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KD7YUF
25-11-2009, 16:49
I am seriously looking into the Elektor SDR in order to receive DRM broadcasts and have a question involving the use of external antennas with the receiver. Given that there is no obvious antenna connector on the radio I am wondering if its possible to wire up an external antenna for the receiver to improve reception since I am in a rural area and AM broadcast is fairly weak and also because of the existing band conditions on shortwave.

mvs sarma
26-11-2009, 05:22
I am seriously looking into the Elektor SDR in order to receive DRM broadcasts and have a question involving the use of external antennas with the receiver. Given that there is no obvious antenna connector on the radio I am wondering if its possible to wire up an external antenna for the receiver to improve reception since I am in a rural area and AM broadcast is fairly weak and also because of the existing band conditions on shortwave.
an active external Antenna like that of PA0RDT's active miniwhip antenna (please Google for the link of a PDF file) would help you.
BUT you have to take protective action against Lightening activity damaging your entire RIG.

dadalbinder
26-11-2009, 08:20
Hallo,

the impedance of all inputs is high and not 50 Ohm.

One should have a try with a balun transforming upwards. From a 50 Ohms antenna input in the ratio of 1: 2 or 1:3.

Separate output grounding from internal groundings. (Balun)

The danger of lightnings is high. Try to find a solution for this problem or take the antenna inputs away from the receiver at these times.

There is an extension for the receiver, a preselector, with 4 inputs and software automatically controlled tuning.

At least: Put Your finger on one entrance and You are able to receive some stations without antenna.

Happy experimenting

Wolfgang Hartmann, Nürnberg

Digger
27-11-2009, 20:31
If you do connect an active antenna, such as the PA0RDT, remember to block the DC supply voltage to the antenna from the Elektor, as there is a 2.2 uH inductor to ground across the antenna input (smoke guaranteed).

I'm using a slightly modified PA0RDT antenna both in Switzerland and here in Sweden at my temporary QTH although with another RX, and I didn't have time to test it much on the Elektor yet. As far as I recall at the moment, the active antenna was not the optimum solution, but the Elektor is new to me and I did not have time to make any tests in detail.

Happy experimenting.

KD7YUF
27-11-2009, 21:49
I am thinking about using a normal long wire antenna but most likely a vertical on the receiver. The problem being is I can't seem to find a procedure to connect an external antenna of either type to the receiver. Or a picture detailed enough for me to see what type of connectors are there despite the ones for USB and 12 KHz AF out.

Digger
28-11-2009, 07:38
The antenna connector is at the lower left in this picture:

http://www.elo-web.de/elo/entwicklung-und-projekte/kurzwellenempfaenger/der-elektor-sdr

There is a schematic diagram a bit further down on the page.

GL

dadalbinder
28-11-2009, 09:48
Hallo,

it is the left side of the picture.

Parallell to the input there is a choke, which reduces the inputs of lower frequencies.

The software switches between the inputs 1, 2, 3 of the circuit-ic at this place.

The first try: Connect a wire 5 m long on the input jack and turn it vertical besides Your home. This for first tries.

Try to find a suitable grounding for the input.

Shorter wires have higher impedances. Because of that, You are able to experiment with a short wire of some meters.

You will be astonished, how nice it works.

With some soldering, one is able to activate special inputs at the switching ic-circuit. You are able to connect some special antennas as an example a special ferrit-rod with a tuning capacity.


Wolfgang Hartmann

mvs sarma
28-11-2009, 15:02
One can also use TV ribbon cable (300 Ohms) and have necessary matching at the top itself with a HF loop antenna, perhaps.

KD7YUF
28-11-2009, 20:22
Thanks for the info, the link posted earlier pretty much answered my question as the Elektor photo did not show enough detail of the sides in the case of the board. This really does look like the ideal solution for me to receive DRM then and my existing sound card will work for decoding which was proven thanks to 12 KHz IF samples of DRM transmissions in Dream. Maybe for other modes also including C-QUAM AM stereo as there are transmissions being conducted still here in the US but the number of them seems to be shrinking.

mitajohn
29-11-2009, 09:34
Hi all,

With some soldering, one is able to activate special inputs at the switching ic-circuit. You are able to connect some special antennas as an example a special ferrit-rod with a tuning capacity.

