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-   -   Spektrum SR300 antenna mod? (http://www.rcuniverse.com/forum/rc-boats-general-discussion-77/8647144-spektrum-sr300-antenna-mod.html)

Elnino 04-04-2009 01:56 AM

Spektrum SR300 antenna mod?
 
Hi all, I'm hoping for some advice.

First off, let me say that i KNOW spektrum do not recommend the use of their products for water use (something about the water reflecting the radio which has to be crap since FASST is RECOMMENDED for water...?)

Anyways, I have an SR300 (not SR3000) that came with my DX3s and i was told by the LHS they have used them fine in the water as long as the antenna is above the water level. Well, in my gas boat, the radio box is lowish in the water but i want to use the Spektrum because the AM radio i have in there now is crap. So, in trying to stick with what the guy at my LHS said and in combination with what i know about 2.4ghz in general I was thinking that i should be able to extend the antenna.

i have a lot of experience with 2.4ghz wireless networking antennas, i have built them and modded heaps of USB wireless adapters to support external antennas so i know the theory behind it all. Spektrum is theoretically the same so the principals of the antennas should be the same. The main problem could be with impedance and possibly overloading the antenna driver circuit.

My theory is to extend the antenna to be able to mount it higher on the boat but also extend the ground plane/shielding for the longer run using a shielded coax. Basically the same as the one on the old SR3000's but then expose the 30.5mm of 'core' at the end (30.5mm being 1/4 wavelength for 2.4ghz). The total lengthening of the antenna would probably only be 5cm, if that.

I'd like to hear your comments if you have or do use Spektrum in your boats and/or if you have done any mods to the antennas to make it work as it should. it just seems a shame to have such a good radio but i'm being told it's not a good choice for a boat.

P.S I thought it was funny that Spektrum failed to comment when i asked them "If 2.4ghz is reflected by water, why is it that Futaba's FASST system is recommended for use in boats - Since they both use 2.4ghz, wouldn't they both have issues"? Clearly it means that somehow their product is not as good as Futaba's. If only i knew that before i got into boats...



danielplace 04-04-2009 06:48 AM

RE: Spektrum SR300 antenna mod?
 
Quote:

ORIGINAL: Elnino

Hi all, I'm hoping for some advice.

First off, let me say that i KNOW spektrum do not recommend the use of their products for water use (something about the water reflecting the radio which has to be crap since FASST is RECOMMENDED for water...?)

Anyways, I have an SR300 (not SR3000) that came with my DX3s and i was told by the LHS they have used them fine in the water as long as the antenna is above the water level. Well, in my gas boat, the radio box is lowish in the water but i want to use the Spektrum because the AM radio i have in there now is crap. So, in trying to stick with what the guy at my LHS said and in combination with what i know about 2.4ghz in general I was thinking that i should be able to extend the antenna.

i have a lot of experience with 2.4ghz wireless networking antennas, i have built them and modded heaps of USB wireless adapters to support external antennas so i know the theory behind it all. Spektrum is theoretically the same so the principals of the antennas should be the same. The main problem could be with impedance and possibly overloading the antenna driver circuit.

My theory is to extend the antenna to be able to mount it higher on the boat but also extend the ground plane/shielding for the longer run using a shielded coax. Basically the same as the one on the old SR3000's but then expose the 30.5mm of 'core' at the end (30.5mm being 1/4 wavelength for 2.4ghz). The total lengthening of the antenna would probably only be 5cm, if that.

I'd like to hear your comments if you have or do use Spektrum in your boats and/or if you have done any mods to the antennas to make it work as it should. it just seems a shame to have such a good radio but i'm being told it's not a good choice for a boat.

P.S I thought it was funny that Spektrum failed to comment when i asked them "If 2.4ghz is reflected by water, why is it that Futaba's FASST system is recommended for use in boats - Since they both use 2.4ghz, wouldn't they both have issues"? Clearly it means that somehow their product is not as good as Futaba's. If only i knew that before i got into boats...



