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Thorn3

900MHz Patch Antenna/tripod design

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Hello all,

The 900MHz patch antenna is a common arrangement, as described in the RC-CAM site. The backing to the antenna ground plate is made from Acrylic left over from another project. It's goal is to offer the base rigidity to the ground plane and antenna in general, as well as offer a means to provide pivot and angle adjustment.

The legs are made from .625" ID electrical conduit. Bronze sleeve bearings were placed into the ends, to allow the leg extension rods to move in and out smoothly and without slop. The leg extensions are unfortunately low quality steel, .500" rod (turned in the lathe for more accuracy). Cold rolled would have been better, but I didn't have any laying around. The leg extensions are made from steel, to provide a good surface for the bronze sleeve bearings, as well as add weight to prevent gusts of wind from knocking over the antenna. The purpose of the extensions is to take into account, irregularities of the ground. The ends of the leg extension rods were turned down to .250" Dia, X .500" long. These ends fit into drilled out rubber stoppers.

The locking nuts are made from brass thumb nuts. I needed thumb screws, but did not have any. Instead, I used some brass screws, as all thread to give the nuts screw ends. The screw threads were soldered into the nuts. The ends of the threads were smoothed out as to not mar the surface of the extension rods. The screws are located such that a person can adjust the leg heights without having to move around the antenna. All can be adjusted from behind the antenna.

The 'umbrella' type mechanism is made from hobby, square, brass tubing. This assembly insures that each leg is in proper reference to the others, keeping the legs equidistant. It works just like an umbrella. This assembly was silver soldered, using a Smith Little Torch. Although, any hobby torch would do.

A brass rod was used for the main pivot for the antenna. A brass washer specially made for it, was soldered to the end of the rod to act as a 'head'. The other end of the tube has a turned down, brass nut soldered into it. A brass screw with lever arm was made in the lathe, to adjust tension for adjusting the angle of the antenna plate.

The antenna plate pivot bracket, is aluminum sheet, drilled and bent for the purpose of allowing the antenna plate to pivot from horizontal to a bit less than 45 deg.

The main leg pivot head was machined from some left over 2" OD 6061-T6 aluminum round stock. The tongues for the legs were machined from .750" Dia, round stock. They extend into the legs .750" and are pinned in place with spring pins.

Washers were made from .010" thick Nylon sheet that was once used as a strap for... something. Had it laying about the stock pile. All metal to metal surfaces use Nylon washers to prevent wear or binding.

I plan to modify the SMA cable further, to include the use of a 90 deg., connector on the antenna end. This way the connector will allow the antenna to pivot freely all the way around, as it will keep the cable away from the tripod more efficiently. Each end of the cable is male. The cable used, was taken from an RF antenna intended for wireless uses on my computer. Since I don't use such wireless devices on my computer, the cable was used instead for the antenna project. Both ends were female. I modified them to be male. The cable is 3' long.

Tests show the antenna works very well. It is low to the ground, easy to set up and adjust and cost very little to make. Most materials were already in the shop. It is not a design that people without shop machines would make however. A mill and lathe were used. The antenna is also very portable, as can be seen in its folded up position. A similar setup can be made using only commonly available hobby materials, without machines. With some modifications to the design of course.

Well, I hope you like the design of my antenna. I enjoyed reading through this site and found the information to be very useful. I use a Fat Shark, head goggle set, modified of course. I hard wired a computer monitor cable directly into the goggles. This allows the ability to provide video, audio and power, all in one multi-shielded cable with built in toroid, as is common on monitor cables. The cable protrudes out of the top of the goggles, allowing the cable to easily lay over the shoulder and not down the side of the face like side burns, as with the original goggle setup.

I use a 500mW video Tx from Range Video and their dual output Rx. Other FPV projects are in the works.

post-4039-1248543053_thumb.jpg

post-4039-1248543071_thumb.jpg

Edited by Thorn3

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I can only add two pictures at a time, so multiple replies will be used to show more images.

post-4039-1248543481_thumb.jpg

post-4039-1248543493_thumb.jpg

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Picture of goggles. These are wired as explained in the first post, using a computer monitor cable. The input power lines are first run to the onboard power input jack, that is native to the goggles. This way, the input power from the new cable, goes to both the Rx board as well as the original input power jack. This way, the original input power jack can be used as an 'output' power jack, to power any accessories that may be added, such as head tracking devices etc. Presently, the input power is supplied via a 3000mAh NiMH battery pack, at 8,4 volts. Any input power can be used, up to nine volts. The goggles internal Rx board, contains a 7805, linear voltage regulator on board. This converts whichever input voltage is applied, either the 8.4 from a NiMH battery pack, or line powered nine volt supply, to 5 VDC for the goggles circuits.

