Sydney-CFA Details (History Check by Antennex 2001):

Several years back Jack Stone wrote in the antenneX issue January 2001 "for purpose of posterity":

When Kabbary built the "serious CFA" a 500-watt B. E. transmitter was installed to feed it. This was installed in the room (second hand construction site office) immediately below the CFA. The tuning was all done with the transmitter only a few feet away from the CFA feed network making it a convenient test signal generator for the tuning work. VSWR protection was very good on B. E. transmitters, and apparently it did not have any problems powering the system.

(He was not giving the source of information.)

What is particular good with the Broadcast Electronics VSWR protection that the transmitter is so good that it makes (as we are told) a non working antenna into a working antenna? According to the data sheet, their 500 watt AM Transmitter

http://tinyurl.com/23kouq

AM 500 W can handle a nominal VSWR of 1.3:1 - there is nothing peculiar about that, it needs a proper load as any transmitter do.

So we know that the CFA worked in 1997, then about two years later (that will be in 1999) this happens:

the station wanted to move the transmitter to a room at ground level in the building. They ordered a new 1 kW transmitter and installed it there with a length of 1/2" foam Heliax connecting it to the matching network in the hut on the roof.

Hey, wait a minute! They installed the CFA in 1997 and were using it for two years and as it seems without any problems. But we have been told elsewhere by the antenneX that the CFA was not working and it was causing interference to the neighbours and the station was forced to reduce the output power to 200 Watts to avoid losing their license.

So how do they tackle this problem? Did they order a 1000 Watt transmitter replacing the old 500 Watt transmitter to feed into their (as we are told) non working CFA and wanted to use that to please their neighbours?

It is more likely that the CFA worked for the first two years and then the station wanted to re-arrange the installation. For that work they used the local Innes Corporation and they messed up the CFA during the work and they could not find out how to get it to work in a proper manner again.

To keep the station on air they had to rebuild the CFA into a fat monopole and tuned it as such. So, that was then in 1999 that the problems started and the neighbours was getting interference in their homes.

So John Innes the owner of Innes Corporation had to protect his company and KAT had to take the blame. Innes gave his side of the story in the antenneX article of June 2000, Jack Stone uncritically wrote what he said.

KAT returned to the station in November 1999 to repair the CFA. At that time the station was moving to an other site as the industrial building was to be demolished leaving place for a new house that can be seen in GOOGLE EARTH at this position 3354'32.78"S, 15110'50.56"E.

here is a large open place, the Sydney Park, http://tinyurl.com/29pzjw in front of the house giving a good opportunity to make field strength measurements.

KAT and Innes did this at this occasion in November 1999 and they agreed that within a few percent the field strength was 170 millivolts per meter at distance 800 meters, and 350 mV /m at 500 meters , for 200 watts feed to the antenna.

How good is that?

According to FCC the standard quarter wave mast with the standard 120 quarter wave long radials buried in the ground around it can accomplish at most 156 milli-volts per meter for 200 watts at that same distance of 800 meters and the stations frequency of 1665kHz.(172 millivolts per meter over a PEC ground [not considering the loss to ground over that distance] and 156 millivolts per meter for a ground conductivity of 10mS/m as listed in the ITU Atlas ITU-R P.832-2 for Sydney)

Innes refused to give out any more field strength readings, claiming that these readings, made on his field strength meter by him and KAT, was the property of the broadcasting station.

Reference:

[1] FCC graph for Effective Field At One Kilometer And One Kilowatt http://www.fcc.gov/mb/audio/decdoc/scanned/73190fig8/1.gif

[2] FCC Ground-wave Field Strength Graph 15 http://www.fcc.gov/mb/audio/73184/index.html


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