K5LAD - 50+ Years of Ham Radio Memories
Working DX With the Panadapter
By Jim Pickett K5LAD
Search keywords: Elecraft panadapter, P3, DXpedition
Have you ever been listening to a DX station or, perhaps, a DXpedition and wonder what it would be like to experience this? The excitement of visiting a foreign country and being a station that hams all over the world sought to contact. You could be so selective and work just the stations you want and in whatever order you wanted to work them . Right? .. yeah, sure. If youre the DX station, there are hundreds or thousands of stations calling you and youre supposed to pick them out, one by one, and give them a report. Some of us call CQ from our home station and have a real problem picking out a single call from the one or two who might be returning our call. Now, multiply that by a zillion and you have some idea of what fun that DX station is having.
On top of that, if its a DXpedition he has probably traded his vacation time with his family to make the trip, paid a large amount of his own money just to be able to participate, and perhaps even brought his own equipment to be tossed around by the airline baggage handlers and subjected to more abuse in a few days than it might see in a decade. All of that so he can be abused on the air by people who think hes avoiding them for some reason. Sure sounds like fun to me . how bout you?
Still, many hams participate in this fun year after year and still anticipate the next exotic trip with their radios as they go to far away places with strange-sounding names. After they return home, they get to be abused by the hams who swear that they worked him and demand a QSL card, even though that station is obviously not in their log.
I recently had the opportunity to work a DXpedition in the Republic of the Congo on 17 meters. The date was January 24, 2012, the station was TN2T and it was just after a large CME (coronal mass ejection) had hit the earth and many were wondering whether it would make propagation useless for the coming several hours or days.
I was using my home station, which consisted of an Elecraft K3 transceiver with the matching P3 panadapter. For those unfamiliar with a panadapter, this is an electronic device that looks at a broad range of frequencies in the receiver. When youre listening, you want to hear whatever is within a very narrow window, which allows only the desired station to pass and to exclude all others close by and on the band. On the other hand, it is desirable to be able to see a much wider window to know how many stations are transmitting and how many are available on what you might have first thought to be, dead band.
The span of viewable frequencies is adjustable on the P3 from as much as 200 KHz to as small as 2 KHz. Markers display on a horizontal line which represents the window youre viewing, i.e., if the span is set to 82 KHz, every signal your receiver is detecting within the 82 KHz total, counting both sides of your listening frequency, will be a vertical blip and the height of the blip represents the signal strength. The stronger the signal received, the taller the blip. Note that on the P3 the vertical range is also adjustable. The P3 also allows the user to freeze the screen and make a print of what was being displayed at the moment of the freeze. The following is an example of one of these picture files:
This picture was made on Jan. 24, 2012 with my K3 VFO sitting on 14.240 KHz. where I was listening. It was about 3:30 PM and the P3 scan was set to 50 KHz so the window was looking at all the signals within the range of 14.215 and 14.265 KHz. The green half-square on the base line shows the width of the roofing filter I had employed at that time which was 2.8 KHz. The indication of the station I was listening to was within that green half-box. He was not particular strong but was Q5 copy. You can see another signal just to the right of the green box and the height of the blip shows that he was quite strong. The nice thing about the K3 and its roofing filters is, they are so tight that I was unable to hear that station displayed on the right. The roofing filter also is so tight that the AGC (automatic gain control) in the K3s receiver was unaffected (no pumping from a close-by signal) and if I had not seen the blip I would never have known he was there.
You can see several other signals within the window both above and below where I was actually listening. The very narrow blip that is just to the left of the center is not being modulated since it is very narrow. It was probably a station tuning up their transmitter or perhaps their amplifier. The waterfall on the bottom of the display shows what had been heard just milliseconds before. Note that the tune up signal had been on-off-on.
Meanwhile, back to the story about DXing. Again, I had the opportunity to work a DXpedition that was in the Republic of the Congo and on 17 meters at the time. The date was January 24, 2012 and the station was TN2T. Note in the print here, I was tuned to 18.132.1 KHz listening to the DX station. He was operating split and would announce that he was listening up 5 to 10. There seemed to be jillions of stations calling him. I had my station configured where the DX station was in the left ear of my headphones and the other receiver (which was being tuned up and down from 18.137 to 18.143) was in the right ear. I became absolutely fascinated by the panadapter patterns and Ill describe what I was seeing.
When the DX station announced he was listening, all stations started transmitting within that 5 KHz window where he said he was listening. Often, when working DX stations on split I can see small null space where no stations, or only a few stations, are calling and I can set my transmitter to that spot. In this case, there were zero spaces of no one calling and the hump of the display from the right side of the green box to the right side of the purple box was filled with hundreds of stations calling him, perhaps even thousands.
One other explanation of the picture; the purple half-box shows the listening window of the second receiver (the K3 has the option to add a second receiver, which is an exact duplicate of the standard receiver. This allows several benefits over the dual-watch feature of many other transceivers where a second VFO allows listening on one or the other frequency but not both simultaneously like is possible on the K3.) When the transceiver is set to split this is also where I will actually transmit when I key the transmitter.
The red half-box around the purple half-box tells me that my transceiver is set on split so I dont accidentally transmit on the DX stations frequency. My second receiver (purple box and the frequency where I would be transmitting) was sitting right on 18.142.1 KHz so you can get an idea of the frequencies youre seeing in the display. Theres nothing special about where I chose to transmit to him. It just happened to be exactly 10 KHz above his frequency.
I might also mention another interesting thing that was happening during the time I watched this. Another DXpedition, HK0NA on Malpelo Island off the NW coast of South America, came on the band just a little lower in frequency than was TN2T. They also announced they were listening up 5 to 10 which put callers for their station (and there were also jillions) right on the top of TN2T in the Congo. When a station would call HK0NA on top of TN2T, the UP Police would yell at them to tell them that TN2T was working split and theyd better get off that frequency. It was all a comedy of errors and provided me with quite an afternoon chuckle.
-- written January
24, 2012 Published TARC Newsletter February, 2012
Published TARC Newsletter February, 2012