s-band
Member
- Joined
- Feb 7, 2016
- Messages
- 1,252
- Reaction score
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- Points
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- My Satellite Setup
-
1.5m IRTE PF, Invacom SNF-031, TBS6983,
Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El (being refurbished), 1.8m Precision PF with Bullseye Ku LNB or various C & X bits
- My Location
- Essex
@sat-tv-fan This is how I started on Ka Ka with Prodelin/Viasat 1.2m Band B
It's stil the cheapest way of getting Newsnet that I know of. In order of difficulty:
1 Get a Gilat AN8002 ODU (outdoor unit) form an old broadband set-up, remove the polariser. Use only the RX port (ignore the TX it won't do anything). This works but the ODU is heavy. Total cost ~£30 for ODU + £50 for a 1.2m offset, less if you are lucky. The dish that comes with the ODU is too small for Newsnet.
2 Remove the LNB and attach the feed directly (see link above). This gets you another dB or so but it's no longer waterproof (look for @John posts to waterproof it)
3 Tune the filter better at 18.5GHz by adding a piece of 2mm thick PTFE over the top (shaded red in picture). You can see what's happening by looking at the noise level vs. frequency. The resulting response is not flat but improves Newsnet by 2-3dB. You can get a bit more with other tweaking but it's physically more awkward.
4 Replace the crystal with 27MHz one to move the LO to 17280MHz (shifts the IF into the normal band)
Note: options 1-3 put the IF frequency of Newsnet 18557 at 307MHz so you need a tuner that goes that low e.g. TBS 6983/6903.
Also, have a look at @John and my other posts mentioning "Gilat".
It's stil the cheapest way of getting Newsnet that I know of. In order of difficulty:
1 Get a Gilat AN8002 ODU (outdoor unit) form an old broadband set-up, remove the polariser. Use only the RX port (ignore the TX it won't do anything). This works but the ODU is heavy. Total cost ~£30 for ODU + £50 for a 1.2m offset, less if you are lucky. The dish that comes with the ODU is too small for Newsnet.
2 Remove the LNB and attach the feed directly (see link above). This gets you another dB or so but it's no longer waterproof (look for @John posts to waterproof it)
3 Tune the filter better at 18.5GHz by adding a piece of 2mm thick PTFE over the top (shaded red in picture). You can see what's happening by looking at the noise level vs. frequency. The resulting response is not flat but improves Newsnet by 2-3dB. You can get a bit more with other tweaking but it's physically more awkward.
4 Replace the crystal with 27MHz one to move the LO to 17280MHz (shifts the IF into the normal band)
Note: options 1-3 put the IF frequency of Newsnet 18557 at 307MHz so you need a tuner that goes that low e.g. TBS 6983/6903.
Also, have a look at @John and my other posts mentioning "Gilat".
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.... here's what it would look like for option 1. , which is the easiest thing to do, mounted on a CM 1.2 test dish earlier on in the year to document it's performance before any mods are done to it. Removed the original poloriser and just re-bolted the scalar feed to the main ODU lump and it does work pretty good without having to do any internal mods on the Gilat unit. It would need a decent 1.2 Offset dish to be able to support the weight though as Graham said.
