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DISH SETUP: Single sat, Multi-Sat & Motorised
X band Milsat and Deep Space Set-up
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<blockquote data-quote="s-band" data-source="post: 1060066" data-attributes="member: 407744"><p>This is what I based my helical feed on <a href="https://ieeexplore.ieee.org/document/1447513" target="_blank">Modifications on the axial-mode helical antenna - IEEE Journals & Magazine</a> (paywalled)</p><p>If you don't have an account, you'll need to use your favourite search tool to find a copy.</p><p></p><p>I'd be wary of some of the wide band, Far Eastern "LNA"s. They may work but the NF can go through the roof at the high end. It can also be a problem having such high gain out of band. Have a look at the data from Minicurcuits, Qorvo etc for actual figures. If you can find one, a used Miteq LNA is safer. They can be as low as £40-60 but working out the spec can be hard and Ebay listings can be creative. The ones I bought are AFS3-08500960-15-10P-4 which are meant to be 8.5-9.6GHz <1.5dBNF and work well down to 7GHz with a measured NF ~1.3dB.</p><p></p><p>The easiest WG feed is a 1/4 wave probe in the guide as per most LNBs. You need to scale the probe length to take account of the wavelength in the guide. <a href="https://www.microwaves101.com/encyclopedias/waveguide-mathematics" target="_blank">Waveguide Mathematics</a></p></blockquote><p></p>
[QUOTE="s-band, post: 1060066, member: 407744"] This is what I based my helical feed on [URL="https://ieeexplore.ieee.org/document/1447513"]Modifications on the axial-mode helical antenna - IEEE Journals & Magazine[/URL] (paywalled) If you don't have an account, you'll need to use your favourite search tool to find a copy. I'd be wary of some of the wide band, Far Eastern "LNA"s. They may work but the NF can go through the roof at the high end. It can also be a problem having such high gain out of band. Have a look at the data from Minicurcuits, Qorvo etc for actual figures. If you can find one, a used Miteq LNA is safer. They can be as low as £40-60 but working out the spec can be hard and Ebay listings can be creative. The ones I bought are AFS3-08500960-15-10P-4 which are meant to be 8.5-9.6GHz <1.5dBNF and work well down to 7GHz with a measured NF ~1.3dB. The easiest WG feed is a 1/4 wave probe in the guide as per most LNBs. You need to scale the probe length to take account of the wavelength in the guide. [URL="https://www.microwaves101.com/encyclopedias/waveguide-mathematics"]Waveguide Mathematics[/URL] [/QUOTE]
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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
X band Milsat and Deep Space Set-up
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