, 2.4gHz RC is more of a problem to the FPV'ers video than the FPV'ers video is to the RC'er.

So, it's no more micro waves at the club field BBQ. I'll just have to use use my Wi-Fi linked lap top to email the other half to have dinner ready. Although, it is some way to the nearest access point but it should boost the o/p to make the connection Or, should I use my Bluetooth enabled mobile

(gota have my little joke)

[Chris Johnson 1]

Hi Guys,

Of course you are all very welcome to check out our FPV site www.fpvuk.org and hopefully you'll see that we do not condone or advertise illegal setups. Of course you'll always get those that do push the limits but it's the way of the world' i'm afraid.

As a matter of interest I work in Afghanistan for most of my time and therefore don't get to fly as much as i'd like, but in May I hope to maiden my 1/5 scale K&W BE2c. When I am happy flying LOS I will be putting FPV gear in her and flying through the goggles with a Co-pilot on the Buddy lead or at least there to grab the transmitter. If I had any doubt of the capabilities of the Flight Controls and/or the FPV gear I would not be putting almost 1k GBP in the air now would I?

BTW I was an avid watcher of the Wings TV series in 1977-78, anyone remember it?

Pity they only screened it once but I have the DVD set so no problem.

Chris

[Biggles' Elder Brother - Moderator]

Steve/Chris, I actually think that much of your comment supports my point not contradicts it. Firstly there is a website - yeah, I'm not disputing that FPV fliers talk to each other, and that's great, its the dialogue with the rest of us that I feel is missing!

 

Chris you state you have been modelling for many years - again I said I was sure that there were indeed folks such as you, but my impression is that they are not the norm in FPV - the publised side of FPV that I see seems to me to have a disproportionally high element of folks with a non-modelling background.

 

Now - please read this bit...

 

1. Again I stress I'm not anti FPV, and I'm not blaming anyone for anything - I'm just making a personal observation about the FPV scene in the UK generally.

 

2. My post was never intended to represent a "thread of reasoning", again its just a personal emprical observation.

 

3. There's nothing in my post to suggest that I view all FPV fliers as irresponsible!

 

All I'm saying is it seem to me to be a pity that FPVer's appear to be isolated from the mainstream of the hobby and I believe it would be better if they were on the inside looking out. Now we can debate who's fault that is - personally I think BMFA was very slow to respond to this area of the hobby - but it does appear to be the case to me.

 

BEB

[Chris Johnson 1]

Absolutely BEB. I am as they say caught in the middle. A conventional modeller who is now getting into FPV. Like most of us no doubt I have been into anything that would fly since birth I think.

It would be great if more BMFA Clubs explored it and accepted it as mine has done. I like to be a social flyer and spend as much timing talking about flying as actually doing it. That could prove a little difficult if I was to be a lone flyer.

As with all "new"ideas, people just have to get used to it and if they like it embrace it.

A lot of misleading stuff seems to come from RCGroups where there are many forum members who are not open to new ideas and are relentless in their berating of FPV which just leads to high blood pressure for no reason.

RCM&E did a good article on FPV a while ago with David Ashby I believe.

Maybe that's what we need, some more enlightened articles like that for the wider audience.

As I said in a previous post, I am in Afghanistan and have a lot of time on my hands, maybe I could write a regular column.

Watch this space

Cheers

Chris

[Snorbitz]

I've never had any problems on my 35meg system....oh thats rite it wasn't broke in the first place so no need to fix......sorry had to get that in there..

[Peter Beeney]

Just to recap on some previous posts, and to test the ancient memory, the dB is a logarithmic ratio of two values, in this case power, or perhaps more precisely, transmitted power, expressed in watts. dBm. The m indicates milliwatts, so the value given is is a power level with respect to a one milliwatt reference.

The basic expression is 10 log (Pout/ Pin) dB. If the power out, (Pout), is 10 milliwatts then 10 log (10/1) = 10 dB. (Pin = 1). If the power out is 500 mW, then 10 log (500/1) = 26.989, say 27 dBm. A 1,000mW power level would be 30m dB. 2,000 mW = 33 dBm and 4,000 mW = 36 dBm. 10,000 mW will be up to the 40 dBm level. Steve W-O’s middle of the field example I think is a difference of 20dBm, 40 to 20 dBm, assuming the ground based tx is a hundred milliwatts output.

