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Old 09-20-2011, 08:32 PM   #1
GreenAce92
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Default One day an autonomous plane (Primarily Antenna talk for FPV)

Hi guys and girls,

I'd like your help and information (let's contribute our knowledge to accomplish one goal)

So I have this Infuse 4G here, I'm learning Linux so that one day (hopefully soon) I can write a program which will be a tracking device for my global flying aircraft.

We know as a whole that it is possible for a glider aircraft to fly for days on end using an efficient system, aerodynamic design and a recharging system (solar).

Using thermals and other natural forces of nature, I think it is definitely possible to achieve my dream goal:

An aircraft that flies on it's own for days, which I can track through my cell phone and command to land or take control of when I need to.

It would have a service ceiling of say, 5000ft (not Impossible) (that's very low actually).

So basic payload would be:
Aircraft-
Folding propeller/Motor
Fuselage
Battery
4 Servos
Rx / Telemetry system / GPS unit
Solar System / Trailing generator.
(sorry if I'm forgetting something this is a lot of data)
Autopiloting System

I've got so many ideas firing in my synapses oh God help me...

The motor (if it is non folding) could be programmed to (when spinning due to on coming air) recharge the battery.

Anyhow, using a program (see we also need a variometer) to thermal itself to use 'free energy (as in provided by nature not the plane)' this plane could stay up for days.

Also weather proofing would be accounted for, what about lightning protection?

Please help me do this. On board camera as well (sort of like a diagnostic test to see what's going on up there) able to rotate 360 degrees and transmit down to the phone.

It would be a pretty big plane at least 2m span sailplane.

Any input? I've got more to put in but I want the idea to be up there so others may be bugged by my idea.

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Old 09-20-2011, 08:36 PM   #2
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I had this idea of a tape made of solar panels (flexible panels) and the circuitry would be over lapping (like Christmas Tree lights if you will) where no matter where you cut the cells, there will always be an out and in so to speak. And one side would be sticky, so that you could make anything be a solar panel (say the wings).

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Old 09-20-2011, 11:33 PM   #3
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Yeah, it's possible, providing you have a milti-million $ budget and some of the worlds leading experts to work with. In fact something similar has been done already, which may give you some idea of what's required to reach such a goal: http://www.bbc.co.uk/news/science-environment-10664362

With current 'affordable' technology any form of solar power flight is a real challenge. With realistic hobbyist's budget and available technology you would be doing really well if you could achieve any form of sustained flight on pure solar power.
For instance; some guys posted a thread about a solar power sailplane on RCGroups recently: http://www.rcgroups.com/forums/showt...ighlight=solar
They made a real nice job of it and designed some clever bespoke electronic circuitry. Even so the plane needed a normal LiPo battery to boost the power of the solar cells in order to have enough power to fly. Longest flight they had is a little over 142 minutes on a very sunny day.

Fully autonomous around the clock flight is on the very bleeding edge of what's possible even with near unlimited budget and expertise. I'd suggest something with more modest aims might give you a better chance of success.

Sorry to be the one constantly pouring cold water on exciting ideas but the first and most important key to success in anything is start with a realistic target

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Old 09-21-2011, 07:42 PM   #4
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Will you get approval from the FAA, CAA, all the various countries you will 'globally' cross ?

What about small civilian aircraft flying within the 5000ft ceiling, are you fitting a transponder, collision detection, radar reflectors.

How do you keep the model away from restricted airspace, airports, military sites, etc etc

Sorry GreenAce92, but I have this horrible feeling that sooner or later the 'UAV' model fraternity is going to get very heavy flying restrictions put on the rest of us hobby fliers, (hopefully not a total ban).

The risks involved with other peoples lives are just too horrendous to continue with your 'dream' in my opinion.

Ray in Wales
As I get older I think more and more about the hereafter.
I walk into a room, and think, 'now what was it that I'm here after?' :o
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Old 10-12-2011, 06:29 AM   #5
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Well ket us not forget that this is only on mind not reality yet

and no it is not impossible, hard it is, but a smart person can make something work withpt much $$$

it's one thing to take something which has already been made, it's another thing to understand how it functions and build it.

