So John (W1TAG) was right with his second guess.
However it is interesting that the 135 m tower was used on 1097 kHz (273 m
wavelength), so it acted as a lambda/2 monopole. Since such antenna is high
impedance (typical 1200 Ohm) the decoupling impedances of the light cables
should be high too (probably several up to 10 kOhm at 1097 kHz). If it is
non resonant (inductance only) then it should be still over 1000 Ohm at 136
kHz. But if the decoupling is resonant the impedance at 136 kHz may be as
less as a few Ohm.
It is likely that all 4 lamps are fed through a single decoupler, if you
have access to that you can try to replace it by a one that is suitable on
136kHz.
73, Rik ON7YD
At 16:13 19/01/2004 +0100, you wrote:
Hi Rik and others...
After I discuss this problems with Bob OK2BVG and we found the problem. The
tower itsefs is DC isolated, but...on the tower are 4 lihgts (2x in 70m and
2x in 135m) powered by 410m of twisted-pair cable. So, this is total 820m of
wire well cupled with the antenna. This antenna has been on air for about 20
year on the frequency 1097kHz. The filters are designed for this frequency
and have a very low reactance on 136kHz. Any idea?
73 de Rich OM2TW
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