1700-1900 mile Indonesian UHF TVDX

Great Circle Distance from Perth (miles)
Jakarta	Bandung	Purwokerto	Semarang	Surakarta	Yogyakarta	Madiun	Kediri	Malang
1880	1820	1760	1760	1720	1710	1710	1690	1680

Transmitters were logged and identified by their exact carrrier frequencies, most of which remained relatively stable, often over many months. An up-to-date list of TV stations in Indonesia was compiled from several sources: the Indonesian DX Club (IDXC); Alan Davies' website http://www.asiawaves.net/instv.htm; TV stations' websites; and the Engineering Dept. of the SCTV Network.   Note that Indonesian channels for a given city are almost always all odd or all even, and often the channel spacing is only 1 adjacent channel. On the island of Java, "even" cities outnumber "odds" like Jakarta and Semarang. Denpasar, Bali (just off the right side of the map) seems to have a mixture of odd and even channels.

This list enabled Yogyakarta's frequencies to be easily identified. Yogyakarta is only one of two cities that use ch24 which is frequently received (as often as channels 38 and 46).  Identification of the other cities relied on statistics and logic, so are theoretically not 100% certain. The three channels, 39, 41 & 45, that have identical propagation are clearly from Purwokerto west of Yogyakarta. The channels 38 and 46 that are received a bit less frequently than Yogyakarta's ch38 and 46 are from Madiun to the east of Yogyakarta. The high odd numbered channels 51 and 57, only received when there's also propagation to Madiun, are most probably from Kediri. 

On 12 Nov 2003 a large number of new and odd numbered channels appeared, and exactly the same frequencies were noted in a weaker opening on 2 Jan 2004.  These channels almost certainly originate from Jakarta and Bogor, despite being on the wrong side of a (1200-3000m asl) mountain range. Their signals enter the duct by means of knife edge diffraction over the mountains, with losses that are generally negligible compared to the coupling loss into the duct [1].  Jakarta ch45 has so much ERP that its carrier was subsequently detected by moonbounce (EME). This is possible because Jakarta's coastal plain is flat to the east so moonrise is unobstructed. The carrier frequency measured by EME (after correcting for Doppler) is in agreement with that measured by tropo!  On 2 Jan I was able to compare signal strengths on channels 45 and 47 only two minutes apart: ch45 was several dB stronger than 47, in agreement with the known Jakarta ERPs.  That two high even channels (58 & 62) were also received on 12 Nov 2003 with Jakarta and Bogor is strong evidence they were from nearby Bandung.

The Indonesian UHF TV reception was highly correlated with tropo DX from WA txs a few hundred miles north.  This was evidenced by reception of  94.9, 96.5 and 99.7 MHz FM and 555.224 MHz UHF TV from the coastal town of Geraldton, 240 miles, at a bearing of 343 degrees.  Also from UHF TV further inland (bearing ~360 degrees) from Morawa (180 miles) 541.25 MHz and 583.25 MHz. The bearing of Yogyakarta is 347 degrees. Near the peak of a few openings I monitored 102-107 MHz briefly for Indonesian FM but nil was heard.   

Bill Hepburn's tropo maps for the Indian ocean were indispensible for predicting these Indonesian tropo openings. The 20 Oct (1800 UTC) 2002 map shows good tropo conditions in the eastern Indian Ocean & Timor Sea extending down the West Australian coast to Perth, and is pretty typical of the conditions prevailing until the end of October!  Temperatures east of Port Hedland were near seasonal highs: 46.7C at Mandora station.  Anecdotal evidence from 2m radio amateurs in the Pilbara is that this time of year is the best for tropo from Indonesia. It's typically stifling hot in the Pilbara just before the cyclone/monsoon season begins. Here in Perth it was struggling to get to 24-28 C.  I think the reason we have any Indonesian tropo at all in Perth is largely fortuitous: the coastline to the north of Perth runs on the same bearing as central Java (Yogyakarta), as can be seen in the table of Indonesian and WA tx sites here.  The central WA coast/sea interface running for several hundred miles acts to provide enhanced tropo or coastal ducting, which extends the path southwards. You can see this on Hepburn's map where a small "finger" of colour runs down the coast towards Perth.  Denpasar's high power channel 23 (487.25 MHz) has never been received here, indicating that propagation due north is severely attenuated, but <350 degrees is allowed.  This path is somewhat analogous to the 1500-1700 mile north-south paths on either side of the Bermuda-Azores high pressure cell: Scotland to the Canary Islands and southeast USA to St Vincent in the Caribbean [2].

(from http://www.iprimus.ca/~hepburnw/tropo_ino.htm )

The Hepburn predictions were not always accurate: some days there was contiguous bright colour over the entire path but no reception eventuated (possibly this occurred past my bedtime). On other days there was still a lot of colour and a gap south of Java, yet there was propagation.
 

[1] Acknowledment: I am indebted to Don Graham, VK6HK, for alerting me to the Hepburn charts in mid-October 2002, and estimating the order of magnitude of extra path loss of the Jakarta signals due to diffraction over the intervening mountain range (~ 6dB).

[2] "Transoceanic Ducting at VHF and Above", Emil Pocock W3EP, QST, pp 41-46, March 1996.

1750 mile VK3 UHF TVDX

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