As long as the antenna is above the water level, do you think the ones that crashed might be because the antenna's were run out the bottom of the boat? How do you manage to get the antenna below the water level? A deeeep vee maybe? Ask that LHS if they are going to replace your crashed boat? Get it in writing you'll be back. They will sell you anything, sometimes innocently as they are just misinformed.
I beleive the technology they use is somehow absorbed by the water is what JR told me. It is very different than a Fasst system which are awesome.
A brand new JR Spectrum radio with 2 new receivers crashed 2 separate boats on the first runs because of complete loss of control. I absolutely would not put that system in a boat. IT will NOT work at all.
Know of half dozen others who thought it was ok because people said so and they all ran there boats ashore also. Trust me it is not a good feeling. It leaves you totally helpless and does not ever regain control. Till you go to fetch the pieces then it works of coarse so you might get to put it back in again and finish it off, if the first crash didn't, like I did.
Don't do it. Really if the people making it say it doesn't work don't you think they based that decision on the many phone calls they received about how their radio crashed someones boat.

Daniel

Dan S 04-04-2009 10:17 AM

RE: Spektrum SR300 antenna mod?
 
Elnino,

you are correct when saying that both system uses the same 2.4Ghz technology, the difference between the 2 of them is what make makes FASST the winner for over water.
FASST is frequency hopping, Spectrum on the other hand isn't.

I don't know how the antenna is designed on the Spectrum receiver, but on the FASST receiver only the last inch 1/2 is the antenna, everything else before that is only a coax.
yo can also Call Futaba and buy a replacement coax that is I believe a little over 15", again the first 14" is the coax and only the last 1 1/2" is the actual antenna.

if the antenna on the Spectrum receiver is similarly design you could make the coax itself longer.

But I am with the thousands of people that the Spectrum 2.4 is not recommended, way too many threads on this subject including transcript from Spectrum services not recommending it for boats.

Futaba FASST,
Airtronic's new FHSS 2 (developed for boats) and I believe Nomadio are your better choice (and mine).

Dan.

Elnino 04-04-2009 06:32 PM

RE: Spektrum SR300 antenna mod?
 
ok, ok. Perhaps i'll get a cheap FM for the boat then - Something that is at least better than the AM i have in there now. It's not a multi thousand dollar boat and the area i have to use it is not overly big.

I still don't understand how Spektrum can claim it is due to refelctions when futaba's system doesn't suffer this same problem. It's the same frequency. Yes, i know FASST changes channel every X ms but it's still the same radio frequency band. I acknowledge FASST is better but it still does not make sense. There must be something Spektrum is not telling us. The only other thing i can think of is that the prop generates the reflections, not the water and that somehow the FASST system swapping channels avoids this problem. Either that or Futaba just simply puts out more mw of power from the TX so the rf penetrates the water better. I don't believe that simply changing channels is going to change the laws of physics - either 2.4ghz is reflected by water or it's not.

Elnino 04-04-2009 06:37 PM

RE: Spektrum SR300 antenna mod?
 
I also see that this guy uses an SR3000 in his RC Yacht with an external antenna mod:

http://www.anderswallin.net/2005/10/...-modification/

Reading his other posts, he's using a DX6 now but that is still Spektrum DSM

Which further leads me to believe the problem is not due to water surface reflections. Perhaps it's the rooster tail?? Prop?? not sure.

nomobux 04-05-2009 06:42 AM

RE: Spektrum SR300 antenna mod?
 

Quote:

ORIGINAL: Dan S

Elnino,

you are correct when saying that both system uses the same 2.4Ghz technology, the difference between the 2 of them is what make makes FASST the winner for over water.
FASST is frequency hopping, Spectrum on the other hand isn't.

I don't know how the antenna is designed on the Spectrum receiver, but on the FASST receiver only the last inch 1/2 is the antenna, everything else before that is only a coax.
yo can also Call Futaba and buy a replacement coax that is I believe a little over 15", again the first 14" is the coax and only the last 1 1/2" is the actual antenna.

if the antenna on the Spectrum receiver is similarly design you could make the coax itself longer.

But I am with the thousands of people that the Spectrum 2.4 is not recommended, way too many threads on this subject including transcript from Spectrum services not recommending it for boats.

Futaba FASST,
Airtronic's new FHSS 2 (developed for boats) and I believe Nomadio are your better choice (and mine).

Dan.
I'm not disputing that the Spek is not a good choice on water. The 3000 ant has to be totally diff. You can run it the stock length OR cut it to approx 4" per Spektrum.

