WXSat proof of concept

[Analoguesat]

That dual wire antenna is strictly to prove the concept works. (Get some sort of live image downloaded)

Once thats happened & I know the system works Ive got the summer to play with improving the antenna design - in amongst setting up the new dish farm.

 

[Terryl]

I'm going to try the "S" bend approach as I mentioned to Chris1979 in one of my posts above, this may work out, I have some stainless steel welding rods to play with.

 

[Archive-8]

I'm going to try the "S" bend approach as I mentioned to Chris1979 in one of my posts above, this may work out, I have some stainless steel welding rods to play with.

Yes I have mine in the s shape now. The pi has stopped working for a day or so.

I later found out it was due to no ntp server setup.

I have sorted that out now, and will check the pictures.

 

[Archive-8]

This one about the best of them.

 

[Analoguesat]

^^^

Thats no good - its dark & you cant see any weather!

 

[Archive-8]

^^^

Thats no good - its dark & you cant see any weather!

I know, hopefully I can sort something a bit better.

 

[Analoguesat]

I know, hopefully I can sort something a bit better.

You need a daylight pass

 

[Terryl]

It looks like NOAA 15 will be coming right over the UK in about 15 or so.

NOAA 15 RX freq =137.6200 MHz.

Now for some info, I have improved my antenna system bu going to a 1/2 wave setup, this makes it look like a cats whisker type of antenna.

Using Analogs basic design you add two more sets of radials, all cut to the same length as the first, but all have a small bend right at the start where it connects to the coax, (will supply photos later) this bend is 120 degrees on all and the spacing between the main and ground radials is still 120 degrees.

I tried to bend these as I said into an "S" curve but it got messy as to the layout, so they are kept straight.

So the finished design will have two radials sticking up and two radials sticking down, all this is aligned Due North from the center of the antenna.

Worked a bit better but I think I need a wider bandwidth on the receiver.

 

[Terryl]

OK fiddled with the antenna and also used a scanner,a bit better this pass but I still see some drop out from the South and a bit of speckling due to the receiver bandwidth, I may have to fork out some cash and get a dongle for my PC, and one have some ideas on this??

In the $25 to $390 dollar range would be nice as the property taxes are due this month.


The speckling you see at the bottom of the photo is due to the directional problems of the antenna, the speckling on the center right is due to receiver IF bandwidth, needs to be wider. (35 KHz or better)

 

[Terryl]

OK kids, I tried out two antennas types this week, too bad we cant record an RF signal as it takes time for these satellites to come over.

The first one was a cats whisker antenna, this uses two 1/4 wave radials and two 1/4 wave ground reflectors, all bent to 120 degrees between them all, and orientated due North/South.

The second was a modified Discone antenna, this consisted of the bottom ground plane reflectors (left intact) and the secondary active section setup for a half wave at 137.5 MHz (horizontal section), then two circularly polarized radials at a half wave set to 137.5 MHz.

Of the two the cats whisker antenna out performed the modified Discone by at least 50%.

I wish I had the RF cage and test gear from back in my antenna days, but sadly no more.

This is the cats whisker.



And this is the modified Discone.



This before mounting on the support mast.

 

[Analoguesat]

Well it was a lousy pass, I knocked the settings whilst I was watching it, the antenna is blocked by the house for any northern part of the track and the location appears to be 400 miles too far south.......

But I got something! There is a definite hint of cloud out to the south west

 

[Terryl]

What dongle are you using, and what program to decode it?

 

[Analoguesat]

The dongle case is branded

NooElec
R820T & DVB-T
NESDR mini

and its black plastic

SDRSharp as the main bit of software.
One of the free vitrtual audio cables to pipe the audio into WXtoImg

 

[Terryl]

Looks like you don't have enough signal to the dongle, what coax did you use?

I used RG-8X down to the receiver, with a UHF to BNC adapter at the scanner, I'm looking at this for a dongle.

https://www.amazon.com/dp/B01HA642SW/ref=sspa_dk_detail_0?psc=1

but will have to craft up a UHF female to SMA pigtail.

 

[Archive-8]

@Terryl what did you make the cats whisker from?

I have just come across a website selling turnstile antenna for wx

http://www.geo-web.org.uk/shop.php

They want £80 for it. I just wondered if you had considered that type of aerial?

 

[Terryl]

I made a turnstile antenna but do not have the proper connection to terminate it properly, so I just soldered the coax directly to the radials, it didnt work out as good as the cats whisker.

I'm using some stainless steel welding rod to make up the other antennas,(cats whisker) I had some left over from a different project.

It's the best to use as it will not corrode in the weather.

If you have an old TV antenna lying around you could use the radials from it if they are 55 CM or longer.

And the modified Discone did not work out that good, the cats wisker so far is the best one tested, still working on other types.

 

[Terryl]

The cats whisker also uses a piece of old nylon cutting board as an insulator, also a couple of #8 AWG copper lugs for electrical contacts.



The coax is soldered to these lugs, the lugs are bolted to the nylon base, the ground side lug has a bolt (stainless steel hardware used for this) long enough to mount the assembly to an "L" bracket and a couple of small radiator hose clamps hold it to the mast, this was a proto type and I'm working on a better connection for the coax.

 

[Archive-8]

Also found a j-pole

http://www.jpole-antenna.com/shop/railroad-band-noaa-weather-160-162-mhz-j-pole-antenna/

 

[Terryl]

Thats not for the satellites but for the weather marine forecasts.

The satellite we are looking at are at 137 to 138 MHz.

 

[Analoguesat]

Thats a bit more like it. Again not a particularly favourable pass, and remember Im using that crap antenna sitting on the bench outside the south facing window.

Location cross fixed - now to work out how to process it to get the weather on it