I also think the airborne transmission limit is 10 mW, that’s 10 dBm. Relate this to the ground based tx, 100mW, and it’s -10dB, or 10 dB down. I think, very roughly, the transmission power of the signal is attenuated inversely as to the square of the distance. Or, in other words, and turning this around, if we double the distance, we reduce the signal strength to one quarter. I think this is -6 dB, or the 6 dB down point. The - 3dB point is considered to be the half power point down. A 5W transmitter would need to be 7.07 times further away to have the same signal strength at the model, the 10W emitter would need to be 10 times further. If the 1W FPV interfering tx was 3.2 times the distance of a 100mW tx, then the received signal would be the same. This makes me also think too, that any potentially interfering source would have to be fairly close.

Hopefully I’ve got this at at least somewhere near correct, if not I shall have to rethink. I’m also not sure if it’s of any use, but at least it’s a thinking exercise! For me, at least.


As with some other posters, and from the experience of many other little ‘scare’ stories in the past, I would consider this one would need considerably more checking out before reaching any conclusions. We’ve also had a few 2.4 GHz ‘happenings’ too, which I’m convinced are nothing whatsoever to do with FPV!

Chris, You mentioned the BE 2c, I have a friend building one, albeit quite slowly. His has a wingspan of 14 feet, so I think it’s between half and one third scale. It’s of a particular full size version, No. 1741. Also the Wings series, I certainly watched that; I think that some of the flying scenes were models, made and flown by David Boddington. I was on holiday in Cornwall just after that and in Penzance, a favourite haunt, at the top of Market Jew Street, there was a shop with some of David’s actual film models in the window! I have a feeling this was connected to the Flambards Theme Park just round the corner at Helston at the time. David also did some DC3 models for Airline, the tv series with Roy Marsden, also from yesteryear. I remember he wrote about it in the mag, saying how they'd reduced the oil content in the fuel to below 10%, to try and reduce the smoke. Apparently it didn’t have any adverse affects on the engines, Webra 61’s I think. He was asking then, the question, - ‘Do we put too much oil in the fuel?’ Nothing changes very much! I was always a David B fan.

We have a FPV enthusiast, so far an observer only, he's not actually flown via the link. We’ve all had a look through the goggles, though. I like it, as you say, some better and more informed views can only be a good idea, such as your column, maybe,?

PB

[Steve W-O]

Yes, correct, I just used convenient distances and signal strength (power density would be more correct) as a way of illustrating the point without the maths.

 

I didn't work out your distances, but they show the same trend anyway.

[Chris Johnson 1]

Hi Peter,

for a second there I thought i'd stumbled into a foreign language thread. All this electrickery stuff is all but a mystery to me, that's one reason I prefer nitro engines to the electric stuff, I understand them. I do like the idea of the clean model and just charge and fly but to me it has to sound right as well. Please don't tell me I can fit sound systems to my models, I have enough trouble plumbing up all the FPV gear at times. It's a mystery to me how it works most of the time.

Anyway onto the BE2c of your friends. I'd love to see that build. I guess he'll be putting a big petrol in there then?

A few people have built full size flying replicas as I believe the only original 2c is in the Imperial War Museum in London.

I'm rather hoping the tail number on mine, 4395, isn't an omen as the fullsize "crashed and was extensively damaged" in Arabia.

Tail no.1741 of 12 squadron - France. This aircraft was shot down 4 months after being delivered to the above Sqn. It was repaired and while at Farnborough, had a Lewis gun fitted on an experimental mounting. After returning to France, it was struck off the books when wrecked on March 1 1916.

Let's hope this is also not an omen.

As for the column, I think that will remain just a dream for me.

I have my own website I just do as a hobby really but there's some pretty good stuff on there.

www.bardney-flyers.co.uk if you would like to check it out.

Cheers

Chris

[Biggles' Elder Brother - Moderator]

Hi Peter,

 

having checked through your sums I agree with them. But, I'm a bit more circumspect about the conclusion you draw. You use the example of the interfering signal being the same power as the main signal. But as a determinant for interference I would suggest that might be generous. If you redo the calculations on the basis that the interfernce signal threshold for effective interference is -6dB (i.e. the point at which the interference signal is one quarter the strength of the main signal - while being a more demanding case is possibly a more realistic one in terms of the Rx's ability to reject noise) then the non-linear nature of the sums kicks in and you get the result that a 1W Tx would need to be 6.33 times further away.

