I'd be interest to hear/see what the 10G fraternity are using to obtain fairly accurate dish pointing when in the field. I currently use a readout that provides 1 degree steps and initial setup is done
by setting the 0/360 pointer to North allowing for magnetic variation with the aid of a compass. Having had only around 10 contacts over distances up to 140k where signals are strong leads me to
realise perhaps a better method can be put in place for longer distances. I'm aware some use maps and pick out a target and with the aid of a scope adjust the setup accordingly however during field
days this is not always possible particularly if you don't have access to the internet.
All comments welcome.
Ian - VK3AXH
10 GHz dish pointing arrangements for portable use
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VK3HZ
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Re: 10 GHz dish pointing arrangements for portable use
Hi Ian,
When Rex and I attempt AE contacts on 10 and 24 GHz, we don't have a signal to peak on so we have to accurately calculate and set our dish directions. Otherwise, no contact
From my personal experience, I don't think that a heading from a magnetic compass (whether manual or electronic) is good enough for 10 GHz.
Also, I don't think that a dish can be pointed from behind without some sort of sight. We both have rifle scopes on our dishes (there are cheapies on eB*y), and azimuth rings that can be moved around for calibration. We now both use old Telescope Az/El mounts which are very sturdy, can easily be moved and locked in both Az and El and can be calibrated.
What we do is find a reference point with a known bearing to calibrate the dish mount. This might require a bit of homework beforehand, and/or a bit of preparation on-site. There are several approaches:
- on site, look for a suitable reference point at least 1-2 km away (e.g. road sign, power pole ...). Use a handheld GPS to first log where you are operating. Then move to the reference point and the GPS should be able to tell you distance/bearing traveled. Otherwise, determine the exact lat/lon of each location (use averaging) and there are a number of programs that will give you the bearing between the two points.
- if the operating location is not too far away, I go there and take photos in the direction of interest. Then I identify possible reference points. Back at home, I use Google Earth to identify these points and calculate bearing, using the Ruler function.
- again using Google Earth, I draw a path between the operating locations. Then I zoom in towards my location and and point the view towards the horizon. I look at where the path meets the horizon and take a printout. Then on site, I can often visually correlate the distant horizon with the printout and work out the correct direction. I often use this technique as a cross-check for one of the above techniques.
It's worth taking the time to get the right dish pointing as it removes one variable from the equation. If both stations are GPS-locked, that removes another variable. Then all you need is for conditions to be right!
Regards,
Dave.
When Rex and I attempt AE contacts on 10 and 24 GHz, we don't have a signal to peak on so we have to accurately calculate and set our dish directions. Otherwise, no contact
From my personal experience, I don't think that a heading from a magnetic compass (whether manual or electronic) is good enough for 10 GHz.
Also, I don't think that a dish can be pointed from behind without some sort of sight. We both have rifle scopes on our dishes (there are cheapies on eB*y), and azimuth rings that can be moved around for calibration. We now both use old Telescope Az/El mounts which are very sturdy, can easily be moved and locked in both Az and El and can be calibrated.
What we do is find a reference point with a known bearing to calibrate the dish mount. This might require a bit of homework beforehand, and/or a bit of preparation on-site. There are several approaches:
- on site, look for a suitable reference point at least 1-2 km away (e.g. road sign, power pole ...). Use a handheld GPS to first log where you are operating. Then move to the reference point and the GPS should be able to tell you distance/bearing traveled. Otherwise, determine the exact lat/lon of each location (use averaging) and there are a number of programs that will give you the bearing between the two points.
- if the operating location is not too far away, I go there and take photos in the direction of interest. Then I identify possible reference points. Back at home, I use Google Earth to identify these points and calculate bearing, using the Ruler function.
- again using Google Earth, I draw a path between the operating locations. Then I zoom in towards my location and and point the view towards the horizon. I look at where the path meets the horizon and take a printout. Then on site, I can often visually correlate the distant horizon with the printout and work out the correct direction. I often use this technique as a cross-check for one of the above techniques.
It's worth taking the time to get the right dish pointing as it removes one variable from the equation. If both stations are GPS-locked, that removes another variable. Then all you need is for conditions to be right!
Regards,
Dave.
Re: 10 GHz dish pointing arrangements for portable use
David,
Some pictures of your tripod would be good, and probably make more sense to a thick head like me.
