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Satelite Rxs

Why, where, when?

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Foxfan10/08/2013 13:40:16
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Hi,

I keep reading about satelite Rxs, but not always are they used or specified. Why are they necessary? Why doesn't the "proper" Rx do its job properly? IF they are really necessary, why aren't they sold as a pair as a matter of course? Do they only become desirable or even necessary on very large models or those with a lot of aluminium skin/carbon structure and the like?

I build traditionally with balsa, aircraft of between 32" and 63" (super 60), but normally would be no bigger than 4 foot span.

I've just splashed out(<G> on an Orange 6 Function RX to go with my Spektrum DX5e and don't want to have the extra hassle and expense of yet another RX to ensure the first does what it was designed to do on its own.

Thanks,

Martin

NigelH10/08/2013 14:32:22
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The aerial in the RX will be most effective when it is at a specific orientation relative to the TX aerial(s).

By having one or more satellite RXs, orientated differently from each other, there should always be at least one RX getting a solid signal from the TX.

Also, things such as batteries and engines along with CF can cause signal loss so it's useful to have the extra RXs in place.

There are plenty of full range RXs without satellites so as long as a range check works, you should be good.

Pete B - Moderator10/08/2013 14:56:07
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I can add some personal, experience-based musings rather than high-tech info, although Nigel's covered most of the points.

I've used half-a dozen or so Orange 6ch Rx's over the past two or three years, both with and without satellites, and haven't yet run out of range either way.

I've used satellites in the larger, more-loved models or gliders - they don't extend the range at all, just provide signal reception diversity - so are really there for insurance and peace-of-mind, really.

Darn it - I've gone and mentioned the 'I' word.....crook

As Nigel indicates, placement is all important. Keep the aerial away from shielding materials and agglomerations of wiring and you should be fine thumbs up

Mind you, I can't say the same for a pair of Orange 9ch Rx's, which I wouldn't trust in a boat on a puddle......sad

Equally or perhaps even more important as aerial placement, IMHO, is to establish a reliable power source.

Pete

Foxfan10/08/2013 17:06:35
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Interesting, thanks, chaps. It seems we're not talking Orange only here, as all the main R/C people make and, no doubt, persuade us to buy, their satelites.

It isn't exactly easy to properly orientate two tiny aerials that are an inch long, if that. The spring of the wire stops that on such short lengths, so presumably we must tack them down with a quick release type of glue.

I'm just a bit bothered by an apparent fashion for what seems to be a tacit admission that the main RX. ain't up to the job in some circumstances, dsregarding CF and wiring and obvious potential hazards to a signal.

I also don't know which I should consider as I really don't understand all the acronyms used in modern R/C in the adverts!

Working on a VERY tight budget, I would obviously prefer not to have to buy TWO Rxs. when one SHOULD be sufficient. Especially for a smallish, balsa-built model of a scale type, flying (one hopes!) scale manoeuvres.

Martin

Pete B - Moderator10/08/2013 17:27:01
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I wouldn't glue them to the model surface, Martin. If you are attaching the Rx to the fus with servo tape or, my standard method, hook-and-loop tape, you'll probably get some fatigue at the aerial.

A better way to beef up the aerials is to slide a bit of 2mm heatshrink over them - on Spekky Rx's there is often a tubular protrusion from the Rx and the h/shrink will slide over it nicely. If there's nothing, then a touch of hotglue at the base will provide some additional support.

I shouldn't be too bothered about the concept - if the manufacturer recommends a sat, then use one. Some Spekky Rx's can work without, such as the AR6210 - with Spektrum's warning that it should only be used at parkfly range - and other's like the AR8000, must not be used without.

It's not a case of 'not being up to the job'. You have to bear in mind these are tiny aerials - typically 31mm long - and it is very much easier to mount them in a 'shadowed' position than the 35Mhz aerials of earlier systems, so clearly the manufacturers have had to take this into account. It's probably easier to provide discrete Rx's than check every user's installation....teeth 2

There have been many, many tens of thousands of successful flights using the Rx's in accordance with the manufacturers' recommendations, so they might know a thing or two about it..... so trust them! wink 2

If your Orange Rx doesn't specifically state a requirement for a satellite then install it, with some thought on positioning, and go fly - I'll put my shirt on it not letting you down.....smile

Pete

Foxfan10/08/2013 19:06:06
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Thanks, Pete. Maybe the otherwise excellent reliabiity of 2.4 Gig has led to the satelites being needed sometimes because of the extremely short aerials which are a necessity with that wavelength.

Alas, my Orange came with no instructions except how to bind it, which I don't understand a word of, but fortunately have a chum who is very patient with me on such matters, so I won't trouble the good members here with my dumb questions!

I suppose in the end, the only answer is to fly and see what happens, as always, in the absence of any absolute instruction to use a satelite. I am unlikely to take a model to any extremes of range, because I like actually looking at them fly!

Martin

Biggles' Elder Brother - Moderator10/08/2013 20:09:42
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Posted by Foxfan on 10/08/2013 17:06:35:

It seems we're not talking Orange only here, as all the main R/C people make and, no doubt, persuade us to buy, their satelites.

Martin

 

Not strickly speaking so Martin. As a Futaba user (I think they still warrant inclusion in the description "main R/C people") I have never even seen, let alone used, a satellite Rx.