 

Now a modeller could easily have a model 400m away from him - routinely in fact - that would mean that the interference source could be over 2.5km away from the model and still exceeed the -6dB threshold I am suggesting for possible interference. So if the interference source was the other side of the model he could be more or less 3km (almost 2 miles!) from the flier himself. That's not that close! Its certainly out of sight and mind in most instances in the UK.

 

BEB

[leccyflyer]

Posted by GONZO on 26/02/2011 13:58:18:

Other FPV video frequencies available - 900mHz, 1.2/1.3mHz and 5.8gHz. First two not legal, but whos checking frequencies and o/p power. I suspect its like most law enforcment - don't cause any major(financial) problems then no one whants to know.

On the question of RC for FPV - some use 35mHz with longer Rx aerials for increased range. Others use 430-440mHz UHF frequency agile spread spectrum sets.

Which begs rthe question of why would they need increased range, if they are operating legally, namely within direct line of sight control?

[Martin Harris - Moderator]

And mightn't it be significant, BEB, that the "interference" source transmission could be at considerable atlitude while the conventional model is being controlled from the ground?

 

...and to expand on Leccy's point, I think any "opposition" from conventional modellers is nothing to do with FPV being seen as different, "not what we do" or any sort of blind prejudice - indeed I would assume that the majority of us wouldn't be averse to having a go ourselves if it wasn't such a considerable financial commitment to get started in what might be a fringe interest. The main concern is of an irresponsible operator causing a high visibility incident that could have negative consequences for the established hobby.  Couldn't happen?  One of my clubmates has had to virtually give up on his other hobby of pistol shooting, at which he was at a high standard, as a consequence of blanket regulation post Dunblane.

Edited By Martin Harris on 27/02/2011 14:21:16

[Steve W-O]

Posted by Martin Harris on 27/02/2011 14:06:33:One of my clubmates has had to virtually give up on his other hobby of pistol shooting, at which he was at a high standard, as a consequence of blanket regulation post Dunblane.

Edited By Martin Harris on 27/02/2011 14:21:16

 

 

I didn't know that, but it is typical of any government, clamp down on the law abiding citizens, but it makes zero difference to the criminals, they wouldn't apply for a permit anyway.

 

Rather like visa applications, make it expensive and difficult for the people who do it the right way, and help the people who don't!!!

 

 

When you look at other things, it does become rather worrying from that perspective, knowing that if anything had to go wrong, the authorities would have an illogical knee-jerk reaction.

[Peter Beeney]

BEB,

I didn’t really intend my ramblings to be any sort of determinant for interference calculations. They were just a little exercise in fiddling about with power levels. I’m not even sure how this would even apply to narrow band, such as 35 MHz, let alone wider band 2.4 GHz. I was just trying to show how the power levels might vary. I certainly wouldn’t be convinced that the - 6dB point is anything to do with interference, just a little indicator that the signal strength attenuates proportionally to the inverse of the distance squared. And I guess that’s only a very general statement anyway, in practise each situation might be different.

Interference and 2.4 GHz is a bit different anyway. Many tx’s can all operate together without problems, I have read that the Americans have had up to a 120 all operating together without any evidence of interference; so any signal that can cause trouble must be pretty unusual. I’ve no idea how it works, but Steve W-O’s description of the experiments with the laptop computer and router seemed to bear out in some small way what I fancy might be going on. So this all supposition and guesswork.

I understand there are about 83 channels available, each one at 1 megahertz wide. 1 MHz is quite a lot of bandwidth for the control information to start with, I would think. Leaving aside the transmission techniques, channel hopping etc., I would then say this information is sent to the receiver with a unique identifier, which the rx processor recognises and thus then passes on the information to the decoder. Anything it doesn’t recognise, and I think there must be plenty, it just ignores. As long as the right code gets through fairly often then that is sufficient. As I said, this is all relatively speaking. If the channel get too crowded the (model) radio will start to slow up, as demonstrated by Steve. But to get to this point I’d say the rx has to be virtually overwhelmed, with the transmitter very close to the rx. Perhaps similar to the ‘IF breakthrough’ that can happen with a little transistor radio when it gets very close to a powerful national transmitter. This is what makes me think that the interfering source must necessarily be very close to the rx indeed.

If the ISM radio bands do tend to get increasing congested in the future, then this may show up eventually as a problem; not physical interference, just generally slowing up, but I’d think there’s quite a way to go yet. Interestingly I note this is forecast to start to happen to mobile phones around 2014-15. It seems it already does happen to some extent at large crowd events, I believe, such as football matches etc.

