HDSDR & RTL Dongle. Upconverter, Panadaptor.

 Showing HDSDR using an upconverter.  HDSDR main page https://sites.google.com/site/g4zfqradio/installing-and-using-hdsdr



A really cheap SDR is available in the form of digital TV USB "dongles".
These use 8 bit sampling but can produce very useable results. HDSDR may be used with these dongles to give a display width of up to 2MHz, sometimes more.
Depending on the actual model their frequency range is from 24-55MHz up to over 1, maybe 2GHz.

For this you need a dongle, search Ebay, for example for "RTL2832U" a description is "FM+DAB USB DVB-T RTL2832U+R820T w/ MCX antenna" RTL2832U and R820T will give the required device. I have had several from the East at around 6UKP.
A little more "expensive" from Jersey https://www.cosycave.co.uk/category.php?id_category=61

First read this from the HDSDR site:- http://hdsdr.de/RTLSDR_with_HDSDR.pdf this should get your dongle's driver installed. Download the HDSDR DLL for the Dongle here and place it in HDSDR's program folder.


You should have no difficulties but, if you do, perhaps the following might help. Zadig driver (Sept 2013 new page 
http://zadig.akeo.ie/ with link to "Usage" instructions.) 
 
http://wiki.spench.net/wiki/USRP_Interfaces If you are new to this read carefully and use the install package. At the top 1 "Download the self-contained installer" Note there is a separate Zadig driver for Windows XP. If you are lucky this is all you need.
Check the dongle and driver independently of software or DLL, also shows writing to it's eeprom so that if you use more than one HDSDR can tell the difference. Use with care! 
This shows Zadig setup. http://rtlsdr.org/softwarewindows. Also it shows SDR# but I think HDSDR is more suited.
DLL https://github.com/josemariaaraujo/ExtIO_RTL Click ExtIO_RTL at the top, select "Zip".  This must be placed in the HDSDR program folder. You may need to select it when starting HDSDR. 


HDSDR's ExtIO button brings up the dongle controls. See my pages about HDSDR https://sites.google.com/site/g4zfqradio/installing-and-using-hdsdr

Now when all is installed correctly a dongle with a R820 will receive directly from just below 25MHz to well over 1GHz. I have not confirmed how high. The whole of 2 metres can be shown. (Later versions of "RTL Settings" show a "Direct sampling" mode for lower frequencies, the dongle requires modifying. Some have had success but I have not.) Note that these dongles are prone to overload. Use manual gain as shown below, increase the gain so the noise floor just begins to rise. Filters may be needed to reduce out of band signals.

 
For HF fair results can be obtained with an up-converter.
Performance is not outstanding. Overloading may give spurious signals. Keep signal levels as low as possible maybe an antenna attenuator and/or a BPF will help. Certainly a soundcard SDR like the Softrock will be far better but will not have such a large span.
With a dongle "Tuner Gain" will need careful adjustment. At the bottom of this page I show a later version of HDSDR which makes this control easily available (RF).
This picture shows a dongle used with a 100MHz conversion oscillator. A R820 tuner will cover all HF with a lower frequency oscillator, maybe 50MHz the exact frequency is not critical.
The ppm figure in the RTL Setting box is obtained by calibrating against a VHF standard when the dongle is used on its own.
Calibration is not going to be precise, drift and the bug below will give variations.
HDSDR's "RF Front End..." tab shows two ways of calibrating when using an up-converter. The exact LO frequency, or as near as you can get is placed in the LO box. Here 99.999090MHz Then HDSDR's calibration might be used. Remember, absolute accuracy will not be obtained, if it ever is then the dongle will soon drift a little.
October 2014 Warren, 9V1TD, discovered a bug in the RTL DLL code, the R820 does not tune smoothly, frequency jumps occur 55, 110Hz probably more at higher frequencies. 

Sample rate:- I have been advised to use a high rate to enable the anti-aliasing filters to reduce spurii. However, less CPU load and finer resolution of the observed signal is possible using lower rates.


