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Solar-Terrestrial-Data
Software Defined Radio with a Flex-1500

I once used to own an Icom IC-7000 but somehow I was disappointed in sensitivity; so I decided to sell the TRX and decided to move towards Software Defined Radio.

When checking the web you'll find a lot of SDR TRX suppliers; both in kit form as complete product. A lot of these solutions use the onboard soundcard of your PC or laptop. Since I know from experience that laptops normally don't have the best soundboard I wanted to have a soundcard independent solution.

As said there are a lot of different SDR TRX suppliers. To name a few:

  • the G Fifty-Nine concept of Genesis Radio; you can build your own 10W 160-6m SDR TRX in parts. When you check the photo's it does like like a quality product.
  • Softrock has the Softrock RXTX Ensemble Transceiver kit; it can be build for one of the frequencygroups 160m, 80m/40m, 30m/20m/17m or 15m/12m/10m; unfortunatelly there is no overall solution that covers all bands.
  • Our German friends of Funkamateur offer the FA-SDR TRX, a 1W transceiver with a range up to 30 MHz.
  • Worthwhile to mention is the HASDR initiative of Henk Jenniskens (PE0SSB). He offers a clone of the FlexRadio SDR-1000; the kit can be expanded with a 25W amplifier as well. The TRX has a bandwith of 192 khZ and can be tuned anywhere between 0 and 65 MHz. The standard output power is 1W but as said there's an amplifier as well. Unfortunatelly I don't know if the kit is still available.

Since I know how I respond to failures while building a kit (throw in a corner and don't look at it for a long long time...) I've decided to go for a Flexradio. The Flex-1500 is a 5W SDR TRX, bandwith 48 kHz and tunable from 0 - 54 MHz. The big advantage is that the TRX contains a soundcard itself. So the only connection between your PC/laptop and the TRX is a USB cable.

Another advantage of this concept is that it's easy to make use of digital modes. The only thing you need to do is install an external program (like Virtual Audio Cable), create virtual audiocables and use them within PowerSDR (the software to steer the SDR).

The Flex-1500 is being delivered (or at least in my case) with two different versions of PowerSDR. First you need to install 2.0.2 beta and then upgrade to 2.0.5 beta. At this moment 2.0.6 beta is available but it somehow has problems when you want to transmit VAC signals.

Before first usage you need to calibrate the RX level; this is an automated process that takes care of correct signals on the S-meter.

When I decided to hook up the Flex-1500 to my Vista laptop the calibration process didn't run very smoothly. Result: corruption in the EPROM and a maximum output power of only 0.5W. After consulting the technical support department of Flexradio the problems was solved very fast (excellent support!)

My experience with the Flex-1500:

  • the software isn't clearly ready yet; previous versions of PowerSDR had the option to use VOX or show reflected power and SWR with the Flex-1500. In the contrary to it's larger brothers (Flex-3000, Flex-5000) the Flex-1500 doesn't have the hardware to fullfill these requirements so it had to be removed from the software.
  • by following the recommendations in the manual to get the best audio possible there's hardly any TX power; you can easily increase the DX level to 10
  • some microphones don't go well with the Flex-1500; my Yaesu MD-200 had this problem. Though the audio sounded very good there was an annoying beep. So I replaced the MD-200 with the standard handmike of the Yaesu FT-857.
  • excellent sensitivity

Up until now I mainly used the TRX for WSPR; with 5W TX power, an indoor 20m dipole I've had these results:

VU2LID (8018 km), WA7KGX (8051 km), W0OGH (8702 km), 7L4IOU (9274 km), PY4BL (9338 km), FR/F6AAO (9513 km) and 9V1AL (10467 km)

One of the next things I want to try is PSK31; based upon my experience with WSPR my expectations are high.

Always nice to try is monitor your own phonesignal on a different TRX. There's some delay so start laughing while doing your best to speak as normal as possible...

PowerSDR has the option for selecting several audioprofiles; you can select a default DX profile but additional profiles like AM, Heil HC4/5 or even ESSB as well. And you can tailor every profile to your specific needs as well.

I was a little bit concerned about the effect PowerSDR would have on the CPU usage of my laptop. But there's no need to worry. Sometimes overall CPU usage is peaking between 25 and 30% when using a Lenovo T-400.

The biggest advantage you have when using an SDR TRX is the software can be improved and possibilities added. It's sort of upgrading the firmware of a conventional transceiver though in this case the "firmware" is contained on your PC or laptop. 


 

 

 

 

 

 


Comments

Koen on 2011-01-28 17:12

Hoe krijg ik WSPR aan de gang op de flex1500 ?? Heb je ook een eenvoudige uitleg ??

Heb er ook een HM-31 mike aan. Beetje dof geluid !!

Groeten Koen de PA0KNW.

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