The end of the cable, shows both the input power connector and the video input connector (RCA), which plugs into the video Rx. I plan to make a simple 7809, 9 volt linear regulator circuit, to be built into the video Rx. The power plug on the main cable will be changed to accommodate a more appropriate jack that will be installed in the video Rx housing. This way, the 12VDC powering the video Rx, will also power the 7809 regulator, which will provide power to the goggles, instead of having to use a separate battery for the goggles at the Rx end. This way, in the field, all that is needed is a single sealed lead acid, 12 volt battery to power my entire system, as well as provide a convenient means to re-charge my flight batteries.

post-4039-1248545881_thumb.jpg

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Hello all,

The 900MHz patch antenna is a common arrangement, as described in the RC-CAM site. The backing to the antenna ground plate is made from Acrylic left over from another project. It's goal is to offer the base rigidity to the ground plane and antenna in general, as well as offer a means to provide pivot and angle adjustment.

The legs are made from .625" ID electrical conduit. Bronze sleeve bearings were placed into the ends, to allow the leg extension rods to move in and out smoothly and without slop. The leg extensions are unfortunately low quality steel, .500" rod (turned in the lathe for more accuracy). Cold rolled would have been better, but I didn't have any laying around. The leg extensions are made from steel, to provide a good surface for the bronze sleeve bearings, as well as add weight to prevent gusts of wind from knocking over the antenna. The purpose of the extensions is to take into account, irregularities of the ground. The ends of the leg extension rods were turned down to .250" Dia, X .500" long. These ends fit into drilled out rubber stoppers.

The locking nuts are made from brass thumb nuts. I needed thumb screws, but did not have any. Instead, I used some brass screws, as all thread to give the nuts screw ends. The screw threads were soldered into the nuts. The ends of the threads were smoothed out as to not mar the surface of the extension rods. The screws are located such that a person can adjust the leg heights without having to move around the antenna. All can be adjusted from behind the antenna.

The 'umbrella' type mechanism is made from hobby, square, brass tubing. This assembly insures that each leg is in proper reference to the others, keeping the legs equidistant. It works just like an umbrella. This assembly was silver soldered, using a Smith Little Torch. Although, any hobby torch would do.

A brass rod was used for the main pivot for the antenna. A brass washer specially made for it, was soldered to the end of the rod to act as a 'head'. The other end of the tube has a turned down, brass nut soldered into it. A brass screw with lever arm was made in the lathe, to adjust tension for adjusting the angle of the antenna plate.

The antenna plate pivot bracket, is aluminum sheet, drilled and bent for the purpose of allowing the antenna plate to pivot from horizontal to a bit less than 45 deg.

The main leg pivot head was machined from some left over 2" OD 6061-T6 aluminum round stock. The tongues for the legs were machined from .750" Dia, round stock. They extend into the legs .750" and are pinned in place with spring pins.

Washers were made from .010" thick Nylon sheet that was once used as a strap for... something. Had it laying about the stock pile. All metal to metal surfaces use Nylon washers to prevent wear or binding.

I plan to modify the SMA cable further, to include the use of a 90 deg., connector on the antenna end. This way the connector will allow the antenna to pivot freely all the way around, as it will keep the cable away from the tripod more efficiently. Each end of the cable is male. The cable used, was taken from an RF antenna intended for wireless uses on my computer. Since I don't use such wireless devices on my computer, the cable was used instead for the antenna project. Both ends were female. I modified them to be male. The cable is 3' long.

Tests show the antenna works very well. It is low to the ground, easy to set up and adjust and cost very little to make. Most materials were already in the shop. It is not a design that people without shop machines would make however. A mill and lathe were used. The antenna is also very portable, as can be seen in its folded up position. A similar setup can be made using only commonly available hobby materials, without machines. With some modifications to the design of course.

Well, I hope you like the design of my antenna. I enjoyed reading through this site and found the information to be very useful. I use a Fat Shark, head goggle set, modified of course. I hard wired a computer monitor cable directly into the goggles. This allows the ability to provide power to the goggles, audio and power, all in one multi-shielded cable with built in toroid, as is common on monitor cables. The cable protrudes out of the top of the goggles, allowing the cable to easily lay over the shoulder and not down the side of the face like side burns, as with the original goggle setup.

