Author Topic: Homemade 137mhz - 138mhz Weather Sat Antenna?  (Read 6913 times)

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Offline Lord of nothingTopic starter

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Made in Japan, destroyed in Sulz im Wienerwald.
 

Offline CopperCone

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Re: Homemade 137mhz - 138mhz Weather Sat Antenna?
« Reply #1 on: May 13, 2018, 07:57:11 pm »
build a giant horn antenna which you can aim at satellites  :-DD
 

Offline dazz1

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Re: Homemade 137mhz - 138mhz Weather Sat Antenna?
« Reply #2 on: May 13, 2018, 10:49:37 pm »
Hi
 Quadrifilar Helix but not the short fat version.  These are designed to be on a satellite.
You want the taller version like this:

which are designed for terra location.

Dazz
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Offline tautech

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Re: Homemade 137mhz - 138mhz Weather Sat Antenna?
« Reply #3 on: May 13, 2018, 11:20:13 pm »
Hi
 Quadrifilar Helix but not the short fat version.  These are designed to be on a satellite.
You want the taller version like this:

which are designed for terra location.

Dazz
And yet I guy I knew was using squat versions for weather satellite reception to get sea surface temps for the commercial fishing industry and selling his package worldwide. Handmade the antennae were too.  :)
Admittedly his squat version was for marine use but he had test setups on poles in a paddock.

Think he's passed now as I can't find any record of his package on Google now.  :(
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Offline hendorog

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Re: Homemade 137mhz - 138mhz Weather Sat Antenna?
« Reply #4 on: May 19, 2018, 12:44:16 am »
You might get away with one of these, it is a very simple way to start:
https://www.rtl-sdr.com/simple-noaameteor-weather-satellite-antenna-137-mhz-v-dipole/

I built one, and then a low pass filter to try and knock down the very high levels of FM BCB radio here - as I'm quite close to the transmitter.

It does bring in the signal, but not quite well enough to work well in my location. I have a cheap LNA from eBay now and need to try it with that.
 

Offline Lord of nothingTopic starter

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Re: Homemade 137mhz - 138mhz Weather Sat Antenna?
« Reply #5 on: May 19, 2018, 08:06:00 am »
I have this for the Air Band: http://www.sirioantenne.it/en/products/vhf/gp-lb-series
So I would guess just and "specialised" Antenna for the Sat would bring some additional Gain.
Made in Japan, destroyed in Sulz im Wienerwald.
 

Offline Fraser

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Re: Homemade 137mhz - 138mhz Weather Sat Antenna?
« Reply #6 on: May 19, 2018, 12:03:29 pm »
I started out by building, then buying, crossed dipole + reflector antennas for my 137MHz WESAT work. That was back in 1992 when I was in Darwin N.T. When I returned to the UK, the biggest problem was interference from Pager signals at 139MHz. That required better receiver disign rather than a better antenna though. Crossed dipoles work well and are easy to build accurately. The down side of them is that the have a null directly above them.

Over the years the QFH has become popular. I have made them and they do work well. As a first antenna build they can be a little daunting though. I was happy that I started with crossed dipoles and proved my comp,eye receiving system, before trying a QFH. Commercial QFH antennas used to be very expensive when compared to crossed dipoles.

My commercial maritime WESAT system from ICS uses a very high quality crossed dipoles antenna rather than a QFH. That ICS crossed dipoles performs very well indeed, but was very expensive new. There are pro's and con's to both antenna types.

A decent receiver with the correct IF bandwidth is also important for best results. Normal NFM and WFM IF filters found in commercial scanners are far from optimal. A 50kHz IF filter bandwidth is about right.

Fraser



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