I’m sure that what I’ve said is probably all wrong, but I have read that computers can be slowed down by having too many wireless enabled peripheral devices switched on at once. The trick is to switch as many off as possible. Some accurate information on the modus operandi of 2.4 GHz radio, and some serious investigation into interference would be very useful.

Perhaps FPV is going to emerge as the bogeyman of 2.4 GHz, much as CB radio did with 27 MHz AM. As far as we were concerned, that was never an issue, either.

Steve,

Please forgive me, but I thought that power density was a measure of battery capacity, in watts, per unit of volume, mostly in litres. This is sometimes confused with specific power, which is the measure of capacity, in watts, per unit weight, (or mass), usually in kilo grams. The term, ‘energy density’, too, is always used, when it should be ‘specific energy’ Sorry about that, and it’s of no consequence anyway, but this is the one thing that has always tended to slightly niggle me.

Chris,

These are a couple of photos from January. The wings are made but not finished covering yet. The history is indeed very familiar, that’s exactly what the builder has. I know he was talking about replicating the Lewis gun. I have a feeling that it’s a 50cc motor but I could be wrong and it doesn’t really look that big in the photo anyway. The builder is only a learner flyer, so this will be an interesting first flight for someone. He’s also started on a big Spad, I believe.
Sorry about the foreign language, but power levels are at least straight forward. Something like AC theory really is an unknown foreign language, and in code to boot!

PB

[leccyflyer]

Posted by Martin Harris on 27/02/2011 14:06:33:

And mightn't it be significant, BEB, that the "interference" source transmission could be at considerable atlitude while the conventional model is being controlled from the ground?

 

...and to expand on Leccy's point, I think any "opposition" from conventional modellers is nothing to do with FPV being seen as different, "not what we do" or any sort of blind prejudice - indeed I would assume that the majority of us wouldn't be averse to having a go ourselves if it wasn't such a considerable financial commitment to get started in what might be a fringe interest. The main concern is of an irresponsible operator causing a high visibility incident that could have negative consequences for the established hobby. Couldn't happen? One of my clubmates has had to virtually give up on his other hobby of pistol shooting, at which he was at a high standard, as a consequence of blanket regulation post Dunblane.

Edited By Martin Harris on 27/02/2011 14:21:16

That certainly part of my position Martin and I was definitely keen to have a go at FPV. I have to say though that, having seen the attitudes that are all too prevalent and the routine breaking of all manner of regulations, with regards to maximum power output and endangering other modellers an the public, that I'm now a lot less likely to want to be associated in any way what part of the hobby.

[flytilbroke]

Been watching the responses. So, first af all I am not against FPV, I do however support the initial guidelines as to how it must be practised, as I will likely support any changes that may occur over time. The start of this part of model flying was persued somewhat childishly and appears to have matured a bit.

 

To deny that Illegal equipment cannot have a detrimental effect is less than sensible. Let us wait till time and further enquiry proves or disproves the robustness or not, of any Equipment which may be affected.

 

I was pleased to have some of my initial concerns re 2.4Ghz equipment allayed, although there were some issues which had NOT been addressed by the manufacturers.

 

Remember the equipment we use is designed to price, not the absolute best it could be.

 

It must surely be best to be aware that a problem may exist, than to deny it might.

 

Anyone can look at the thread on the LMA website, it is not hidden.

 

The LMA and the SAA are allowing use only of 2.4 Ghz systems at public shows, so the risk at present must be small.

[Steve W-O]

Posted by flytilbroke on 28/02/2011 21:29:56:

.

 

To deny (say) that Illegal equipment cannot (can) have a detrimental effect is less than sensible.

 

 

 

I am guessing that the double negative was unintentional, and one them replaced would be what you meant.

 

I don't think anyone said that illegal equipment was the right thing to use, or that it would cause no harm. Everybody who commented was against the use of illegal equipment.

 

What was said was that the 1000mW equipment alleged to have caused the problem was not likely to have had the effects stated without other problems being present as well, backed up by the facts in solid maths.

 

 

I wonder what the clubs motive was by posting it on the LMA forum as a threat to their safety? They obviously didn't get the dramatic reaction they seemed to be hoping for, as several there questioned the facts as well. If it was politics, it would be political opportunism after their recent decision to go 2.4 for public displays.