But to answer your original questions to be the best of my (in this case limited) experience and ability:

Why: to promote signal diversity in non Futaba systems which, presumably, would otherwise have some difficulty in achieving this.

Where: I believe usually in the tail - or least some distance from the "main" Rx - but I stress I have no experience of them - or so far any demonstrated need for them.

When: presumably when you are using Specktrum or similar systems that seem to need this assistance and support.

BEB (With his tongue very firmly planted in his cheek) wink 2

Edited By Biggles' Elder Brother - Moderator on 10/08/2013 20:11:19

Foxfan10/08/2013 20:44:27
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And are Futaba as small as the others, BEB? That seems to be a reasonable explanation. If Futaba are bigger, maybe they do something the others should and hang the tiny stuff in normal sized a/c.

How does the expense comparison work out, I wonder.

Martin

Frank Skilbeck10/08/2013 20:59:09
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Spektrum do Rx's in both satellite and non-satellite full range versions, the full range non-satellite versions are similar to the Futaba Rx's in that they have the aerial on a fly lead so you can orient the two aerials at 90 deg to each other and position them apart, that way one aerial will always be able to see the Tx.

Some of the Orange recievers (and Spektum parkfly Rxs) only have short aerials protruding from the case so giving them a clear line of sight to the Tx and making sure that the tip doesn't point at the Tx can be hit and miss, hence the recommendation to use them for Parkfly models or add a satellite Rx so provide this additional diversity.

Interestingly Multiplex recommend on their single aerial Rxs that you orient the aerial so it is vertical, they also don't call then parkfly but give recommended wingspans for power, gliders and helicopters (well rotor dia)

Foxfan10/08/2013 21:10:55
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Thanks, Frank. My Orange hs two aerils, so what orientation would you recommend? I was thinking one to the left of the fuselage (left hand circuits) and one vertical.

Martin

Biggles' Elder Brother - Moderator10/08/2013 21:20:22
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Martin - they should be at right angles to each other. As along as you achieve that it doesn't matter in what particular arrangement - just right angles. So, one runing fore and aft and one up and down is fine. But so is up fore and aft pointed up at 45 degrees and one fore and aft pointed down at 45 degree. And so on.

BEB

John Privett10/08/2013 21:29:38
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Does any manufacturer other than Spektrum even have satellite rxs? (Genuine question, I haven't seen any others, so guess it's only Spektrum.)

Now Spektrum were the first onto the 2.4 market - ahead of Futaba, Hitec, and the rest... I have heard claims that Spektrum tried to do 'proper' frequency hopping (like most/all use now) but couldn't get it to work. So in order to beat the competition and get to market first they launched with the original DSM system that simply shuffles back and forwards between two frequencies - and seemed to need the satellite receivers.

Now, roll forward a few years and Spektrum have DSM2 and DSMX. So are the satellites just a 'hangover' from the early days of DSM? Are they used on DSM2 and DSMX?

Foxfan10/08/2013 22:14:52
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Thanks, BEB.

John, very good points. Not that I have a clue what all those acronyms mean!

Martin

Frank Skilbeck10/08/2013 22:27:57
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JR DMSS does satellites as well and Jeti allows you to add satellites should you decide you need/want them.

Some other manufacturewrs allow you to hook up to recievers together to provide additiona diversity.

Might seem ove the top but if you have an airframe you paticularly value and it has a chance of blanking the aerials then additional security is no bad thing.

NigelH10/08/2013 23:08:34
891 forum posts
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Fuel tubing is also good for slotting over the aerials. Get the correct bore and not only will it fit perfectly over the Spektrum plastic mouldings, it will protect them and keep them at the correct angles.

Foxfan10/08/2013 23:45:33
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Good idea with the tubes, gents, thanks.

Martin

Frank Skilbeck11/08/2013 08:11:47
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Good tip on fuel tubing on the Spektrum Parkfly Rxs, on Rxs with fly leads I use small sections of the flexible inner from the Sullivan snakes (off cuts of course), the aerials are a nice fit in these.

Based on the Multiplex recommendations I also try and orient at least one aerial vertically, but then again on all my Multiplex Rx's even with single aerials not vertical I've only ever seen 100% LQI (signal quality) on the telemetry, except on a range check where the plane is on the ground and Tx aerial pointing directly at it. I also use Spektrum DSM2 and FrSky, neither of which have telemetry, but never had a fault with any.

Percy Verance11/08/2013 08:43:12
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8108 forum posts
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Hi Frank

Having used both dual and single antenna M-Link receivers, I've not noticed any reduction in LQI either. In their advertising, they do seem to imply there might be some reduction in LQI or ultimate range with the single antenna rx's, but I haven't found this to be the case. Having said that, for my more valuable models I do tend to stick with the dual receivers (two receivers in a single case for those not familiar with Multiplex systems).

I was somewhat surprised (shocked!) to discover just how low 100 metres was when I began using my Vario, but that's another story........

Foxfan11/08/2013 13:14:49
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903 forum posts
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Just looking at suppliers of the Orange satelite Rx. and am shocked to see that they're twice the price of the basic Rx! For what is basically a supplementary object, that seems a bit odd.

Martin

Percy Verance12/08/2013 09:00:45
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It may be as well to remember one thing when buying oranges. You sometimes get the odd lemon in there too........

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