NACHO,

IMHO: Your T2FD could also use a "Feed-Line-Isolator" at the
'junction' of the Receiver and Coax Cable.

Take a look at the Wellbrook "Low Noise Antenna" 'design concept'
using two components they manufactu the Universal Magnetic
Balun (UMB) and the Antenna Feed Isolator (Feed-Line-Isolator).

GoTo= http://www.wellbrook.uk.com/longwire.html

FWIW: This webpage has two Drawings/Diagrams "The Wrong Way"
and "The Correct Way" plus a brief description of the 'Whys'
and 'Hows' of this "Low Noise Antenna" design concept.

NOTE: These are labled as "Longwire" Antenna Baluns, but
in reality they are mostly used on the more common
"Random Wire" Antennas that the majority of SWL are able to
build and use in their backyards or outside/inside the house.


iane ~ RHF
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= = = Nacho wrote in message
= = = ...
I see... thanks for the reply.

I was confused by the toroid in transmission. When transmitting, the
ferrite toroid is usually near the transceiver, but for other reason: to
avoid the RF catch by the coax shield or reflected due to a mismatched
antenna to reach the transceiver (it can cause RF shock to people and
interferences). In reception, yes, you're right, but I think that only
if the coax shield is correctly grounded.

The signal at the received is not the one coming through the line, but
the difference between the signal coming through the line and the signal
coming though the shield, so grounding the shield puts the shield signal
to zero, and then only the line signal is considered. If the radio is
operated from batteries or ungrounded, both signals will count and the
noise will be noticed, whether it comes through the line or through the
coax.

Maybe I'm wrong. RF is a very empirical "science" and experiencie is
more valuable than books . I have little experiencie and few books

I spent great moments with a long wire (30 meters or 100 feet) coupled
with a MFJ antenna tunner with long wire coupler (MFJ-941E) in the
country. Now I have a constant electrical noise in the city in all the
band, about S7-S9, 24h... I'm limited to strong signals.

Best regards.

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