Sub Forum - Radio

[John Kim]

This sub forum will cover:

Transmitters
Receivers
Batteries/chargers

[John Kim]

제가 소장하고 있는 Transmitters. 이 것이 전부가 아님니다.

원래 아마무선사 (HAM) 로서, 무선조종에 흥미를 늒여서 시작한 취미 라서,
RADIO에 더 많은 흥미를 갖이고 있읍니다. 저의 call sign 은 KC6WJD.

1960년대에 시작할 때 는, RADIO 가 간단해서, 자작한 송수신기를 사용했읍니다. TRANSISTOR 가 새로 나올 때 였으니가요. 그 때 가 더 자미 있엇든 것 같습니다.

RADIO에 관한 질문이 있으시면, 물어 보세요.
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These are not all. I started this hobby as a ham operator and am more interested in radio. My call sign is KC6WJD.

When I started RC hobby in 1960s, radio was much simpler and I used home-made radio. Transistors were making apperance then. Those early days were more fun-filled.

Please ask if you have any questions on radio.

[askman]

73s. mine is KI7LG. :) nice collection there john. I never kept mine. I astarted in 80 with two channel sanwa. had futaba, hitecs, and now I am running multiplex evo with space box. I know it is geeky to run tray, but I am comfortable with it, and like it for heli flying.

[John Kim]

Askman,

I've never had an opportunity to use European radio. To us who are more familiar with Japanese design, European radios are strange because of different stick mode and switch arrangement.

Do you like Multiplex Evo better compared to Japanese?

Do you still operate ham radio? I quit it long time ago. Internet is faster and more far reaching. DXing seems things of the past.

[askman]

I don't do much HAM much either anymore.

Well, I just got the EVO7 for great price. (250 shipped from hobbyhorse.com) it is very German if you understand what i mean. flexible, comfortable etc. I actually like the switch locations, etc and everything has that solid german feel. I also like the syntheized module. (better than spectra on my hitec eclipse) gimbal is smooth and adjustable and I love the spacebox. I've used lower end futaba, hitec eclipse (I need to send it in, and will be my backup) airtronics, but this is very nice radio. Frankly, there are no bad radio from reputable manufacturer, but I like it. plus, multiplex is owned by mr Park, who owns hitec.

[John Kim]

Hmm, it might be worth spending $250.

Do you know Pres. Park of Hitec? I met him few years back when he was stationed here in US. I gave him some marketing advice.

[askman]

just know him by reputation. never met him. one of the few Korean success story in this hobby business. btw, 250 does not include the spacebox. I got that from tower for 80. ouch, but I love it.

JR is easier to program than evo, but evo is much easier than eclipse.

[Runsthroughit]

I really envy you, but I don`t understand why you need so many transmitter.
I have only one Hitec Eclipse 7, a secondhand goods. I bought it for repairing easily in Korea.
During past 3 years in my flight time with R/C planes, there`s no trouble with it.
First I started R/C car, then I flied R/C planes.
Some people said I have to buy more famous and functional transmitter(Futaba or JR), but I don`t agree with them. I love my Hitec Eclipse7.

[John Kim]

Runsthroughit,

I like Radio and am a collector (수집광). Whenever new model comes out, I become curious to know its capability and to compare it with others.

Many were picked up at the second-hand market at a half price. I cannot resist a bargain price and kept buying more and more.

Eclips 7 is fine. Only when you fly a sailplane with 4 servo wing and crow set-up, some more convenient features found in other top class transmitters will beome desirable.

According to my experience, JR had the most advanced sailplane program until Futaba caught up with 8U and now 9C.

[John Kim]

Horizon Hobby finally made a technological breakthrough and came out with spread spectrum radio for airplane use.

The car radio using spread spectrum was introduced already last year but the munufacturer could not solve the problem of RF link and was hesitant to apply the same technology to airplane radios because the airplane will crash if RF link is broken during flight.

They now came up with new idea to solve the RF link. In their new airplane radio, DX6, a redundant dual receiver is employed using two separate radio channels out of 80 available channels. Under this dual system, if radio link is lost on one channel, there is always a back up channel and receiver to take over and radio control is not interrupted. (Should you land your plane immediately when RF link is interrupted to avoid the second chance?)