It is an interesting point, for as you say, as we chase the higher frequencies the pointing becomes a challenge.
It occurred to me that you can buy computer controlled telescope mounts that can point at distant stars. Can these be used to point at a distant lat/long terrestrially? I can already hear the cries about the cost, but that is academic at this stage, and I am justed interested to know if that would work. We now all GPS lock our radios, so surely the developmont to eliminate guess work with dish pointing must be the next challenge, particularly for millimetre wave operation.
Michael
VK3KH
Some pictures of your tripod would be good, and probably make more sense to a thick head like me.
It is an interesting point, for as you say, as we chase the higher frequencies the pointing becomes a challenge.
It occurred to me that you can buy computer controlled telescope mounts that can point at distant stars. Can these be used to point at a distant lat/long terrestrially? I can already hear the cries about the cost, but that is academic at this stage, and I am justed interested to know if that would work. We now all GPS lock our radios, so surely the developmont to eliminate guess work with dish pointing must be the next challenge, particularly for millimetre wave operation.
Michael
VK3KH
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VK2ZIM
Re: 10 GHz dish pointing arrangements for portable use
How it is done commercially with broadcast microwave links on 7 Ghz and 13 Ghz is quite simple.
They typically use 1.2 metre to 1.8 metre dishes so they are even more directional than the average amateur dish for 10 Ghz.
On the pan and tilt heads on the tripods there are scales in degrees, 90 in elevation and 360 in azimuth.
The most accurate way of pointing a dish in a given direction is to turn it 90 degrees from the desired heading and simply sight to a recognizable landmark across the edges of the dish.
Then note the reading on the scale and turn it 90 degrees.
The dish will then be pointing exactly at the landmark.
If it is the other end of the path then nothing further is required.
Usually tilt in elevation will be almost horizontal in most cases.
if the desired path direction is say 10 degrees from the landmark then the heading can be corrected by using the degree calibrations on the pan and tilt head.
I have used this method frequently on paths of over 70Km on 7Ghz.
They typically use 1.2 metre to 1.8 metre dishes so they are even more directional than the average amateur dish for 10 Ghz.
On the pan and tilt heads on the tripods there are scales in degrees, 90 in elevation and 360 in azimuth.
The most accurate way of pointing a dish in a given direction is to turn it 90 degrees from the desired heading and simply sight to a recognizable landmark across the edges of the dish.
Then note the reading on the scale and turn it 90 degrees.
The dish will then be pointing exactly at the landmark.
If it is the other end of the path then nothing further is required.
Usually tilt in elevation will be almost horizontal in most cases.
if the desired path direction is say 10 degrees from the landmark then the heading can be corrected by using the degree calibrations on the pan and tilt head.
I have used this method frequently on paths of over 70Km on 7Ghz.
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VK3HZ
- Forum Diehard
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- Location: Melbourne, Australia
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Re: 10 GHz dish pointing arrangements for portable use
With a commercial dish and feed, yes probably. However, I wouldn't be so sure with an amateur-built setup that may have some squint.VK2ZIM wrote:The dish will then be pointing exactly at the landmark.
I've used a distant source to make sure that both dish and sight are pointing in the same direction.
Below is a pic of the telescope fork mount with 24 GHz system plus 370mm dish attached. I've also got a 10 GHz system with 600mm dish that sits on the same mount.
The telescope is a Meade LX200 8" Schmidt-Cassegrain. I've removed the optical tube and mounted an aluminium tray in its place. The 24GHz and 10GHz systems sit on the tray.
- 24 GHz System on Telescope Mount
It can also be PC controlled so, with a relatively trivial bit of programming, could be made to automatically point wherever you want. For example, with position and height from an ADS-B receiver, it could track an aircraft perhaps opening up new Aircraft Enhancement possibilities.
Now, this sort of telescope is not cheap, but I already had it. However, the fork mounts sometimes come up on "that" auction site because people sometimes use the optical tubes on better mounts. Several amateurs have already picked up mounts like that. Celestron is another make to look out for.
Regards,
Dave.
Re: 10 GHz dish pointing arrangements for portable use
Thanks Dave.
