Re: QO-100 Finally!


Ryan Butler
 

Might check out this page:


It's for EME but same band,same principal, took one of these $5 LNBs and modified it with an SMA jack instead of the crystal to inject something stable from the shack for the LO.

Ryan, NF0T


On Fri, Apr 2, 2021 at 6:47 AM Simon Brown <simon@...> wrote:

Yes,

 

That’s what I thought. It would be nice to have a more stable LNB but I’m not going to build a POTY at the moment, no time.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Matthias Bopp
Sent: 02 April 2021 12:25
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] QO-100 Finally!

 

Hi Simon,

 

forget those BS numbers of 0.1dB noise figure for LNBs.

 

If you just look up the NF of the transistors used in the LNBs they are typically above 0.5dB at 11GHz.

 

I would guess your LNB has a noise figure of about 0.8dB or worse.

 

Which is still a good number for a PLL based low noise downconverter which costs less than 10 Euros.

 

Kind regards

 

Matthias

 

www.dd1us.de

 

 

Von: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> Im Auftrag von Simon Brown
Gesendet: Freitag, 2. April 2021 12:40
An: main@SDR-Radio.groups.io
Betreff: Re: [SDR-Radio] QO-100 Finally!

 

Ah,

 

My LNB has a NF of 0.1dB (sceptical).

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Simon Brown
Sent: 02 April 2021 11:39
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] QO-100 Finally!

 

Mike,

 

I see 5 to 6dB. I can’t put 18v into my LNB for vertical polarisation, that’ll be the main problem.

 

I can probably squeeze 1 dB more out of my system, I may do that if I ever have time.

 

What’s the NF for a LNB? I’m using the Single Opticum LSP-02G.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Mike Willis
Sent: 02 April 2021 09:57
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] QO-100 Finally!

 

I can receive my own DATV signals sent with under 1 watt. I have a 2.4m dish, That is equivalent to 4W for a 1.2m dish so Simon will have enough EIRP. On receive the difference between a 2.4m and 1.2m dish is under a dB. This is because you are receiving the transponder noise floor and the link limited by the SNR on the uplink. A 30m dish would only be a dB better. Diminishing returns. Simon's dish is in between these so should be getting around 11 dB MER on the DATV beacon. There are various reasons this might not happen, dosh pointing and focus being two but phase noise being a third. Knowing what he has I would think the dish might not be totally optimised. It is easy to tell, measure the noise floor of the narrow band transponder relative to the band just below, there should be an uplift. for me it is nearly 10 dB. for a 1.2m dish it should be more than 4 dB, for Simon perhaps 6 dB.


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