RF link is lost when airplane flies into weak signal zone which is a result of antenna orientation, reflected signal, interference, distance, etc. Once RF link is lost, it cannot be reestablished automatically. Radio must be started all over again for tuning process to take place in spread spectrum radio. With the cell phone which uses the same technology, all you need is to redial. But airplane would have already crashed by the time.

New spread spectrum radio for airplane, Spektrum DX6, made a debut at Los Angeles Hobby Show this weekend. I saw it myself and handled it to check its quality. Stick movement was smooth and positive. Switch placement is well designed. It is a 6 channel radio with 10 model memory, digital trims, 3 programmable mix, dual/exponential rates, etc, using direct sequence spread spectrum operating on 2.4GHz frequency band. Radio was made in Malaysia.

The dual receiver is even smaller than single receiver. It's size is about Hitec 555 receiver but only half its thickness and weighs only 7 g.

Because of the short wave length used, the transmitter antenna length is about 8", no more than a rubber duck antenna. The receiver antenna is even shorter, only about 6", which will fit inside the smallest park flyers.

Radio automatically select unused two channels of 80 channels available. No frequency selecting crystals are used either on transmitter or receiver. Frequency is synthetized.

Finally, RC fliers are freed from radio interference. The day we were waiting has arrived.

I believe this is the final solution for radio-interference-free flying. Any radio manufactuers who fail to jump on this band wagon will fail in this competitive business. I told Hitec last year that they should immediately start research and development in this technology if they wish to maintain a lead in the industry. I wonder what they are planning now. I wish we get some feed back from Hitec engineers.

The radio is available in Christmas time but orders are being taken now.
Price is $199.99 including 4 micro servos, batteries, charger.

For more info, see http://www.spektrumrc.com/DSM/Better/DX6-glance.html
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비행기용 SPREAD SPECTRUM RADIO, SPEKTRUM DX-6, 가 드디어 LA HOBBY SHOW 에서 첫 선을 보였읍니다.

KRG site 에서 몇 달 전에, spread spectrum 을 비행기에 적용했을 떼, RF link 가 끊어 지면, 어찌 되느냐고, 어느 전문가 회원이 걱정한 것을 기억합니다. 그 문제 때문에
비행기 용 radio 가 나오지 못 하고 있었는데, 이 번에 RF link 문제를 해소하고, 신제품이 나왔읍니다.

RF link 문제 자체는 해결을 못 하고, 그 대신 Channel 를 둘, 수신기를 둘 을 사용하여, 만약 RF link 가 끊어 지면, 다른 수신기가 이어 받어, RF link 가 끊어지지 않도록, fail-safe 설게를 했읍니다.

비행기가 전파가 약한 곳 으로 갔을 때, RF link가 단절 되면, 다시 자동으로는 수복이 안 됩니다. 같은 기술을 응용한 휴대전화는 다시 다이얼을 돌리면 되지만, 비행기는 그러는 동안에 추락하고 맙니다. 이것이 과거에 문제 였읍니다.

쑤신기는 하나에 두 개 가 들어 있음에도 불구 하고, size 는 Hitec 555 의 반 (널비는 비슷 하나, 굴기는 반) 밖에 안 된는 극소형.

주파수가 극조단파 (2.4 GHz) 이기 떼문에, 송신기 antenna 는 8", 수신기 antenna 는 6", 중양 7g. 아주 편리합니다.

사용 channel 는 80 개. switch를 넣으면, 송수신기가 사용하지 않는 2 channels 을 자동으로 선택,동조하여, 작동을 개시. 송수신기 모두 X'tal 이 필요 없는, freqency synthesizer 사용.

Stick 동작은 smooth 하고, 정확하며, switch 배치는 일제와 비슷. Dual/Expo Rates,
3 programmable mixings, digital trim, 등등 최신 설게.

가격은 $199.99 출하는 Christmas 때, 주문은 받기 시작했음.

Spread Spectrum 기술 등장으로, 전파방해 문제는 완전해결이 됬으며, 우리가 오래 동안 바라든 꿈이 실현 됬읍니다.

Hitec 도, 이 신 기술 개발이 늦어지면, 업게에서 뒤떨어 지게 될 것 입니다.

