Fixed elevation - how many elements?
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so not limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM
Hello Martin,
I use 2 x 5 elements yagis, for UHF & VHF horizontaly polarized on the same boom inclined 25 degrees up, using FT-897 or FT-736, handled by only azimuth rotator.
Decent results for FM and SSB Sats throughout all the pass.
73, lu7abf, Pedro
On 6/16/19, Martin Cooper via AMSAT-BB amsat-bb@amsat.org wrote:
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so not limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Hi Martin,
I think you've analyzed your situation pretty well when it comes to numbers of elements, beamwidths, etc. A few thoughts: - if you can try a few satellite passes from around your property with a handheld yagi, like an Arrow just gain a little first hand experience to see what your minimum elevations are going to look like. - you might be surprised to find that some houses are more "transparent" to VHF/UHF signals than others. There are several ops here who regularly work satellites with portable antennas from inside their houses. Don't consider every obstacle to be impenetrable.
With all that said, if I was in your position I'd go for a 3 or 4-element 2m yagi and I'd go to the extra trouble of getting crossed yagis so you can use circular polarization to reduce signal fading. For 70 cm the 7-elements on my Arrow handheld antenna has always been sufficient, and go for crossed yagis again. If you think the trees will really be a problem then go with 4 elements on 2m and a few extra on 70 cm, but realize that if you're buying commercial antennas you're stuck with what the sellers offer. This is about as much as I'd want to swing around with an inexpensive azimuth rotator (You didn't say what kind of rotator it was)
Finally, my antenna situation at home was even more awful than yours. My back yard was smaller than my living room and it was surrounded by 3-storey townhouses on all sides. I decided to become a rover and it was the most adventure-packed 2 years of my life! I travelled all over eastern VE3 and western VE2 and activated just over 70 grids, many of which had never been activated before. Amsat ops are always looking for new activations and are very grateful to thos who have the chance to get out there and activate them.
I hope this helps a little. You'll get plenty more replies and have lots to sort through soon!
73,
Ken Alexander (VE3HLS) So Phisai, Thailand Blog: bueng-ken.com
On Sun, Jun 16, 2019 at 2:44 PM Martin Cooper via AMSAT-BB < amsat-bb@amsat.org> wrote:
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so not limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
10 dBi gain antennas have enough 3 dB beamwidth that you can fixed EL at 15 deg, and still have good horizon gain (where it is most needed), and only see loss directly overhead for a 20 or 30 sec period (Might even be shorter). See Bob Bruninga's posting about how this works, it is VERY informative. Applies only to LEO birds.
I am about to use an EAntenna with 5 el on 2m, 8 el on 70cm, with specified gain of 10 dBi
73, N0AN Hasan
On Sun, Jun 16, 2019 at 12:19 PM Kenneth P Alexander via AMSAT-BB < amsat-bb@amsat.org> wrote:
Hi Martin,
I think you've analyzed your situation pretty well when it comes to numbers of elements, beamwidths, etc. A few thoughts:
- if you can try a few satellite passes from around your property with a
handheld yagi, like an Arrow just gain a little first hand experience to see what your minimum elevations are going to look like.
- you might be surprised to find that some houses are more "transparent"
to VHF/UHF signals than others. There are several ops here who regularly work satellites with portable antennas from inside their houses. Don't consider every obstacle to be impenetrable.
With all that said, if I was in your position I'd go for a 3 or 4-element 2m yagi and I'd go to the extra trouble of getting crossed yagis so you can use circular polarization to reduce signal fading. For 70 cm the 7-elements on my Arrow handheld antenna has always been sufficient, and go for crossed yagis again. If you think the trees will really be a problem then go with 4 elements on 2m and a few extra on 70 cm, but realize that if you're buying commercial antennas you're stuck with what the sellers offer. This is about as much as I'd want to swing around with an inexpensive azimuth rotator (You didn't say what kind of rotator it was)
Finally, my antenna situation at home was even more awful than yours. My back yard was smaller than my living room and it was surrounded by 3-storey townhouses on all sides. I decided to become a rover and it was the most adventure-packed 2 years of my life! I travelled all over eastern VE3 and western VE2 and activated just over 70 grids, many of which had never been activated before. Amsat ops are always looking for new activations and are very grateful to thos who have the chance to get out there and activate them.
I hope this helps a little. You'll get plenty more replies and have lots to sort through soon!
73,
Ken Alexander (VE3HLS) So Phisai, Thailand Blog: bueng-ken.com
On Sun, Jun 16, 2019 at 2:44 PM Martin Cooper via AMSAT-BB < amsat-bb@amsat.org> wrote:
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so not limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
Opinions
expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Thanks very much, everyone, for all of the feedback and suggestions. Much appreciated!
Now to figure out how to adjust the DK7ZB designs slightly for satellite frequencies...
Martin. KD6YAM
On Sun, Jun 16, 2019 at 7:32 AM Martin Cooper kd6yam@amsat.org wrote:
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so not limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM
Why not an LFA from G0ksc?
