Other videos on 48250 KHz:
Re: African 48 MHz TV transmitters.The info at kb2wf 's web site was incorporated from information I had published/sent some time ago. The main change is that there are only two transmitters on the African continent (that I know of). They are 3C Equatorial Guinea on ~48250350 plenty drift upwards during the warm-up cycle, and Kenya on 48249982, eastern shore of Lake Victoria. Most hams call out 3C when they are probably receiving Kenya. As Alan 3C5I has repeatedly pointed out, 3C TV only starts up at 14.30z. Kenya seems to on most of the day, as I have received it on MS early in the morning over weekends. 3C TV can be readily IDed by the extremely grotty carrier sound when listened to in sideband mode, presumably caused by the tube being thrashed, as the first 50 Hz sidebands are (were) only 10 dB down! No wonder the TX went belly-up. This parameter should be around -25 to -30 dB in a correctly set-up TV TX. There are no QRO indicators on low VHF in Southern Africa. Other 48 MHz TV in the "region" is high power Homs Syria on 48250168 24 hours and a new medium power Middle East TX on ~48249990 that started up some months ago tending to zero-beat Kenya at times, drifting around a bit. TV-DXers in northern Europe regularly receive the high power Iranian outlets on 48239620 and 48259440/712 MHz in the spE season, and these are also candidates for the "3C-TV" ID, although it should be easy to separate them simply by antenna direction from there. Measuring TV carriers: the info at kb2wf is fine, but these days it is easy to use software such as Digipan 1.6 (recommended), Spectran or Hamview to measure the audio offset. cusn on 6m!
This is Ian's view of Kenya TV:
Measuring TV carriers with Windows sound card:
Seems everyone has a sound card these days: In USB mode (1 kHz steps on rig) tune 1 kHz low of TV carrier to obtain an audio howl. Use Cool Edit 96 (download free from Web) and Win '95/98 to grab the audio frequency from the rig's speaker (LINE input to sound card). In the Analyze/Frequency Analysis window of Cool Edit, read off the audio freq. Add to the RF freq, eg, 48.249 MHz + 1171 Hz = 48250171 Hz (Syria). Do exactly the same on WWV on 15 MHz to find rig's frequency error, should read 15000000 Hz. Multiply this error by the TV carrier freq, divide by 15000000 Hz. Add or deduct this answer to get the exact TV freq. Expect result within 4-5 Hz of the actual carrier freq. This is good enough to identify any TV carrier. If there is more than 1 TV carrier in the SSB bandwidth, the sound card will display the strongest audio tone. Add that to the RF freq as before. This method takes the accuracy of the rig and sound card out of play, and automatically calibrates the system (allow system to warm up!). With this method you can measure any AM or SSB freq, but not an FM carrier.
Ian ZS6BTE [email protected], Tuesday, November 16, 1999 at 11:23:06 (GMT)
Other videos on 48250 KHz:
These are the TX freqs of the transmitters in the West African area: 48.250.246-279 Central North Africa (QTH unknown), 48.250.295-332 Siera Leone, 48.250.356-383 Ghana, 48.250.390-427 Equatorial Guinea. All display pronounced drift for the first hours, rising in freq as the evening gets older hence the last 3 digits covering the range. The best sig here is "Ghana". All three have a peculiar growl on their carriers, one can only imagine what the video low freq response looks like. The best ref freq on Band 1 is the German transmitter on 48.247.400 Biedenkopf (always within 1 Hz). This is also a specific offset, easy to confirm by amateurs. Further east, Homs, Syria is on 48.250.167 +- 3 Hz. This is also the "big signal" in these parts. By the way, it's impossible to reasonably establish the TV carrier freq using only the "zero beat in USB" technique, because the SSB rig runs out of audio output long before the carrier freq is neared. Some more info for Atlantic area: Portugal (Muro) is currently on 48.242.209, drifts a few Hz, specific offset easy to identify) and Madrid is on 48.250.088, now displaying poor carrier stability as it approaches the rumoured coup de grace at the end of the year, a big loss for us in the southern hemisphere.
Courtesy of Ian ZS6BTE [email protected], Monday, October 18, 1999 at 13:12:46 (BST)