[amsat-bb] Re: Using AO-40 in Rx for Ham TV?

[Bill Ress]

Hi Andy and Graham,

To provide a "visual" understanding of what the HAMTV spectrum will look 
like I have included a screen shot of the HAMTV 2.4 GHz test source 
using Digilite and built by Kerry N6IZW taken on my spectrum analyzer. 
Note the first two spectrum nulls are at +/-1.3 MHz and approximately 
-43 dBc. Hence as Graham point out the spectrum BW is over 2 MHz (2.6 
MHz between the first nulls). This will be the same spectrum whether a 
"black" picture is being sent or a full video scene.

Now to the question of what you will see with a "wideband" SDR like the 
NooElec. I have taken screen shots of what you will see using a 2.4 Msps 
SDR (I was using SDR# and the NooElec SDR) driven by Kerry's 2.4 Ghz 
test source feeding a 2.4 GHz to 144 MHz down converter (the SDR tuned 
to 144 MHz) and run at various input signal levels. I'm putting together 
the "report" now but the upshot pf the tests indicated that while you 
cannot decode any video or audio, you will be able to detect (see) the 
HAMTV noise spectrum as shown below.

Hope this helps clarify what the signal will look like.
Test HAMTV Spectrum

Regards...Bill - N6GHz

On 1/27/2014 8:41 AM, Graham Shirville wrote:
> Hi Andy
> In a word..NO...the signal even without any actual video content is still around 2MHz wide.
> If you have simple rtl type dongle you might be able to see the signal tho
> 73
> Graham
>
> -----Original Message-----
> From: "andy thomas" <andythomasmail at yahoo.co.uk>
> Sent: ‎27/‎01/‎2014 16:25
> To: "amsat" <amsat-bb at amsat.org>
> Subject: [amsat-bb] Using AO-40 in Rx for Ham TV?
>
> I was just wondering if the AO-40 LNBs connected to a Funcube dongle (and a bias tee for power) would recieve the carrier (is there one on DATV) from the ham TV test transmisisons?
>
>
> If so, that should be a project that could show AOS/LOS , power levels etc, even if it's a black screen being sent: after all, it's RF.
>
> maybe this has been thought about before? But I could use my converted blue lnb...
>
>
> 73 de andy g0sfj
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb