Архив за 10.08.2019

Comment on POLL: What do you want in a future low cost SDR? by snn47

To have all 3 sounds tempting ,but I assume unfortunately to expensive or you wouldn’t have asked where to put the preference on .Having a hardware that is supported in the available programms is also a good idea.

Other ideas that come to mind for an improved functionality,
– add a switchable (Pin-)Diode attenuator to allow to detect/reduce IM
– ext. synchronisation add cut/soldering point for
– pcb design to allow optional metall shielding

Nooelec 1:9 balun setup

Hi all, recently purchased a nooelec hf sdr kit, and it came with a 1:9 antenna balun. I'm a noob when it comes to balun/unun stuff. I've read online that I can use this balun with two pieces of equal length wire to make a dipole, and I have also read that I can ground one receptacle and place a random wire length in the other receptacle of the balun to make a long wire antenna. Which is recommended? I plan to use a 20 foot piece of ksr-195 cable to connect the balun to the upconverter which then connects to the sdr.

Link for kit: Nooelec NESDR Smart HF Bundle: 100kHz-1.7GHz Software Defined Radio Set for HF/UHF/VHF Including RTL-SDR, Assembled Ham It Up Upconverter, Balun, Adapters & Cables https://www.amazon.com/dp/B0747PX3NZ/ref=cm_sw_r_cp_apa_i_RuXtDbNZFRR3J

Link for balun: NooElec Balun One Nine - Tiny Low-Cost 1:9 HF Antenna Balun with Antenna Input Protection for Ham It Up, SDR and Many Other Applications! https://www.amazon.com/dp/B00R09WHT6/ref=cm_sw_r_cp_apa_i_bwXtDb1R554KZ

submitted by /u/NodakTwoBravo
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RTL-SDR Discussion • Newb trying to receive Weather Faxes

Hi all,

I'm a complete newbie to SDR, but I've managed to get the RTL-SDR dongle working with my Mac and using the GQRX software to tune in local FM radio stations and AM air traffic communications. <whew>

With that said, I have ZERO radio experience - this is me just dipping my toe into it. The main driver for me to get started was an interest in receiving Weather Fax information at sea.

I've just come to understand that the dongle I have will work down to 24MHz and the information I found on the stations that broadcast weather fax data is as follows:

"The only requirements of the radio are that it tunes the frequency ranges of interest. A general purpose communications receiver tuning 0-30 MHz is ideal, SSB marine radios may also be used, if they can receive the frequency bands of interest. The radio must be able to tune in USB (upper sideband) mode. Inexpensive portable radios are not as satisfactory, although higher-end units can work well. The radio must be able to tune in small steps (10 Hz), or have some sort of a fine tune adjustment."

So...it seems that the dongle I have won't work as-is? Do I need an "upconverter"? (I don't really know what that is but have seen that term used in some of my research).

If anyone would share any tips for getting Weather Fax info onto a Mac, it would be very much appreciated.

Thank you and cheers!

-Dingus

Statistics: Posted by Dingus — Sat Aug 10, 2019 8:41 pm


Interactive SDR Live Stream | 10K Subscriber Celebration and Giveaway!

Interactive SDR Live Stream | 10K Subscriber Celebration and Giveaway! submitted by /u/HS524
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Comment on Updated Meteor M-N2-2 Tutorial and Decoder Now Available by Mike

SDRHobbist:
I too having issue with the exact issue you are. No version of sdrsharp seems to work on my W7 PC (Net4.6). The magic line is clearly in the plugins.xml but doesn’t show up in sdrsharp when its launched. when you shutdown SDR# is when you get the debug msg
System.NullReferenceException: Object reference not set to an instance of an object
I’ve seen this brought up before but no one wants to address it or has no idea why this happens on some installs and not on others. An older version of SDR# (1337) works with the QPSK plugin but not the OQPSK version of the plugin. Did you ever get it working for Meteor MN2-2?