 

I'm not a supporter of FPV any more than any other aspect of the hobby, I just feel that the way FPV has been painted by unproven guesswork and "drama queen" antics is unfair, and a danger to the reputation of the hobby as a whole, after all, to the uninformed, it is still a RC aeroplane.

 

 

[GONZO]

Well I've enjoyed the witch hunt for the boogy man FPV flyers and the diversion into the realms of power o/p's etc. But, as I've said before 2.4gHz is a 'catch all' band where users have to accept interference from other(legal/ligitimate) users and I feel we have sold our souls to the devil, so to speak, in the persuit of conveniance and laziness. Concientious frequency control (good pegboards etc) on 35mHz made the band a reasonably safe option IMO.

So, lets forget any illegal users and look at the legal/legit users on the band and their allowed p/o. 2.4gHz RC is from 2.4000gHz to 2.4835gHz with 80 channels and an ERP of 100mW(frequency agile). If you go to THIS OFCOM SITE you will see listed the parameter tables for frequency bands for use by the three grades of radio amateurs. You will notice that a full licence holder can transmit at 400W PEP in the band 2.400gHz to 2.450gHz(over half of the RC band). Even an intermediate licence holder can transmit at 50W PEP.

I would think that if flying near(urban housing estate) a 'ham' (legally) operating at the higher RF power levels then the RCRx would suffer a degree of problems.

Any full 'ham' licence holders care to comment?

[Steve W-O]

Posted by GONZO on 01/03/2011 12:56:14:

Well I've enjoyed the witch hunt for the boogy man FPV flyers and the diversion into the realms of power o/p's etc. But, as I've said before 2.4gHz is a 'catch all' band where users have to accept interference from other(legal/ligitimate) users and I feel we have sold our souls to the devil, so to speak, in the persuit of conveniance and laziness. Concientious frequency control (good pegboards etc) on 35mHz made the band a reasonably safe option IMO.

So, lets forget any illegal users and look at the legal/legit users on the band and their allowed p/o. 2.4gHz RC is from 2.4000gHz to 2.4835gHz with 80 channels and an ERP of 100mW(frequency agile). If you go to THIS OFCOM SITE you will see listed the parameter tables for frequency bands for use by the three grades of radio amateurs. You will notice that a full licence holder can transmit at 400W PEP in the band 2.400gHz to 2.450gHz(over half of the RC band). Even an intermediate licence holder can transmit at 50W PEP.

I would think that if flying near(urban housing estate) a 'ham' (legally) operating at the higher RF power levels then the RCRx would suffer a degree of problems.

Any full 'ham' licence holders care to comment?

 

 

 

What are the permitted modes?

[GONZO]

RSGB told me that all modes are allowed but few use that part of the band as its too noisey(the world, his wife and uncle tom cobly and all are there). He did point out that there are many elegal(high power) video senders in peoples homes and that lots of equipment operates at this frequency. It is a 'dump band' with lots of ISM (industrial, scientific and medical) applications, Wi-Fi, Bluetooth etc. This and poor instalation not having sufficent regard for the RF aspects of 2.4gHz..

How long will the (spreading) PN codes and frequency agility of RC system be able to stay above an ever increasing noise floor and maintain effective control as the band useage increases?

[Peter Beeney]

Steve, I would definitely agree with all these sentiments. It’s maybe a bit difficult to consider the moral aspects, I’m sure there’s the odd individual who would use illegal equipment without giving it another thought. The legal aspects too, easy to say it’s illegal but perhaps not that easy to monitor and thus unlikely to be policed.

The LMA post gives some information, but perhaps not the most important criteria, the distances involved. Also some statements maybe slightly misleading; I quote - ‘The issue is that many of the video transmitters being bought are ilegal and transmit at 1000mw which is way above the UK 100mw limit’. I think I’m correct in saying that the UK limit for airborne transmitters is actually 10mW, not 100mW. The post also mentions the scanner, and the fact that it gives the relative signal strengths. I’m not sure that indicates that the FPV signal is necessarily going to interfere with the model, even if the signal is stronger. After all, if there were 20 model control transmitters switched on at the same time they would all show up on the scanner, but in practise they would not be interfering with each other. I still tend to think that the power required to completely swamp a one mega-hertz channel, over what might be a considerable distance, we don’t even know if the errant FPV model could be seen by the model flyer, would have to be considerable. If it extends over the whole bandwidth I think it would have to be even more so.

