Iridium antenna - patch vs helical

[andy]

Many of you are using Iridium RockBlock for communication. I am going to use an external antenna, so I am comparing two antennas - patch and helical:

https://www.rock7.com/shop-product-detail?productId=15

https://www.rock7.com/shop-product-detail?productId=20

In the description they say that helical is better in "marginal conditions". When I tried both antennas outside, the signal quality is almost the same, so I am not sure what is the advantage of the helical antenna. The antenna will be mounted on top of the hull and covered with fiberglass, because the hull is carbon fiber (blocking the signal). See the picture below how both antennas would look like:

If the helical antenna is just slightly better than patch, I would go with patch, because patch is low-profile, and therefore more robust (the helical antenna is sticking from the hull and may be hit by a floating object). But if it is a lot better, i.e. less missed updates in bad weather, I would go with helical. What do you think?

[Colin Sauze [cos]]

Andy,

Looking at the datasheets for each (http://www.farnell.com/datasheets/1937456.pdf and https://www.rock7.com/downloads/IAA01121111_Patch.pdf).

The polar plot of the antenna radiation pattern shows the patch antenna having a wider angle signal emitting from it. This means the signal will spread more widely on the patch antenna. I think this will be a good thing as the satellite isn't guaranteed to be directly overhead and if your boat is rolling and pitching you're increasing the chance of the signal going in the direction of the satellite. However the signal will be a bit less concentrated so the amount of power in the received signal will be less. I can't find a directly comparable gain measurement in the datasheets to actually put a number on this.

For receiving at the boat end the same rules apply in reverse, but the satellite has a more powerful transmitter than you do so i'd worry more about it receiving your signal than you receiving its signal.

If you're finding them about equal then perhaps other constraints such as cost, size and the potential to snag rigging on the antenna is more important.

Colin.



________________________________________
From: microt...@googlegroups.com [microt...@googlegroups.com] on behalf of andy [andrej...@gmail.com]
Sent: 25 November 2017 10:47
To: Microtransat
Subject: [microtransat] Iridium antenna - patch vs helical

Many of you are using Iridium RockBlock for communication. I am going to use an external antenna, so I am comparing two antennas - patch and helical:
https://www.rock7.com/shop-product-detail?productId=15
https://www.rock7.com/shop-product-detail?productId=20

In the description they say that helical is better in "marginal conditions". When I tried both antennas outside, the signal quality is almost the same, so I am not sure what is the advantage of the helical antenna. The antenna will be mounted on top of the hull and covered with fiberglass, because the hull is carbon fiber (blocking the signal). See the picture below how both antennas would look like:

[https://lh3.googleusercontent.com/-N4smyHEVIHY/WhlIpBoW1DI/AAAAAAAAAEQ/da_FtyhnwPcBuqTvTLpZkLfJ34u__V2MACLcBGAs/s320/patch_vs_helical.jpg]<https://lh3.googleusercontent.com/-N4smyHEVIHY/WhlIpBoW1DI/AAAAAAAAAEQ/da_FtyhnwPcBuqTvTLpZkLfJ34u__V2MACLcBGAs/s1600/patch_vs_helical.jpg>

If the helical antenna is just slightly better than patch, I would go with patch, because patch is low-profile, and therefore more robust (the helical antenna is sticking from the hull and may be hit by a floating object). But if it is a lot better, i.e. less missed updates in bad weather, I would go with helical. What do you think?

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Prifysgol y Flwyddyn ar gyfer Ansawdd Dysgu - The Times & The Sunday Times 2018.

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University of the Year for Teaching Quality - The Times & The Sunday Times 2018.

[andy]

Thanks Colin, it leads me to the next experiment - I will try pitching and rolling both antennas next to a building and I will log the signal quality. 

On Saturday, November 25, 2017 at 3:01:47 PM UTC+1, Colin Sauze [cos] wrote:

Andy,

Looking at the datasheets for each (http://www.farnell.com/datasheets/1937456.pdf and https://www.rock7.com/downloads/IAA01121111_Patch.pdf).

