[HCDX] Results of my EWE remote termination experiments.

[J999w@xxxxxxx]

Work is still in progress, but I have had pretty good luck remotely 
terminating my EWE antennas from the shack. Instead of the pricey vactrols 
that are suggested in construction articles, I bought some dirt cheap 
photocells from American Scientific and light them up with standard 12v 
automotive lamps placed in small metal boxes purchased on Ebay (had to make 
the covers myself). I was afraid that the photocells would get overloaded 
from the strong local stations, but I have had no problems at all. Eight 
conductor control cable was also purchased at a discount price from American 
Scientific. Although I am only currently using one twisted pair, this will 
leave me room for working relays, or other expansions. The photocells will 
provide roughly 100ohm to 500k ohm resistance with the small 12 volt lamp 
which worked great on longwave, but I needed less resistance to get nulls 
above 1000khz. I am getting around that by putting two or three in parallel. 
A brighter lamp would also give a lower resistance. Unequal vertical portions 
of the antennas may be making deep nulls impossible on some stations, but on 
others, I can null them into the noise. For example local NDB MK on 410khz 
can be nulled from S9+10 to S0. Chicago's WIND on 560 can be nulled from 
S9+30db down to S9 making it just weak enough for strong DX to override. The 
same with local WEMP on 1250khz. At night, I can null them just enough to 
hear background stations underneath, and am able to listen to adjacent 
channels without interference. Other Chicago "pests" such as 670 or 890, I am 
unable to null at all. Probably due to a mix of ground wave and sky wave 
propagation.

Additionally, I am unable to get any nulls above 1400khz. This may be due to 
the fact that my antenna is too large since I get great nulls down as low as 
100khz. The antenna is currently 15 - 20 ft high, and 75 feet long. I'll try 
smaller dimensions and see if that affects frequency range.

In summary, I have found the common photocell a nice way to remotely 
terminate EWE antennas.

73,

John Wilke
WB9UAI
Milwaukee, WI



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