10x8 04-06-2009 02:58 AM

RE: Spektrum SR300 antenna mod?
 
Gday Elnino,
The Mrs is sitting where all my radio gear is at the moment and I cannot shift her:)

I am sure I use older Spektrum gear, as well as new, and no probs what so ever over water, EVER!!! I must represent the other 1 billion happy customers that use them.

I do elec tunnels, and all ant wire is min 3 inches out of the cowl. You can see pics in the official elec tunnel thread.
I will check when her buttocks has left my r/c area/bedroom.:):D

Peter

Elnino 04-06-2009 07:47 AM

RE: Spektrum SR300 antenna mod?
 
Could it be something to do with electric vs gas?

nomobux 04-06-2009 10:20 AM

RE: Spektrum SR300 antenna mod?
 

Quote:

ORIGINAL: Elnino

Could it be something to do with electric vs gas?
I don't think so. I run nitro and elect. I know people running gas and no probs with new and old Spek. These are all land based. I was scared off using it on water and use reg FM. Not brave enough to try :eek:

Elnino 04-06-2009 06:12 PM

RE: Spektrum SR300 antenna mod?
 
I think i'm prepared to have a shot at the mod. There are plenty of people here that suggest spektrum is no good in a boat but lets say for example this IS to do with water reflections - then getting the antenna further from the surface of the water should help. I've also read that some people only have problems when the water is glassy. This could also be why 10X8 is not having problems with his - The antenna is much more out of the water on top of the tunnel. Also though, a tunnel does not produce such a rooster tail as the prop is submerged rather than a surface prop like most gas boats. Either way, i think i'm prepared to give it a shot. As i said before, my boat is nothing special and in fact (other than the time i have put into it) the Spektrum RX would probably be the most expensive thing in the whole boat...

The problem would be that given other peoples experiences, i am not keen to try it in it's stock form so it will be hard to tell if my antenna mod works, whether it will be because of the mod or pure luck.

My theory is to get a U.F.L Connector and solder it to the underside of the board. I will then use a pre-fabbed 2.4ghz antenna on a pigtail. These are the connectors commonly found on laptop wi-fi cards...
http://www.hux.net.au/wp-content/upl..._Connector.jpg

Problem is, my pond is empty at the moment! Waiting for rain....


10x8 04-06-2009 11:17 PM

RE: Spektrum SR300 antenna mod?
 
Elnino,
I am mistaken. I have DX3 & DX3.0, I got mixed up and shot off my fat mouth as usual.[:@] Both of them use SR3000.
I also have another elec tunnel with an FM system, JR with RS300.
I don't race my tunnels but I like to go to Penrith and watch the elec boats and .21 class nitro tunnel races. A few of them use spektrum, some use FM and alot Futaba 2.4. The racers are up high on a stand and hold their pistols slightly angled down from vertical.
I have used my spektrum in nitro .21 tunnels too, no probs, same theory - get the antenna out 3-4 inches. My pond is only 3 feet deep & always like glass if that has anything to do with anything? I have no fear of loss of my gear as it's sealed up tight, taped & taped again. If I have a mishap, lucky me can just waltz out there and pick it up.
My skills in 2.4ghz are that they talk to each other.

Good luck, let us know what you find.

Peter

Elnino 04-06-2009 11:35 PM

RE: Spektrum SR300 antenna mod?
 
Great to hear back from you peter. It's interesting to hear from someone that actually USED or has TRIED spektrum in thier boat. It seems that many just tell someone elses story. I mean, i do believe these people that they have heard of problems and you pretty much know that FASST is going to work 100% but to actually have someone give specific details on thier boat and say spektrum works fine is great.

The problem for boats is that there are so many different configurations that can affect this problem. Even the fact that you have DX2, DX3, DX3.0, DX3.0s and DX3.0r (DSM2) and the multitude of receivers out there for these can make a difference. Then we put on top of that the type of hull, composite, power plant, size etc - the possible combinations are pretty much infinite. For one or even 100 people to say 'I tried spektrum in my boat and it was crap' is only a drop in the ocean (no pun intended).

So peter, your tunnels is wooden construction right? And how high from the waters surface would your antenna be? Are you still running the full length of antenna on your SR3000?

thanks for your input!

10x8 04-07-2009 12:38 AM

RE: Spektrum SR300 antenna mod?
 
