Hello David,
Thanks for the comments. I have done some more tests and perhaps can clarify
a few of my earlier comments.
The problem exists whether there is an antenna or a signal generator
attached so is certainly happening within the radio.
On checking the different bands the problem varies although the triggers to
start and stop it seem to be the same.
The start trigger seems to be a momentary switch on of the transmitter while
the ATU is out of line. It doesn't need any signal to be transmitted but
just appears to be a product of the switching process.
The stop trigger is the momentary engagement of the ATU whether it has been
tuned to that band or not. The extra signals remain stopped until the TX is
again activated.
Band by band the problem varies.
On 28, 24, 21, 14 MHz the signals seem to be generated as originally
described.... a "copy" of the original signal every 17.4-17.5 KHz away from
the real signal but decreasing in signal strength each "17 KHz step" away.
The extra signals seem just as stable as the radio and when tuned to one of
these signals 1 MHz away from the fundamental there is no sign of drifting.
On 10 MHz the step size seems to be 8.7 KHz.
On 3.5 and 1.8 MHz the signals at the 17.4 KHz spacing from the signal
generator fundamental are quite weak but there but there are strong signals
drifting across the RX passband at 17.4 KHz apart. These signals are
stronger than the signal generator fundamental signal.
The attenuator is interesting. It works as expected on the incoming signal
from the signal generator.
On one of the nearby extra signals the frequency of the signal changes by
about 200 -300Hz as it is switched from between the adjacent positions from
IPO to 6dB and again from 6dB to 12dB. This is very noticeable audibly and
doesn't happen with the fundamental signal.
Regards,
Chris ZL2DX
-----Original Message-----
From: yaesu-bounces@contesting.com [mailto:yaesu-bounces@contesting.com] On
Behalf Of K1TTT
Sent: Sunday, 2 January 2011 1:51 a.m.
To: yaesu@contesting.com
Subject: Re: [Yaesu] FT-1000 mystery signals?
Yes, that is odd. I have never heard of one that bad, especially at such a
low repetition rate so this is just a guess. Normally you get images like
that when there is a very strong signal mixing with the desired one enough
to cause distortion in the receive chain. Since it goes away when you put
the tuner in line that would tend to indicate that it is in the first rf
mixer, the tuner would act as an attenuator if not tuned, or as a
preselector if it is... does turning on the radio attenuator also get rid of
the products? Do you have a signal generator so you could eliminate
external sources, just to be sure its not something gone bad in the radio?
When you say it returns after tx, does that mean that when you have the
tuner in line, then tx, then go back to rx they are there? Does the tuner
stay in line or drop off or automatically tune itself??
If it is an external mixing source the key of course is to find it. The
17khz step is probably related to the device that is generating the
interfering signal. That frequency could be a monitor, tv, switching power
supply, LED lamp, just about anything new that was installed about the time
the problem started, and probably pretty close to the antenna. Double check
shield connections on coax IN the shack, and all ground connections also to
make sure you aren't picking up noise from a monitor or something else in
the shack. Otherwise you are on a hunt for a loud signal around that 17khz
range, if you can pick it up on a hand held shortwave receiver that would
help.
The sweeping carriers on 75m could be related. Its possible your tx on that
band is disrupting the device a bit and shifting its frequency. After you
stop transmitting it goes back to its normal frequency. However, I have
seen one like this caused by an oscillating voltage regulator in an
amplifier. As the temperature in the amplifier changed the regulator
oscillation frequency changed. Do you hear carriers every 17khz across 75m?
if so they could be used to help track the source.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: Chris Hannagan [mailto:zl2dx@xtra.co.nz]
> Sent: Saturday, January 01, 2011 05:34
> To: yaesu@contesting.com
> Subject: [Yaesu] FT-1000 mystery signals?
>
> Hi All,
>
> My FT-1000 has an unusual problem and I would appreciate some help to
> track down the issue.
>
> On the bands there are extra signals being generated in the receiver.
>
> I can hear a "copy" of the original signal every 17.4-17.5 KHz away
> from the real signal but decreasing in signal strength each "17 KHz
> step" away.
>
> On my local 10 metre beacon for example, I can hear these "copies" to
> well above 29 MHz.
>
> As you can imagine it makes 20 metres sound really busy in a contest
> but often the signal I'm hearing is not the fundamental one..
>
> This "feature" switches off by momentarily putting the tuner in line.
> It's not necessary to actually have the tuner operate.
>
> The extra signals re-appear when the rig is momentarily put into TX mode.
>
> Possibly related to this is that when chatting on 75 metres, on
> returning to RX there are often strong whistles (carriers or images?)
> that sweep across the received frequency for about 2 seconds or so.
>
>
>
> I would appreciate any assistance with this and would like to hear
> from anyone else who might be seeing the same events.
>
>
>
> Thanks and 73
>
> Chris ZL2DX
>
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