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Sepulveda Basin

Old 08-08-2005, 01:36 PM
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Default RE: Sepulveda Basin

Based on the last Board meeting, There will be a lot less races next year if we can meet the quota with other type of events.The dilemma is that we need more input and participation from general public to set more user friendly events or we will be back
to the old !QUOT!so many races per season deal.
Lets define who is The Valley Flyers.
Valley Flyers consists of average Joe's like you and I.Unfortunately most of the members that show up to the meetings and get to vote and decide the faith of our fun, do not represent the true crowd that uses the Basin.
The board elections are held every fall.Even-though the Valley Flyers does not control the Basin, It is the only buffer between the Basin and
the Parks & Recs/Airport
So, as one of my friends always says, if you want to have at least your finger on the throttle, Get involved and make your voice count.
Vote active fliers into the board that represent the true usage of our beautiful field.
It is easy to criticize and difficult to make constructive changes without involvement.

For your info Mr Matt there will be a scale contest at the Basin on August 21st-05. There will be 2 classes.
1 will be judged as sport scale meaning that if you have an ARF that resembles the scale airplane then you will get your 25 static points.
This will make it a flying contest more than anything else and allows guys that do not have $5000000.00 income per year to compete.


Jason Pakfar
Old 08-08-2005, 07:48 PM
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Default RE: Sepulveda Basin

20/20 is $23.00 and 15% is $18.00 GET SOME. Flying my dago three time last week and my twist one day i whent through 4 gal. The price you pay for speed. Taking about speed i heard you are going to replace your ys 110 with a fire breathing 91 MAGNUM. see you sat.
Old 08-08-2005, 08:36 PM
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Default RE: Sepulveda Basin

i guess it's in the best interest of the race guys to ''hold it together'' because they know that the basin os one of the premier sites to race.

it's not like they can just go out and race anytime either.

with respect to acrobats and helicopters, why they can do their helicopters and acrobatics anytime at the basin.... so what is the advantage (and the motivation) of organizing an event when they can fly their stuff any ol' time (cept during events) at the basin?


on the other hand, the GSS toys-for-tots is always a big hit.... can anyone explain why?
Old 08-08-2005, 08:49 PM
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Default RE: Sepulveda Basin

i think that because of that price hike, i will be forced into buying magnum fuel again by the case. 20/20 works out to $15.5 after magnums price hike. i guess you better stock up with 50 gallons powermaster during the labor day sale - hahaha. yeah, Cya sat
Old 08-08-2005, 09:48 PM
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Default RE: Sepulveda Basin

That,s if it is 13.80. The last sale was 16.99 YOU KNOW GOOD
Old 08-08-2005, 11:02 PM
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Default RE: Sepulveda Basin

I personally like the fun flys for the impound





on the other hand, the GSS toys-for-tots is always a big hit.... can anyone explain why?
It's easy to explain. It's a fun fly and not a race for a small group. Plus they are all involved.



JasonP
Old 08-10-2005, 02:58 AM
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Default RE: Sepulveda Basin

12 x 9 apc with 60%. That is the winning combination.

Good fly'n the other day Goe, that was awesome. Your plane is really dialed in.
Old 08-13-2005, 12:59 AM
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Default RE: Sepulveda Basin

Ok Guys
I talked to the local FAA office.
You can request a flight diversion for an event but it does not change the 400 ft ceiling.



JasonP
Old 08-13-2005, 06:02 AM
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Default RE: Sepulveda Basin

So there wouldn't be much purpose to getting one other than reducing the chance of somebody reporting a stray model momentarily breaking the 400' ceiling which happens on rare occasions. If a tree falls in the woods and nobody is there to hear it, does it make a sound?

I wonder exactly how it works, I seriously doubt the tower tells everyone to not fly over the model field when they give them clearance to take off. Maybe Dave or one of our other full scale guys could enlighten us....Somes, are you listening?
Old 08-13-2005, 09:16 AM
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Default RE: Sepulveda Basin

The only time I heard of this being done was the jet rally a couple of years ago, Torry went up and told them we were operating. There was some sort of official recognition or sanction, but in what form I do not know.