Elnino,
Not a problem. I like this r/c forum.
Nitro tunnel is TS2, fibreglass, MAC .21 powerhead, sal piped. I use the SPEK DX3 radio and SR3000. In this case, the radio box is located right up the front. My aerial wire protrudes about 5 inches out from the top of the canopy. The SR3000 unit is wrapped in 2 balloons, sealed in a wooden box, taped shut & under a glass cowl. I have the 6v batt pack, 3 servos & steering metal rods in the same box. Funny, the vibration from this boat is insane and I did ponder what electronics on earth would work in ere'?
The electric tunnels, are indeed a wooden DUMAS 3.5 Hotshot and a H&M Skater which is glass. I use the JR FM system in the wood and the Spek in the HM. Same as before, SR3000, ballooned etc, but the radio box is located dead middle of boat & under perspex lids, 2mm thick. Same, 5 inches of antenna coming out. Battery is up front.
I do not want to post links or pics as I would feel to be hijacking your thread. They are all there in the 'official elec outboard tunnel thread' on this site.

Also, the rubber cap that fits on the antenna top when tubed mounted, I have 1cm of exposed aerial. I also bring my milk crate to stand on: A/ to feel like a Pro and B/ cause I believe it may extend my performance.:D We run the boats right under Bankstown airport if that means anything?

I hope I have given you some positive, good information about the Spektrum. I am not a Spek salesman. I own Futaba, JR as well, but my Futaba is the attack 2 ch AM, ha ha.:D

Peter

Elnino 04-07-2009 05:42 AM

RE: Spektrum SR300 antenna mod?
 
1 Attachment(s)
Ok, i've done it!!

See the pics. It's pretty self explanatory but basically i have removed the UFL connector from a wireless card in a busted wireless access point, soldered it to the board and hey presto!

Procedure:

Step 1 - Grab the RX and undo the four screws holding the 2 shells together

Step 2 - Using a hobby knife or similar, gently scrape the CA glue from the base of the stock antenna. Take your time, do it a little bit at a time. Remove the old antenna by 'tinning' the solder point on the bottom with more solder, then the antenna will pull free. You need to add solder as these are RoHS boards which means the solder does not contain lead and is a pain to de-solder. By adding some, it melts easy.

Step 3 - I'm not sure if this is really needed but i did it to make sure there was no shorts in the connector. Using hobby knife again, scratch the area under the UFL connector where the center pin conductor goes.

Step 4 - Scrape the green copper covering off where the ground pads go and then tin them very lightly

Step 5 - Place the UFL connector and reflow the solder to the 2 ground points then the signal connector.

Step 6 - Connect new antenna to board. You'll need to cut a slit in the side of the case for the coax to exit

All done.

I have put the RX in my drifter for testing for the moment, range seems good so far but i have not been able to do a full range check just yet. Once the range is tested (and we get some rain) i'll try it in the boat. I have 3 of these antennas of varying lenghts, the longest being almost 25cm long and that will go on the boat.

I'll update this thread as i do further testing....

Dan S 04-07-2009 07:57 AM

RE: Spektrum SR300 antenna mod?
 
Elnino,
keep us posted on your progress.

There are a good number of people that have had and still have great success with their Spectrum radio in boats and I am more than happy for them.
Trying to find a good system is not always easy and buying a different radio because there may be a problem with them in certain configuration when you just bought the system is not something everyone would do (I know I wouldn't).

being the only member having replied to the post regarding the subject looks kind of odd but I think the guys felt that there was too many threads and pictures regarding the subject.

with that said, for those using the Spectrum in their boats with success, great, don't replace your radio unless there is or you have a problem.

Dan.

LtDoc 04-07-2009 09:28 AM

RE: Spektrum SR300 antenna mod?
 
