Module and antenna question with new Turnigy 9XR

[Scott Page]

So, which antenna should I buy to replace the cheap antenna that came with my frsky module??

Sparkfun has 5db antenas -- I use http://www.alofthobbies.com/5db-module-antenna.html but with a 5db you must be very conscious of the direction it's pointing -- toward the ground in front of you or toward your head are the best -- as your model is not likely to be in either of those places -- but if you point the antenna toward the model it will be in the ground as it has a larger signal hole.

[Scott Page]

> So, which antenna should I buy to replace the cheap antenna that came with my frsky module??

I ordered one like this...
http://www.hobbyking.com/hobbyking/stor ... ules_.html

You can search HK for antennas, they have tons of them. Most are in the $4-10 range. You can't trust the rated dBi of the antenna, quality and performance is pretty much a random crapshoot IMHO. You can also go on ebay and find tons for cheap. It's always a crapshoot, so order a few and find one that works.

I just don't understand why anyone would be satisfied with a cheap 1 dBi antenna when they can double, tripple, or quadruple their range for $5-10.

As I mentioned, stock antennas are throwaway garbage unless you don't care at all about performance. That's why it seems especially stupid for companies to be building garbage antennas that the user will certainly want to change right into the unit with no way to change them.

Dude -- that patch antenna has a monster dead area - you really need to pretty much track the model with the antenna. Yes, you'll have fantastic range -- but you must be very conscious of the direction you are pointing the antenna. I do use that antenna when I have a lost aircraft -- because it can be used to locate the aircraft by watching the RSSI as it's got such a narrow signal beam.

[Scott Page]

More gain from these types of antennas comes from modifying the 360 donut radiation patten into something much more directional like pear shape.
Of course more gain but no free ride, The pattern becomes more directional. This defeats the purpose of a non directional antenna system.
To put it technically, more peaks of signal strength and more lower signal strength valleys.
Not perfect for omnidirectional flying.
Of course most reading up on antenna theory knows that so this is old news.
It's hard to argue antenna theory in the hobby world so I'm just happy I get paid for it in the professional word.
Try it, if you're happy with the results then your good to go.
SM

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SM what antenna do you use on your FrSKY modules? I know that my choice of a 5db for more range is sort of like kissing your sister -- it's better than nothing at all but certainly not the best.

[Rob Thomson]

Guys... I think this issue is bouncing around with too many people who are not actually experts in the area giving their opinions.

If I am correct we have a few antenna design chaps who do this for a living on the forum. I suggest we listen to them.

Now... To my knowledge - the higher the DBI the more range, but the lower the signal density. The result being that increasing DBI does not necessarily mean better signal.

More often than not higher gain requires high directionality, meaning that you need to point the antenna at the model at all times.

This is the simple reason why you find manufacturers provide low DBI omni directional antennas. Good quality, decent range.

Simple, and serves 99% of people's needs.


Now... I stand to be corrected on this. I am no expert.

How about we let guys who like Groot who actually do this for a living, give the correct answer.

[Kilrah]

I ordered one like this...
http://www.hobbyking.com/hobbyking/stor ... ules_.html

I have one, and it performed worse than the stock one. I flew with the stock antenna, watched the RSSI values evolve during flight, then changed to this antenna, and flew again comparing and trying to adjust antenna orientation during flight. Even when perfectly aimed, I always had a lower signal than with stock.

So if you're OK to "believe" you can slap on and it will be so much better, great for you - but in practice, the stock antenna is ideal for most uses. If you want to really optimize it takes a little more care than just slapping the $5 "miracle antenna" on.
For example a little "free" work on the receiver antennas can do much more, and this time without losing omnidirectionality.

[jhsa]

guys, when I asked about the antenna, I meant the quality, not the type. It was mentioned the bad quality of some of these antennas, so I would like to know where to get a better quality 2 db one. I do understand the radiation pattern of the different types of antennas...

[Scott Page]

guys, when I asked about the antenna, I meant the quality, not the type. It was mentioned the bad quality of some of these antennas, so I would like to know where to get a better quality 2 db one. I do understand the radiation pattern of the different types of antennas...