나도 곧 하나 주문해서, 사용해 보겠읍니다.

Spectrum site: http://www.spektrumrc.com/DSM/Better/DX6-glance.html

[gymguy]

The car radio using spread spectrum was introduced already last year but the munufacturer could not solve the problem of RF link and was hesitant to apply the same technology to airplane radios because the airplane will crash if RF link is broken during flight.

They now came up with new idea to solve the RF link. In their new airplane radio, DX6, a redundant dual receiver is employed using two separate radio channels out of 80 available channels. Under this dual system, if radio link is lost on one channel, there is always a back up channel and receiver to take over and radio control is not interrupted. (Should you land your plane immediately when RF link is interrupted to avoid the second chance?)

RF link is lost when airplane flies into weak signal zone which is a result of antenna orientation, reflected signal, interference, distance, etc. Once RF link is lost, it cannot be reestablished automatically. Radio must be started all over again for tuning process to take place in spread spectrum radio. With the cell phone which uses the same technology, all you need is to redial. But airplane would have already crashed by the time.

I'm confused. There are two types of spread spectrum. One is called frequency hopping where the transmitter and receiver hop over a range of frequencies in a random pattern established by the transmitter. Other TX/RX users can use the same set of frequencies if their random hopping pattern is different from others using the same spectrum. A relatively short synchronization process takes place between each TX/RX pair in the order of microseconds. There will be interference in the unlikely event that users happen to transmit on the same frequency at the same time but the amount of interference is minimum if the number of hopping frequencies is large and the hopping pattern is sufficiently random. In the case of the ISM band the FCC mandates at least 75 frequencies be used out of 100 Mhz of bandwidth and it examines the randomness of each hopping pattern before granting approval. The data lost in transmission in the case of a collision (2 users transmitting at the same time) is 1 out of 75. This data can be totally recovered by redundant transmission if desired but would only cause a small servo error so it wouldn't probably be necessary. I had assumed that spread spectrum radios would use the ISM band since there is nothing forbidding its use for airplanes. The use of only 2 frequencies doesn't make sense to me.

The other type is called direct sequence spread spectrum where the transmitter uses one carrier frequency but spreads the energy over the 100 Mhz bandwidth by modulating the carrier with a "chipping code". This one is a little more difficult to understand without mathematics but relies on "processing gain" to recover the data. The code is a random digital pattern that is set by the TX and is followed by the RX. Other user TX/RXs would have their own unique chipping code. All radios use the same carrier frequency but each has a unique spectrum. Again these radios need a relatively broad frequency spectrum and a sufficiently random chipping code to allow many radios to operate in the same environment. I believe they also must operate in the ISM band since this is the only one I am aware of that is approved by the FCC for 2.4 Ghz.

All spread spectrum schemes can fail if a very strong broadband signal blanks the entire spectrum. This is very unlikely in the case of 2.4 Ghz unless your receiver is near a leaky microwave oven. These ovens use 1000 watt TXs so it is not uncommon to see 100 millowatts leaking from them as they get older. I haven't seen many flying microwave ovens however.

It is true that the cell industry uses SS but it operates at cell frequencies. In this case however full duplex communications between the phone and the cell tower is used so if data is lost the RX requests additional packets be transmitted to recover it. Dropped calls therefore are not the result of intermittent interference.

GPS receivers also use direct sequence SS techniques to literally pull weak satellite signals out of the noise level by processing gain but they use a relatively wide spectrum of frequencies and do not use single channels.

Somebody help me understand this 2 channel thing.

[John Kim]

gymguy,

You are already an expert in this field of SS. Your discourse was much more easily understandable than same found in the text book. You don't need any further explanation from a layman like me. Only person who can satisfy you is probably a guy in the engineering dept. of Horizon Hobby. I think his name was Paul. I am not sure.

I am waiting some feed back from SS engineers in Korea. Since cell phone industry is most advanced in Korea, I am sure there are many bright brains out there. Some of them are RC model airplane fans.

Can I recommend you to Hitec as a technical consultant on SS research?
Pres. Park, what do you think of gymguy?

If you email me your resume, I will pass it along to Hitec.