Hello Laurence,

For your interest.

I do not know how you couple the E-probe to your receiver.
For years, I have been using a rf - isolating transformer to 
separate antenna and receiver ground.

This is a home made transmission line transformer, consisting of 11 
bifilar turns on a small high mu toroid (AL=8300). The inductance is 
1.2 mH. The measured -3dB bandwidth in a 50 ohm system covers 4 kHz 
- 200 MHz.

It appeared that the isolation was not perfect, due to the 
inter-winding capacitance. I have made a new transformer on the same 
core with two windings of each tree turns. The windings are opposite 
each other on the core. The bandwidth is now 45 kHz - 50 MHz. The 
loss is 1.3 dB.

Despite the raise in the lower -3dB point, reception at VLF is much 
improved due to lower noise ingress. See attachment.
The screen runs from 1 kHz - 13 kHz. At the right hand the dashes  
from the Russian Alpha system can be seen. The white band is with
common ground. Harmonics of the 50 Hz mains can be easily spotted. 
In reality the picture will be better,as the sensitivity of the 
PERSEUS drops considerable below 10 kHz.

The level of interference on 380 kHz caused by a plasma TV in the 
neighbourhood is also much reduced.

Like you, I found that local noise on a loop is much worse.

73,
Roelof, pa0rdt 

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