Most people would say"oh that can't be done" well here's an example

People say "once a lipo is dead, it's dead" not true a lipi can be broight back by using a nimh/nicd charve setting to get a 3-cell say to 9 volts and then continue charging it as a 3s

it is dangerous if you don't pay attention but it can be done.

I'm not sayimg that I am invincible here, I am a common peasant, an animal, but oen is only limited by his imagination (and of course, money government etc.. )

Even still, no one owns the sky, the sky is there

Yes authorities can arrest me because of their laws but the sky is nature mans machines are there.

Anyways regardless of that, this project could be done.

Not today or tomorrow, but in the future.

Not trying to break any rules, certainly I'd notify the human animal 'sky gods' that I would like to put my toy up there with their toys too.

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Old 10-12-2011, 01:49 PM   #6
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In 2003 a man named Maynard Hill flew a model non-stop from the United states to somewhere in the U.K. Some guy in Ireland (I Believe) took control of it when it got close and landed it for him so I am assuming it was autonomous for the majority of it's flight. Needless to say this was a record setting flight. He used an internal combustion engine but still an amazing accomplishment. The energy density of IC fuels is high but still...

http://www.progressiveengineer.com/p...aynardHill.htm

So, with your idea, the issue really is efficiency. Right now the solar systems that are available are just not good enough. However, a journey of a thousand miles does begin with the first step.

I have been an engineer for 30 years designing devices with extremely challenging goals and we always had a saying that our job was to defy the laws of physics. So, here is how I would approach it:

1. Start small and with the goal of maybe setting a record.
2. Work in achievable increments and test various systems as you go
3. Get a group together and approach it like some of the "X" prize teams so you can pool resources and design ideas as a group.
4. Find group members with various skills: electrical engineer, someone who has designed or scratch built before, someone who is a talented fabricator etc....
5. Have fun testing wild ideas.

There are folks around trying to do something fun, seemingly impossible all the time. Here are a couple of examples:

1. A kid and his dad build a balloon that holds an iPhone (for telemetry), a small HD video camera, some insulation and heaters and achieve a flight that costs only a few hundred dollars and exceeds 100,000 feet. They took some phenomenal sub-space images!

http://www.dailymail.co.uk/sciencete...o-footage.html

2. A small model rocketry group sets a record for a flight of over 100,000 feet and records several video accounts that are incredible. To set this record it requires not only attaining the altitude but you have to recover the vehicle. Their goal is to be the first amateurs to launch a device into low orbit.

http://www.space.com/13227-amateur-r...ntent=My+Yahoo

Keep dreaming and maybe you will have a lot of fun and set some records.

Dave
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Old 10-12-2011, 03:12 PM   #7
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Hi Payne9999,

I appreciate the support, this is one of the better posts that I've received.

It always seems like people are so against new ideas until they see that it works, then suddenly they're all around you

Anyways, indeed I may have been too drastic in saying "global" but I just sit in my classes and wonder how neat it would be to have this aircraft up there (flying around my school on its own) and I could command it through my phone (and also my transmitter).

Similarly, I'd like to have a 360 degree top and bottom camera that broadcast live, where I can check on the airframe and note any irregularities.

Thank you for these links, I will give them a read to give me an idea of what has to happen.

I'd surely like to get some help on these projects of mine, people are great to be around with long as they're willing to be great to be around with or something like that.

Again thanks for the input, much obliged and love the "can-do" attitude

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Old 10-12-2011, 03:25 PM   #8
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I'm at a small start right now, I'm not too filthy stinkin' rich yet, but I started flying FPV recently, I'm working on building a Quadrifilar Antenna for my receiver so that I can increase my range, but for now I'm limited to low level and close proximity flying.

The videos aren't edited (sorry) I run a pen drive Linux OS on my 2gB flash drive, not a lot of room for an HD Video editor nor the computing power (my computer sucks I broke my new one)










Curious why the rocket seems to slow down once it gets near the edge of outer space (in relation to earth) I thought gravity got weaker the farther you get from the mass ie earth ? or does the rocket simply run out of fuel / acceleration at that point? Wonder what # of Mach that rocket flies at.