The polar plot of the antenna radiation pattern shows the patch antenna having a wider angle signal emitting from it. This means the signal will spread more widely on the patch antenna. I think this will be a good thing as the satellite isn't guaranteed to be directly overhead and if your boat is rolling and pitching you're increasing the chance of the signal going in the direction of the satellite. However the signal will be a bit less concentrated so the amount of power in the received signal will be less. I can't find a directly comparable gain measurement in the datasheets to actually put a number on this.

For receiving at the boat end the same rules apply in reverse, but the satellite has a more powerful transmitter than you do so i'd worry more about it receiving your signal than you receiving its signal.

If you're finding them about equal then perhaps other constraints such as cost, size and the potential to snag rigging on the antenna is more important.

Colin.



________________________________________
From: microt...@googlegroups.com [microt...@googlegroups.com] on behalf of andy [andrej...@gmail.com]
Sent: 25 November 2017 10:47
To: Microtransat
Subject: [microtransat] Iridium antenna - patch vs helical

Many of you are using Iridium RockBlock for communication. I am going to use an external antenna, so I am comparing two antennas - patch and helical:
https://www.rock7.com/shop-product-detail?productId=15
https://www.rock7.com/shop-product-detail?productId=20

In the description they say that helical is better in "marginal conditions". When I tried both antennas outside, the signal quality is almost the same, so I am not sure what is the advantage of the helical antenna. The antenna will be mounted on top of the hull and covered with fiberglass, because the hull is carbon fiber (blocking the signal). See the picture below how both antennas would look like:


[https://lh3.googleusercontent.com/-N4smyHEVIHY/WhlIpBoW1DI/AAAAAAAAAEQ/da_FtyhnwPcBuqTvTLpZkLfJ34u__V2MACLcBGAs/s320/patch_vs_helical.jpg]<https://lh3.googleusercontent.com/-N4smyHEVIHY/WhlIpBoW1DI/AAAAAAAAAEQ/da_FtyhnwPcBuqTvTLpZkLfJ34u__V2MACLcBGAs/s1600/patch_vs_helical.jpg>


If the helical antenna is just slightly better than patch, I would go with patch, because patch is low-profile, and therefore more robust (the helical antenna is sticking from the hull and may be hit by a floating object). But if it is a lot better, i.e. less missed updates in bad weather, I would go with helical. What do you think?


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[andy]

So I understood that even though the helical antenna is better in terms of coverage and reception in bad weather, the patch antenna is more suitable for our application, because it covers a wider angle and the boat is heeling most of the time.

[Dermot Tynan]

On Mon, Nov 27, 2017 at 8:04 AM, andy <andrej...@gmail.com> wrote:

So I understood that even though the helical antenna is better in terms of coverage and reception in bad weather, the patch antenna is more suitable for our application, because it covers a wider angle and the boat is heeling most of the time.

I'll confess I haven't done a lot of research on this, so take the following with a grain of salt. I suspect that the patch antenna is horizontally polarised. A vertically polarised antenna is great for talking to someone in the same plane (on Earth, in other words) but is relatively useless from above, unless it's a simple (low gain) dipole. If it's horizontally polarised, you will see different signal strengths with different compass headings. Looking briefly at the gain plot, it does seem to be quite omnidirectional with around 6dB attenuation off-axis. I know that to pick up signals from the ISS, you need a helical antenna, but those things are focused like a laser on the space station, which is not something you'll be able to do. I would echo what Colin says, and stick with the patch as the boat will probably either be heeled a lot of the time, or rolling. I'm definitely interested in hearing how you get on with your experimentation.

        - Der

--

Dermot Tynan

Kalopa Research

[andy]

Maybe you can help me with another antenna. I want to use a satellite phone for sending pictures from the boat (the one you see in the picture). I would tear down the phone and mount its antenna horizontally under the fiberglass deck, because vertical antenna is prone to damage or snagging. Do you think it makes any difference whether the antenna is mounted horizontally or vertically?

