(copy of email for archival interest - MSE 3/2014)
Date: Mon, 07 Mar 2011 15:04:25 -0500 To:This email address is being protected from spambots. You need JavaScript enabled to view it. From: Joe Taylor <This email address is being protected from spambots. You need JavaScript enabled to view it. > Subject: HFTOA: first radiolocation results Hi all, I'm happy to report that last week four of us (AA6E, K1JT, K9AN, and W3PM) successfully measured the location of a radio transmitter by time-of-arrival measurements. Our "unknown" was the broadcast station WCKY in Cincinnati, at 1530 kHz. Details of the measurements and analysis procedure are posted at http://www.physics.princeton.edu/pulsar/K1JT/HFTOA_2.pdf . If you no longer wish to participate in this project, you may stop reading here. (Send me a brief note and I'll remove your address from the email list.) Otherwise, ... read on. We'd like to try another test soon, perhaps this week. This time it would be good to use a test signal at HF. We'll want a signal predictably copyable by many of us. One possibility is the SSB bulletin broadcast nearly every evening at 0245 UTC by the ARRL headquarters station, W1AW. Frequencies for the voice bulletin are 1.855, 3.990, 7.290, and 14.290 MHz. Ordinarily in this project we'll want everyone tuned to the same frequency, but since W1AW will have identical modulation on all four bands, we should get nearly equivalent results if everyone uses the band on which they copy W1AW best at the appointed time. [Note: if you have another good suggestion for a predictable HF test signal, please share it with the group. A shortwave broadcast station? (Any modulation type, including DRM, would be OK.) A cooperative ham with a good signal who would put a signal on the air at a specified time and do something like read from QST for a few minutes? A net with a known schedule and lots of good signals, especially from the net control?] The suggested data-taking software is called "hftoa.exe", which operates in a manner similar to "wwv.exe". You can download it from http://www.physics.princeton.edu/pulsar/K1JT/hftoa.exe . Install it in the same directory where you already have WSPR and 'wwv'. Typing the program name at the command prompt gives you a brief usage message identifying 4 required arguments: C> hftoa Usage: hftoa <f_kHz> <mode> <nsec> <tstart> Example: hftoa 3990 AM 300 0200 The parameters are as follows: f_kHz - Rx frequency (kHz) mode - Rx mode (AM, USB, or LSB) nsec - Duration of recording (s) tstart - UTC start time (HHMM) Thus, for a five-minute recording of the W1AW bulletin on 3990 kHz the command would be: C> hftoa 3990 AM 300 0245 Please note that we want recordings in *AM mode*, even though the transmission is SSB! That means you will be listening to the bulletin in "Donald Duck" mode. You radio should be configured as for the 'wwv' tests: mode=AM, bandwidth around 6 kHz, RF gain reduced as needed. The 1 PPS pulses from your GPS receiver should be clearly audible but not so strong that they pump the AGC. You can brief test observations by typing something like: C> hftoa 3990 AM 10 -1 This will cause hftoa to make a 10-second recording; the "-1" start time means "starting immediately". At the end of the 10 seconds the program will report the average, rms, and maximum absolute values of the 16-bit integer samples, something like this: Ave: 0.3 Rms: 355.9 Max: 2721.0 Signal level is not critical, but good target values have "Rms" around several hundred and "Max" maybe 10 times larger. (This is for the combination of an over-the-air signal and your 1 PPS pulse.) Aim for "Max" to be much larger than 10000. At the end of an observation there will be a wave file with a name like K1JT_110307_024500.wav ... that is, MyCall_YYMMDD_HHMMSS.wav When we get to the point of making a scheduled test run, this is the file that should be sent to me as an email attachment. We'll do the cross-correlations to determine differential propagation delays for each pair of receiving stations. Finally: Martin, AA6E, has set up an a "HF Time of Arrival Project" Yahoo group at http://groups.yahoo.com/group/hftoa/ for those who wish to continue with the project. The email address isThis email address is being protected from spambots. You need JavaScript enabled to view it. . Please join that group to discuss progress and receive future communications relevant to HFTOA. -- 73, Joe, K1JT