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Old 10-12-2011, 03:27 PM   #9
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I just added the TransAtlantic thing sort of as a joke, but wouldn't it be neat if the aircraft was able to soar like an albatross on the crest of a wave? Neat... Course it is risky.

Perhaps hydrogen batteries are the answer.

Whoa neat!

This is from that article:

" FAI requirements limited airplane takeoff weight to eleven pounds and engine displacement to 10 cubic centimeters (.6 cubic inch). The preferred four-cycle engine had been out of production for two decades, so Hill advertised on E-Bay to buy a stock of these. He replaced the glow plug with a spark ignition with a Hall effect sensor for timing and added a generator to eliminate battery weight. Coleman stove fuel was used because of its low carbon buildup, with an additive for lubrication. "

He also joked about Trans-Atlantic flight (well maybe not joked but mentioned it) great minds think a like eh? I find that a lot of ideas that I have are already called for or thought up of as well for example a cell phone that uses a laser projected keyboard and a projector to view the screen on a wall, somebody already called it their own damn... there are 7billion+ people in this world, it's not impossible that two or more people can have the same idea

All I need is a Napier Sabre Sleeve Valve engine... hahaha

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Old 10-12-2011, 04:33 PM   #10
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If your designing antennas you probably know this but just in case:

A quad element antenna or any high gain omni antenna such as stacked collinear arrays get their gain from a compressed signal pattern. So, if you imagine a big fat doughnut with a tiny hole in the center that is the radiation/reception pattern of a simple zero gain single dipole or whip with counter-pose ground (1/4 wave). Any effort to increase so-called omni-directional gain will compress the shape so it looks like a doughnut that has been run over by a steam roller. The reason I say so-called is the high gain omni works really well for terrestrial applications because the strongest lobe of the signal is basically parallel to the earth. In flight you have a 3 dimensional problem and your strong lobe could be pointing the wrong way most of the time. Imagine a frisbee shape and how the edges of the frisbee would pitch and roll away from the transmitting device. The edge of the frisbee is the strong lobe.

A zero gain dipole:


A high gain omni antenna:


A better approach is to use a directional transmitting antenna that has a fairly reasonable beam width (say 30- 40 degrees) and then plan your flights to stay in that 40 degree cone (so-to-speak). The nice thing about a ground based directional antenna is it has a more 3D pattern, it diverges in both the horizontal and vertical planes giving you a giant cone that you can safely stay in. Of course you have to have the piloting skills to know where you are!

I would suggest a simple dish array that has just enough GAIN to keep the signal integrity in your target area.

I saw a guy do this with a circular polarized array and also with a small dish. He was flying about a mile away and at 2,000 feet. However, be careful, FPV is an experimental area and in many places you are not supposed to fly over 500'. Also, if you are following AMA guidelines FPV has to be line of site. For experimental FPV though it really seems like there needs to be some other allowances in the rules. LOS really limits the potential to learn, test new ideas etc. However, I understand the concerns the AMA and FAA have regarding this activity.

Dave
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Old 10-12-2011, 04:43 PM   #11
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Hi Payne999,

Boy am I glad that you had cleared that up, I'll definitely keep that in mind.

Have you heard of the Dragon link systems?

Their claims of "Low ground level FPV flight at far distances without signal loss (long as you have rc signal) " is quite attractive.

Can you support their claims? I'm unfamiliar with their technology, except that it has something to do with attaching the transmitter for the video ( I think) to their transmitter for their airplane.

I'm going to have to read this more than once, to fully understand what you have posted, but thank you non - the less.

Also I would like to add that these Quadrifilar antennas are used a lot in weather data receiving systems, (civilian stuff) so that's what had drawn me but your claims make sense.

I will have to re ask the person who suggested it to me and ask him, perhaps he took my purpose wrong (plane vs. satellite) though he stated that it has LOS 'receiving' capability.

