Preliminary Review: The Winradio G31DDC Excalibur

I have uploaded a pdf with my initial impressions of the Excalibur SDR. It hasn't yet been tested in real DX situations, so it's bit early to be conclusive. However, it is indeed an interesting receiver and should be a good choice if you want to buy an SDR. Or if you want to buy another SDR...

Download from here.

Excalibur's Readout Accuracy

Many DX-ers (MW DX-ers in particular) are concerned about the Excalibur's ability to show the exact frequency down to the hertz. While most SWLs will be indifferent about this, quite a few are monitoring a station's offset from it nominal frequency, and it is also helpful for tentatively ID-ing stations (assuming their offset is reasonably constant).

By zooming in the demodulator panel and by using 1 Hz RBW, monitoring offsets is indeed possible, as illustrated above. Two stations are visible (and audible) on this screen dump from 999 kHz, a Russian-speaking station on 999.008, and a presumed Arabian station on 998.992 kHz. Prior to monitoring, I calibrated the Excalibur using a tone from the signal generator on 1000 kHz. Of course, in order to monitor offsets in the range of 1-5 Hz, the readout must be exact.

Excalibur Sensitivity Measurements

When the Perseus and the Excalibur are monitored side by side, the Excalibur's S-meter consistently reads 6-8 dB lower than the Perseus. One might be tempted to believe that the sensitivity is lower. Well that is not the case. More on that later.

I found these sensitivity measurements using a signal generator with 400 Hz tone and 30 % modulation:

200 kHz: -103 dBm

300 kHz: -102 dBm

600 kHz: -106 dBm

1000 kHz: -107 dBm

1500 kHz: -107 dBm

5000 kHz: -107 dBm

10000 kHz: -107 dBm

20000 kHz: -106 dBm

In terms of sheer numbers, the Excalibur is the most sensitive SDR I have measured, with a good 1uV sensitivity throughout most of the MW and SW spectrum.

So why does the S-meter read much lower than the Perseus? It is apparently not calibrated. When I fed a -107 dBm signal from the signal generator to the Excalibur, the S-meter read -115 dBm. This is roughly consistent with the difference between the Perseus and Excalibur S-meters.

Update July 20: Martin Kent at Winradio suggested that there might be a bug in version 1.06 that caused the erroneous signal level readout, and asked me to check the signal level with version 1.10. Indeed, the difference between the signal generator at Excalibur was reduced to 3 dB. My signal generator may not be 100 % calibrated, so I have no way of saying if the signal generator or the Excalibur was correct. Or any of them.

Now, for those who want to compare Perseus and Excalibur recordings, I have uploaded two 1 MHz recordings with 6120 kHz as center frequency. The recordings contain a lot of static due to nearby thundershowers, giving their AGCs something to work on. The signal levels aren't too high, with the exception of semi-local Murmansk 5930. This should be a good opportunity to compare selectivity.

(Update Aug 6: The download files are deleted due to server limitations. If you want to check out an Excalibur MW file, please download from here)

Excalibur Has Arrived

Got it on Wednesday evening, July 7th. I ordered it with Waters & Stanton on June 20nd, and received confirmation on same-day despatch. However they didn't send it until I made an inquiry nine days later. The question why it took so long remained unanswered. Anyway, I was lucky enough to be able to buy from the first batch of receivers sent to Europe. Thanks Tracey Gardner for alerting me.

The Excalibur came with a 12VDC linear power supply, a proprietary USB cable and an SMA-to-BNC adapter, rather fragile in appearance in fact. Surely, nobody uses SMA connectors for their HF receivers??? A comprehensive (107 pages in fact) user's guide, based on the Excalibur software help function was also enclosed.

The hardware is more or less identical to the other Winradio receivers. The footprint roughly equals that of the Perseus SDR, but slightly taller.

As I learn more about the receiver I will post some theme-based impressions on the blog. More as it happens.

Playing With The Excalibur Demo Software

The Excalibur software is downloadable from Winradio's download pages, working in a demo mode as long as the receiver has not been installed. It has a test signal on 15 MHz, as you can see from the screendump.