One situation that might be considered is that of the model flying away from it’s transmitter and towards the FPV vehicle. Maybe then they could conceivably get very close together. Could that be a receipt for disaster? Difficult to comment on all these little scenarios, it seems that until we can see some documented proof of some checks as to what is is actually going on, it will remain a mystery. And from the experience of tinkering about with other such devious devices, things don’t always do like what they’re supposed to do!

One experiment that might be worth a try, with respect to power output, a full ground range check on a 2.4 model with a small number, say, of other tx’s switched on and very close to the model. When the limit is reached switch off the tx’s, perhaps one by one, and see if it increases the range. If it’s possible to reach around say 600 metres without blinking then is there a problem? Particularly if the test tx’s are only about half a metre away from the model.

GONZO, Interesting stuff, I certainly hadn’t seen any of that. So now even more questions!
With regard to the ‘catch all’ state, we’ve been here before, on 27MHz; but back then we made some attempts to see if the general consensus was correct but we were never able to prove that CB radio interfered with model radio. But that’s not to say that all other circumstances were the same, of course. Pegboards or other types of frequency control were borne out of necessity, I guess, otherwise chaos. Back at the start of 35 I monitored the airwaves regularly with a scanner and I never found anything, nor on either side of the band, either. If there had been very much other traffic then I don’t think that 35 would have ever been the success it was. I suspect it was used more or less in isolation by the modellers. As I understood it, it was once used by the military, but had long been abandoned.

On the OFCOM site, in the 2.4 slot is the statement: Users must accept interference from ISM users significant? In other words, does that work both ways? Radiating at those levels, is it possible the transmissions can affect many other ISM users and not just model flyers? Conversely, is it possible that other ISM users make the band difficult to use, perhaps to the point where it’s not used a lot anyway? Certainly your invitation for ‘ham’ comments is very appropriate.

It seems to me that if there were high levels of interaction between ISM users then this would be a topic of conversion. Up to now I’ve not read that this is happening. However, if just raising the power output to 1 watt can cause model to crash then suddenly the 2.4GHz band is starting to look a whole lot more vulnerable.

PB

[Peter Beeney]

Sorry, slightly cross posting, I’m late again, as always, the story of my life!

PB

[Steve W-O]

As you asked for comments-

 

A radio amateur would not knowingly transmit on a busy frequency.

 

The signal from an amateur transmitter would be clean, and not spread outside the specific bandwidth.

 

To get as far as using this frequency, the amateur would have done research and would have a good understanding of the principles involved.

 

I am talking about UK amateurs, not some of our European colleagues

 

I realise that there may be a few who would not comply with the "rules", but I have never met any.

 

 

I don't think it was the intention of these threads to show this, (same on on several forums) but it is a good thing that Spektrum brought out a proper hopping system!!!!

[Peter Beeney]

Interesting stuff! Do we know to what extent the model 2.4 radio rx’s will tolerate a noisy environment? Probably not, but I say this because referring back to the days of 27 once again I can remember listening to the tx on a monitor whistling up and down as the sticks were moved flying the model. Then a CB transmission would break in and drown the tx but the model never saw this. We never saw the CB talk cause any model to deviate at all. By the same token, CB outfits on the field could also not be persuaded to influence the model, either. There may be reasons, the two frequencies were not exactly the same perhaps, I think this would have be necessary, combined with the two different types of modulation.
But, of course, I do realise that 2.4 really is a completely different kettle of fish…

At some time in the past, quite a while back, in fact, I can remember reading an article about how the military had developed a frequency hopping system of transmission, primarily to maintain the integrity of their information sent. No one could overhear, apparently. The article also said that yet another technique was already being considered, because of the fact that as the airwaves were getting more crowded the system was slowing down. It relied on speed. I’ve no idea what the frequencies were, or what the new ideas were. Top secret, I guess. I’m pretty sure 2.4 wouldn’t be a contender, though.

Could it be that the days of frequency gridlock are still a little way off yet? I say this because when we get to that point would not all the users be suffering? Then the pressure will be on to ease the congestion. I‘ve no idea how this will be done, maybe some brand new ideas not yet even dreamt up. But I’m sure there is no doubt that more will be squeezed into less, frequency wise, as time goes by.

When we see a brand new foolproof 35MHz radio on sale at a major model symposium we shall know in which direction it’s all changing……...

PB