The Winradio Excalibur Pro G33DDC

© Bjarne Mjelde, October 18, 2011

Introduction

The G33DDC (or “G33” from now on) Excalibur Pro was released the autumn of 2011, and is the successor to the G31DDC Excalibur, which was released in the summer of 2010. The release follows Winradio’s tradition of first offering an entry-level followed by a more sophisticated “Pro” receiver. The third release is expected to be the scanner edition, G39DDC. I don’t know if there is an official release date for the G39 “Excelsior”, but it is rolling off the production line, as per info from Winradio in October 2011.

This is not a review as such. It is a test of the G33 from the perspective of a MW DX-er with a certain way of operating. Other DX-ers may have other interests or priorities.

G33 Overview

The G33 is a basically traditional HF-range SDR, with the ability to tune up to 50 MHz. What is novel in the amateur SDR world of 2011, is the 5 MHz DDC recording sampling rate, which gives a bandwidth of up to 4 MHz to be recorded for later analysis. One can choose between 24 bandwidths from 24 kHz and up, all are 32-bit except 3.0 and 4.0 MHz which are 16-bit. It’s a good thing that terabyte hard drives are available for reasonable prices now.

So how does it perform?

Graphical User Interface

The G33’s GUI is divided into three main panels: The Wideband spectrum scope is placed at the bottom, which shows the entire spectrum from 0 to 30 (or 50) MHz. Then at the left is the 24-4000 kHz DDC spectrum, and at the right the 20-64 kHz demodulator spectrum. The wideband and the DDC spectrum can also be viewed as waterfalls.

The panels can be resized to almost any position you want, and the often less interesting wideband panel can be all but minimized to allow better space for the other panels. The main window is resizeable too, and can even be expanded to a second monitor, allowing for very detailed view once you select the appropriate resolution bandwidth.

The vital controls are available within the tabs to the right hand of the S-meter. The layout of the GUI and its controls appear to be well defined and easy to work with - especially if you combine mouse control with some of the 96 keyboard shortcuts (more of that later) which are available for you.

The Options menu allows you to select a different “skin” than the default one. In fact, the grey skin in the illustrations here is not the default, but in my opinion much less fatiguing than the sharp blue Winradio has selected as default.

Tuning the G33

There are several ways to tune the G33. The most visible, but still least used (by me), is the rotary control next to the frequency display. A mouse right-click moves it 1 kHz down, a left-click moves it up. Holding either mouse button down enables fast tuning up or down.

A more straightforward way to get to an exact frequency is simply to enter the frequency number and press Enter.

The mouse scroll wheel will also increase or decrease the frequency by 1 kHz, as will the keyboard up and down arrows.

In other words, there are lots of ways to tune the SDR in 1 kHz steps, but only two if you want to use one of the pre-defined tuning steps. Within the “Tuning” tab you may choose one of three configurable tuning steps (default is 5, 9 and 10 kHz) with corresponding left and right arrows. Or you can use the keyboard shortcuts. If you aren’t within the “Tuning” tab, you have to select it first to get to the arrows, so the best solution is actually to learn to use the keyboard shortcuts. While tuning the G33 this way is quite effective, I would have preferred to at least be able to use the keyboard up and down arrows.

A third tuning option, which allows you to fine-tune down to 1 Hz, is to press Shift while you hover the mouse pointer over the frequency display. It will then change to an odometer-like decadic display, and allows you to change any of the digits separately.

Sensitivity

For an SDR, this is a very sensitive receiver. Winradio’s own specification says -106 dBm for AM mode, 30 % modulation, with preamp on. My own measurements say -106 dBm with preamp off, -110 dBm with preamp on. It’s the first SDR I know of having sensitivity levels lower than 1 uV, and even if some conventional receivers like the NRD-525 and R390A are measured at -112 to -115 dBm, I am quite satisfied with these results. At any rate, you will need an extremely low noise environment to be able to benefit from such high sensitivity levels.

Selectivity

The G33 has bandpass filters which will reduce out of band interference. These filters are selected automatically, or you can configure them yourself. There is also a high pass filter labelled “MW Filter” which will reduce interference from strong MW stations into the HF bands. Other than that, ultimate selectivity depends on the “Demodulator filter length” function in the Options menu. A first time user should pay special attention to this, because the default length from installation is the one that gives least selectivity on a given bandwidth. The default length is the minimum of 200, but should be increased to at least 5000 if you want tight bandwidths. How high you want to go (up to 20000) is a trade-off between PC CPU and your own requirements.