Hmmmm. Makes me ponder on ideas about homebrewing a fork mount for a dish. Might take a bit of forking around
Not quite sure that this would work with an offset dish
73, Roger Harrison VK2ZRH
Hmmmm. Makes me ponder on ideas about homebrewing a fork mount for a dish. Might take a bit of forking around
.VK2ZIM suggests:
The most accurate way of pointing a dish in a given direction is to turn it 90 degrees from the desired heading and simply sight to a recognizable landmark across the edges of the dish
Not quite sure that this would work with an offset dish
73, Roger Harrison VK2ZRH
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VK2ZIM
Re: 10 GHz dish pointing arrangements for portable use
It will Roger as the reflector of an offset dish is simply a section of a full parabola but is symetrical in the horizontal plane.
Re: 10 GHz dish pointing arrangements for portable use
Greetings to all readers.
After seeing recently G8CUB's portable set-up that was experimentally using a magnetic compass sensor designed for marine use, I decided to try that approach to the continuing problem of obtaining an accurate bearing indication for my portable station by way of sensing the Earth's magnetic field.
We all, presumably, have experienced the often confounding variations when using a hand-held compass, variations that are due to near-by ferrous metal objects, both big and small, on the ground or under the ground.
I am also aware that at least a couple of VK radio amateurs have been recently experimenting with electronic magnetic sensor modules/components but I haven't seen definitive reports of their final successes (or unsolved problems, if they exist).
So I reckoned that I should explore what's 'out there' in the off-the-shelf commercial world, and indeed there are solutions available, many costing in excess of $2K. But I did come across a much more cost effective ready-to-go unit intended for marine use that I reckoned others may like also to know about. The URL for this UK-manufactured item itself is:
http://www.nasamarine.com/proddetail.ph ... er_Compass
and its accuracy specifications as well as the large LCD display seem quite nice, worth following up.
(I did also find on Australian eBay one of these units available from a Brisbane supplier at a price considerably better than the UK or US asking prices so, as I write this, that is on its way to me.)
But I wonder just how sensitive these types of units are to extraneous magnetic field pertubations caused by the likes of steel masts, U-bolts, etc. So I'd like to ask what are other folk's experience(s) with how far the sensor should be mounted away from the inevitable steel items that we use for supporting our antennas? 0.5 metre, 1 metre, or more? Vertical versus horizontal separation, etc?
I am reckoning that mounting the sensor on an aluminium extension way above the top of the mast should greatly reduce sensitivity to these factors, and maximise the possibility of the sensor correctly sensing the direction of the earth's magnetic lines of force at the current location.
And on another tack (another marine reference!), how immune are these types of sensing system to the expected RF fields that we may generate in the area where the sensor is located?
Any comments, based on conjecture, anecdote or personal experience will be received with thanks!
Cheers and 73,
--Doug Friend, VK4OE.
After seeing recently G8CUB's portable set-up that was experimentally using a magnetic compass sensor designed for marine use, I decided to try that approach to the continuing problem of obtaining an accurate bearing indication for my portable station by way of sensing the Earth's magnetic field.
We all, presumably, have experienced the often confounding variations when using a hand-held compass, variations that are due to near-by ferrous metal objects, both big and small, on the ground or under the ground.
I am also aware that at least a couple of VK radio amateurs have been recently experimenting with electronic magnetic sensor modules/components but I haven't seen definitive reports of their final successes (or unsolved problems, if they exist).
So I reckoned that I should explore what's 'out there' in the off-the-shelf commercial world, and indeed there are solutions available, many costing in excess of $2K. But I did come across a much more cost effective ready-to-go unit intended for marine use that I reckoned others may like also to know about. The URL for this UK-manufactured item itself is:
http://www.nasamarine.com/proddetail.ph ... er_Compass
and its accuracy specifications as well as the large LCD display seem quite nice, worth following up.
(I did also find on Australian eBay one of these units available from a Brisbane supplier at a price considerably better than the UK or US asking prices so, as I write this, that is on its way to me.)
But I wonder just how sensitive these types of units are to extraneous magnetic field pertubations caused by the likes of steel masts, U-bolts, etc. So I'd like to ask what are other folk's experience(s) with how far the sensor should be mounted away from the inevitable steel items that we use for supporting our antennas? 0.5 metre, 1 metre, or more? Vertical versus horizontal separation, etc?
