-----Original Message-----
From: Eric Scace [mailto:eric@k3na.org]
Sent: 2001 March 20 Tue 11:54
To: Towertalk
Subject: RFI suppression
Hello everyone --
I'm sure this problem has been solved effectively before. I'm looking for
suggestions for effective techniques.
PROBLEM:
1., When transmitting, RF disrupts my computer-to-radio keying systems.
2. On some frequencies RF appears to be causing problems in the transceiver
itself:
a) The final stage's forward and reverse power detectors will, on some
frequencies, report irregular values. These values are
not consistent with a conventional Daiwa dual-needle SWR meter installed
immediately adjacent to the transmitter's output
connection.
b) The transmitter's internally generated sidetone occasional shifts
frequency at the start of keying.
SITUATION:
-- My station is on the 6th floor of a 6-floor apartment block.
-- My antenna is a vertical dipole, cut for 7.15 MHz, and fed by an antenna
tuner to force it to accept RF on 80m thru 10m. The
feedline is coax. There is no balun at the antenna feedpoint.
-- There is no safety ground in the local power system in this building. 220
VAC is provided as a pair of wires.
-- I can not bring an earth ground into the apartment from outside. The
apartment overlooks the grounds of the French embassy,
which I can't enter. In any event, a 20m long "ground lead" will certainly be
floating by the time it enters the apartment.
COMMENTS:
-- I suspect the coax between the antenna and tuner is hot with RF on its
shield.
-- Since the chassis of the tuner can not be earthed, it's likely that the coax
between the tuner and transceiver is also hot with
RF.
Your ideas?
Eric R3/K3NA
....................
PGP fingerprint: F40B A402 795B 3F52 43B0 47B4 3576 BA88 3A34 5058
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