In the December's 2009 Elektor magazine is presented a very interesting preselector for the SDR unit in question.

KD7YUF
04-12-2009, 18:16
I saw the preselector but I will give the radio a try without it first just to see if the stock one fits my needs which it could very well do if I can find a good software demodulator and I think I already have as well. Originally it was going to be an R75 mod to receive DRM but the more I read about SDR, the more it intrigued me and I also want a receiver which can get a wide range of modes including C-QUAM AM stereo and also have highly flexible filters so it looks like this is the way to go.

dadalbinder
04-12-2009, 20:20
Hallo,

there is a new version of SoDiRa programm. Now continued to version 0.80.

It has the possibility to demodulate this mode too.

This programm has a lot of features, try it.

There is even a function MIRROR, which is looking (mostly downwards) for mirror frequencies for the received signal on other frequencies than this You are using. If You tuned to the original frequency, chosse MIRROR and DOWN to find the frequencies, Your receiver "generates" the signal.

If You now engage a preselector, You will probably note, that the receiver could be better secured in respect to MIRROR frequencies.

Best regards,

Wolfgang Hartmann, Nürnberg

KD7YUF
05-12-2009, 04:38
I tested that version already and its implementation of Motorola C-QUAM AM stereo seems like a software version of Sony's CX20111 decoder IC but with the platform motion reduction of the official Motorola MC13022 IC. This was with IF samples of France Bleu on 864 KHz from Paris France which is experimenting with the system. Its quite impressive from my observations and the decoding is 100% accurate compared to the same thing on a Sony SRF-42 which decodes the system in hardware using the Sony IC mentioned earlier but locked to the Motorola mode as it does Kahn/Hazeltine, Harris, and Magnavox stereo modes as well which are pretty much dead systems on anything but low power license free transmitters. Also an amateur radio operator here in the US is experimenting with AM stereo in the Motorola mode on the 80 meter band so with a software defined radio it would be possible to listen to the stereo transmissions without a converter of some sort.

mitajohn
05-12-2009, 08:15
Hi all,

Talking about preselectors I would like to mention the ones from Heros Technology Ltd , found searching the net, which as the manufacturer claims are suitable for SDRs. Have anybody an idea?

dadalbinder
05-12-2009, 12:08
Hallo,

Preselector in combination with the Elektor_USB receiver

If one could see by experimenting, the mirror frequencies will be weakened by a preselector. You have to compare working without preselector and in a second step with preselector. This generally. Although the receiver has some filtering before the input, one is able to see some advantage by a working preselector.

For a direct test, You could choose just by switching one input with the normal filtering and by switching to a tuned preselctor.

There is the new preselector announced by Elektor. It is tuned by connection to the receiver and is able to give 4 tuned entrances. Inclusive automatic tuning by the receiver.

This means, one has not to tune the preselctor by hand, it is done automatically. Should have the best effect at all!

FM

You could enhance the receiver by giving an input from a FM-receiver with a intermediate frequency of 10,7 MHz als an example. Then You are able to decode FM-wide in Mono, Stereo, RDS. It works after You have found a reasonable point for the 10,7 MHz-signal. As with the standalone preselector one has to tune the chosen FM-receiver by hand.

Happy further experimenting

Wolfgang Hartmann, Nürnberg

mvs sarma
06-12-2009, 05:44
Thanks for the info, the link posted earlier pretty much answered my question as the Elektor photo did not show enough detail of the sides in the case of the board. This really does look like the ideal solution for me to receive DRM then and my existing sound card will work for decoding which was proven thanks to 12 KHz IF samples of DRM transmissions in Dream. Maybe for other modes also including C-QUAM AM stereo as there are transmissions being conducted still here in the US but the number of them seems to be shrinking.
The decoder referred was by G.Baars in his article of Shortwave radio capture published in Elektor Dec2006 issue.
the entire article can be downloaded for approx $1.6 ( 10 credit points)

KD7YUF
06-12-2009, 05:46
I am giving up with the Elektor SDR since they don't have a department in North America and shipping charges are too expensive ($16 US for the cheapest and slowest 4 weeks+) so it would not be practical to ship it from Europe.