The normal AFIS information could easily add this, but I do not know if they do that for the field, they do it for cranes and other construction stuff all of the time
Old 08-13-2005, 09:26 AM
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Default RE: Sepulveda Basin

You would apply for the TFR (temporary flight restriction) and once granted by the local FSDO, they would issue a NOTAM (Notice to Airmen). This would become part of the pre-flight briefing that all pilots go through prior to departure. When you call Flight Services to either file a flight plan or get a Wx brief, that person would advise you of the NOTAM along your route of flight. You could also find it online as well. They have an online version of the Wx brief that an individual pilot could access instead of talking to a real person.
Regarding the ATIS at Van Nuys, they may or may not include that in the recording. I imagine they would in response to the NOTAM (being so close to the field) but I believe it is at their discrection. Burbank does it all the time for hang gliders in Mendenhall Pass and there isn't a NOTAM issued for that. So it may also depend on the mood of the tower that particular day.
Old 08-13-2005, 09:26 PM
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Default RE: Sepulveda Basin

Dave
I think you are correct. Though the last sentence out of the guys mouth was:

"Remember, the air traffic always has the right of way."

Edit:It is nice to see some of the club members becoming active in field improvement.
Leroy spend the whole day making frequency flags for people. He stopped when he ran out of cards at about 6PM.
It was a very rare moment but at one point in the afternoon, There were no Stanely's (Screw Driver) on the frequency post.

Thanks Leroy for all the effort.




Jason
Old 08-13-2005, 10:35 PM
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Default RE: Sepulveda Basin

Yeah, good job JAson and especially leroy, he really did get into it.
Old 08-15-2005, 12:59 AM
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Default RE: Sepulveda Basin

Today was an interesting day at the basin.
One of the war bird guys came back from the flight line claiming a lot of radio hits.
After making sure that his picture flag was up I started scanning with an Icom scanner. Sure enough there was
a very strong signal on his channel. AS we walked toward the Heli area the signal got stronger.
There was a guy flying an electric Heli in the circle but he swore that he was on channel 19 and showed us the sticker on the back of his transmitter reading
19. We looked around some more but the signal was strongest clise to the heli guy.
After he finished his 25 minute flight and shut his radio down the signal disappeared from my scanner.
We went back to him for the second time and demanded an inspection.He got really worked up but there was more than 5 of us. His transmitter had a channel 19 sticker on it but his receiver had a channel 56 Crystal.
Later in the afternoon another guy had a lot of trouble with his radio so I started scanning his channel. There was a lot of noise on his channel.
To make a long story short, Two of the war bird guys, one on channel 38 and the other on channel 46 when running their radio at the same time were bleeding onto channel 57.

Later in the day, 2 israeli guys decided to fly their electric airplane from the runway. The problem was that he wanted to stand on the runway on the TarMatt and fly his electric.
After asking him 3 times politely to stand back, he warned me to "watch myself". I really wanted to put my foot in his ***** but decided to land and call it the day.


Jason
Old 08-15-2005, 01:22 AM
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Default RE: Sepulveda Basin

For sure a lot of things are happening during the weekends at the field.
Today, Roamie ( I hope I'm not baptize him ) went to the guy he was sharing the channel to let him know he's going up. I was 10 feet away and I heard the conversation. 5 minutes later when he was taxing his miss america to the runway he saw the guy ( with a white pilatus porter) starting his engine.
It was quite puzzling to hear the guy saying he completly forgot to check the channel and put his flag on.

Boby
Old 08-15-2005, 07:33 PM
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Default RE: Sepulveda Basin

Jason P - any idea why the two channels would bleed into one?

How can someone forget to check their channel? Frequency checker would have help there.
Old 08-15-2005, 09:22 PM
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Default RE: Sepulveda Basin

The only thing I could think of is what's called 3rd IM but I don't really know any details about it.

Jason P
Old 08-15-2005, 09:29 PM
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Default RE: Sepulveda Basin

OK JudoGuy
I found this article I saved a while ago regarding 3rd IM. I hope you find it useful.



3IM is the "stray image signal" produced when the radio frequency (RF) signals from 2 transmitters combine in the input stage of a receiver. Basically, 3IM is produced by the mixing of the 2nd harmonic (or overtone ) of one Tx signal with the fundamental (1st. harmonic) of the 2nd Tx.

When any two RF signals "mix" or combine, they produce two "stray" frequencies, namely a "sum" frequency and a "difference" frequency. This is not restricted to RC, it is a physical fact of nature.

Now, using an example, with RC38 and RC39, 72.550MHz and 72.570MHz.

The first 3IM product comes from 2 x RC38 and RC39...