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Old 10-12-2011, 04:56 PM   #12
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Maybe if the signal pattern is not compressed in an extreme manner it might be fine, (depends on actual range) you just have to be aware of the "null" part of the pattern. The higher the gain the more the null areas actually go minus (-db) and actually begin to attenuate.

Highly directional arrays will actually null out quite strong signals.

I am assuming that since you are a student you are young....It is nice to see students that are interested in experimenting in science and engineering.

Dave
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Old 10-12-2011, 05:14 PM   #13
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The dragon link is using a 1/2 wave vertical dipole on the plane which makes sense to me. It has some gain over a 1/4 wave antenna and has a little advantage. If you notice the null points of a dipole are fairly narrow but are quite sharp right at the end of the antenna. This is why the dragon link folks tell you to never point the end of the transmitting antenna right at the plane (loss of signal is almost certain).

It looks like the rubber duck transmitting antenna is a stacked collinear these 435mhz rubber duck antennas are typically moderate gain. To approximate the needed length of a 1/2 wave element divide 468 by the frequency in mhz. So, 435 would be about 1.02 feet or 13".

I wonder if you have to have an FCC amateur license to operate these since they are in the "ham" band?

I can't vouch for their claims but from reading their website it looks like a well thought out system and reasonable cost for sure. It would be hard to fly too far away with a basic FPV system since the Lipo's have a limited run time and you have to reserve enough power to return, maybe plan for multiple "go-arounds" and to avoid draining the battery to less than 10-15% capacity. However, with a sailplane type of model the distance or altitude wouldn't be as much of an issue unless you run out of battery and/or lift to get home.

BTW, 435 is an excellent frequency for line-of-site. Multi-path phase problems and other issues are not as much of a problem as it is once you get into the microwave spectrum. UHF is a good choice. LOS of 20+ kilometers is not a problem for ham radio and with the right receiver and antennas it can be much farther (terrestrial). I used to use a 50 watt transmitter to reach low earth orbit satellite transponders (about 300 mile altitude) and have conversations (albeit quick, 10 minutes or so) with other land based radio stations that were over the horizon, thousands of miles away. My uplink frequencies were in the 432 band. So, it isn't out of the range of believable that Dragon Link could make these claims.

Dave
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Old 10-12-2011, 06:10 PM   #14
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Well, I am glad that you can confirm these claims with personal knowledge in this area.

To be honest, I'm lost at a lot of what you have said.

I am still learning, I have only recently gotten into the FPV side of the hobby, I would like to learn about transmitters and receivers (in general) using RF

When I was 12 years old (6 years ago ) I always wondered why the 27mhz rc trucks from WalMart were limited in range, so I would try to boost their range, I tried lots of things (not with power but with antenna modification) though I realize now that what I had doing wasn't helping at all...

One thing I tried was to take the springs of one of those 'crazy-eyes' goggles and use that coil of flat plate metal (stretched out) as a transmitter antenna... it seemed like it would work to me but I couldn't explain why.

Now I realize that of course it wouldn't work, and that in fact I had severely limited the range (that's what I think anyways).

I would really like to learn about this side of technology, I am still unsure on dBi and wavelengths the formula lambda/2 etc...

Does the gauge of the single strand wire matter? (I believe it does as a formula for a Quadrafilar Helicloidal antenna had asked for the thickness of the wire)

I really appreciate your input, once I learn some more, I will understand what exactly you are saying, but I am getting the gist.

Yes I am young, 18 and a sophomore in college, unfortunately I'm not doing too hot, my interests aren't here at the moment, but I have to get through it.

As far as the FCC, the standard FPV (above 10mW) requires a license.... (what do our rc aircraft transmitters put out?)

Do you have any suggested reading materials that could help me understand more of what you have described?

I am enthralled by the idea of 300mile altitude, but I would like to understand the basics, build my own etc...

That way you're not talking to a rock.

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Old 10-12-2011, 06:26 PM   #15
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The ARRL publication "Amateur Radio Handbook" is excellent and there are several antenna handbooks out there for amateur radio folks.

