Daily Archives: February 24, 2022

4 posts

Chairman’s Corner for Feb – Mar 2022

Hello Members of SEFSD, I hope all are well and all are doing fine!  How about our banquet?  Did that not turn out to be a fun event this past Friday, held at the Air and Space Museum.  We all were in the middle of the museum just about under a PBY.  It was protecting the Bar of course!!!  Special thanks go out to Quan for putting this event together.  At the last minute, Quan was able to find us a new location due to Edgewater backing out, so Quan got to work and got us to the Air and Space Museum and locked in a date for us, just that it was on a Friday and that did not seem to bother the folks who arrived.  Which sure was close to 100 people. It was great to meet our members as much as I could since I was MC for the banquet. 

The food provided by Lisa Bender was the best, from the meatballs to the roast beef and the salad and not to forget about the chocolate covered Strawberries…… it was just all amazing.   I was amazed to see how many prizes we had to give away.  Even our ladies, matter of fact, I believe all the ladies walked out with a gift which was also provided for us by Lisa Bender, wow that amount of work she put in for this was also just amazing.  Thank you both, Lisa, and Quan for all your efforts that you contribute to our club, Thank You so much!!!!

The prizes, for us guys, were also cool, however not everyone got a prize, not as lucky as our better halves that really do deserve it.   But we did have a great line-up of gifts, from Motionrc, Tower Hobbies, Hitec, Bee and from Steve Neu shops we had power supplies, chargers, and a couple of other items too.  It was fun to give out our prizes, it was fun to see the expressions on the person who won the prize, including George Sullivan who won a Hitec hat and took it in stride.  Same goes for Skip (our lawyer) who also won a hat from Hitec.  Ty won a power supply earlier but was lucky to exchange his gift when Steve Neu won which was a Timber and decided to give it to Ty.  Ty’s gift was given to a winner who won a charger. We had a couple of special gifts that were given to two people.  First one was when Claire Diffenback received a very nice set of flowers for her helping with T-28 races.  Congrats Claire, and to Brad Bender for his 12 plus years in supporting and keeping our club going in the right direction, he receives a very nice plaque that Steve Manganelli gave to him.  Thank You Brad for all you have done and congrats!    It over all turned out to be a lot of fun and was fun walking around the museum!   Thank You all for coming to our event!   The club looks forward to next year’s banquet. 

In the past couple of weeks, we had our gate tampered with.  They appeared to have cut the top bar to get the chain undone.  Since then, it has been fixed.  As a reminder, before you are the last one to leave the field, and as you start to drive away and you see someone, just go over, and let them know that they could be locked in once you leave.   Also, as a reminder that at the field, Please follow these guidelines:

  • Make sure you are always wearing your badge when flying your aircraft
  • Call out loud that you’re taking off, low fly by and landings.
  • Never fly over the Parking Lot and Pitts
  • And always fly on the north side of the fence.

As my last note for this month, I am in the midst of starting to build my Top Flite, Gold Edition DC-3 kit. As I have mentioned in my Chairman’s Corner: The nice thing about the Gold Edition DC-3 is that although it is a highly detailed scale model with all the goodies such as a realistic looking scale outline, built up tail surfaces, retracts and flaps.  The offset pinned hinge features the offset hinge line characteristic of the DC-3.   It is a model of a transport plane that is a stable model that I look forward to flying often!  Converting this kit into an electric airplane will have some challenges, but a challenge that will be fun!   I will also be sharing with the club the construction of this model with photos each month.  So let’s begin with a box full of wood turned into a DC-3.

In the meantime, I look forward to seeing you all at the field and don’t forget your batteries, radio, charger, and most important, your airplanes and let’s go Fly!


Jovi Murek

President’s Corner for Feb – Mar 2022

By Steve Manganelli

Oh what a night! The stars aligned to have our Winter banquet at the Aerospace Museum catered by Lisa Waln (Mrs. Brad Bender) this past Friday, February 18th. The food was fantastic, the ambience beautiful and the turn out awesome. I want to thank everyone whom bought tickets as early as 4 months ago, expecting a Saturday event for making it on a Friday. I had the privilege of checking people in and doling out tickets (with help from the  Mrs. Michelle M.) to what was certainly the best raffle we’ve ever had.  Congratulations to Larry (Lucky) Kosta and Mary Riney (also a pilot), whom both won airplanes!

I also need to thank the people whom worked selflessly to bring the banquet about. Our Chairman of the Board Jovi Murek did a fabulous job as Master of Ceremonies. He kept us entertained and on the edge of our seats anticipating the next airplane give away.  Jovi was also the procurer and selector of the airplanes in the Raffle (great choices Jovi!). Thanks also to Lisa Waln for procuring the Women’s prizes. Fortunately, that was long done before she knew she was also going to be the Caterer. Our Vice President and temporary Treasurer Quan Nguyen did all the arrangements with the Museum and the caterer to keep the bills straight, well done, Quan! Thanks to Steve Neu of Neumotors for providing a nice selection of chargers for the raffle at cost and to Jim Bonnardel for donating a Hitec charger and some Teeshirts and hats. Many thanks to Claire Diffenbach for drawing the tickets for the airplanes. The last person I want to thank had something to do with the banquet (there were rumors about the delicious appetizer meatballs…) but Mr. Brad Bender was called to the stage and recognized with a plaque commemorating his selfless leadership to the Silent Electric Flyers of San Diego. Thanks to you Brad, for all you did officially over the last 9 years and what you continue to do for us unofficially.

