Saturday, March 29, 2008

Report on 2008 Free State Aerobatic Champs -- Walter van Huyssteen

Report is here.


Dear MAASA Members

Time never ceases to fly and our National event, the highlight of our competition calendar is to take place shortly at the end of April 2008.

On behalf of MAASA, our sponsors, and hosts, you are all invited and encouraged to join us for an event filled competition. This will include various activities, presentations, demonstrations and, of course, the all important opportunity to get together and reacquaint ourselves with old friends from far and wide. This all over and above the serious business of getting the flights in and the points on the board.

Please find attached the entry form and broad programme, with all the details of the event.

Regular updates, news and information will be posted on the GAA Blog from now and leading up to the event. So keep your eyes on the pages and new postings as we head towards what is going to be a great event. GAA blog page.

Should you have any queries, suggestions or comments, please feel free to contact me on 083 381 8124 or email

We look forward to seeing you all there.

Warm regards and happy flying.

Paula Bester

GAA Chair
(Gauteng MAASA Representative)

Wednesday, March 26, 2008

Why is my PPM Transmitter not on frequency? -- Piet le Roux

We have had a lot of reports of interference on 35MHz lately. One suggestion to avoid planes being "shot down" was to get a radio scanner or frequency monitoring equipment to detect the interference before it becomes a problem. With the introduction of relatively cheap frequency measuring devices and scanners, it has become more and more common to find these devices at flying fields. It is a good idea to check your radio's frequency regularly but with basically only two service centers in South Africa it is not practical to send it away every time so it is great that more clubs can have access to suitable equipment. But users must note that they will display the frequency of a positive shift PPM (pulse position modulation) transmitter about 1,25 KHz low in frequency although its is perfectly on frequency. All JR equipment and most other makes in South Africa uses positive shift FM for PPM transmissions.

Both PPM and PCM information are transmitted via FM so in order to understand the reasons for this incorrect reading we must first understand the basics of FM (frequency modulation). When information is transmitted via FM the frequency (that is the frequency on your crystal) is varied in accordance with the data signal. If the data signal were a perfect sine wave the transmitter would be on frequency when the data signal crosses the zero point and at maximum deviation (1.8 KHz) at the peaks of the sine wave. The negative side of the sine wave would cause deviation in the opposite direction as the positive halve of the signal. We would the end up with a radio signal that varies +- 1.8 KHz around our channel frequency and have a bandwidth of 3.6 KHz. When this signal is measured the average frequency measured would be the center frequency (crystal frequency) because the two halves (positive and negative halves) of the data signal are equal and thus also the amount of positive and negative frequency deviation of the radio signal. This is how a PCM (pulse coded modulation) is transmitted and the frequency of a PCM transmitter would be displayed correctly.

Most transmitters these days can transmit both PCM and PPM, in order to achieve this flexibility the modulator has to do a balancing act in order to keep the transmitter inside its allotted channel. It does this by Making the zero point of the PPM data signal - 1.8 KHZ instead of the center frequency like with PCM. The PPM data signal consists of short positive pulses. The peaks of these pulses would cause the radio signal to deviate to + 1.8 KHz from the center frequency. Because the data signal consists of short positive pulses and a long reset pause(where the transmitter stays at -1.8 KHz ) the radio signal would spend most of its time in the negative halve of it allotted channel and thus the average frequency would be about -1.25 KHz from the center frequency and this is displayed by most measuring equipment.

To cap. If you want to check the frequency of your PPM transmitter, set one of your unused model programs to PCM mode and select this model when you want to check your frequency. If your transmitter does not support PCM just remember that your frequency would be displayed as about 1.25 KHz low. NB. Remember that only technicians that have been authorized by ICASA can make adjustments to transmitters. So if you think your transmitter is faulty send it to the nearest service center and do not attempt to DIY!

Monday, March 24, 2008

SAMAA General Manager away from the office

The GM of SAMAA, Bob Skinner, is away from Wednesday 26th March, to return on Monday 7th April, to attend the CIAM (Commission for International Aeromodelling) meeting in Lausanne.

Membership queries will be handled upon his return; please leave a message on the answering machine (011-907-4652), or send an e-mail to You may view your membership status on the website and change your own details, if you have a valid e-mail address on the website. This will allow you to request log-in details.