An upconverter may be purchased, there are several models designed for these dongles or the Funcube dongle but note my notes about the performance.
I built mine from the circuit here http://www.george-smart.co.uk/wiki/FunCube_Upconverter. Home construction from the junkbox makes this an economic project.

My crude copy looked like this!
 HF and VHF selected by plugs. The dongle plugged into a USB socket from an old motherboard. The converter oscillator fed from USB 5 volts.

Below, optimised to monitor the UK 5MHz band sections. The whole range is seen, clicking on a signal shows more detail in the lower display.
The bottom display shows the beacon frequency, 5.290MHz. GB3RAL and it's PSK burst with the beginning of the GB3WES transmission.








Our available frequencies. Signals must fit between the two figures. 















An SDR will show exactly where the RF is in terms of frequency.

Below, RAF Volmet on 5.450MHz USB.
The lighter blue in the upper spectrum shows the response of a normal amateur 2.5KHz SSB filter.
Note NO RF at 5.45MHz. This signal is wider than normal amateur SSB should be. RF is seen from 5.4502 up to 5.4534MHz. This is 3.4KHz ABOVE the nominal frequency.
The filters in an amateur transceiver should limit this to less than 3KHz above the nominal frequency.

The "S" meter in these shots is not calibrated.


Note that if you use the DLL from the HDSDR site you will have the "RF" control as shown below.

I have tried a RTL dongle with a R820 tuner for a panadaptor with my FT840's IF of 47.05MHz. Performance will be nowhere as good as using a Softrock-type SDR as shown here https://sites.google.com/site/g4zfqradio/hdsdr-if-pano but it can make a quick introduction to a panoramic display for receiver or transceiver.
The link above gives details of how I took the IF from my FT840. Just the JFET buffer is needed, signal levels should be adequate.
Connecting HDSDR to a transciever with CAT will enable you to tune with HDSDR and transmit.
June 2013 There are now more options for tuning HDSDR in conjunction with the panadaptor function. Look at this updated page  https://sites.google.com/site/g4zfqradio/hdsdr-if-pano


Here I am using an offset of 50KHz, 50000Hz to keep the tuning away from the centre. I have added this to the IF frequency and carefully trimmed the IF-Frequency so a known signal is accurately tuned. Then I applied the corrections for other modes. This page gives details of CAT connection and frequency correction. https://sites.google.com/site/g4zfqradio/hdsdr-if-pano

LOW IFs, Using a HF downconverter before the RTL dongle.
The "Local Oscillator" frequency will need to be set as the sum of the IF frequency + the frequency of the converter crystal. For example if the converter crystal is 125MHz add 125000000 to the IF frequency.
Note most receivers will have a roofing filter and narrow IF so only a very small spectrum will be seen at full sensitivity.

As the dongle has a low dynamic range performance is likely to cause some problems with overload of the dongle. Taking the IF from the first mixer bypasses any AGC in the radio. Careful adjustment of the dongle's tuner gain helps. This is available on the ExtIO and also as a button/slider in HSDR. Advance the gain so only the slightest rise in noise is seen. This will be very  dependent on the frequency and band conditions. In some cases I've found an attenuator, 10-20dB, between the radio and dongle is useful.






A quick way of getting frequency calibration fairly close is just to use the PPM correction. Use the up/down arrows to tune in a known carrier on CW. Then apply any corrections for other modes. This appears to work but the correction will have to be reset when using the dongle in other ways.
Here, using the European RWM standard. 4.996, 9.996, 14.996MHz. Continuous carrier 0-8 and 30-38 minutes past the hour.




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https://groups.yahoo.com/neo/groups/sdr-radio-com/files
RTL2832U_Support.rar DLLs 32 and 64 bit
https://groups.yahoo.com/neo/groups/sdr-radio-com/files/RTL%20DDL/32%20bits/









G4ZFQ April 2013
alan4alan at googlemail com
More of my pages related to SDR




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