I am reckoning that mounting the sensor on an aluminium extension way above the top of the mast should greatly reduce sensitivity to these factors, and maximise the possibility of the sensor correctly sensing the direction of the earth's magnetic lines of force at the current location.
And on another tack (another marine reference!), how immune are these types of sensing system to the expected RF fields that we may generate in the area where the sensor is located?
Any comments, based on conjecture, anecdote or personal experience will be received with thanks!
Cheers and 73,
--Doug Friend, VK4OE.
Re: 10 GHz dish pointing arrangements for portable use
Doug,
Damien 3KQ and Ralph 3LL will be giving a talk on their magnetic compass work at Gippstech next weekend.
They can get down to 1 degree (or better) and knowing the declination from Geophysical maps for the areas they operate from can program that offset into their software.
Definitely worth talking with them about the way they do it and the compensation software and rotator controller system that they use.
The following video shows the sensors above the dishes on the various masts. https://www.youtube.com/watch?v=WdT7bIAAbCk
Cheers
Peter VK3QI
Damien 3KQ and Ralph 3LL will be giving a talk on their magnetic compass work at Gippstech next weekend.
They can get down to 1 degree (or better) and knowing the declination from Geophysical maps for the areas they operate from can program that offset into their software.
Definitely worth talking with them about the way they do it and the compensation software and rotator controller system that they use.
The following video shows the sensors above the dishes on the various masts. https://www.youtube.com/watch?v=WdT7bIAAbCk
Cheers
Peter VK3QI
Re: 10 GHz dish pointing arrangements for portable use
Hi Doug
Did you see the CMPS10 compass that I did several years ago, had a demo of it at Redcliffe.
They work well BUT are subject to external influences, but saying that it let me align the 47Ghz dish on Peter (4EA) during the last field day and was spot on first time.
I also hard coded in the mag deviation so compass shows both mag and true, and with the built in circuits it also allows you to set the leveling of the platform.
The quoted accuracy is "interesting" but has shown to be within the beamwidth of the 47G dish.
Rex
Did you see the CMPS10 compass that I did several years ago, had a demo of it at Redcliffe.
They work well BUT are subject to external influences, but saying that it let me align the 47Ghz dish on Peter (4EA) during the last field day and was spot on first time.
I also hard coded in the mag deviation so compass shows both mag and true, and with the built in circuits it also allows you to set the leveling of the platform.
The quoted accuracy is "interesting" but has shown to be within the beamwidth of the 47G dish.
Rex
Re: 10 GHz dish pointing arrangements for portable use
Hello Peter, Rex and other readers.
Peter, please ensure that questions about aberrations like those I have put forward are asked/talked about at the Gippstech meeting. (I won't be there.....) I had lost contact with the VK3 fellows who were doing that experimenting, so it's great that the conversation can go forward at Gippstech.
And, Rex, I knew that you were working on such things but I had not taken on board your apparent success with your design. I don't remember seeing the gear actually working alongside the radio 'kit' it's intended to support. I still want to ask the same question about sensitivity to magnetic field perturbations caused by ferrous objects in the vicinity. What separation distance is advised? Is it really something to be worried about at all? Your words make it seems that all should be mostly OK for our purposes.
Cheers and 73,
--Doug.
Peter, please ensure that questions about aberrations like those I have put forward are asked/talked about at the Gippstech meeting. (I won't be there.....) I had lost contact with the VK3 fellows who were doing that experimenting, so it's great that the conversation can go forward at Gippstech.
And, Rex, I knew that you were working on such things but I had not taken on board your apparent success with your design. I don't remember seeing the gear actually working alongside the radio 'kit' it's intended to support. I still want to ask the same question about sensitivity to magnetic field perturbations caused by ferrous objects in the vicinity. What separation distance is advised? Is it really something to be worried about at all? Your words make it seems that all should be mostly OK for our purposes.
Cheers and 73,
--Doug.
Re: 10 GHz dish pointing arrangements for portable use
Doug,
Might I suggest you address specific questions to Ralph and Damien.
My understanding is:
(1) at least a metre or so from other steel (aluminium masts don't count)
(2) the software that controls the rotator has the ability to shuttle back and forth to bring the rotator to the exact position - in other words, has the ability to overcome the slack and overshoot in the rotator gearing.
ralph@parkhurst.com.au and dayers4@bigpond.com
Cheers
Peter VK3QI
Might I suggest you address specific questions to Ralph and Damien.