[Colin Sauze [cos]]

Andy,

It will depend on the polarisation of the antenna(s) on the satellite as to whether it matters. If the satellite only has a vertically polarised antenna then it will matter a lot. If the satellite has both then it doesn't matter so much. I don't suppose the manual for the phone says anything about which way to point it?

I know that terrestrial mobile phone antennas have multiple polarisations to cope with people holding their phones in different orientations, but i'm not sure about globalstar.

It should also be noticeable on the signal strength indicator, cross polarisation losses can be around 20dB which should be easily detectable.

Colin.


________________________________________
From: microt...@googlegroups.com [microt...@googlegroups.com] on behalf of andy [andrej...@gmail.com]

Sent: 10 December 2017 20:21
To: Microtransat
Subject: [microtransat] Re: Iridium antenna - patch vs helical

Maybe you can help me with another antenna. I want to use a satellite phone for sending pictures from the boat (the one you see in the picture). I would tear down the phone and mount its antenna horizontally under the fiberglass deck, because vertical antenna is prone to damage or snagging. Do you think it makes any difference whether the antenna is mounted horizontally or vertically?

[https://lh3.googleusercontent.com/-roYOktoDUc4/Wi2WwYFc4fI/AAAAAAAAAFM/3Li0KUjcBykYpNy1RA28PSUjJkl0UpbXgCLcBGAs/s320/phone.jpg]<https://lh3.googleusercontent.com/-roYOktoDUc4/Wi2WwYFc4fI/AAAAAAAAAFM/3Li0KUjcBykYpNy1RA28PSUjJkl0UpbXgCLcBGAs/s1600/phone.jpg>

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[andy]

Great advice, I found a manual for a similar phone and it says that the antenna should be pointing towards the sky. They even made a picture, so it's important.

On Sunday, December 10, 2017 at 9:46:39 PM UTC+1, Colin Sauze [cos] wrote:

Andy,

It will depend on the polarisation of the antenna(s) on the satellite as to whether it matters. If the satellite only has a vertically polarised antenna then it will matter a lot. If the satellite has both then it doesn't matter so much. I don't suppose the manual for the phone says anything about which way to point it?

I know that terrestrial mobile phone antennas have multiple polarisations to cope with people holding their phones in different orientations, but i'm not sure about globalstar.

It should also be noticeable on the signal strength indicator, cross polarisation losses can be around 20dB which should be easily detectable.

Colin.


________________________________________
From: microt...@googlegroups.com [microt...@googlegroups.com] on behalf of andy [andrej...@gmail.com]
Sent: 10 December 2017 20:21
To: Microtransat
Subject: [microtransat] Re: Iridium antenna - patch vs helical

Maybe you can help me with another antenna. I want to use a satellite phone for sending pictures from the boat (the one you see in the picture). I would tear down the phone and mount its antenna horizontally under the fiberglass deck, because vertical antenna is prone to damage or snagging. Do you think it makes any difference whether the antenna is mounted horizontally or vertically?

[https://lh3.googleusercontent.com/-roYOktoDUc4/Wi2WwYFc4fI/AAAAAAAAAFM/3Li0KUjcBykYpNy1RA28PSUjJkl0UpbXgCLcBGAs/s320/phone.jpg]<https://lh3.googleusercontent.com/-roYOktoDUc4/Wi2WwYFc4fI/AAAAAAAAAFM/3Li0KUjcBykYpNy1RA28PSUjJkl0UpbXgCLcBGAs/s1600/phone.jpg>


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[Robin Lovelock]

This is very interesting stuff Andy. I can't help on the antennas's but the relevant page on my site is the "AVL" page on www.gpss.co.uk/chase.htm where near the top you will see mention of the cheap "PocketCam" GSM/GPS/Camera from Longboom in China that I tested last year, as a cheap "throw away" camera, able to send pictures from anywhere with GSM range of a coat. i.e, about 5 miles, based on our old GPS Bottles projects. These work by the user sending SMS to the unit, to triger GPRS data from the camera, to upload the image onto the supporting server in China. The user is then given the URL of the image. Products like this, and PocketCam, cost about 50 GBP (but you must add SD card and SIM card ). I have spare units here, but Team-Joker did not have time to deploy them this year.