"Sum frequency"
2 x 72.550 + 72.570 = 217.67MHz (too high for the RC Rx's to worry about)

"Difference frequency":

2 x 72.550 - 72.570 = 72.530MHz (argh! This is RC37!!)

The 2nd. 3IM product comes from RC38 and 2 x RC39...


(In general, we can safely ignore the "sum" freq), so...
2 x 72.570 - 72.550 = 72.590MHz (aieee... this is RC40!!)

So... your 2 Tx's, operated simultaneously and close together, potentially generate "strays", in our example, at RC37 and RC40. These are your 3IM products.

In general, any two RC frequencies will produce two 3IM “strays”, one above the higher of the two, and one below the lower of the two, spaced apart by the difference between the two.

What a mouthful! In simple terms… take the two RC channels, subtract the channel numbers to find the difference. Add it to the upper channel, that’s 3IM #1. Subtract it from the lower channel, that’s 3IM #2.

Using another example, RC40 and RC56… Difference = 56 - 40 = 16. Your 3IM “strays” will be at RC24 (40 - 16) and RC72 (56 + 16). Of course, “RC72” doesn't exist, being outside our band, so in this case, only RC24 is in jeopardy.

Notice that it did not matter whether you are PCM, FM or AM... 3IM's are produced by the radio carrier frequencies, not the modulation method!

Why does it matter that the Tx's are "close together" and "strong"? When Tx's are in close proximity and at high output levels (measured at the Rx), the Rx input stage is driven into non-linearity, which causes the 2nd. and higher harmonics of the Tx signals to be produced, which can mix like we calculated. Also, Tx's in close physical proximity can mix their signals inside each other, re-transmitting the mixed 3IM frequency! Whoa!

Note, however, while 3IM strays can cause shoot-downs, IT DOESN'T ALWAYS... the conditions have to be "just right". Tx's have to be physically in close proximity, the Rx's have to be "close enough" to the offending Tx's, etc...

Simple precautions such as keeping Tx's separated per AMA recommendations (minimum 10-foot separation), and using a good-quality Rx greatly reduce or virtually eliminate the 3IM hazard.

What does this mean in practice?

Any 2 Tx’s potentially produces 2 stray channels. On a flight line with 6 radios running, you potentially can generate as many as 30 distinct stray signals!

Imagine what can possibly happen at a big meet!

Consider what mayhem can possibly be generated as a pilot walks behind the flight stations to get out to his assigned station, along a walkway less than 5 feet away from active Tx’s, generating strays whenever he gets close a pilot that’s flying!

Worse yet, what’s happening in the pits, and startup areas with fully extended antennas on Tx’s less than 5 feet apart?

Recommendations:

Always, but always observe the 10-foot minimum spacing rule, for the sake of your fellow pilots.
Set up a walkway behind the flight stations at least 10 feet away from the active pilots. Don’t loiter behind your buddies-in-flight with your Tx’s active in close proximity.
Keep at least 10 feet away from other Tx’s in the pits and startup areas.
If at all possible, keep your Tx antenna collapsed or extended only one section while in the pits or working on your airplane.
Old 08-15-2005, 09:33 PM
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Default RE: Sepulveda Basin

all radios bleed over into other channels. you need to look at the RF spectrum of a transmitter to understand HOW MUCH bleeds over. at the other end of the link, one of the functions of a good receiver is to FILTER out-of-band information.

at some point in time, i will have to try to remember to put up a picture of a typical FM-PPM spectrum to show you how much bleeds over. typically, the bleed-over is hopefully less than 30 dBc.

IM products are a function of frequency upconversion in the transmitter as well as in a receiver (down conversion). IM products are always present and can be considered as part of the bleed-over spectrum. they have much to do with how linear the electronic devices are. typically, the cheaper radios put out more crap - but i can't really sunstantiate that claim without doing some testing.

one thing to remember is that it's important to send yoiur radio in every now and then for a checkup. if you have a spectrum analyzer (like at work), you can check it yourself.

one thing to keep in mind is that radio transmitters are only 1/2 of the equation. the quality of the receiver is the other 1/2.
Old 08-15-2005, 09:51 PM
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Default RE: Sepulveda Basin

if ya want to get a little more technical (and accurate), read up:

http://members.tripod.com/michaelgellis/mixersin.html

scroll down and take a look at table 1 as well. it shows you that not only 3'rd order IM's are important but 7'th order & 9'th order IM's can be equally problematic.

this article also shows you how dual conversion works using an intermediate IF.
Old 08-16-2005, 01:59 AM
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Default RE: Sepulveda Basin

Wow, just when I thought it was only important to be narrow band and not on other people's freq. Thanks for the info. What do they do at the big events like Top Gun?
Old 08-16-2005, 08:50 AM
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Default RE: Sepulveda Basin

I don't understand why it is so hard to believe that a radio could be causing problems on another channel.