Of course there is a lot on line. Basic books about electronics principles and radio frequency design would also be of use. If you have a fair grasp of math and some algebra it is helpful.

High frequency signals travel on the skin of conductors so wire gage isn't super critical but if you are using some automated antenna calculators/programs they will generally want to know the conductor gage. If you use a coil at the base, middle or top of an antenna it gets more complicated (like what you were trying to do with 27mhz devices).

I don't remember what the exact output of RC equipment is but it is very low power. The other issue with longer range FPV is definitely going to be the radio link to the aircraft servo control receiver. Without special modifications they are quite range limited. I would imagine the Dragon Link website would have info on how to solve that but I need to read more.

Dave
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Old 10-12-2011, 08:08 PM   #16
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Oh fantastic, I bought a coaxial cable for my tv, I plan on using the inner wire (not the shielding) for the antenna material.

I will have a look at these books and read,would you mind if I ask you questions from time to time?

Thanks again for what you have helped me with.

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Old 10-12-2011, 08:41 PM   #17
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I am not an expert but I would be glad to help with any question you may have within the knowledge I can draw on.

I am sure others will chime in as the thread is out there a while.

Dave
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Old 10-12-2011, 11:52 PM   #18
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There certainly must be an easier way to get the antenna wire you need than shredding a coax cable. That sounds like no fun at all.

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Old 10-13-2011, 05:09 PM   #19
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Green Ace,

Here is an antenna design page that covers most antenna types. If you search the web for ham radio antennas or antenna design you can pick up a lot of understanding of how antennas work.

http://www.ve3sqb.com/

BTW, I really like your airplane. Is it scratch built?

One thing I remember from being a full scale pilot is: At airports some of the antennas that are critical are true omni-directional systems. When they want to be sure they hear a plane from any direction they use a circular polarized "eggbeater" antenna. They are low gain but will receive a signal equally well from any direction or angle. So, if you use a high gain directional array on the ground the plane should be as "omni" as possible.

With the exception of the very narrow "nulls" at the end of a dipole, the 1/2 wave vertical dipole is probably fine for the plane. Just don't fly directly overhead or sweep through an angle that points the axis of the antenna right at the ground station.



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Old 10-18-2011, 09:19 PM   #20
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Hi Dave, thank you for your interest in the design, yes it is a scratch built, unfortunately it is quite ugly at the moment as I have it built for robust/durability, though my flights have been very good (as in I don't crash)

The wings are an SD7037 airfoil variant, hot wire cut and fiber glassed (weak resin)

I had this antenna in mind (using formulas from wikipedia on helical antennas)

It seems rather big, there weren't any units so I assumed that I was dealing with mm

I'm sorry for the delay in the response, I've been busy with school, today was the first day I was able to fly.



More images, I attempted to solder on a half wave antenna (111mm long) to my Vtx I fear it may have made it worse.







This camera is absolutely terrible, I'm going to rewire the coaxial cables for the HD bloggie as this camera is absolute junk.

Thank you for the links, perhaps this will straighten out my design flaws.

That is quite an interesting antenna, I'll need to look into it for dimensions.

What antenna would you recommend for the Vtx (antenna on the plane) ? I have heard of cloverleafs, biquads, yagis etc.. can't make up what I would want, my intent is to fly high, medium range (2miles under) and also low to the ground with foliage (high speed) and lots of possible interference.

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Old 10-18-2011, 10:06 PM   #21
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If your college has an electrical engineering dept. you may be able to use some of the test gear. An antenna is very much like a guitar string and will have a very specific resonant frequency and this is purely based on geometry (element lengths and spacing). If the geometry is wrong it will not resonate but will actually attenuate and worse it will send the RF energy back to your transmitter. Too much of this can overheat and damage the final amplifier parts. So, one instrument that is handy is a "Standing Wave" meter. The is a meter that indicates how much energy is leaving the antenna as opposed to be reflected back because of a non-resonant system. Anything under a 1.5 to 1 ratio is considered resonant. This is a ratio of energy leaving vs. returning. Without an SWR measurement you are guesing at antenna construction. inexpensive ones can be purchased from ham radio supply places.

