RC Slope Soaring in Hong Kong

今日與電訊管理局聯絡，証實今日早上電訊管理局已開放多8條35Mhz 及4條40Mhz頻道給與遙控器使用，
連同之前的6條72Mhz，總共有18條。
已領有牌照的人士，電訊管理局將於日內寄出牌照第二頁之更新附表。
電訊管理局亦將會於下次立法條例中更新該18條頻道列入豁免領牌，
現有豁免領牌頻道為26.96 Mhz至27.28 Mhz，當然亦須附合遙控器之規定。
頻道於下
35.150 Mhz
35.160 Mhz
35.170 Mhz
35.180 Mhz
35.190 Mhz
35.200 Mhz
35.210 Mhz
35.220 Mhz
40.665 Mhz
40.675 Mhz
40.685 Mhz
40.695 Mhz
72.010 Mhz
72.130 Mhz
72.170 Mhz
72.190 Mhz
72.210 Mhz
72.270 Mhz
電訊管理局亦再次提醒各位，任何遙控器如超過10mW須領有牌照，豁免頻道並在0.5W以下除外。

Hi Brother Billy,

Thanks for your information and great news!!!

Hello Billy,

新 frequency 中的 40MHz 有些奇怪 40.665MHz 及 40.695MHz 即十多年前的 A band 及 B band，現已不用。現在買到的 40MHz 都是 40.XX0，好像沒有 40.XX5 . . .

仲要留意兩點﹕

1) 遙控頻道每條係相隔 0.02 MHz﹐所以 35.160 下一條係 35.180﹐中間唔可以攝一條 35.170, OFTA 似乎一時匆忘搞錯左。

2) 市面上買到既晶體頻率似乎有雙單數之分﹐我到依家都唔知背後原因﹐有可能係唔同國家有唔同既頻率方案,或有D方案已屬過時﹐譬如 35MHz 可能有兩組頻率﹕

A﹕ 35.160, 35.180, 35.200, 35.220
B﹕ 35.150, 35.170, 35.190, 35.210

我地只可以二擇其一。呢方面要同 OFTA 傾下。

我咁q中左 40.665 喎,因為佢系十多年前既 band 我先用嗎!不過都jam好多機友既 band 喎!!

Hi CM, Y.C.......

頻道係佢地一路講，我一路寫，除非佢地講錯。各位意見我已即時講過，但係佢地話商討後批出這些頻道。

I don't know what you mean, YC. I'm on 35 and had been flying with others on adjecent bands (i.e. 10kHz apart) with no problems at all. Is it that we can only accept group A or group B only?

I believe we should keep asking for more exempted frequencies and exempted output rating at 1W. Please keep up the good work.

CT

我以前都試過用41.000 MHz (JR)而朋友就用 41.010 MHz (Futaba)﹐一齊飛無問題﹐相信原因有兩個﹕

1) 我地用既接收機性能較好(我用既係 JR SPCM 9ch )﹐ 選頻能力(frequency selectivity) 較高﹐可以有效壓抑鄰頻干擾。

2) 飛個陣我同朋友企得好近﹐所以兩個頻率既訊號到達接收機時既強度經常都保持差唔多一樣﹐令接收機唔需要好?#36027;力?#23601;可以壓抑鄰頻訊號﹐所以無干擾問題。

如果換上選頻能力較差既接收機﹐又或者機師企既距離較遠﹐當隻機飛近鄰頻發射時﹐鄰頻訊號就會強過正頻訊號好多﹐到時接收機就未必夠能力壓抑鄰頻訊號﹐導致出現干擾﹐以前我都見人撞過咁既問題。

依家睇落 OFTA 似乎係撥出一個連續既 35MHz 同 40MHz 頻段俾我地用﹐係頻段範圍內我地可以自由決定發射頻率既分隔 ( 27 MHz 就係咁既情況 ) 。35MHz 頻段既問題不大﹐如果撞到有機友既頻率同你相隔 10 kHz,只要事前試清楚唔會互相干擾就可以一齊飛。但 40MHz 頻段就比較 ?#39438;哩?#65104;除非發射頻率相隔 5 kHz 都唔會干擾(睇怕好難)﹐否則就會變相少左頭尾兩條合法頻率﹐要同 OFTA 傾傾。

[quote="Billy"]今日與電訊管理局聯絡，証實今日早....
電訊管理局亦再次提醒各位，任何遙控器如超過10mW須領有牌照，豁免頻道並在0.5W以下除外。[/quote]

Heard that JR tx has higher power than Futaba.
Can JR 9x still get the license?

Do we need to have the crystal/module sealed after the checking by OFTA?

Thanks!

Don't know about Fut but the JR Rx specs says a selectivity of 8kHz/50dB, and 50dB sounds alot to me (no expert tho) not to mention that at 10kHz it should be somewhere above 50dB. And if I'm worrying about some other guy flying from far away I'll be worrying about him flying on exactly my frequency than 10kHz up/down.

And the Tx specs does seem to say 1W (can't read Japanese...) so I believe we should keep talking with OFTA.

CT
P.S. Any news from our two subjects?