RTL-SDR Discussion • antennas with limited bandwidth, HP- LP-,BP,BR- Filters, vs. isolators or bias

It depends on the frequency range you want to receive and your RF enrionment, what is the best (affordable) option to reduce interference or in most cases it is overloading of the receiver.
Interference are signals or spurious emmisssions that fall within the receiver RF bandwidth.

Since RTL-SDR do not have any RF selectivity like a normal receiver design they will, unless you use HP-, LP-, BP or Bandreject-filters, receive all signals that you get from the antenna.

If a receiver is not overloaded it will amplify all signals by the same factor e.g. 20 dB. When reaching overloading not all signals will/cannot be amplified by 20 dB any more and as consequence due to intermodulation (IM) additional signal (interference) will be generated. If you add an attenuator of e.g. 20 dB and many signals that were stronger than 20 dB are gone you had Rx IM.

If you live in an area with transmitter having high EIRP (e.g. TV, BC) the only option for you are filter to reduce those frequency ranges with the strong signal or using antennas that be design are like a bandpass on for the frequency range they are designed for and in most designs also reveive multiple of these center frequency.

Both Isolators e.g. Transformer just avoid DC-pass through and do not filter. While a BIAS T is intended to allow injection of the DC e.g. for a preamp if the DC pass is interrupted.

Statistics: Posted by snn47 — Sat Aug 10, 2019 7:47 pm


Antennas • Re: Antenna for encrypted scanner frequencies

For your understanding:

Antenna are passive they don't care about what signals are transmitted or received by the it.

It's Transmitter and Receiver that provide en-/decoding of signals.
a) its illegal
b) there is a reason for why its encrypt
c) depending on laws of the country you try to receive such signals you may be fined or at worst imprissoned.

Statistics: Posted by snn47 — Sat Aug 10, 2019 7:29 pm


Antennas • Re: Folded dipoles and quad loops with SDRs

Those antenna types do not necessarily create a short for the DC path, but It depends on how the antenna is matched to the transmission. But mostly they do, but you can also add a a DC isolation via e.g. a HP-filter.

Statistics: Posted by snn47 — Sat Aug 10, 2019 7:23 pm


RTL-SDR Discussion • Slider Lock «Zoom» in SDR #

Hi

Did anyone discover a fix for this zoom slider issue (it defaults to the zero position every time you launch SDR #)?

Many thanks,

Rob

Statistics: Posted by RobBain — Sat Aug 10, 2019 7:19 pm


Antennas • Re: Signal Splitting?

As always, if you ask for advice you should explain what you need/want to do. We do not have a crystal ball to find out what you want. This is for you to decide and tell us before anyone can give you an advise. Similiar if you say I need transportaion is a motorcycle or a car sufficient, dou you need a truckor a bus to allow you to transport what you want ;) . It is similar for RF devices, there are many different options how to achieve distriution of signals from a single source to multiple outputs. To give you an idea:

-How many ports 2, 4 or more do you want?

-How broadband/which freqncy band do you want to use the Divider/Combiner/Splitter for?

-Which coax connector type (e.g. C, N, SMA, SMB, SMC)?

-WHich impedance 50, 60 75 Ohm?

-DC-pass through or not?

-Are you willing to built it yourself, or want to buy it?

The cheapest Divider/Combiner/Splitter that does not maintain the impedance asr T-coax connectors, they are just the inner conductor to all three ports

Crude resistive devises are made/sold for CATV/SAT-TV use like RCA T56476 4 Way Signal Splitter Coaxial Cable which are broadband.

Than there are other option like a rat race or splitter which have a limited bandwidth

Directional coupler provide a low attenuation through path (>0.5 dB) and have one or more pickups each 10 or more dB attenuated, while the feed through attenuation is >0.5 dB, which are broadband.

If you start searching you can easily find manufacterer names and their distributors e.g. minicircuits.com, mcli.com

Statistics: Posted by snn47 — Sat Aug 10, 2019 7:15 pm


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