Further down my ancient "AVL" page is a section entitled "Communications are important" with links to the various satcomms systems that exploited GPSS, the first being Inmarsat - antennas too big I think. The most interesting could be Thuraya, and I'll paste in a small section from that old page. Graham Avis from Hughes Network Systems (HNS) came over from the USA for our first meeting and gave me that old Thuraya 'phone, that I still have. Some lovely technical collaboration then followed, with a three cornered email dialogue, between myself, HNS and a radio HAM in Baghdad - under Sadaam, and before the 2nd Gulf War. This guy did amazing pioneering work, and I've reason to believe he is alive, well, and operating his HAM station from Baghdad still.

Robin

www.gpss.co.uk

www.gpss.co.uk/chase.htm "AVL" page

from linked "Thuraya" page >>>>>

Thuraya

Thuraya is the arabic word for the constellation of stars known as "The Pleides" or "The Seven Sisters". The Thuraya Satellite Telecommunications Company operate a mobile satellite system and provide handsets that integrate satellite, GSM and GPS. Coverage will extend to 99 countries, spanning Europe,North & Central Africa, Middle East, Central Asia and the Indian Subcontinent. Thuraya's service rollout begins this year. For more information on the company and their services, visit their web site at www.thuraya.com When within GSM coverage, the 'phones can be used with GSM, but can still be used with Thuraya in the most remote of locations not covered by GSM. The GPS within the 'phone provides accurate location, for display on the 'phone, and transmission by SMS text message to another Thuraya or GSM mobile 'phone. An optional data lead is provided, to permit the 'phone to be connected to a Laptop PC running fax software, or GPS Software from a GPSS CDROM.

Early testing of GPSS with Thuraya

In May 2001 HNS purchased a GPSS demonstration licence, and Graham Avis, the HNS-7100 Project Manager, kindly gave Robin Lovelock an HNS-7100 for testing with GPSS. The pictures on this page show a few of the tests being carried out - in Italy, during Robin and his wife June's recent HOLIDAY , and then in Robin's back yard, which is included in the most detailed GPSS Baseline map. Tests conducted so far include voice calls, sending SMS text messages, in-car use with GPSS on a Laptop PC (the mode in which most users will use GPSS), and remote tracking with GPSS. The Po River was a most pleasant test site :-) 

Use of the GPS for Navigation

Here is Robin, below, in his back yard, testing the HNS-7100 directly connected to the Laptop PC running GPSS ......

etc

[andy]

Isn't the GSM range limited to max. 20 miles from the shore?

I see the phone antenna is very sophisticated:

https://youtu.be/uyr1ICZxJYI?t=1607

It's a helical antenna with a separate transmitter and receiver.

[Robin Lovelock]

20 miles sounds really good news for us Andy. Seems very probable, with the GSM antenna up high on the mast. Might depend upon wave height. My 5 miles from the coast is what we achieved all those years ago from the GPS Bottles, VERY low in the water ! We tracked the bottles out from Ramsgate, to about 5 miles. They then reappeared 5 miles off the French coast. We then tracked them up the Belgium coast. and the furthest came ashore near Den Helder in Holland - but we never got it back. I did not have Dick to help me :-)

Robin

www.gpss.co.uk

www.gpss.co.uk/bbcbot.htm last GPS Bottle project, with a link to the earlier one.

Home . GPS . Download . Business . Partners . Contact . Family . AVL . Links . History . AsOnTV . Forum 

the GPS Bottle page

found a strange bottle near the UK south coast ? please click here

from Robin in July 2011: Can it really be 7 years ago that the artist Layla Curtis launched those GPS bottles into the sea ?

We've made some more, for the BBC, based on more recent electronic and GPS tracker products.