2.4GHz Duck Antenna 2.2dBi with Reverse Polarized - SMA RF connector. 50 ohm impedance. 4" long

https://www.sparkfun.com/products/145

Datasheet is attached.

[Scott Page]

I'd like to see Groot or ShowMaster address this antenna. It looks very attractive in some RC applications.

https://www.sparkfun.com/products/11320

[ShowMaster]

Actually the radiation pattern looks pretty good. I'm not sure about what to do with the extra coax length and wouldn't want to cut it. It may be critical to keeping the SWR to a 3 and putting the connector at a SWR low point on the return energy.
For line of sight flying the stock rubber duckie on the Frsky has severed me well enough and for FPV adding this to the RX may be a big improvement over the stock antennas for sure.
I'm not sure about sticking one of these on the back of our tx however? Any hand influence could alter it's pattern and SWR properties.
SM



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[aesmith]

Now... To my knowledge - the higher the DBI the more range, but the lower the signal density. The result being that increasing DBI does not necessarily mean better signal.

More often than not higher gain requires high directionality, meaning that you need to point the antenna at the model at all times.

You should also reduce the electrical output if you fit a higher gain antenna, as the allowed limits are for ERP.

[Kilrah]

has severed me well enough

Gotta love autocorrect!

The antenna looks good, but won't bring any improvement over the stock antenna oif we talk of specs, and it's not really a convenient shape that makes it more practical in our application either...

[JakeStew]

Do you have any antenna recommendations? I've found that buying cheap Chinese antennas is a total crapshoot.

If you look at the antennas on ebay or HK most of them seem to have ridiculous dBi claims.

[ShowMaster]

Yes, more gain by antenna magic, no added power basically redirect all available power going in all direction to a more confined direction. Much like a flood light mode or a spot light mode on a flashlight. Same light just redistributed in a tighter beam.
To increase the range and still have a 360 deg pattern the power has to be increased. No null spots or directionality issues this way.
As for legality,
Yes upping ERP, effective radiated power out, whether by TX antenna design changes or added power results in making the system illegal from its certification. To be technically correct read your countries RF certification rules.
It does not violate these rules to modify or amplify the RX only end. Trouble is our 2.4 systems are 2 way, TX/RX so any modification to add gain and distance to the TX or RX most likely violates the certifications.
What's the harm?
The only real harm is if there is liability issue and it's proven that the equipment has been modified. It could even thou low risk, cause interference to other flyers close by.

Again talking concepts here, we do what we think we can get away with so it can't be argued please.

In the USA, it could in certain conditions be considered a felony act to modify your equipment that you're not licensed to do or in a band with power limitations.
Pretty heavy info here but it was brought up. With out hobby being eyed as a possible tool for spying or terrorism it may be something to at least be informed about so one can stay under the radar.
We brag and instruct on forums on how to modify our equipment with how to's even never thinking about who's reading it or gathering data on us, even brag videos.
So..
Be smart, fly safe, don't brag too much, stay under the radar and have fun.
Oh, do power mods for profit and you attract a whole other group of people watching you.
SM




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[ShowMaster]

has severed me well enough

Gotta love autocorrect!

The antenna looks good, but won't bring any improvement over the stock antenna oif we talk of specs, and it's not really a convenient shape that makes it more practical in our application either...

I hate auto correct but when it works, really helpful.
Yes you're right on! The antenna is bulky for our usage.
Maybe giant scale?
So much worry about antennas? I go with my Frsky setups and I'm good as long as I see it.
FPV is another issue that many of us are not going to use this 2.4 setup with in any case.
SM


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[Kilrah]

I actually do fly FPV perfectly happily with my stock antennas. But I'm not the "American-type" FPV flyer, for me 1.5km are more than enough

[JakeStew]

You should certainly be careful that any modifications don't cause interference for anybody. But using better antennas is far better than using more power IME.