There will be a temp in the office, Anja du Plessis, to answer simply queries. Please direct your queries that are not membership-related, to:

Percy Attfield - SAMAA chairperson
Dirk Meyer - Vice-chairperson, HR matters
Keith Nicolls - Secretary, Proficiencies, Sporting, Code, Safety
Dave Armitage - Technical issues, frequencies
Ludwig Steyn - Budget, finance
Vic de Vries - Clubs, club registrations, promotions, PR, marketing
Johann Coetzer - Transformation, airspace issues
Johan Sieling - Insurance
Tony Stockwell - Regions
Allen Fraser - Dealers
Lionel Brink - Special Interest Groups

E-mail addresses and contact numbers are on the website.

Thursday, March 20, 2008

Chasing Kangaroos -- Piet le Roux (or perhaps Piet le Kangaroux)

In the last issue of SAMAA news we were treated with a report back of the editor’s visit to Australia. He went to one local club, met with the president of the MAAA, Mike Close, and gathered an astounding amount of information about model flying clubs in the whole of Australia. He mentions the "30 meter rule" and that alcohol are not allowed at any of their clubs. These must be "unwritten rules" because in their Manual of Procedures no mention is made of any "30 meter rule" and as far as alcohol goes it just states that you may not operate a model aircraft while under the influence. It does not prohibit alcohol at any club. I don’t know in what they were partaking while having this conversation or maybe it’s just a case of hearing what you want to hear. He attempts to give the impression that the Aussies have a "no drinking" culture and any misconduct is severely punished by law. The fact of the matter is that the Aussies have always had a culture of heavy drinking and it is because of this that they have very strict anti drinking laws. They have recently admitted that the country is currently experiencing an unprecedented wave of drug and alcohol abuse and even more severe laws were needed. So if Mr. Ruzzier ,or anyone else, thinks that by immigrating to Australia he and his family is going to have less exposure to the evils of alcohol they would be sadly mistaken.

But there are certainly a few things that we can learn from the Aussies. As mentioned by the editor their insurance policy is something that we can only dream about at this stage. I am sure that we can afford such a policy if we utilize our available funds in a more responsible manner and make service to our members a priority. Their Manual of Procedures is made up of different chapters which consist of individual PDF files. So if you are looking for information on a particular subject it is easy to find. Presently I do not want to consult our manual because it is simply too laborious. Theirs is also easy to update or to change any of the different chapters. They emphasize the fact that their Manual of Procedures is a "live" document and is continuously being updated. Members are made aware of updates via their newsletter and their website. This insures that the document is always current and correct. Some of the contents of our manual were copied from the MAAA manual but some of the contents in our manual were already outdated when it was written. So we must take good look at the MAAA manual and adapt ours in such a manner that it becomes a current, meaningful and a user-friendly document. At this stage it is just a white elephant.

Sunday, March 16, 2008

Tuesday, March 11, 2008

Results of 2008 Helicopter Nats -- Johan Sieling

Free State Aerobatic Champs -- Piet le Roux

It looks like the economic hardships of the country is impacting directly on Pattern competitions. To date we have received only eighteen entries, seven sportsman, eight F3A, two advance and one expert. We need at least 20 entries just to break even. All the trophies and badges have already been made. We know what the price of petrol is and we have decided that there will be no penalties for late entries. Come on all expert and advance pilots please make a effort. I can nearly guarantee you that you will take a very nice looking trophy home!

See you at CRF in Bloem

Piet Le Roux

Gliding postal scores for Feb. 2008 -- John Lightfoot

Scores and comments here.

Blog Archive

Total Pageviews


Web site terms and conditions

Copyright of material on all the pages of this site is vested in the SAMAA or the original authors. You may use the material in terms of the Creative Commons license for non-commercial purposes on the condition that you acknowledge its origin.

This work is licensed under a Creative Commons License

The views expressed on this web site, or on any directly or indirectly linked site, are not necessarily those of the SAMAA Committee, or the web editor. The information provided on this site is provided for recreational purposes only. The SAMAA and the authors of presented content assume no liability whatsoever on the use of information contained in this site. The information on this site is provided on an "as-is" basis, without warrantee of any kind. Links provided on this site will let you leave the SAMAA web site. The linked sites are not under the control of the SAMAA, and the SAMAA is not responsible for the contents of any linked site, or any link contained within a linked site, or updates to such sites.