I use a 500mW video Tx from Range Video and their dual output Rx. Other FPV projects are in the works.

very nice mate ;) now how much would that cost to make and ship to the u,k? im totally useless at making things like this but could really do with one if you can help please :) or even point me inthe direction of someone who could make the antenna for me over here? t,i,a

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Alas, thorn3 is in Arizona, where 900MHz is legal. I fear, n3m1s1s, here in the UK we're stuck with:

4 x 20MHz-wide or 8 x 10MHz-wide channels @ 2.4GHz (max 10mW)

1 channel @ 1.394GHz (max 500mW), and

7x20MHz-wide or 15x10MHz-wide channels at 5.8GHz (max 25mW)

And I think 1.394 is for 'fixed installations' only i.e. ground-based transmissions. Indeed, here in the UK the notion of 'establishing an airbourne platform' is expressly excluded from all amateur radio licences - a common way of getting to use different frequency bands and/or higher power elsewhere in the world. As far as I'm aware the only loophole in this blanket ban are the 'licence-exempt' low-power options above at 2.4 & 5.8GHz.

Wretched, isn't it...

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Both the 1.394 and 5.8 bands are for ground use only !

2.4 is the ONLY legal band for us at 10mW.

Wretched indeed.

Terry

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very nice mate ;) now how much would that cost to make and ship to the u,k? im totally useless at making things like this but could really do with one if you can help please :) or even point me in the direction of someone who could make the antenna for me over here? t,i,a

n3m1s1s: Thanks for liking my antenna and tripod design!

This antenna was made as a 'one-off'. It was designed around available stock materials laying about. Now that the design is completed, it would be possible to make more. However, with my machines, which are manual machines, it would take some time to machine all of the parts, as it did with the first one. With the cost of new materials, worthy of being sold to someone, machining and fabrication time, shipping/import costs to the UK, etc... it would be much more financially feasible for you to make one there in the UK. I make things the way 'I' want them, which usually means going way overboard with design. Tolerances on most of the parts are .0005"! Everything would have to be scaled down for a higher frequency, including the tripod itself.

As doofer mentioned in his follow up post, this sized antenna could not be used in the UK anyway. The 2.4GHz antennas are much smaller and much easier to make. I am sure that a simple camera tripod, possibly cut down to keep the antenna close to the ground would do well for a 2.4 GHz antenna. Much more cost effective as well, compared to my manually machining specialized parts for you, then shipping them to the UK. I am sure that any sheet metal shop in the UK, would cut the sheet steel for you according to the dimensions for the patch antenna found in the RC-CAM website. Then it is a simple matter to install the SMA connector and glue in some spacers.

This puts me in a bind! I would like to help. I really would. But, would it be financially feasible? My setup is complex and not easy to make.

One option would be to use lamp parts. The base for a lamp should be more than enough to act as an anchor for a vertical pipe, to keep an antenna close to the ground. Typically, all kinds of all-thread tubing, with nuts, for lamps can be found in hardware stores, as well as larger tubing to fit over them, as is seen in many lamps. Amazing what you can do with lamp parts.

I have a friend here in Arizona that has a CNC mill. I do have another design for a small tripod that would be perfect for higher frequency patch antennas. It is capable of folding up flat. Let me talk to my friend and see how much it would cost for him to machine the parts from aluminum. Let me get back to you on that. It is possible, that if I can have the new tripod design made at a reasonable cost, the antenna and tripod could be mailed in a standard sized box for a set price, anywhere in the world. So, it just may be possible. Let me examine the costs first, then get back to you. For me to have my friend machine one-off parts, the costs are higher. If more people were interested in a specialized, collapsible design, with the patch antenna included... then the costs would come down quite a bit.

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Both the 1.394 and 5.8 bands are for ground use only !

2.4 is the ONLY legal band for us at 10mW.

Wretched indeed.

Terry

Thanks for that update Terry - updates are never good news are they?

What was your source for this? I've been in discussion with a guy who dishes out ham licences, but regulations around usage of 'license-exempt' kit is much less clear - since by definition they aren't covered by the main regulations. (e.g. I thought we merely had an absence of a ban on using 2.4 for airbourne platforms, rather than something saying airbourne platforms are OK...)

It would be nice to know if there's an easy-access source - I've looked at several huge PDFs about the Telecommunications Act that webfolk have directed others to, as if the answers to these sort of questions are in there, but I'm not certain that they are. Especially at these frequencies, with massive markets in WiFi etc. opening up, there's a clear sense of the tail wagging the dog...

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This patch is amazing in my last flight I flew about 500 meters behind the patch with just one or two glitches and had flown 1.7 km away till my rc receiver heavily glitched. I found its performance superior to L-Com 8 dBi Patch when flying around the antenna. I got more glitches than the gp patch. Here is a page showing the patch mounted directly to the dual out put receiver.

http://www.pistbasi.com/forum/viewtopic.php?t=891

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Doofer,

I use ofcom for all my info.