My understanding is:
(1) at least a metre or so from other steel (aluminium masts don't count)
(2) the software that controls the rotator has the ability to shuttle back and forth to bring the rotator to the exact position - in other words, has the ability to overcome the slack and overshoot in the rotator gearing.
ralph@parkhurst.com.au and dayers4@bigpond.com
Cheers
Peter VK3QI
Re: 10 GHz dish pointing arrangements for portable use
I daresay you can now use Google earth to fairly accurately define the points at each end of the path and use magnetic compasses of whatever sort takes your fancy to set the direction. You also need a chart of the earth's magnetic deviation which is obtainable here http://msi.nga.mil/MSISiteContent/Stati ... -world.jpg as this varies quite considerably as you go from east to west and it also varies slowly over time at about 1 degree every 30 years hereabouts.
CU at Gippstech
73,
David
CU at Gippstech
73,
David
Re: 10 GHz dish pointing arrangements for portable use
VK4REX wrote:Hi Doug
Did you see the CMPS10 compass that I did several years ago, had a demo of it at Redcliffe.
Rex
But the basics are already there Heading ( easily add a decimal point if required) a basic cardinal points indicator, pitch and roll in degrees.
Pretty simple stuff really. BTW, thanks for the tips REX.
Paul vk4apn
Re: 10 GHz dish pointing arrangements for portable use
Hi Chaps,
I think from memory, Google Earth bearings are True...take off the local Variation ( 11 Deg good enough for around here ) to get Magnetic, then apply Deviation if you have a deviation card for the compass you are using...and hey presto..A Magnetic bearing !. From my days of hurtling around in aluminium tubing, again from memory...take a reading off a Chart which gave you a True heading, then apply local variation, or mid track variation, to get magnetic, then have a look at the deviation card in the aircraft to see what deviation may have to be applied. But...no one uses the wet compass to navigate by unless everything else has failed...the HSI was the best invention since sliced bread, using a remote mounted fluxgate sensor to give you a constant readout and saved all the mental arithmetic.
I use a good quality hand held compass to check my beam headings on the tower..and it noticeably deflects within 2 meters of the steel in the tower supports.
I can remember mounting the fluxgate remote sensors in the plastic wingtips of light aircraft many years ago, for obvious reasons.
My efforts to get a magnetic bearing from Google Earth appear to be OK, as I did what is mentioned above, and came up with 160M from here to the Brissy Beacons, which is what I worked out years ago using a WAC Chart, Douglas Protractor and a pencil, and using 11 deg Variation. All these flashy fluxgate/rate/wet compass thingy's will still probably react badly to any close ferrous material, so you may have to experiment a bit by approaching the proposed mounting spot and see if the compass has a wobbly. Standing back behind the mast/tower a few meters, and siting over it seems to work for me.
73
Glenn
VK4BG
I think from memory, Google Earth bearings are True...take off the local Variation ( 11 Deg good enough for around here ) to get Magnetic, then apply Deviation if you have a deviation card for the compass you are using...and hey presto..A Magnetic bearing !. From my days of hurtling around in aluminium tubing, again from memory...take a reading off a Chart which gave you a True heading, then apply local variation, or mid track variation, to get magnetic, then have a look at the deviation card in the aircraft to see what deviation may have to be applied. But...no one uses the wet compass to navigate by unless everything else has failed...the HSI was the best invention since sliced bread, using a remote mounted fluxgate sensor to give you a constant readout and saved all the mental arithmetic.
I use a good quality hand held compass to check my beam headings on the tower..and it noticeably deflects within 2 meters of the steel in the tower supports.
I can remember mounting the fluxgate remote sensors in the plastic wingtips of light aircraft many years ago, for obvious reasons.
My efforts to get a magnetic bearing from Google Earth appear to be OK, as I did what is mentioned above, and came up with 160M from here to the Brissy Beacons, which is what I worked out years ago using a WAC Chart, Douglas Protractor and a pencil, and using 11 deg Variation. All these flashy fluxgate/rate/wet compass thingy's will still probably react badly to any close ferrous material, so you may have to experiment a bit by approaching the proposed mounting spot and see if the compass has a wobbly. Standing back behind the mast/tower a few meters, and siting over it seems to work for me.