I think is a good option
73's from EA5WA Juan Carlos
En 17 jun. 2019 19:21, en 19:21, Martin Cooper via AMSAT-BB amsat-bb@amsat.org escribió:
Thanks very much, everyone, for all of the feedback and suggestions. Much appreciated!
Now to figure out how to adjust the DK7ZB designs slightly for satellite frequencies...
Martin. KD6YAM
On Sun, Jun 16, 2019 at 7:32 AM Martin Cooper kd6yam@amsat.org wrote:
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so
not
limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Hi Juan Carlos,
Good question. There are a few reasons I'm leaning towards the DK7ZB designs. No doubt others will have differing opinions, and I'd be more than happy to hear them.
* The G0KSC antennas are based on an aluminum boom, whereas the DK7ZB PVC designs are based on a PVC boom (duh!). For a given design (e.g. 5-el 2m), the boom is also slightly longer in the G0KSC design. Those factors mean more weight. I want to keep weight to an absolute minimum to avoid having to deal with stronger cross-boom, stronger mast, stronger rotator, etc.
* Related to the aluminum boom, G0KSC makes quite a fuss about the importance of insulators, about the importance of the insulator design, and about the materials used to make the insulators. He even includes links to commercial insulators. Going with a PVC boom, this is a non-issue, since there's no need to insulate the elements from the boom.
* G0KSC provides a design that is built with 10mm diameter tubing. DK7ZB provides measurements for several diameters, from 2.4mm to 8mm. This gives me the option to use narrower (thus both lighter and cheaper) material for the elements. If I build X-pols, that's twice as many elements, so it matters.
* A while ago, I built an IOio antenna, so I'm quite familiar with having to use a pipe bender to get the tubing bent correctly. It's not easy (at least, it wasn't for me) to get the curves in exactly the right places, trying to measure from the center of one curve to the start of where to bend the next one. Also, with 3/16" tubing, which I used for the IOio, it wasn't too big a deal to twist the tubing when I didn't get two corners exactly parallel to each other. With the larger tubing of the G0KSC design, though, that would be harder. (This is evidenced by the fact that G0KSC even sells loop ends, noting that "The most difficult part of building an LFA Yagi is bending the Loop Ends and getting them right!".
So, in short, the DK7ZB designs seem, to me, simpler to build, possibly less error-prone, and will give me very lightweight options, even if I build X-pols.
Martin. KD6YAM
On Mon, Jun 17, 2019 at 12:49 PM Juan Carlos Reig ecoalfa5wa@gmail.com wrote:
Why not an LFA from G0ksc?
I think is a good option
73's from EA5WA Juan Carlos En 17 jun. 2019, en 19:21, Martin Cooper via AMSAT-BB amsat-bb@amsat.org escribió:
Thanks very much, everyone, for all of the feedback and suggestions. Much appreciated!
Now to figure out how to adjust the DK7ZB designs slightly for satellite frequencies...
Martin. KD6YAM
On Sun, Jun 16, 2019 at 7:32 AM Martin Cooper kd6yam@amsat.org wrote:
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so not limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
The EAntenna is a DK7ZP design, 5 EL on 2m, 8 EL on 70cm single feed, designed for LEO sats. 73, N0AN Hasan
On Mon, Jun 17, 2019 at 12:21 PM Martin Cooper via AMSAT-BB < amsat-bb@amsat.org> wrote:
Thanks very much, everyone, for all of the feedback and suggestions. Much appreciated!
Now to figure out how to adjust the DK7ZB designs slightly for satellite frequencies...
Martin. KD6YAM
On Sun, Jun 16, 2019 at 7:32 AM Martin Cooper kd6yam@amsat.org wrote:
I'm contemplating building a couple of yagis, possibly even crossed ones, and putting them up at fixed elevation (i.e. az-only rotator). What I'm unclear about is how many elements to consider.
My location is really pretty dreadful for seeing sky. There's a big hill to the NE that restricts me to above 40 degrees in that direction. I'm in a single-storey house, with neighbouring two-storey houses to the NW, SW, and S. In between all that, there are other single-storey houses, and trees in most of the gaps between houses. I can't afford to put up a tower (and it could never get above the hill anyway), so I'm looking at not too much above my roofline.
To at least get through the trees, I'd think more elements would be better. But more elements narrows the beam, and at fixed elevation, that, at some point, will restrict even further how much of the sky I can play with.
I'm looking for thoughts on how many elements would be recommended, and how many would be too many, for a fixed elevation, both for VHF and UHF. Ultimately, I'd like to be able to get on the linears, so not limited to the FM sats. Any thoughts would be much appreciated.
Thanks in advance.
Martin. KD6YAM
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
participants (5)
-
Hasan al-Basri -
Juan Carlos Reig -
Kenneth P Alexander -
Martin Cooper -
Pedro Converso