This is a very intuitive cross needle meter that visually shows the forward and reflected energy and indicates the SWR reading at the cross of the needles.

The other item that is helpful is a field strength meter. This will help you compare actual antenna performance and will aslo give you some indication of how directional and antenna is and where the dead spots are in the pattern (null lobes).




With high gain directional arrays making them resonant is even harder than a whip or dipole system. Your experimental antenna is likely out of spec. It's not your fault, even if you built it with extreme care it would have to be tuned and matched (with and SWR meter) to make it resonate efficiently. It is easy to get a good 1/4 wave antenna to work but a helical array is challenging. With an SWR meter that is sensitive enough for a low power transmitter you can validate the construction. However, there is another subject that you may need to study. A 1/2 wave dipole (1/4 wave radiator and 1/4 wave counterpoise) has an input impedance of about 50 ohms. Most transmitters and coax are also about 52 ohms. this works great. however stack arrays and directional yagis, helicals etc. have a very different input impedance. So, these arrays require an input matching network. this can be an adjustable inductor or a gamma match rod that is adjsutable or some kind of inductor capacitor array. However, without it your antenna can be very resonant but will never accept the energy because there is no input match.

Also at 1280 Mhz connector and coax losses can be extreme. Sometimes these low power transmitters will just connet directly to the antenna to avoid the loss and cost of a connector. Be sure to pick a good connector. At those frequencies an "N" connector is the minimum but some of the better SMA connectors and some hardline (rigid copper coax)may be advised. Keep your coax as short as possible. You can loose half you signal strength in coax losses.

No problem on the response, school is really important! get a good degree in a field you like and you will be less likely to dread going to work every day or you might own you own business...who knows.

Dave
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Old 10-18-2011, 10:23 PM   #22
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Oh my goodness! This is so much information!!!

But I love it, I just need to understand every aspect.

So, I was following this page:

http://www.rcexplorer.se/page14/hwwa/hwwa.html

I was looking at the 1/4 wave antenna and he suggested soldering off the connector (not sure what kind it is SMA?) for a standard 100mW Vtx (like the one he has on his page).

How hard is that to perform, un-soldering this piece.

Again I have to reread your posts, it's a hefty amount of information.

I appreciate your responses, you have quite the collection of information on this subject.

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Old 10-18-2011, 10:56 PM   #23
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You are on the right track. This web site is describing a situation where they are removing a inductively loaded "rubber duck" antenna and replacing it with a good 1/4 wave monopole. Also, since he is tuning it with a signal strength reference signal from the unit, he is accomplishing what would normally be done with an SWR or field strength meter.

Looks like a good technique and reassembling it later shouldn't be difficult. However, if it works that much better you probably won't go back. Rmoving the connector is exactly what I was talking about. He is removing the losses from the output connector and the input connector of the antenna by directly attaching the antenna element. Seems like it should be a good bet. I do wonder where the counterpoise or ground reference half of the antenna is though. Maybe it is the case of the transmitter...

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Old 10-18-2011, 11:11 PM   #24
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There was one thing I was wondering, on these golden connectors what part is the ground?

Golden connector as in the screw connection for the antenna for the Vtx.

I have heard of using an RF attenuator to lower the signal ? Not sure if that is quite correct, but I'm interested in the capability of testing an antenna by going 10ft away from the tx and seeing how the signal is at the rx.

Not sure if this is possible, but what I mean is, testing by walking distance (I hold the receiver and the small monitor, and see how far my range would be.

I have so much to read, but currently I need to fix my bombed physics test on point charges and Gauss's law know anything about those? LOL

Class average was a 25% yeah...

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Old 10-19-2011, 12:10 AM   #25
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Doing a range check would be a good test if you can get far enough away to measure or see a significant change change between antenna types.

On SMA, SMB, N and pretty much all coaxial connectors I can think of the center conductor is the radiator and the outside (threaded portion) is the ground or RF reference. I believe this is universal.

We use Gaussian diagrams to look a thermal topography but it has been too long for me to remember the theory behind it.

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