1.42 GHz Cantenna Beamwidth ?

[Martin Pepe]

Team,

  Can anyone detail the expected beamwidth of a cantenna designed for 1.42 GHz ?

I have a team of undergrad engineers working on a 1.42 GHz design for H1 hydrogen.

They are using a Nooelec LNA tuned for 1.42 & a SDR receiver.

  Presently they are looking into various antenna designs.

1) A standard horn design is disadvantaged here in western New York (WNY) due to it filling with snow. :-(

2) A large solid dish ( ~ 2 M) is also not optimum due to wind loading.

So that seems to leave the following;

3) A custom Yagi LP designed for 1.42 GHz.

4) A modified DTV (Dish TV) type dish (~ 1.5' x 2').

5) A grid type parabolic dish.

The discussion presently, has been possibly using a cantenna optimized for 1.42 GHz as the sub feed for items 4 or 5. That being said, what should be the expected beamwidth of said 'can' ?

Attached please find two images;

 a) A plot of the optimum cantenna response @ 1.42 GHz, showing the LNA saw filter bandwidth imposed on the plot.

 b) An image of the cantenna diagram with three possible divergences (bandwidth sensitivity);

       1) Parallel Sensitivity (pseudo collimated  ===) Probably not likely ?

       2) A divergence angle of 132* (degrees), when calculated from the 1/4 w stub location.

        3) A slightly smaller angle (116*) when calculated from the back of the can resonator.

Getting this right is important if one is expected to use it as a sub-feed to maximize response & minimize noise & side lobes to either of the two main antennas.

Has anyone had any experience with this type of work?

A full (excel) worksheet is available for perusal, for serious inquiries, not included here for size/space reasons.

Thanks in advance for your time & efforts.

Sincerely,

Martin Pepe

Cloudy Skies ? Switch to a LONGER Wavelength !

Adjunct Faculty, Multidisciplinary Senior Design Program

Kate Gleason College of Engineering

Rochester Institute of Technology

[Marcus D. Leech]

A few comments.

A "cantenna" I assume you're referring to a open circular waveguide with a coax transition near the back.  This will have a beam width of about 100deg or thereabouts.

A horn antenna of perhaps 1-1.2m opening aperture will be good, and you can deal with the filling-with-snow issue using a chunk of coroplast over the opening.
  That will attenuate the incoming signal only very very slightly.  Granted, when it gets covered with snow, you'll have to clear the snow off, but won't have to
  dig it out of the horn.

Wind loading is always an issue, and you just need to build a suitable support structure for a dish of any size if you're using a dish.  CCERA did their 21cm sky-map using
  a 1.65m dish on a reasonably-stout support structure on the roof of a building, weighed down with many concrete blocks.

CCERA deals with snow all winter:



You have to build your support structures strong enough to withstand both wind and snow-loading.  DIY radio astronomy requires a certain amount of
  "can do" attitude and skill in disciplines other than what you might expect.  Get comfortable with pouring concrete and making strong mechanical structures, etc...

[Anthony]

Yep, you learn fast how to pour concrete, hardest part is getting the cement dropped off, if your situated up on a hill top, to steep for trucks. 

DIY, is a must in this complex hobby! That is one thing among others to get use to. 

--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/738b2099-3da8-9f6e-afc0-94bd3ced5642%40gmail.com.

[Marcus D. Leech]

On 2022-03-13 17:32, Anthony wrote:

Yep, you learn fast how to pour concrete, hardest part is getting the cement dropped off, if your situated up on a hill top, to steep for trucks. 

DIY, is a must in this complex hobby! That is one thing among others to get use to.

We had to mix our own concrete in small batches, a few bags at a time, for the support pads for the dishes at the main CCERA site.  This also involved
  us learning about rock drills and anchor epoxy.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAKU65Ty50XEuYQGydp9ECgv8eGNa3kMTPsCMxwAdEEX-LVOHzw%40mail.gmail.com.

[Anthony]

Now that's, DIY!

😁

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/d481ef78-8b52-ac61-a4b5-c83e588fd23f%40gmail.com.

[Marcus D. Leech]

On 2022-03-13 21:32, Anthony wrote:

Now that's, DIY!

😁

Also taught myself how to weld.

People discover this and say "Oh, you're a welder?!"  To which I must honestly reply "no, I'm someone who welds."

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAKU65TwsFH9JiQGyxivNZC0DjuH%3DWe8Vh8JDmYi-CWiqTPwPUw%40mail.gmail.com.

[Hamish Barker]

Also known as metal hot glue. 🙂

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/206ebd62-5f28-368f-68cf-3ecfdee251bc%40gmail.com.

[fasleitung3]

Hi Martin,

Please find attached the measured beam profile of a cantenna with a diameter of 150 mm. Please note that this is not the far field profile but rather the profile you will encounter at a typical distance between cantenna and a dish. In this particular case, the cantenna is used as a feed for a 1.2-m dish with a 0.5 f/D ratio, so the distance was 60 cm.

I have also attached a (relative) frequency response of this feed. The lenght of this cantenna is 45 cm, the low frequency cutoff will become sharper if the cantenna is longer.

With respect to snow, I my experience a grid type parabolic antenna will collect practicaly the same amount of snow compared to a solid dish. At least this is the case in our area where snow tends to be on the wet side.

Best regards,

Wolfgang

--

--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/98232655-623c-4b23-b626-a2adcaadcb43n%40googlegroups.com.

[Shef Robotham]

or “metal splashing”,,,, 

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_K_HNw-P3KKO%2B7qzpOaBo_bW96sOvf3EZvfKGTcXHu_AQ%40mail.gmail.com.

[Anthony]

🤣

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_K_HNw-P3KKO%2B7qzpOaBo_bW96sOvf3EZvfKGTcXHu_AQ%40mail.gmail.com.

[Shef Robotham]

I believe 4NEC2 has a ‘cantanna’ utility so making a model should be fairly easy,,,, The probe needs to be inserted,,,, and if the cantanna length and diameter and probe position and length set up using variables, the ‘antenna’ can be optimized.

Later

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAKU65Ty27BzEEG4dZz3S0Sm9njapu-DpTfYOJ%2BaoOe_V6s-PTQ%40mail.gmail.com.