I have received the replacement schedule for the OFTA license today. For those who got the OFTA licenses applied through HKRCSS, their replacement schedules are now in my hand and I will distribute them to you during weekend in the flying site. For your reference, here is a scanned schedule:
http://www.hkrcss.org/license_schedule2.jpg

Basically, there are two changes as summarized below:

1. Twelve new channels (8 in 35MHz and 4 in 40MHz) are allocated; however, the operating power of these channels is limited to only 100mW. This is somewhat restrictive, so I think I will write to them again to ask for the rational behind the restriction.

2. There is no restriction on the location of r/c transmitter. Note this was well-defined in the old schedule. That means we do not need to restrict ourselves to fly in certain areas.

If OFTA limit the transmitter to 100mW, they are cheating us at all. We need to continue our complains and discussion to get a higher power limit to 500mW.

In fact, the 100mW limited is used in Toys planes, not Hobby. In Australia, the toy plane power limit is 300mW, the government only limit the frquency. Hobby is not Toy, OFTA staff should realize this.

I'm fed up with OFTA. Practically nothing's changed and we may still get busted in flight this weekend. Let's save our time with these people and talk to the director or secretary. If a protest is what it takes, call me any time! Corrupt cops did that back in '79 with great success and thousands got away with millions, escaping justice. Give them the pressure they need to treat us rightly.

CT

Hi,

I have written to OFTA asking for the rationale behind the 100mW limitation on the 35 and 40MHz bands. They said they are following the European standard for flying model control which is indeed 100mW ERP. Unless we have strong justification otherwise they won't relax the restriction.
Here are the documents from ESTI:
http://www.rcsail.com/tmp/DEC0111E.doc
and
http://www.rcsail.com/tmp/DEC0112.doc

I've also checked with many European countries including UK, they also have the same transmitting power limitation on 100mW ERP, please see
http://www.ofcom.org.uk/static/archive/ra/publication/ra_info/ra60.htm

So we go nowhere!

I am now puzzling how the guys in UK manage to fly sailplanes using only 100mW transmitters. Are there manufacturers producing 100mW transmitter? Does anyone know the real situation worldwide in using these 35/40MHz bands?

Sure folks in the free world use Fut/JR! Maybe they have a hobby rule or exemption hidden somewhere (e.g. the Fut Act, JR Order, Multiplex Amendment or the R/C Clubs By-law) and we're just looking at the toy plane standard... This is not uncommon in Homg Kong either. The restrictions and provisions for something are rarely found all in one ordinance only.

Will post in RCUniverse and seek advice.

CT
PS. shall we request for 1W instead of 500mW?

OFTA 可能仲未知道香港已經回歸﹐仲跟D鬼佬標準﹐我地祖國對遙控模型既發射功率限制係 750 mW.
http://www.carms.org.cn/itcm/zcfg/hkmx-2.htm

香港行緊一國兩制﹐當大陸既法律唔可以作參考啦﹐不過美國既限制都係 750mW ....

http://www.rcwebboard.com/rcfreq/cfr_fcc_title47_part95/index.htm

尋晚上德國既 forum 問過﹐原來歐洲個邊 D 人真係用 100mW 發射架﹗點解我部 JR 9X 既說明書話 1 Watt﹖有無搵笨﹖
http://www.rclineforum.de/forum/thread.php?sid=0aca01a4db24b1d93d1afb22b8e8504f&postid=562713#post562713

有樣野要留意﹐OFTA 定既唔係 chassic power, 而係 Effective Radiated Power (ERP). 除非條天線係 tune 到正晒(我地 D 玩具多數唔正)﹐否則 ERP 就會低過 chassic power。所以我地手頭上 D 發射既 ERP 係有可能係 100mW 以內。

I think 100mW ERP may be good enough for r/c aircraft.

The formula for calculating ERP is:

ERP = Transmitter Power * Feedline Loss * Antenna Gain

For example, if you hook your 0.5 Watt transmitter to a 0dB gain dipole antenna, thru a 1 ft cable having a total loss of -1dB, and you would have an ERP of 0.24 Watts. This is only in theory but I think the ERP would be much lower in practice.

If the European have been using 100mW ERP without porblem, we can also accept that.

So we should request OFTA to write down specifically on the schedule that the transmitter power is 100mW ERP instead of just 100 milliwatt.

Problem is, how would one know if the Tx is within the ERP limit?

And can we get away with changing the antenna?

CT

剛剛同我 D JR 發射做左 D 測量﹕

Current drawn withOUT the RF module:


Voltage withOUT the RF module:


Current drawn with the RF module:


Voltage with the RF module:


Power consumption of the RF module
= Total power consumption - Power consumption of the base band part
= ( 10.47 V x 175.8 mA ) - ( 11.09 V x 52.4 mA )
= 1.26 Watt !







Measurement results for my JR Tx modules ( 41MHz, 35 MHz, 72 MHz, six modules in total ):

CT,
We are checking with Futaba, they should have data on hand and give us the power strength very soon.

YC, Is it you want to tell us that your JR transmitter only give output power 109mW ERP? If so, it is a great news because I know that JR has higher power than Futaba 9C, that means most of our transmitters will have no problem to meet the 100mW ERP requirement.