Weekend before last, we had some outstanding weather for February.  Temperature was in the 80s and the field was packed for T-28 Racing : 16 participants, and all time high. I want to recognize and thank Frank Sutton for designing the new Medals and was proud to award him the first one as medal artwork designer. Frank is our “house” photographer and put out a fabulous 2021 retrospective in January’s newsletter. It is truly our year in pictures and urge you to go back to last month’s newsletter to find the link: https://www.sefsd.org/club-info/sefsd-memories-2021-video/.   Speaking of medals, they are also to be awarded to the 1st 3 places in our monthly Members Meeting/Fun Contest so even non-T-28 racers have a chance to earn one of these custom beauties. So come on out this Saturday and take your chances at the Poker fly and maybe pick up a medal!

If you are the last one out, it is important to close and lock the gate! Our permit with the City requires us to have the gate locked when we are not flying.  As a practical matter, if you are flying toward early afternoon on a weekend day and it looks you and only a few others remain, it is prudent to communicate among yourselves as to whom is to lock the gate. There have been situations that non-members are the last ones there and as non-members, do not have the combination to do so.  It is necessary and polite to warn any spectators in vehicles to be on the other side of the gate once you lock it lest they be locked in.  Most people that are there to spectate are in or near their cars to be warned to leave, but not always. The other week we had an unfortunate incident where an apparent locked in person, used a Sawzall on the gate latch fence to free his vehicle.

To preserve the operation of SEFSD, we need a new Treasurer as soon as possible and longer term, a new Membership Chairman. Quan Nguyen has done a fabulous job of keeping us in the black while George Sullivan has been selflessly printing and handing out badges for several years. The current office holders have honed these jobs to the minimum efforts required and will train you.

Lastly, I’d like to call your attention to Minutes of the February BOD meeting. The most important item therein is the possibility of having our altitude limit increased. It’s going to be a long row to hoe, but for now, it is absolutely vital that we adhere to current rule (200 ft) and 50 to 75 feet when full scale aircraft are passing over.  Our compliance to the current agreement will be a factor in any decision to increase our limit!

Servo Twitching in Large RC Planes

By Mark Davis

I recently had a problem with a servo randomly twitching, and was able to solve it, so wanted to share what I learned.  It is a large plane and there are 10 feet of wire between the Rx (Spectrum 12310T) and the servo (Hitec 7950TH “ultra torque”).   Because of this, I ran 17 gauge power/ground, and used MR30 connectors (instead of 20gauge heavy duty extensions with normal servo connectors).   But even with this, the servo exhibited erroneous twitches, especially when moving.


I found the problem could be remedied by placing (near the servo) a capacitor across power & ground, or a signal booster, or both.  This problem depends on the servo also, and for example the D625MW did not exhibit the same issue, and needed no remedy.  It appears that this is because Hitec 7950TH (“ultra torque”) draws high current for brief snippets of time, and thus causes large power transients.  These will appear also on the ground, and therefore the PWM signal can be affected.    A power bypass cap by itself fixed the problem.   A signal booster by itself was helpful but not entirely reliable (Spektrum and Hitec both make them).  I believe the best solution is to use both a supply capacitor and a signal booster, based on the oscilloscope plots below.  


First, some background information and definition.  

When ground currents are present, we have to designate a specific point as “0 volts”.  In text below I treat the ground at the receiver as the definition of 0v.  The oscilloscope probe was connected with its ground near the servo, 10ft away.  So it is not necessarily at 0v, by this definition.

The oscilloscope horizontal scale (time / division) appears in the upper left of the screen next to the letter “H”.  The vertical scale for each channel (volts/division) is shown in the lower left of the screen.

When a servo was connected, it was connected without load or with light load (sitting upright on a table, or in some cases on its side, so the arm was just lifting the weight of the servo).

The capacitors I had on hand were 8200uF 10v, and 4700uF 16v.  Since my system runs on 2S LiPo, this is sufficient voltage.

The signal boosters I tried were:

  • Spektrum Signal Line Voltage Booster SCMCP
  • Hitec Signal booster HRC58496

I have grouped scope traces into 5 sections:

Section Servo Capacitor Across power/ground Signal Booster included
1 7950TH No No
2 7950TH Yes No
3 7950TH No Yes
4 7950TH Yes Yes
5 D625MW No No

First see picture 1B below.   I put a scope on the signal wire.  You can see the servo is approximately centered here, with a 1.5ms positive PWM pulse.  But you can also see frequent artifacts.  I didn’t immediately notice a very regular period, but they seemed to occur every 4-10ms.   Unfortunately I didn’t capture the power line here, but from later plots I believe it would show exactly the same artifact at double the magnitude (I’ll explain why later).   

Now consider the structure of one such glitch.   It appears the servo decides to draw a large amount of current for about 50us – 200us, depending on which glitch we are looking at. This pulls down the power line voltage, and pulls up the probe ground (servo ground).    The signal is looking into a high-impedance FET, and so draws insignificant current, and so should have insignificant voltage drop even over 10ft of wire.   This explains why we see the oscilloscope voltage go negative at the start of the glitch; the signal wire remains at 0v but the probe ground “bounces” up due to the current being dumped into it.   The voltage appears to be asymptotically approaching a steady state value (with the expected exponential shape) by the end of the 200us.   This steady state should be the current of the servo times the wire path resistance.  Then when the current draw stops, the inductance of the wire keeps pushing current for a small transient.   Thus, the opposite effect will occur;  The voltage of the local ground will dip below 0v and so the signal wire sitting at 0v appears to go positive on the oscilloscope.  Note that this positive glitch can be quite high.  This plot has 1v/division, so the first glitch captured here is around 1.6v, which I’m guessing is quite close to the detection threshold for a PWM pulse.

Picture 1B:  No capacitor, no booster

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