Bandwidth control are via preselected bandwidths inside the “Tuning” tab, an always visible dropdown control, or by dragging the edges of the grey areas inside the demodulator panel with your left mouse button. If you place the mouse pointer at the center of the signal, you will be able to move the passband with the right mouse button. Passband tuning is also available as a dropdown control inside the “Tuning” tab.

Once the appropriate filter length has been chosen, I find the G33 to be a very selective receiver, with easy and quick controls over bandwidth selection, making it possible to adjust the bandwidth and passband for optimum readability.

Audio quality

The audio quality of the G33 is excellent - after a little fine tuning. In AM mode, I am not at all impressed as I find that audio distorts rather easily. AMS mode provides excellent audio, and AM signals are also well reproduced in LSB and USB modes. AMS can be selected into upper or lower sidebands, or both.

A nice feature especially for AM use is the configurable Audio filter - it is a highpass/lowpass filter allowing the user to remove low-frequency distortion with the highpass filter and hiss with the lowpass filter. Sometimes, the audio recovery in noisy conditions is remarkably improved.

Audio output level is adjusted within the selected mode. There is no “master volume control”, so if you want to change the general audio level of the G33 you need to use your PC controls.

Three receivers in one

Within the DDC range, you can operate three virtual receivers, each totally configurable, selectable with a mouse click or Ctrl 1/2/3 on the keyboard. If you are monitoring three frequencies, this is an effective way to keep control. All three can record audio into separate audio files. It’s a bit like the VFO A/B options in some conventional receivers.

Noise removal

Sometimes, sharp bandwidths aren’t enough. The G33 has two independently configurable notch filters. They are very effective. I do miss a tracking automatic notch filter though, but I haven’t seen a perfect implementation of this since the days of the Kneisner & Döring KWZ-30 many years ago.

There is also a configurable noise blanker available. It does a good job removing Loran C noise on many frequencies (I live 14 km away from a 250 kW transmitter), at the cost of reducing intelligibility of low-level signals, and distortion on signals not affected. However, this is normal, and using a noise blanker is always a trade-off.

Recording and playback of the DDC spectrum

One of the virtues of SDRs is the ability to record a full spectrum for later playback and analysis. The G33 can record a record-breaking (for this market segment anyway) 4 MHz. For the MW DX-er, this is more than enough, but I suppose there are other users who will benefit from being able to monitor 4 MHz. Moreover, contrary to other SDRs in the amateur market, the spectrum is movable during recording. You can in fact move the DDC spectrum from 0 to 30 (or 50) MHz during the recording (more about the unintended side effect of this later).

The DDC spectrum can be saved to disk in one of two formats: A common WAV format (renamed DDC to avoid confusion with audio recordings), or Winradio’s proprietary RXW format. The latter keeps all date, time and frequency information inside the file, and you can name the file whatever you like. A DDC file will not automatically keep this information, so it has to be part of the file name - which it will be if you select“Insert FDT” prior to the first recording. It will then remember the setting. There is a “Split” function to keep the files from growing too large for comfort; it will split into 2 GB file sizes and chain the files.

When using “Insert FDT”, the “If file exists”-options to the right are irrelevant.

Unlike other SDRs, there is even a 3-second prebuffer which is handy if you are just a little too late starting a recording. I would have wanted the buffer to be longer, but Winradio says it takes too much processing power. Understandable, especially when a 4 MHz spectrum is involved.

Starting a DDC recording is extremely quick: Press the red record button, or use the keyboard shortcut. It should not take more than a second from you decide to start a recording until it is underway - with two seconds already in the buffer.

Playing back the spectrum is of course exactly the same as listening to it live - I suppose it’s the closest we get to time travel.

However, the novelty of moving the DDC spectrum during recording posed an unexpected problem: If I tuned around in the Demod panel while recording, the DDC spectrum moved too, thus making it virtually impossible to stay on a selected frequency during playback. Luckily, the Radixon representative I got in contact with understood my problem right away and presented a software fix that allowed the DDC spectrum to stay in one position even if I tuned inside the Demod panel during recording.

The playback bar has pros and cons compared to other SDRs such as Perseus and RF Space (SDR-Radio and SpectraVue). Initially, the “grip handle” on the bar was very small and difficult to catch with the mouse pointer. Also, clicking on the bar itself did little to move the file forwards or backwards. A software fix increased the grip handle to a more comfortable size, and clicking on the bar now actually moves the recording forwards and backwards.

