Why aren't more Rx's antenna-less ?

[properchopper]

I have six boats using the Tactic Tx/Rx combo. No range or glitch problems at all. Outside of the inconvenience of no model memory, I really like not having to deal with antennas. I'm curious about why no other brands have antenna-less Rx's. Anyone ?

[icelert]

Two words- carbon fiber.

It is a conductive material that can shield the RF signal from a rx. A 2.4 ghz antenna can be very short-like an inch or less(depending on the wavelength), so hiding an antenna for 2.4ghz inside the rx isn't a problem. The problem is if the user has a model made of carbon fiber there can be some signal loss. You will see mfr's use a coaxial type antenna which creates a LONGER antenna so the user can get the active part of the antenna(last inch or so) OUTSIDE the model so that issues with carbon fiber can be minimized. If your models are plywood or glass construction, then in my opinion, antenna placement outside the hull isn't so much an issue. I would still recommend however, that the antenna be oriented in a vertical fashion to maximize it's ability to pick up the signal from the tx. Now forget about 75 mhz rx's-they will always need a wire sticking out of the rx!

[Flying Scotsman]

Tony, you are a beauty and a very interesting question. What tech guys know the answer??

Douggie

[hide]

Futaba sell the R604FSe which has no antenna. I use one in my mini buggy for racing because the antenna tube is a pain when racing. No range or glitching issues either.

One problem is that the range is far less than that of one with an antenna. Although still quite good, it doesn't beat the 1500' of the antenna'ed receiver.

[Jeff Wohlt]

Think about why the Stealth fighter and bomber and why it is made with what it is? This was a benefit of CF....not just exhaust gasses.

[properchopper]

I realize that a fully enclosed CF hull would present problems with an antenna-less Rx, but such hulls represent a small portion of the FE mix. I'm still wondering why Tactic/Tower [and their OEM] can present a decent range antenna-less Rx and the major players haven't. Anyone else ? Bill ?

[Bill-SOCAL]

Hide hit the nail on the head. The antenna less receivers, which are not really antenna less since they have an internal antenna on the PC board, have a much restricted range compared to receivers with external antennas. This is independant of the hull material. CF just makes it worse, if not impossible. Bottom line is that the internal antenna receiver cannot have the same or better range than the receiver with an external antenna.

The 604FSe is not available in the US. I am not sure why but I have been told that it will likely not be sold here.


Range is the key issue and so far Futaba prefers to sell the more robust system with external antennas. I have no issues with the tiny antenna as it is. Beats the heck out of the 39 inch long things we used to have to deal with!!

[properchopper]

Thanks, Bill-glad you chimed in. I'll admit that my testing of the Tactic's been limited to Legg Lake where there have been no range/glitch problems. Other locations may not be as optimum. FWIW, I just re-installed the Futaba 3PM in my mono racer in prep for February.

[Fluid]

I realize that a fully enclosed CF hull would present problems with an antenna-less Rx, but such hulls represent a small portion of the FE mix.

And herein lies the rest of the story. FE boats make up a small portion of the buyers of wheel radios (although I suspect that percentage is changing) and the radio makers are not in all that robust financial shape anyway. They cannot afford to market custom radios for just one small market segment, they have to market to the gas, nitro and car guys. So the default is that terrible long antenna we have to put up with....

BTW it isn't just carbon fiber that shields 2.4 reception. Gas racers note that their large engines and tuned pipes interfere with reception too. The Tactic radio was designed for a single model, a single use and a known market. Good work for what AquaCraft did with that one.


/

[tharmer]

I can completely enclose the antenna in my wood sailboats and they never run out of range. In my CF hydro hull, the range is about 150 feet when I do that. Sigh...
-t

[Bill-SOCAL]

BTW it isn't just carbon fiber that shields 2.4 reception. Gas racers note that their large engines and tuned pipes interfere with reception too.

Yep, we learned this right off the bat with the big planes. A large engine, gas tank, etc. all can block 2.4 GHz. Wood, FG, etc. is not an issue. But metal, gasoline, CF, etc. are all bad. The 5-inch antenna on my FASST radios is not really a big deal and it is worth it to me not to have any worries about losing contact with my boat, plane, etc.

[Flying Scotsman]

Yep, we learned this right off the bat with the big planes. A large engine, gas tank, etc. all can block 2.4 GHz. Wood, FG, etc. is not an issue. But metal, gasoline, CF, etc. are all bad. The 5-inch antenna on my FASST radios is not really a big deal and it is worth it to me not to have any worries about losing contact with my boat, plane, etc.

Does that mean that quality FM radios are better than 2.4 Ghz as far as reception issues are concerned?

Douggie

[Bill-SOCAL]

Does that mean that quality FM radios are better than 2.4 Ghz as far as reception issues are concerned?

Douggie

The 2.4 GHz radios transmit in FM as well. If you meant are 75 MHz radios "better", that is sort of hard to say. What the longer wavelength does "better" is penetrate solid objects. So in that sense it is "better".

What 2.4 GHz does "better" is allow for the use of spread spectrum transmission which means that we are freed from the concern about interference from other radios and essentially have no worries about internally generated noise (with some few exceptions). The price we pay for that is needing to pay a bit more attention to how we install the radio in the boat/plane/car in order to minimize the concern of physical blocking of the signal.

This is why Futaba uses 2 antennas for the most part (sometimes one is internal) and why Spektrum uses secondary receivers on their airborne radios systems. All of that is designed to minimize the physical signal blocking issues.

[icelert]

I also remember reading somewhere that 2.4 ghz is way more crowded with other types of users and is largely unregulated compared to 75mhz. Computer routers,wifi, and public service radio users(+many others) all have to occupy a very narrow spectrum. Put all these users in an urban or suburban lake location and you can see why rx's have evolved the way they have lately.

[Bill-SOCAL]

Well, yes and no about the crowding. Yes there are many users, but generally no for it being an issue that needs consideration. Most all 2.4 GHz uses are fairly low power, so even if your pond was ringed by Starbucks with WiFi hotspots it would not really be an issue. The whole point of 2.4 is that the data compression that is used along with the different hopping schemes make it possible for a large number of users to simultaneously use the band with no real issues effecting each other.

This is a decent article that helps explain a lot of what is out there.

http://en.wikipedia.org/wiki/Spread_spectrum

http://en.wikipedia.org/wiki/ISM_band