The initial impression of the GUI is quite good, although they try to put a lot of information into limited space. A good thing is that the program window is resizeable and that several "skins" are available.

The RF recording feature suffers from the same problem as the Perseus: No scheduled recordings. Third party software solved the problem for the Perseus, and I hope that a Winradio plugin, or a software update, will solve the problem for the Excalibur too. There is in fact a very able scheduler in the program, but it only handles audio recordings.

There are some really nice features once you dig a bit deeper into the software. I hope to see the receiver some time next week.

Excalibur Ships!

While there have been no updates on winradio.com regarding the Excalibur (as of June 20 at 1945 UTC), Waters and Stanton announced that the radio arrived there on June 18 and they are taking orders. They have taken mine. Thanks Tracey Gardner for alerting me.

QDFA Project Version 3

Those who followed this blog last season know that we were very satisfied with the performance of the QDFA. There were however some problems:

1. The amplifier transistors blew due to static discharge. Proper surge arrestors were fitted by Dallas Lankford, and the QDFA v. 2 was up late November.

2. Another problem, probably related to static build-up, caused the transistors not to blow but produce excessive noise. The only explanation we can find is that replacing the battery in cold, dry weather caused the problem. Another fix was needed, and the coming season we will supply power to the QDFA box from within the house. Hopefully, the extra cable will not compromise the nulling properties of the QDFA.

3. The cheap angling rods, while surprisingly weatherproof, did not survive the winter entirely intact. One of them failed in January, and another in April. So we decided we need proper supports, and found them at Max-Gain Systems Inc. These are extremely sturdy fiberglass rods, fastened not by friction but with clamps. We got four 21-ft center supports, and eight 12-ft end supports. This allows us to double the area of each loop, giving us another 6 dB of gain. The visual appearance of the loops will be a "house" instead of the common "delta".

The QDFA v. 3 will be up and running as the Arctic DX Summit starts, early September.

Arctic DX Summit 2010

From Sep 3 to Sep 5, Kongsfjord will be the venue for the Arctic DX Summit. Over the last few years, the Kongsfjord (KONG) and Lemmenjoki (LEM) crews have established a closer collaboration with regards to condx alerts, DX openings, loggings, equipment and QSLs. So it's about time we meet!

OJ Sagdahl and Bjarne Mjelde (host) will meet with Finnish DX-ers Jim Solatie, Håkan Sundman, Hannu Tikkanen and Antti Aaltonen. We will test the novel QDFA antenna design, the new Winradio Excalibur SDR, discuss various facets of the DX hobby, eat Norwegian seafood (and surely more than that) and drink good wines (and surely more than that).

Our intention is that the Arctic DX Summit will evolve into an annual event.

EAC R-390A Spring Test

My EAC s/n 204 R-390A isn't used for DX anymore, but I fire it up now and then to make sure that it works properly. And it always does. This time, I connected a pair of Logitech active speakers to the audio and line out connections.

Using the Lankford-designed manual AM sync I can enjoy distortion-free reception with the R-390A. It is enabled by switching the BFO switch on. Tune the Pitch control to obtain zero beat. At the time I took the photo, I was tuned to Radio Romania's German service. The radio on top is a 1950's Radionette. Works perfectly too, except there's no light in the magic eye.

Micronesia Air Checks

the Federated States of Micronesia is an elusive country for MW enthusiasts in Europe, to my knowledge the only confirmed European reception is V6AJ 1503 kHz in Kongsfjord in 2007. Paul Walker is an announcer at Monster Radio 1150 WGGH Marion IL, and he has taken a special interest in the Micronesia radio scene. A result of this is a collection of air checks from V6AI 1494 kHz, relaying 88.1 FM using a "KUTE" moniker. Paul generously offered me to share these air checks with other DX-ers. They are around 45 minutes each and in MP3 format.

Air check 1

Air check 2

Air check 3

Air check 4

Air check 5

Enjoy!