All the chained files in one recording are available on the playback bar, making rapid movements very easy. If you have a two-hour recording, you don’t have to access another file to jump inside these two hours. On the other hand, making small jumps (a few seconds) in such a long recording requires a steady hand and a mouse with a good resolution.

A few words on PC time and UTC: The illustration above indicates that the recording started at 10:37:20, which is the local time of the PC. The playback time is 08:56:38, which is where the grip handle is placed at the playback bar, and refers to UTC. This is because I used the “Time” option in the Options menu to set the G33 time as UTC. The two time indicators will not show the same hour unless you set the PC time to UTC.

Freeze time

If you own a satellite or cable digital TV decoder, chances are that it has a “Pause” function that allows you to put the film or whatever you’re watching on hold while you attend to other business, like keeping your S.O. happy. Well, so does the G33. It stores the DDC spectrum to the hard drive, and you can resume when you return from your duties. Or skip if there was nothing interesting to hear. I haven’t found use for it myself yet but I am sure some will.

Recording and playback of the demodulated audio

Much the same as DDC recording, except of course that recorded audio is saved in WAV format,or Winradio’s proprietary WWV format. The audio prebuffer is up to 30 seconds, and again, a very handy function. If you suddenly hear an identification from a station, you know that it is recorded if the prebuffer is activated. I advise to use the “Insert FDT” option with audio files as well. Be aware however if you record audio from existing DDC recordings, as the date and time in the file name will be that of the current playback, and not of the original recording.

Scheduled recordings

Scheduled DDC recordings is an important factor because it adds flexibility to the DX hobby. A well designed scheduler is the key factor. This is how the Scheduler window looks like (one task is selected):

The figure should be self-explanatory. What I'd like to add is that "Start time" is always the PC's local time, not UTC. Take care in selecting the correct DDC bandwidth (default is 24 kHz), and find a suitable argument for the Stop recording function.

The file is automatically frequency, date and time stamped. There is support for multiple tasks, especially suitable if you want to record different frequency spectra and other bandwidths.

Unfortunately, if you want to set up a handful of tasks, it’s a handful of work as well. I’d prefer to be able to edit one task and save it as a new one, however this is not possible. You have to define each task from the beginning..

You can schedule audio recordings as well, you just select “Audio” instead of “DDC”.

Keyboard control - well almost

As mentioned previously, a massive 96 keyboard shortcuts are available for those who don’t like to use the mouse a lot, and for the visually impaired. You can control just about anything with the keyboard, and you can redefine each shortcut to suit your own preferences. Alas, you have no keyboard control over the file naming properties in DDC and audio recording. And for visually impaired users, it will be very difficult to navigate through the keyboard shortcut display without a braille display. Not being able to navigate with the keys Tab and Shift-Tab violates the principles of universal design. Nevertheless, the G33 (and the G31) probably have the best designed SDR software for visually impaired users today. And once you learn to control the basic functions with the keyboard instead of the mouse, operation speed increases a lot.

And the rest

The G33 has a lot of functions and possibilities that I won’t go into detail about here. We could mention:

What Separates the G31 and G33

Both are basically traditional HF-range SDRs, with the ability to tune to 50 MHz. The price tag is quite a bit higher. If we refer to UK pricing, the G31 sells for GBP 700, while the G33 is GBP 1600 incl VAT. In other words you can have two G31s for the price of one G33 and still have cash left. So why should you leave the G31 in the shelf and pick the G33?

Seen from the perspective of a MW DX-er, there are two important and several less important differences between the G31 and G33. The two important ones are:

Actually, scheduled DDC recordings can be achieved with external programs like System Scheduler, but it’s a lot easier to tailor-suite recordings if you have a dedicated scheduler.

Differences with less priority are:

Differences with little or no priority for the MW DX-er are:

Conclusion

The Winradio G33DDC is indeed a very capable SDR, and well designed for the MW DX-er as well, once the latest software revision (1.66) becomes available. However it is expensive, and has functions that the MW DX-er will not need or benefit from. On the other hand, many DX-ers cover a broad spectrum of interests, and for them, this could indeed be the best choice. If you can live with manually date and time stamping your DDC recordings, the G31DDC will be an excellent budget alternative.