THE PITS IS THE PITS

Just been past the flying site. There are a group of workmen dredging out the stream useing a large tracked JCB. The ground is very chewed up on the access road to the pits and also around the pits area. I would think it will be unsuitable for seting up planes for some time, even when the drier weather arrives.

That would be the environmental chaps doing their stuff then. Not a lot we can do about that, other than repair it when they are gone. We have got a load of work planned for the strip/pits/field entrance this year, so we'll just have to do our best to salvage something from the mess....

Andy

spotted them yesterday, they were even having a fire on what looked like the pits area

M

We could take this opportunaty to move the pits area to the road side of the strip, set back by ??? feet and parrallel to the strip. Use our cars via the current taxi way to transport and deposit planes etc and then park them at the current pits/mud pie area or further back nearer the road. A safer arrangement IMO.

yeah, great idea allan!

I've been there over the last 2 days but couldn't fly yesterday as the fire was filling the strip with thick smoke so I went home to hover in the garden.
They look almost finished now so hopefully if it's not raining tomorrow I'll go for a good session.Tuesday was quite funny now I look back as I hauled all my gear over there sliding round as I battled with the tracks to unpack.Got fired up,went to put my heli down and as soon as I got to half throttle it threw it down with rain.
Here's hoping for tomorrow.

paaahhh!!!
Rain shmame me and tim were flying in rain AND thing fog, visibilty- 0.... fun - 10!!!!!!!!

Allan Warner wrote:We could take this opportunaty to move the pits area to the road side of the strip, set back by ??? feet and parrallel to the strip. Use our cars via the current taxi way to transport and deposit planes etc and then park them at the current pits/mud pie area or further back nearer the road. A safer arrangement IMO.

The farmer has said that he did not want this to happen in the past. Also how can this be a safer arrangement when you would have cars near the strip when they are unloading and you would also have Two targets for a out of control model to hit (the pits and car park).


Roy.

If the farmer don't want it thats that. Or did he think, was told, that the cars would be parked out on the field. To the points you raised:
1/ The cars would approach the strip from behind and be there momentarily, not all the time.
2/ The cars would be parked further down the field edge towards the road. Starting up from the entrance area.
3/ The current layout means that when you are landing from right to left, on base leg, your plane (from observation) the majority of times is pointing directly at the pits area. In my short time I have seen two crashes approx 20' from the end car.
4/Additionally, in this landing sceanario when on finals the plane is low and the rx aerial is vertually end on to the pilots tx (lowest signal strength orientation). But, is abeam any tx in the pits (max signal strength orientation, even with pits tx aerial down) and if on an adjacent channel then there is a high chance of interference. On take off from left to right the same disparity in correct and interfering tx signals still applies. I know this probably only applies to 35mHz (on 2.4gHz your on full power all the time, in the pits and on the flight line, and I don't know how well these rx cope with high signal strength differences for correct versus incorrect channels. Could this cause the planes rx to drop momentarily into failsafe mode?)

As a committee we sweated long and hard on this in the past and the arrangement we have is the best we can have to suit BMFA reccomendations and,as Roy has already said our farmer's demands. The only occasion we have one vehicle out their is on IMAC comp day when there's usually a van for the computer generator and sound system.I think the radio interference/weak signal/failsafe is a total Red Herring sorry Allan Unless it's peculiar to your gear in which case you're probably flying JR/Spektrum

As for the Environment Agency guys being down there it happens regularly and the disturbance left by the tracked vehile soon dissapears. The have a statutory duty to keep the drainage ditches clear so there is no way we or the farmer can stop them . In a few weeks time we'll be down there buisness as usual. I know it's been a long winter but it'll soon be over

Not my gear. Its a known technical effect on 35mHz. Just dont know about 2.4gHz. All the advertising blurb show multiple tx (40+) all working multiple rx OK. But, note that the tx are all together. The current main stream manufacturers of 2.4gHz (Futaba, Spektrum/JR, Hitek, Jeti, Mplex etc) are probably able to cope and not suffer any blocking etc. There are, however, an increasing number of cheaper 2.4gHz systems coming onto the market and their capabilities my not be as great. OK, their transmissions may not affect your rx but their out of control model will hurt just as much.
To me it is bad practice to stress the equipments capabilities un-neccessarily.

The thing to do, is to avoid pointing the T/X aerial at the model as the aerial produces what's known as "the cone of silence" emanating from the tip, so when pointing the T/X aerial at the model it receives the weakest signal this applies to 35Mhz and 2.4Ghz.

I've not been refering to the the dead zone from the tip of the tx aerial (simplisticaly, radiated tx signal is like a doughnut pierced by tx aerial). It's the difference in recieved signal strength, brought about by differences in physical distance of the rx from correct and incorrect tx, seen by the rx and the rx capabilities in dealing with this diference.

If I refer back to the past when 35mHz started. The tx o/p was tightly controlled (and still is) but the rx was not. In fact I tested one of the early Acoms 35mHz AM sets for a retail organisation and found that the tx was fine(HP spectrum analiser) but the rx could not cope with 10kHz spacing. As a consequence we had a situation where some rx (FM as well) had to opperate at least two channels away from the next tx. Market forces and time saw this improve but the signal strength/distance/co-channel effect is down to physics/electronics.
Could be that we may be coming to this situation again, on 2.4gHz, but from the other direction.
Perhaps someone more intamately aware and involved with the detailed technical requirements and specifications of 2.4gHz rx related to in band and out of band high RF fields causeing blocking etc would care to comment?