FWIW

I have used a Spektrum radio system for some time, have had no problems with it (DX-6). I have heard/read where many people seem to have had problems with the DX-3 system. I think that's a peculiarity of that particular radio, not 2.4 Ghz or Spektrum in general.
There are some peculiarities when dealing with 2.4 Ghz stuff. Those peculiarities are characteristic of almost all devices at that frequency, and about as 'normal' as they can be. Futaba's 2.4 Ghz systems don't 'like' water any more, or less, than Spektrum's systems. Either brand would have the same sort of problems if used when it's raining, surface or air (not exactly worth trying to see if that's true, but you certainly can if you want :)). Sort of depends on just how -much- water you're talking about, and in what 'form'.
Why doesn't 'Spektrum' know what they are talking about with the water thingy? I would think that's because 'they' are 'airplane guys', not 'boat guys', primarily. That was the original intent for their radio systems, and probably where most of their 'R & D' was applied. Well, why does Futaba's stuff work well then? My 'off hand' SWAG would be tht they've had a little more experience dealing with boats? I tend to think they're a little larger organization than Spektrum, so that may mean more experience with the whole watery mess?
None of this is intended as an 'excuse' for Spektrum possibly making a goof in designs. It does give you an idea of what some of the qwerks about 'microwave' radios. And the 'worth' of any of this is exactly what you paid for it.
- 'Doc

Elnino 04-07-2009 06:18 PM

RE: Spektrum SR300 antenna mod?
 
Wasn't Spektrum's first release a 2ch surface?? I thought their air models came in later? I wasn't in to Air back then but that's what i thought.

I know the whole spektrum in boats thing has been thrashed to death here but I'll continue my research and i'm hoping to come up with somewhat of a reasonable solution.

I agree that for some reason Spektrum air radios seem to work ok on water compared to surface items. I thought this might be because of DSM2 but the DX3R is DSM2 and still seems to suffer the same fate. Stronger signal? More ECC? Not sure.

I read somewhere that because FASST changes channel, it doesn't see the reflections but that still does not make sense because it 'only' changes every 2ms. RF travels at the speed of light so in 2ms it would cover ~6000km So unless you are getting the reflections from over 6000km away, that is not the case. What i DO believe is that the RX has much better error checking and filtering of the signal so that it can see through these supposed reflections. Based on that, one would possibly think that Spektrum could release an RX specifically designed for water use that has more signal filtering and verification. Then they could make it a special water proof model too! Maybe even just a software update to existing RX's! I really think Spektrum have let us boaters down. There has been plenty of time for them to come up with a solution that is consistant and reliable meaning that they are losing mass business to a rival company.

I have a DX7 for my Heli's and planes and i love it to bits. Never a glitch, never a range issue - nothing! Same with the DX3s on land, range beyond my vision and rock solid, I just hope that i can continue this on water too.

Oh and FWIW, I am a Network engineer (Read: Computer Geek). I run several long range 2.4ghz wireless network links over 5+km and not one of them is affected in any shape or form by fog/rain/hail etc. NO degradation in signal strength whatsoever regardless of the water in the air.

ozzie-crawl 04-12-2009 06:22 AM

RE: Spektrum SR300 antenna mod?
 
i destroyed a boat using a dx3.0 in my hydro but it was made from carbonfibre wich probably made things a lot worse

Elnino 04-14-2009 04:52 AM

RE: Spektrum SR300 antenna mod?
 
Well, i done some range testing using my drifter. So far, i have not been able to go far enough to get it to drop out. I was running it at around 150m away from me and still not a problem at all. I even deliberately held the tx so the antenna was at right angles to the one in the car so it was incorrect polarity and it still worked fine at that distance. For those not in the know, an antenna mounted in the wrong polarity can mean a signal loss of 20+db which is a significant reduction in signal.

i couldn't test further than this just yet because i lose sight of the car. I need to get someone to walk away with it and keep an eye on the light in the RX.

So, in summary, so far i have very positive results. If this continues in the boat i will be extremely happy!

AndyKunz 04-14-2009 07:29 AM

RE: Spektrum SR300 antenna mod?
 

Quote:

ORIGINAL: LtDoc

Why doesn't 'Spektrum' know what they are talking about with the water thingy? I would think that's because 'they' are 'airplane guys', not 'boat guys', primarily. That was the original intent for their radio systems, and probably where most of their 'R & D' was applied.
Spektrum DSM and Marine Applications


Elnino 04-14-2009 05:26 PM

RE: Spektrum SR300 antenna mod?
 
Too little to late probably as most boaters would be using FASST. But here's hoping that it's just a different RX....

I did happen to browse the site last night and noticed that they now have 'carbon shell' compatible RX's for the air radios so hopefully this will carry on to boats.


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