Friday, May 15, 2009

QRP "Contact" Breaks New Frontiers

QRP experimenters K1DNG and AF0OL have potentially set an all-time new QRP record for the most miles/watt for an amateur radio communication, although neither is quite sure how to quantify their achievement.


Tom, K1DNG, of Big Rock Candy Mountain, VT and Philo, AF0OL, of What Cheer, IA have been friends and QRP enthusiasts for many years. They maintain regular contact on 40 and 80m CW over the 1100 miles that separate them.


About a year ago, they began an experiment to see just how little power they could use to communicate with. K1DNG is an avid builder, homebrewer, and minimalist. He began building simple QRP transmitters, each one of a more minimalist design and lower output power. To test their QRP link, K1DNG would pick a random code word and transmit it over and over during a 15 minute window on a regular schedule and frequency each week while AF0OL would attempt to copy it. AF0OL would then email the received code word to K1DNG for confirmation.


This experiment had been going on for several months and reaching lower and lower power levels in the microwatt range. Not all weeks were successful. Sometimes it took two or three weeks to successfully get the code word received at AF0OL. The power levels were getting so low, that K1DNG was custom building new transmitters each time to insure he was getting an accurate output power.


During a two week period in March, K1DNG became overwhelmed with work and personal matters and could not make the usual weekly sked with AF0OL, however, he forgot to contact AF0OL to tell him. K1DNG had already gathered the parts on his workbench for the next generation transmitter, intended to put out just 25 microwatts, but had not had time to construct it. He had also selected the next code word - GUACAMOLE - and written it down on a note card in this station.


Much to his surprise, the morning after the usual weekly sked, K1DNG received an email from AF0OL with the code GUACAMOLE in it. K1DNG remembered the night before thinking about the sked at it's normal time and remembering the code word. However, he was too busy with other matters to go and transmit the code word. Besides, the transmitter to do so had not even been constructed yet. All its pieces still lay on his work bench. So how had AF0OL received the code word?


AF0OL says that after not hearing K1DNG the week before, he had assumed propagation just wasn't good enough for him to hear the new QRPpppp transmitter. So he showed for the next week's sked with low expectations. Without knowledge that K1DNG was not on the air, AF0OL tuned in and began combing the static for the non-existent signal. He was used to digging K1DNG's ultra-weak signal out of the noise, so hearing nothing was not new or unexpected.  AF0OL closed his eyes and let the static in his headphones wash through his brain.


AF0OL describes it as an almost Zen-like moment when he began to copy a rough, ragged signal out of the noise. He says he did not so much hear the signal as sense it. Nonetheless, AF0OL copied the word GUACAMOLE out of the static and nothingness. After the test period passed, he emailed the copied code word to K1DNG, unaware of the situation.


Upon receiving the email from AF0OL, K1DNG was astounded. How was AF0OL able to copy a signal that hadn't been transmitted, especially from a transmitter that hadn't been constructed? Nevertheless, it had apparently occurred.


If so, this represents the ultimate in QRP reception and minimalism. The uniqueness of the achievement presents some peculiar difficulties. The usual metric for QRP contacts is miles (or km) per watt. The distance between K1DNG and AF0OL is know, but what is the transmit power? The transmitter had not even been built. If the transmit power is considered zero, the miles/watt value goes to infinity. Nonetheless, this unique contact rates as the ultimate in QRP and minimalism.



No comments:

Post a Comment