Архив за 10.05.2019

Comment on RTL-SDR Blog V.3. Dongles User Guide by Michael

Stop the operation (click square), then configure and restart

RTL-SDR Discussion • Convertisseur ascendant

Bonjour
Est ce que rtl sdr va sortir un convertisseur ascendant dans les prochains temps ?

Statistics: Posted by Capricorne68 — Fri May 10, 2019 10:09 pm


Anyone else have issues with NOAA sawbird.

Hey there,

I've been making a V-Dipole setup and get good results with some broadcast blocks. I recently invested in a sawbird filter but it seems to have made it way worse.

Here are some images before sawbird https://imgur.com/a/KSEBUud

And After https://imgur.com/a/UxOcEQ2

I have ensured directions are correct, everything is plugged in the right direction, light is on, tbias is on, setup is mobile so I tried in a field with similar results.

This is how my spectrum looks. My noise floor is god awful high and nothing comes through. https://imgur.com/a/QTlfTjC

Picture of setup: https://imgur.com/a/YiwCxFp

submitted by /u/sillyinvesterinpx
[link] [comments]

Strange interference seen on MSI.SDR dongle, but not on RTLv3/HamItUp. Any ideas?

Strange interference seen on MSI.SDR dongle, but not on RTLv3/HamItUp. Any ideas? submitted by /u/sschneikart
[link] [comments]

KerberosSDR • Re: Android app for 1.3

Did the update to my Tinkerboard, the page shows the usual config , Synch and all but does not show a value in the Update Rate even though the field is refreshing...

Statistics: Posted by mdacosta — Fri May 10, 2019 7:36 pm


RTL-SDR Discussion • Re: Dongle Direct Sampling Mode ?

https://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode/

Scroll down to where it says "Software Settings" and the instructions are there. Q branch is what you are looking for to listen to HF. You must switch back to Quadrature to listen to VHF/UHF again.

Statistics: Posted by bmh — Fri May 10, 2019 7:27 pm


RTL-SDR Discussion • Re: Dongle And Sigmira program ?

Yes, it does support the dongle. I suggest reading the manual. I wasn't very fond of it myself but to each their own.

http://www.saharlow.com/technology/sigm ... manual.pdf

Statistics: Posted by bmh — Fri May 10, 2019 7:22 pm


Antennas • Re: Antenna tuning, impedance matching, baluns, common mode currents, my head exploding…

I finally understand what a balun is!
So I'm going to write this down in case some other confused soul comes along and tries to learn the same stuff. Anyway, what is a balun you ask? Well as it turns out I had the correct answer right underneath my nose all the time, but I was too confused with all the terminology that I somehow ignored it the whole time.

Definition of Balun according to Wikipedia (and a lot of other people):
"A balun is an electrical device that converts between a balanced signal and an unbalanced signal."

That's all there is to it. It may or may not also be an impedance transformer, but a balun really is just a device, a converter between balanced and unbalanced signals or feedlines. Finally the next big thing to understand are balanced and unbalanced feedlines - what are they exactly? Most people will probably imagine that feedlines like twisted pair, ladder line, twin lead, etc. are always balanced lines while a coaxial cable would always be an unbalanced line, and they are mostly correct. But the real answer again lies in the definition of balanced and unbalanced lines.

Definition of Balanced and Unbalanced according to Wikipedia:
"A balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits. An unbalanced line is a transmission line (often coaxial cable) whose conductors have unequal impedances with respect to ground."

That's the thing. I.e. for a properly connected ladder line both conductors have equal impedances since the wires are identical (diameter, material, spacing, etc) and both have the equal impedance in reference to ground. Since this is true it is therefore a balanced line according to the definition. A coax is frequently used for unbalanced lines since its shield is normally grounded. So the center conductor will have some given impedance to ground, but the shield's impedance to ground will be zero because it well... it is the ground. Since the impedances to ground are unequal, this is therefore an unbalanced line.

A balun is a device that converts between the two, but may also perform other things like impedance transformation. Not all baluns are impedance transformers and not all impedance transformers are baluns. For example, consider the following image. See that one contact of the coil on the unbalanced side is grounded (so the impedances on both contacts will be unequal in reference to ground) while both contacts on the balanced side are floating. There is no electrical contact between the two coils. Although the center tap may be grounded in certain setups, the impedances of both outputs to ground are still equal.
Image

For a Yagi antenna a lot of people are recommending the 4:1 coax balun. This device is apparently two things in one. First it is a 4-to-1 impedance transformer (I read some theory behind this how the coax loop delays the signal so it reaches the other end out-of-phase) and second it is a balun. The balun function is apparently visible because the feedpoints have no connection to the ground (coax shield) Both are connected to the central conductor and they therefore have equal impedances in reference to ground - therefore a balanced signal.
Image

There is a lot more to this topic, but I'll leave it at that for now.
Also, current baluns = common mode chokes (not really baluns).

Statistics: Posted by Airwind — Fri May 10, 2019 6:54 pm


RTL-SDR Discussion • Dongle And Sigmira program ?

Hello,

Anyone know if you can use the RTL Dongle with the program Sigmira ?

If so, anything extra that needs to be added to the Sigmira Folder like EXTIO, .dll or...
to have it function.

Thanks,
Bob

Statistics: Posted by Robert11 — Fri May 10, 2019 5:55 pm


RTL-SDR Discussion • Dongle Direct Sampling Mode ?

Hi,

Have a new Dongle from Amazon:

RTL-SDR.COM
RTL2832U R820T2
DVB-T+DAB+FM+SDR

Little bit confused over the freq. range that the Dongle I just bought is:

a. What's the upper end ?

b. I thought it was essentially 25 MHz and up, but I saw this note regarding it:

"Can tune from 500 kHz to 1.7 GHz and has up to 3.2 MHz of instantaneous bandwidth (2.4 MHz stable). (HF
reception below 24 MHz in direct sampling mode). Please note RTL-SDR dongles are RX only. "

c. So, how please do I use it in Direct Sampling Mode (using SDR#) ?
Not sure what to do in SDR# to invoke.

Thanks,
Bob

Statistics: Posted by Robert11 — Fri May 10, 2019 4:20 pm


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