Allan Warner wrote:I've not been refering to the the dead zone from the tip of the tx aerial (simplisticaly, radiated tx signal is like a doughnut pierced by tx aerial). It's the difference in recieved signal strength, brought about by differences in physical distance of the rx from correct and incorrect tx, seen by the rx and the rx capabilities in dealing with this diference.

Allan it is now 2010 I think that unless you are using gear from 1970/1980 the swamping of close channels is not now a problem.

Roy

Perhaps I'm simplistically challenged then I've not heard of this effect Allan, I'll bow to your superior knowledge on that one, however I can't say that we've been plagued by out of control models on finals. Apart that is from good old thumb trouble, the moving hedge and strip syndrome

God I need to go flying

It is highly unlikely that a receiver on a model could be swamped by a signal from a nearby transmitter (whilst the intended TX is some distance away). Without getting the old blackboard and colour chalk out, 2.4GHz doesn't use "channels" in the same sense that 35MHz uses channels. The signal does not occupy a 2.4GHz channel completely, instead it is spread about the channel (both in the frequency and time domain) and also encoded quite heavily too. At the low data rates (in comparison to the bandwidth available on 2.4GHz) coupled with the amount of coding gain used, the chances of the signal being corrupted are very, very low. All that is likely to happen, is that the rx has to do some complicated error correction, and maybe disregard the odd packet of information here and there. To the end user, it would be invisible.

For swamping to have any significant effect, it would need to be a very broadband transmission, coupled with a VERY high power output (or directed specifically at a model with a directional aerial, like a Yagi or a dish).

Interestingly, the DSSS systems (like pPektrum) would techincally be more susceptible to this sort of interference than the FHSS systems (Like Jeti, MPX, and Futaba Fasst). Although, that is like saying you have got more chance of winning the lottery, if you wear pink undercrackers. It is still millions to one odds.....

There is probably always going to be room for improvement in the field layout, but we are always going to be restricted by what our landlord will allow. Personally, I don't have any issues with the arrangements we have already. The area is far enough away from the active flying space to minimise risks, and I find the fact we can keep our cars nearby, very convenient.

Andy

Thanks Andy. But, what exactly does the Radio Regulatory Body call for in the specifications relating to the performance of the whole system and specifically the rx. If the specs are loose then the cheaper systems may fail in a harsh RF environment.

apart from the possible radio issues. the pits is located on the fastest drying and best drained part of the field. perfect for driving on

Andy,
Having been retired for getting on for 14 yrs and not having dabbled with RF for 20+ yrs. I, and I'm sure a lot of the club memebers, would be interested if you had a circuit or block diagram of a 2.4 gHz rx. Things are obviousley different from 35 mHz days [double tuned front end for band selectivity, intermediate IF (double conversion rx) giving out of band image rejection, followed by highly selective final IF for adjacent channel selectivity, then demodulation and decoding with possible digital processing to minimise interference effects etc].
A different concept is employed. I presume that the front end is a wide band set up with some RF amplification followed by ????????? before we get to the heart of the rx where the digital processing takes place thanks to a micro p.

Out of interest
http://www.13cm.co.uk/shop/transmitters/200mw-transmitter/prod_44.html
http://www.13cm.co.uk/shop/aerials/13-cm-yagi/prod_21.html?ccSID8643dd60547e611052421a6659ed64d2=6b89211b405cd427b9e8cb3219199c7a

I'm not intimate with the design of the 2.4GHz chipsets, but the receving side of things is almost always a wideband type (i.e. covers all of the 2.4GHz band, so not really wideband, but you know what I mean ) with several filters to cutoff the out of band rubbish. The last chipset I looked at, didn't have much detail on the rf frontend really. That's one of the downsides of 2.4GHz. You don't have discrete components doing particular jobs. You just have a single chip that you attach an aerial to, and data is pumped out the other side. I've just had a scan through some of the wireless USB chipset datasheets that I have (Atmel parts from a project I was involved witha while back) and they don't mention much about the rf frontend at all. They do give detail spec son the power output, and details of a further power amplifier chip though....

Incidentally, the cheaper stuff is likely to be pretty damn good really. If you think about it, the low end manufacturers are much less likely to develop their own rf solutions, and will instead use the cheapest supplier of a chipset. That usually corresponds with the manufacturer that sells the biggest volumes, and that usually makes them much more likely to comply with any regulations that are in force.

That said, absolutely no RF system on the market in the world will be completely resistant to any sort of interference at all. The best you can hope for in a system, is multiple redundancy, and enough clever techonology to make it extremely unlikely that problems will occur. As always though, there are ways around things

Andy

Here's one of the cheap sets. There was an article in one of the mags recently:
http://www.jperkinsdistribution.co.uk/list.php?subcat=152&cat=R/C equipment - Planet 2.4GHz&Navmain=R/C equipment