[Yaesu] 1000MP - Decreased Signal Strength on Low Bands

[Ken Claerbout]

  Thanks for the suggestions Ty.  Using my 80 meter 4 square, I have a local
line noise of S6 when in the tuned position and S9 in the flat setting.
Switching the 4 square between the Antenna A jack and RX Ant In, I did not
see any change.  The same thing happens on 40 & 160 although it seems to be
most pronounced on the low end of 80 meters.  Any other suggestions?

73
Ken K4ZW

----- Original Message -----
From: "Tyler Stewart" <k3mm@erols.com>
To: "Ken Claerbout" <K4ZW@Staffnet.com>; <yaesu@contesting.com>
Sent: Monday, January 01, 2001 6:31 PM
Subject: Re: [Yaesu] 1000MP - Decreased Signal Strength on Low Bands


> Try using the RX In jack and see if everything sounds normal.  If so, it
> sounds like a bad high pass filter section.  The RX ANT In jack bypasses
> this board.  This is on a separate board before the main RX RF board and I
> believe is only IN when in TUNED mode and is not in line when using a RX
> antenna. If it still occurs, I almost guarantee, it's the 80 meter BPF
> section in the receiver.  Note that the BPF's are always in no matter what
> preamp you are using.
>
> I've had problems with this and some of the bandpass filter sections in
the
> receiver.  What I've found every time is that the little molded coils they
> are using short out some turns.  It's not something you can find visually.
> You have to  start lifting leads and measuring or just shotgun
replacement.
>
> I just dug out my tech manual for the MP and have noted that L3503 on the
> HPF-UNIT is the first coil to ground in the 80 M HPF and has failed once
on
> both of my MPs!  It's a 1.8uH rf choke and it's Yaesu part # L1790049.
>
> Note that this is a very easy board to work on.  It's located near the
right
> rear top of the radio behind the AFC board and just in front of the A/B
> relay board in front of the SO239 jacks.  It's mounted on a couple of
> plastic, snap-in standoffs and the board should be marked with the L3503
> designator.
>
> SHould be an easy fix if you can handle basic electronic repair!
>
> 73, Ty K3MM
>
>
>
> ----- Original Message -----
> From: "Ken Claerbout" <K4ZW@Staffnet.com>
> To: <yaesu@contesting.com>
> Sent: Monday, January 01, 2001 2:28 AM
> Subject: [Yaesu] 1000MP - Decreased Signal Strength on Low Bands
>
>
> >
> > I noticed during the CQWW CW contest this past November, that signals on
> 80
> > meters seemed unusually weak.  With all the solar activity going on that
> > weekend, I wrote it off to poor conditions.  Thinking about this a bit
> > further, I recall that over the past month or two, 80 meters has sounded
> > unusually quiet.  I decided to do a side by side comparison with my
> Kenwood
> > 940 and promptly noticed that signals on 80, including power line noise,
> > were 20 dB weaker on my 1000MP.  No wonder I was having a hard time
> chasing
> > the weak DX stations!  Taking a closer look, I also see this happening
on
> 40
> > & 160 although it was not apparent until now.
> >    I swapped the two rigs just to eliminate any potential problems with
> > cables, filters, or something specific to that operating position and
the
> > problem followed the radio (1000MP).
> >     The radio is set for a tuned front end and when I switched it to
flat,
> > using the broad front end amp, signals came back up on all three bands.
> > This would seem to indicate that there is a problem with the low band
> tuned
> > RF amp.  However, the diagram in the manual labels the range for this
amp
> as
> > 1.9 - 7 Mhz.  Is this front end section actually in use on 160 meters in
> the
> > 1.8  - 1.9 Mhz range and also on 40 meters between 7 Mhz and 7.3 Mhz or
is
> > the wide band amp used in these frequency ranges?  If it's the latter,
> then
> > that kind of kills my theory about the low band amp.  Is there anything
> else
> > setting wise etc. that I should be checking?
> >     In the event I have to get this repaired, I'd appreciate suggestions
> as
> > to where I should have this done.
> >
> > 73
> > Ken - K4ZW
> >
> >
> >
> >
> > --
> > FAQ on WWW:               http://www.contesting.com/FAQ/yaesu
> > Submissions:              yaesu@contesting.com
> > Administrative requests:  yaesu-REQUEST@contesting.com
> > Problems:                 owner-yaesu@contesting.com
> >
> >
>
>


--
FAQ on WWW:               http://www.contesting.com/FAQ/yaesu
Submissions:              yaesu@contesting.com
Administrative requests:  yaesu-REQUEST@contesting.com
Problems:                 owner-yaesu@contesting.com