73
Glenn
VK4BG
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VK2JDH
Re: 10 GHz dish pointing arrangements for portable use
Most smart phones have a compass built in. Just install your app of choice.
Re: 10 GHz dish pointing arrangements for portable use
Thanks for additional comments Peter, David, Paul and '2JDH.
I was particularly interested in Glenn's comments about sideways or vertical separation of fluxgate sensors from ferrous metal objects.
Measuring azimuth towards something I can see in the distance is not what the situation I'm describing requires. I need to have a compass sensor mounted/attached to the field station rotating mast. A traditional rotator is not present - rotation of the mast is driven by a small DC motor and gear train. So that's driving my quest to measure the current bearing of the mast-mounted antennas by a method independent from the rotating mechanism. [I will still need to use a hand-held compass (or sometimes a hand-held GPS or 'smart 'phone app) to find where my on-the-ground tripod-mounted dishes should be pointed.] And when it comes to properly pointing antennas, working with the difference between magnetic and true readings is 'par for the course'!
The electronic compass unit (fluxgate technology) that I described in my first posting arrived here today and, after mounting the display unit in an appropriate box, initial testing only in my 'shack' plus reading of the manual with all of its correction possibilities and offsets suggests that I should be able to effectively use it for my purposes. Its LCD display is advantageously huge! I am anticipating that some trial-and-error methodology will need to be engaged to find a good mounting position for the sensor module.
Thanks Peter for the contact details for those two developers. Rex and Paul are obviously local to me and are walking a parallel path. Like with many things we radio amateurs dabble with, we can talk a lot about imagined or heard-about points, but there is no substitute for practically building and optimising something, be it electronic or mechanical or both!
Cheers and 73,
--Doug, '4OE.
I was particularly interested in Glenn's comments about sideways or vertical separation of fluxgate sensors from ferrous metal objects.
Measuring azimuth towards something I can see in the distance is not what the situation I'm describing requires. I need to have a compass sensor mounted/attached to the field station rotating mast. A traditional rotator is not present - rotation of the mast is driven by a small DC motor and gear train. So that's driving my quest to measure the current bearing of the mast-mounted antennas by a method independent from the rotating mechanism. [I will still need to use a hand-held compass (or sometimes a hand-held GPS or 'smart 'phone app) to find where my on-the-ground tripod-mounted dishes should be pointed.] And when it comes to properly pointing antennas, working with the difference between magnetic and true readings is 'par for the course'!
The electronic compass unit (fluxgate technology) that I described in my first posting arrived here today and, after mounting the display unit in an appropriate box, initial testing only in my 'shack' plus reading of the manual with all of its correction possibilities and offsets suggests that I should be able to effectively use it for my purposes. Its LCD display is advantageously huge! I am anticipating that some trial-and-error methodology will need to be engaged to find a good mounting position for the sensor module.
Thanks Peter for the contact details for those two developers. Rex and Paul are obviously local to me and are walking a parallel path. Like with many things we radio amateurs dabble with, we can talk a lot about imagined or heard-about points, but there is no substitute for practically building and optimising something, be it electronic or mechanical or both!
Cheers and 73,
--Doug, '4OE.
Re: 10 GHz dish pointing arrangements for portable use
Doug,
What you describe is exactly what Damien and Ralph are doing.
The detector is mounted on the mast, above the dishes. The software controller controls the motor in the rotator (nothing to do with the indicator control pot on the rotator) using appropriate solid state switching.
Doug - see https://www.youtube.com/watch?v=yLpyk_XCXQs
You will notice the smartfind function on the motor.
Also see https://www.youtube.com/watch?v=I-Cqv6nMQSU with thee mark 2 controller.
Cheers
Peter VK3QI
What you describe is exactly what Damien and Ralph are doing.
The detector is mounted on the mast, above the dishes. The software controller controls the motor in the rotator (nothing to do with the indicator control pot on the rotator) using appropriate solid state switching.
Doug - see https://www.youtube.com/watch?v=yLpyk_XCXQs
You will notice the smartfind function on the motor.
Also see https://www.youtube.com/watch?v=I-Cqv6nMQSU with thee mark 2 controller.
Cheers
Peter VK3QI