This is what they say about 2.4Ghz

Wireless Video Cameras – non broadcast may only be used to transmit Television signals. Typical applications are for general-purpose closed-circuit television applications. The 2.4 to 2.4835 GHz band, a European harmonised band, is also allowed for low-power analogue video applications. You may also use the 2.4 GHz band for airborne video applications, subject to any further regulations required by the Civil Aviation Authority, where applicable.

http://www.ofcom.org.uk/radiocomms/isu/lic...licence_exempt/

Terry

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The 5.8 band not being suitable surprises me...

I've apparently found where the file describing it, however of course the link is broken:

Short Range Device (SRD) use

In addition, some short-range device (SRD) applications are permitted to operate in various designated bands between 5725 - 5875 MHz, albeit at lower power levels. For example video senders can use the whole band 5725 - 5875 MHz at a power level of 25 mW e.i.r.p. The spectrum parameters for licence exemption are set out in IR 2030: http://www.ofcom.org.uk/radiocomms/ifi/tec..._req/uk2030.pdf

(last paragraph on the page)

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Thanks Terry, that's jsut what I've been looking for all these years!

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Alas, thorn3 is in Arizona, where 900MHz is legal. I fear, n3m1s1s, here in the UK we're stuck with:

4 x 20MHz-wide or 8 x 10MHz-wide channels @ 2.4GHz (max 10mW)

1 channel @ 1.394GHz (max 500mW), and

7x20MHz-wide or 15x10MHz-wide channels at 5.8GHz (max 25mW)

And I think 1.394 is for 'fixed installations' only i.e. ground-based transmissions. Indeed, here in the UK the notion of 'establishing an airbourne platform' is expressly excluded from all amateur radio licences - a common way of getting to use different frequency bands and/or higher power elsewhere in the world. As far as I'm aware the only loophole in this blanket ban are the 'licence-exempt' low-power options above at 2.4 & 5.8GHz.

Wretched, isn't it...

yes it is :( just out of curiosity what would be the penalty if you were caught using 900mgz in the UK please? i come from a background where i taught myself to fly, never had an instructor or joined any flying club, not insured at all, but all around me is farmers fields so i fly out in the open by myself most of the time.

my trex 500 setup has a 200mw 900mhz range video tx, ive had a 3dbi antenna on the heli in the past with good results but ended up putting the 3dbi on the reciever, im interested in having a pair 900mhz patch antennas so that a friend and myself can race our rc trucks from his car on a bmx track out in the middle of nowhere that looks perfect for FPV racing (though high speeds might notbe the actual order of the day as 5mph on the ground looks pretty fast through goggles lol)

that said i have had police come up to me twice in the 3yrs that i have been playing around with FPV equipment and what frequency i was broadcasting on didnt even come up in conversation,

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UK penalty is a max of £5000 and 6 months in prison. I don't recall it ever happening though, the worst I remember is all the offenders radio gear being taken and a £500 fine. I belive it all depends on the interferece caused as to how bad the penalty.

Dose anyone else know of a case in the UK ?

Terry

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UK penalty is a max of £5000 and 6 months in prison. I don't recall it ever happening though, the worst I remember is all the offenders radio gear being taken and a £500 fine. I belive it all depends on the interference caused as to how bad the penalty.

Dose anyone else know of a case in the UK ?

Terry

wow that's abit stiff :( yet amazon UK and ebay UK seen to sell loads of 900mhz security cameras a few year back even seemed like it was the only frequency on the market for ages and then they started selling 2.4ghz as well and i thought they were just jumping on the 2.4 bandwagon just so they could sell the same cameras at a higher price

with all that in mind i was thinking that if i were to use the cameras with on board 10mw 900mhz TX's that don't seem to broadcast very far and a goof proof patch i would hopefully be able to pick up a good signal from around 500meters away say? is that feasible please?

and for legal purposes could you tell me in newb terms what i should be using instead please?

my models all run on 2.4ghz heli's use spektrum ar7000 RX's and planes use Futaba FASST with (r607??) RX's im an ideal world i would really like to fly my models to the edge of the range of my rc gear or maybe have video picture start to break up just before my radio gear starts glitching so to speak

hope that all makes sense but if i am thinking anything wrong here please correct me :)

btw thank you for all replies so far GREAT INFO AND HELP cheers

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We need a sticky on this as it comes up all the time.

The only legal set up in the UK is to use 10mW on 2.4Ghz, no other set up is legal at this time and there are no plans to change this as far as I know.

I have never use 900Mhz so Im guessing to say that 500m should be possable but it depends on the quality of your equipment.

Terry

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