[UK-CONTEST] Transmitted Noise

[Cooper, Stewart]

Very many thanks to all who helped me with suggestions. Incredibly, the
noise is actually wide-band noise generated by the tranmsitter chain in
the FT1000mp, and is normal. Two respondents had experienced this - it
is within spec, but can be loud enough to lift the S meter on the second
radio when in the same band. It is present even when the drive is backed
all the way off, and the linear amp is actually switched off. When
SO2R-ing on different bands, the band-pass filters do their job to
filter it.

73
Stewart
GM4AFF

-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com] On Behalf Of Cooper, Stewart
Sent: 18 January 2008 10:12
To: UK Contest Reflector
Subject: [UK-CONTEST] Transmitted Noise

All,
Having seen some comments about SO2R in AFS I thought I would see how my
radios performed while both in the same band. I'm using 2 x FT1000MP.
Neither have any modified front-ends/roofing filter mods. I have found
that when I transmit on the first radio, the second radio is receiving
lots of noise. Read on - this is not what you think. The receiving radio
is using beverages and ewes which are about 100m from the tx antenna.
The received noise is a shhhhhh type noise and occurs even when I reduce
the output of the transmitted signal to NOTHING! In fact, the shhhh
remains there whether I blast 400 watts out, or simply press the
footswitch and actually radiate nothing (nothing perceptable anyway).
The shhhh noise varies in strength when I switch between rx antennas to
a slight degree - the noise is coming in to the receiving radio via the
antenna input - disappears when unplugged. It also doesn't get much
louder as I tune up and down on the receive radio towards or away from
the tx frequency. I do believe the noise is being transmitted and is not
related to the actual power output and happens whether the transmission
is SSB or CW.
I haven't done much investigation, but it is very strange. There are
many things I have yet to try, but I wondered if anyone else has any
experience of this? Please just reply off reflector.
73
Stewart
GM4AFF



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