I had it happen this weekend to me; I had my flag in and I was getting my Ulltra Sport ready for flight when another fellow was coming in. We had a radio monitor on my channel; my plane was wigging out - I had just done a very successful range check (I do those pretty often) but now I was back next to the plane and it was twitchy as heck. So we started looking around. I turned my transmitter off but there was a signal on my channel. We walked about 20 feet and there was a very strong signal but then it went away (the fellow was taxi'ing in and then shut down) He was clear on a channel in the 30s but when he turned on we could hear him on 18.

We confirmed that he was off for the duration and I went and flew uneventfully.

My TX has been into the shop and it is less than a year old, there was some suspect that it was making noise on 11 so I sent it in. The reciever is a standard futaba RD-127FM, the TX is a 6EXA.

It's like with my friend on channel 41 and yours on channel 43; we had his radio next to the mustang and when it turned on the mustang went crazy and we could hear the signal on 41 (your friend's on 43 right?). Plain as day - hard to argue with but you still do from what I recall. All radios spur, but if they spur onto adjacent channels then you should send them in to be repaired because they are out of tolerance and could cause a shoot down.
Old 08-16-2005, 09:33 AM
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Default RE: Sepulveda Basin

you need to understand that a receiver has an AGC which, when your transmitter signal (which is very strong) is turned off, the AGC will go into high gain mode and therefore be extremely sensitive to weak signals such as RF spillover from other transmitters.

also, keep in mind that if your receiver is turned on (and your transmitter is off), that if another transmitter on another channel is turned on, it may or may not cause a turn-on glitch to occur within your receiver. that depends upon how fancy the other guys transmitter is. many of the cheaper transmitters turn on the output RF instantly when the switch is thrown. this causes a very broad band transmission of energy across many bands MOMENTARILY. i think that some of the glitch tuype radio hits might be because of this. some of the better radios will delay the RF output after the switch has been turned on to let the internal electronics (the biggest culprit is the oscilllator but as the power supply regulators ramp up in voltage, the amplifiers & mixers are also highly non-linear as they go through the turn on voltage range) settle.

i'll post a picture of a typical FM-PPM spectrum (next month) if anyone is interested. i'll do PCM modulation as well. i had some print outs i made from my transmitter a number of months ago from a spectrum analyzer plot - richard has seen them... but i chucked them into the recycle bin. didn't think i'd use them.
Old 08-16-2005, 11:09 AM
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Default RE: Sepulveda Basin

I am well aware of the momentayr turn on glitches but what I'm talking about are not momentary turn on glitches and not simply registered while watching the controls of the plane. They can also be heard on a scanner and were verified using such a device in both the incidents I mentioned.

In both cases we could hear the transmission from the offending TX and as soon as the switch was turned off it went away, turn it back on and there it is again on the scanner AND hitting the rx on the plane in a continuous manner. This was the case on my buddies mustang with your buddies radio and the case with my US over the weekend with another fellow who coincidentally flies an US 1000.
Old 08-16-2005, 05:43 PM
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Default RE: Sepulveda Basin

yep... i know all about those too. spillover.

do you know the signal strength?

not sure what kind of scanner you have. if ya turn up the sensitivity knob, you'll pick up a few pacemakers out there too.

what i mean by this is that you can pick up a stray signal that is spilling over into your channel that might be 80dB LOWER than your transmitter. this may or may not be a problem depending upon where your plane is in the air and the orintation of transmit and receive antenna with respect to each other.

remember that when your transmitter is turned off or offers a very weak signal (such as distance and/ot pointing the antenna right at the plane at a fair distance), the AGC (which is really a hard limiter) inside the receiver's FM demod can't offer much small signal supression so any residual spillover (whether it be IM spillover or fundamental spillover) from other radios into your band will cause trouble.




hay basin bum & goekeli - see ya at reno in jason's pit area!!!
don't get too hung over or strapped to jason's pit and miss the ''section 3'' show - it's some awesome stallwork in a yellow cub.

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