When my long-suffering wife June and I were in Sicily, on holiday we got a 'phone call from Helena, a journalist at BBC Radio Solent, who had found this "GPS bottle" page - not to be confused with my hobby page on robot sailing boats. There is a special "Summer Splash" event on the UK south coast starting on 4th July, and lasting several weeks. They hope to launch three GPS bottles. I set up a new "BBC bottle" page, linked from this, as an aid to the BBC, myself, suppliers and friends, communicating and testing the new GPS bottles. You will find it linked from the Where are the bottles ?

from Robin in May 2015: An art exhibition called "Message in a bottle" caught my eye, and this provoked me to add this bit of my own "Art" - created years ago, using one of those bottles used by Layla. It seems I was inspired in squeezing the GPS bottle into a larger one. The label on the "stand", holding the bottle, reads, "GPS Bottle in a bottle - a 'work of art' by Robin Lovelock" :-) The label inside the GPS Bottle reads, "GPS Bottle 4... an Artwork by Layla Curtis..." as in pictures below.

The GPS Bottle Story - from 2004

if you find a GPS bottle please visit www.gpss.co.uk/bottles - also shows latest reported bottle positions. 
to report a bottle find, or see Laylas' GPS Drawing, visit www.fromramsgatetothechathamislands.co.uk

this page updated 1300 Sunday 11th July 2004 UK time

Hi Folks ! the links above will take you to pages automatically updated with the latest GPS bottle positions and to Laylas' web site. This "GPS Bottle Story" page has been changed into what may best be described as a "notebook and diary" of information we used during development of the GPS bottles as part of this Layla Curtis art project. That's Layla on the right, holding GPS bottle 1 and standing with Dominic in front of the "GPS Drawing" at Droit House on 26th May, when the exhibition opened. Dominic is the man behind Laylas' web sites. On the left you can see me, crouched proudly beside GPS bottle 1 where it came ashore at Deal, a few miles south of Ramsgate. This was no big surprise - as you will see below - since it was one of the first to be dropped, and not so far out to sea as the others. This bottle was fixed then re-launched, to help the other four GPS bottles show us how the other smaller 45 bottles holding messages are likely to move with wind and tide. I will end this introduction with some quotes: "The 'message in a bottle' work, by Layla Curtis, is much better than a pickled cow or a pile of bricks" - Robin Lovelock, May 2004. - or as someone else said, "I don't know much about art, but I know what I like" :-)

I hope you enjoy our little "bottle story" and maybe you will be one of those who find a bottle and report its progress to the Chatham Islands :-)

Robin Lovelock 
Sunninghill, May 2004.

On Saturday, 25 November 2017 10:47:05 UTC, andy wrote:

[philip...@gmail.com]

I use RockBlock on my boat, and just use the built-in ceramic antenna. It seems to work fine worked at sea during the week between my boat being launched and recovered. (It also carried on working after my boat was rescued by some fishermen, during which time I suspect is was just lying on its side on the deck of the fishing boat. This would be equivalent to a heel of about 60degrees.) It takes a minute or more to get any message transmitted as you have to wait for a satellite to pass over, so allow for this during any testing. One point to note is that it doesn't take much sea water to block out the radio signals. I tested my phone underwater (in a waterproof box!), and the GPS reception failed with only a few mm of sea water above it. Your antenna is mounted on the deck though, so should be OK. Also note that any external antenna that claims to be waterproof probably isn't, at least not for weeks being submerged. I had a "waterproof" antenna, and it failed after several pond test sessions. I have my GPS and Iridium antenna in the same plastic waterproof box that all the electronics are in: this pokes up above the deck line so is hopefully clear of water most of the time. If it isn't above water level (because of waves), I doubt that the boat is capable of making any progress anyway. Putting everything in the same box removes the problem of having to seal in the cable, and waterproof the antenna. GPS and Iridium don't interfere as they aren't both on at the same time in my system.

Phil

On Saturday, 25 November 2017 10:47:05 UTC, andy wrote: