whipper_snapper
Well-Known Member
You may remember an earlier post about receiving images from NOAA sats for weather forecasting. I was getting respectable results with a vertical VHF antenna intended for 144MHz (sats are on 137MHz).
I spent today making a quadrifilar helix (QFH) antenna based on this description by G4ILO .
It cost me nothing except £1 for 2m of PVC pipe for the main strut. The only other bits I used was some RG58 coax I had lying around and some cable ties. I made the 6 cross pieces by chopping-up 6 of SWMBO's plastic clothes hangers (OK, that may cost me when she finds out).
It went together very easily, except that I built it backwards first time due to ambiguity (or my stupidity) in the description. With the elements wound in reverse I got absolutely zip (when I realised what I had done, that was in fact a very good sign). But once that was corrected, there was a huge increase in performance over the vertical.
Here are 3 images with different image processing from the first pass after the new antenna went up. I reckon they now begin to give useful weather information to add to other sources. They would certainly help dodge a TRS!
These are compressed, the originals are about 1Mb. The improvement over the old antenna is very obvious. There is far more dynamic range which shows clouds and much more 'depth' to the features.
(Thanks Capt. Slarty for suggesting this)
(Satellite: NOAA 15
Pass Start: 25 May 2008 14:20:26 GMT
Pass Duration: 15:14
Elevation: 73
Azimuth: 77
Solar Elevation: 17.3
Direction: northbound
Creation Time: 25 May 2008 14:21:03 GMT
Satellite Type: NOAA
Channel A: 2 (near infrared)
Channel B: 4 (thermal infrared)
Enhancement: top picture MSA-precip, 2nd HVCT-precip, 3rd HVC-precip
Ground Station: Nairobi, Kenya
Latitude: -1.267
Longitude: 36.722
Altitude: 2000.0)
I spent today making a quadrifilar helix (QFH) antenna based on this description by G4ILO .
It cost me nothing except £1 for 2m of PVC pipe for the main strut. The only other bits I used was some RG58 coax I had lying around and some cable ties. I made the 6 cross pieces by chopping-up 6 of SWMBO's plastic clothes hangers (OK, that may cost me when she finds out).
It went together very easily, except that I built it backwards first time due to ambiguity (or my stupidity) in the description. With the elements wound in reverse I got absolutely zip (when I realised what I had done, that was in fact a very good sign). But once that was corrected, there was a huge increase in performance over the vertical.
Here are 3 images with different image processing from the first pass after the new antenna went up. I reckon they now begin to give useful weather information to add to other sources. They would certainly help dodge a TRS!
These are compressed, the originals are about 1Mb. The improvement over the old antenna is very obvious. There is far more dynamic range which shows clouds and much more 'depth' to the features.
(Thanks Capt. Slarty for suggesting this)
(Satellite: NOAA 15
Pass Start: 25 May 2008 14:20:26 GMT
Pass Duration: 15:14
Elevation: 73
Azimuth: 77
Solar Elevation: 17.3
Direction: northbound
Creation Time: 25 May 2008 14:21:03 GMT
Satellite Type: NOAA
Channel A: 2 (near infrared)
Channel B: 4 (thermal infrared)
Enhancement: top picture MSA-precip, 2nd HVCT-precip, 3rd HVC-precip
Ground Station: Nairobi, Kenya
Latitude: -1.267
Longitude: 36.722
Altitude: 2000.0)