Архив за 15.10.2017

WXtoImg overlaying for the wrong satellite

Two NOAA satellites (15 and 18) were passing me nearly at the same. I was recording audio file for NOAA 15, but when I open file in a WXtoImg, it creates overlay for the NOAA 18. I tried altering "created" times of the recording (since WXtoImg bases overlay on this time), but that only shifts entire overlay to the north or south. I checked the Kepler data, and NOAA 18 and 15 are in its database, with correct timings. Does anyone know, can I "shift focus" of WXtoImg, so it will create overlay map for NOAA 15 pass, instead of NOAA 18 pass?

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Comment on Airspy HF+: An upcoming low cost yet high performance HF SDR by Mike

You need to take seriously the need NOT to leave gaps in coverage. Why accept a gap from 31 Mhz to 60 Mhz? Is the 6 meter band irrelevant? No it is not. I won’t buy this for that reason.

Here I sit at work and I get an email…

Here I sit at work and I get an email notification stating that my RTL-SDR has been delivered. Cant wait to get home. I want to hook it up to a raspberry pi, what software do you all recommend?

(RSS generated with FetchRss)

Вариант обработки цвета в AfterShot…


Вариант обработки цвета в AfterShot

Было как то дело решил сфоткать и вот …

Было как то дело решил сфоткать https://vk.com/mytuapse?w=wall-1113580_28455 и вот https://vk.com/mytuapse?w=wall-1113580_40273

Comment on The BIG List of RTL-SDR Supported Software by Triston

Over the past few years this list has helped me immensely! Thanks so much RTL-SDR for all that you do 🙂

RTL-SDR Discussion • How does the image rejection filter in the R820T(2) work?

Reading about the R820T and R820T2, there is something that I find difficult to understand: how do they achieve a variable-frequency image-rejection filter with a -65dB attenuation and very sharp transition?

Suppose, for example, that I tune an RTL-SDR to 903.57MHz. The IF is 3.57MHz so the LO is tuned to 900MHz (assuming a low-side injection) and the bandpass is about 902.5 to 904.5. At those frequencies, the image reject filter needs to have almost no attenuation. From about 900-4.57 to about 900-2.57 (up to 897.43MHz), the image reject filter should have a rejection of 65dB; this is how I understand the data sheet. The filter should be this deep for about 2 or 2.5 MHz (more for 6-8MHz DVB-T transmissions) and should transition to no attenuation a couple of MHz higher.

Is this how things work? Do they really achieve this kind of image rejection and steep transitions?

I ask because I always thought that it is hard to achieve high image rejection when the image and target frequencies are close, and that this is why many receivers have a high first IF, at 45 or 70 MHz, to move the image far out so that it can be filtered easily.

Any insights will be appreciated.

Thanks, Sivan

Statistics: Posted by sivan_toledo — Sun Oct 15, 2017 4:10 pm


RTL-SDR Discussion • How does the image rejection filter in the R820T(2) work?

Reading about the R820T and R820T2, there is something that I find difficult to understand: how do they achieve a variable-frequency image-rejection filter with a -65dB attenuation and very sharp transition?

Suppose, for example, that I tune an RTL-SDR to 903.57MHz. The IF is 3.57MHz so the LO is tuned to 900MHz (assuming a low-side injection) and the bandpass is about 902.5 to 904.5. At those frequencies, the image reject filter needs to have almost no attenuation. From about 900-4.57 to about 900-2.57 (up to 897.43MHz), the image reject filter should have a rejection of 65dB; this is how I understand the data sheet. The filter should be this deep for about 2 or 2.5 MHz (more for 6-8MHz DVB-T transmissions) and should transition to no attenuation a couple of MHz higher.

Is this how things work? Do they really achieve this kind of image rejection and steep transitions?

I ask because I always thought that it is hard to achieve high image rejection when the image and target frequencies are close, and that this is why many receivers have a high first IF, at 45 or 70 MHz, to move the image far out so that it can be filtered easily.

Any insights will be appreciated.

Thanks, Sivan

Statistics: Posted by sivan_toledo — Sun Oct 15, 2017 4:10 pm


So nice to see her helicoidal memories! :D

https://twitter.com/v1rtu0s1ty/status/772840431356743680
I installed her Sept 5, 2016. She worked for few months and suddenly it could no longer acquire a clear picture, it was always noisy. But before that, this was one of her captures - https://twitter.com/v1rtu0s1ty/status/901971127328796672
I'm currently working on an antenna mast support so I can easily do maintenance without asking help from my kids. I think the new height will be 40 ft since I bought another 10ft metal pipe. I'm already 50% complete.
I've also started building a QFH antenna. It's also almost done but I haven't put the wires yet nor welded the corners.
I'll post pictures when I'm done.

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пролёт NOAA 18. 14 градусов. Европа. 15.10.2017 10:01 по мск…








пролёт NOAA 18. 14 градусов. Европа. 15.10.2017 10:01 по мск
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