As far as the law is concerned... I've never had a cop trying to check the FCC ID numbers on my radio. I've also never heard of or read about this happening to anyone else. The only time I could ever imagine anything happening to someone is if they were constantly transmitting a lot of power power on a single frequency that interfered with some sort of regular radio service.

I'm talking 5-10W+ in the TV or radio bands, for at least a few days. I can't see anything less carrying any legal risk whatsoever.

[Var]

To address the guys talking about how the internal antenna connector was a stupid idea..
I don't mind using a stock antenna. DSMX and ACCST with stock antennas should be plenty robust for LOS flying.

It's really the product implementation/launch that sucked. How can you invent a new form factor and not have anything that connects to it? I don't know what they're thinking over there at HK from a marketing and business standpoint. If they launched this product with DSMX, FASST, ACCST, and even crappy FLYSKY modules ready for sale, they would have made a killing on them. At least half if not more of the people would have bought one or more module with their 9XR. The stupidity isn't in the design. Many people would gladly use the stock antenna. But how can you launch a tx with a brand new module setup and not have any modules for sale? Someone will surely build one soon because the 9XR created a market for it, but it should have really been done with the product launch.

On the plus side you can use any old stock module with its own antenna, so they didn't totally screw the pooch on this one. But I'd rather have a plug n play solution.

[JakeStew]

> At least half if not more of the people would have bought one or more module with their 9XR.

You can't really think that people are so dead set on using that crappy internal antenna that they quit buying modules with their radios.

> The stupidity isn't in the design.

Have you actually looked at the design? From the PCB the signal has to run through a connector, through a piece of coax, threw another connector and threw another length of coax just to get to that 1-2dBi internal antenna.

Signal losses are high in coax and connectors when you're using microwave frequencies like 2.4g. You'll also have impedance matching, stray capacitance, and signal reflections from all that foolishness between TX and antenna.

It's just bad design all around. The units are probably delayed because they didn't perform worth a darn and they're trying to figure out a solution.

[Var]

The question is, will it work ? I'm not brave enough to buy one and try, but there are many others who will. I'm still waiting for real world reviews. If it sucks it sucks. If it works I'll use it.

[Kilrah]

Have you actually looked at the design? From the PCB the signal has to run through a connector, through a piece of coax, threw another connector and threw another length of coax just to get to that 1-2dBi internal antenna.

This is exactly the same path the RF signal follows on other modules with their own antenna, just the coax length is a little longer.
If you open an FrSky, Orange, Spektrum, Graupner... module you'll find:
- An u.FL connector on the board
- A coax pigtail that goes to the (RP-)SMA connector on the back
- An antenna, which is nothing else than the connector, a length of coax to go through the bend to the element... which is the same as the one HK has integrated.

Futaba just saves the antenna connector by having a non-removeable antenna on the module.

[JakeStew]

> This is exactly the same path the RF signal follows on other modules with their own antenna,

2 connectors and 2 coax runs in the 9XR system, and the controller run looks fairly long. That's twice as many coax runs and connectors as most TX modules, and the runs are longer. (you don't count the actual antenna connector)

[Kilrah]

I did, even described it completely.
board connector-coax-module connector-coax-antenna element. Same on the others I mentioned. The only difference is the length of the coax between the module connector and actual antenna element.

[jhsa]

I just don't like the type of connector. It doesn't look safe connecting the antenna like that. When you change modules the antenna goes with it.. That's the right thing in my opinion.

[JakeStew]

Sorry if I pissed anybody off. I just think it is a basic feature of a decent radio is that you be able to attach different antennas depending on your needs and budget. That makes an internal antenna that you can't change a very stupid design. I've also always found out that stock antennas are just cheap placeholders so you don't burn out your TX. Best to toss them in the scrap pile and spend a few bucks on a decent one.

Anything I've ever designed has the connector soldered directly to the PCB. This is very efficient IMHO. I've played around with 2.4g wifi plenty and any time there is a significant cable run I've seen major signal losses. IME the best designs have a USB cable running to the adapter, which is directly attached to the antenna connector with no cable.

One short run to the antenna connector is acceptable, but anything more and I feel like I'm being robbed of performance for no good reason. Two runs and two connectors and I really feel cheated.

[G550Ted]

Sorry if I pissed anybody off. I just think it is a basic feature of a decent radio is that you be able to attach different antennas depending on your needs and budget. That makes an internal antenna that you can't change a very stupid design. I've also always found out that stock antennas are just cheap placeholders so you don't burn out your TX. Best to toss them in the scrap pile and spend a few bucks on a decent one.

Anything I've ever designed has the connector soldered directly to the PCB. This is very efficient IMHO. I've played around with 2.4g wifi plenty and any time there is a significant cable run I've seen major signal losses. IME the best designs have a USB cable running to the adapter, which is directly attached to the antenna connector with no cable.

One short run to the antenna connector is acceptable, but anything more and I feel like I'm being robbed of performance for no good reason. Two runs and two connectors and I really feel cheated.

Well Jake, you have expressed your negative opinions non-stop regarding the antenna design and your perceived performance of it repeatedly here and on other forum(s) without the benefit of actually having one in hand or hard data from actual test results. Your point is made. The fact is, that it is what it is. It may be junk but it is similar to the design of most less than high-end radios and I suspect that it will be completely satisfactory for the vast majority of purchasers of this radio. If it indeed proves unsatisfactory, then we might all be able to benefit from any modifications you may develop, test and share in the future. I look forward to seeing those results.

Ted

[ShowMaster]

The real issue with the connector is that there are those that won't purchase the specialty made HK modules but instead attempt to modify their modules to use it.
Any current module with the antenna on the module is not an issue. Any custom HK module is not a real issue except that any connector in the antenna path can be subject to wear after x amount of insertions and removals. This could cause reduced power output over time due to impedance change and SWR.
I said could, so let's not argue about it until there in use for a year.

To be positive about all this,
If used with the designed modules and connectors and not not changing modules constantly, it should work ok.

The only other issue is that the internal antenna is horizontally polarized and many flyers insist the antenna sticking straight out or up, or vertical is the only way they get a good link lock.
That's a debate in itself that most flyers worry too much about I think for sport flying.

I only fly ( Frsky DJT) with my antenna horizontal tucked next to my 9x handle and have never had a range or link issue so personally I'm ok with antenna placement.

My only concern with all this is the fact that dsm2 link losses cost me 5 planes, Frsky zero in 2 years! Except for indoor BNF I'll not worry if my DSM module doesn't use the internal antenna and look nicer, besides a orange module on a black case looks like Halloween?

Hopefully Frsky will make a module with a matching rf connector?

On the other hand, if the rumored Frsky TX is done right, I'll just go with it and pass all this on to club members looking for a tx upgrade. Some flyers collect 37 planes, others collect 37 new radios. It's a hobby in itself.
A friend just sent me a picture of his 400+ RC radio collection asking about putting his favorites on 2.4.
Now that's a dedicated hobby person!
SM



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[JakeStew]

> If it indeed proves unsatisfactory, then we might all be able to benefit from any modifications you may develop, test and share in the future.

The time to point out design flaws is before a lot of money has been spent. I can't count how much money I've saved by listening to advice from others. Most of the time things aren't obvious unless someone points it out.

If HK actually reads this or their own forum they might see the light. If people wisely choose the better design of antenna on the module HK might also decide to make a better design the next time around. If even a few people realize the folly of a design using a low grade, non-replaceable antenna and avoid it then I'll be happy to have saved someone that mistake.

[cr4wler]

hi guys!!

do you think FS-TH9X-B-Module will bind on WLToys v911 or v929?

TIA

[dvogonen]

Mine sure binds on my v911 helicopters.
I have not bought the v929 (yet ), but as far as I can tell it uses the same protocol, so it should bind

[cr4wler]

thanks =)

i bought a 9xr without module as well and i thought i can easily find tg9x module, but im wrong.
is the binding procedure of FS-th9x similar with tg9x?