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Can a receiver's sensitivity diminish over time?

Discussion in 'Electronic Repair' started by Dan_Musicant, Mar 16, 2007.

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  1. Dan_Musicant

    Dan_Musicant Guest

    I have a mini-stereo (5 year old Sony MHCMG110) and stations that it
    used to receive OK now are noisy (static, typical noise for a weak
    station). I almost always listen to low power stations (college radio),
    and their output is weak, of course. However, stations that used to come
    in OK now sound crumby. It varies from day to day, but overall it seems
    worse and I wonder if I can attribute this to some kind of deterioration
    in the system. The last week or so it seems worse than ever. Of course,
    it could just be that the 2-3 stations I listen to have changed their
    pattern of transmission or their transmitters are having problems.

    The antenna I use for this system is a dipole that I have mounted on a
    swiveling rabbit ears, and I've had that antenna since the mid-1970's. I
    have several dipole antennas, but I always got the best reception with
    this particular one, so I use it on the rabbit ears, which is just a
    homemade affair made from wood. The poles are in one straight line, and
    horizontal and I can rotate that line like a compass needle. I tested
    the leads yesterday with an ohmmeter and there's continuity between
    them. Cleaned the leads and reiniserted in the antenna input for the
    system, but there's no evident change.

    The dipole antenna is basically like this, and can rotate around that
    center point for best reception:
    ______________
    |
    |
    |
    |
    |


    I've been thinking of doing an additional split on one or both of my two
    rooftop TV antennas and running feeds to the ministereo. If two coaxial
    feeds, I'd have a switch. These two antennas point in different
    directions, basically 90 degrees apart, so I could get more stations
    that way. I know I'll have to use a balun if I use coaxial antenna
    inputs (I have some baluns).

    Any ideas? Thanks!
    Email: d plus musicant at pacbell dot net
     
  2. Usually caused by a big lump of metal being moved close to the radio. Some
    come with a dipole antenna made of ribbon cable - might be worth a try.
     
  3. Jerry G.

    Jerry G. Guest

    There are many factors that can attribute to deteriation of good
    reception.

    The main causes are from changes of condtions either by weather,
    atmospheric conditions, or some type of interference.

    It is also possible to have one or more components in the front end of
    the receiver's tuner section that are going out of specifications due
    age, or wearing out.

    It takes much more than a simple ohm meter to determine the
    performance of an antenna, or the front end of a receiver.

    Connecting the receiver to a properly installed and tuned outdoor roof
    top antenna will certainly improve the performance compared to a
    simple inside rabbits ears antenna.

    If you have cable TV service, check with your cable provider, to see
    if they offer any type of extended server for FM reception. Many offer
    these services, and provide radio broadcasts from other cities and
    towns. Some of the cable operators do not charge extra for the FM
    radio services.



    Jerry G.
    ======
     
  4. Guest

    tried replacing the valves? :)


    NT
     
  5. Jamie

    Jamie Guest

    Some times if there is a very stong/near by signal being emitted that is
    just below or above your broad range of the receiver, it will saturate
    the pre amp in the RF front end thus causing it to become less sensitive
    to RF in the range your receiver expects to operate in.
    That is just an example. It's also possible you have a bad transistor
    in the pre amp. when this happens, they will pass a DC test but not an
    RF test. THe fix for that is to have it replaced.
    SOme of the old units used Gas Fets, these kind of broke down over
    time..
     
  6. tez

    tez Guest

    The answer is yes. The various componets can change values with age
    and use. Depending on how much you want to spend, the price of a
    replacment radio and senimentality of your existing unit you would
    have to get a tech to test and or replace each componet. Also check
    the output of power supply to make sure it is not giving low voltage.

    Re the antenna If you can afford it you are better off to use a
    seperate FM antenna on a rotor so you can point it to specific
    stations. You may receive stations that you cannot receive with an
    indoor antenna.
     
  7. jonpi

    jonpi Guest

    i don't know but the fact that the ozone hole is bigger than ever could
    have something to do with this

    and now i remember another more feasable fact ... the amount of solar
    radiation is increasing with time and is now highest in 1200 years or
    some large number of years ... i know there is also weakening going on
    at present of the geomagnetic pole strength (gauss) and since this is
    the major shield of solar wind, well you can do the math or maybe i
    should say, someone HAS done the math

    we ARE in the midst of a golden age of science due to our many new ways
    to "see" things

    i love to joke but there is truth above

    john p
     
  8. Dan_Musicant

    Dan_Musicant Guest

    :
    ::
    :> However, stations that used to come
    :> in OK now sound crumby. It varies from day to day, but overall it seems
    :> worse
    :
    :Usually caused by a big lump of metal being moved close to the radio. Some
    :come with a dipole antenna made of ribbon cable - might be worth a try.

    I think mine is made of ribbon cable. It's cable almost 1/2 inch wide,
    IIRC. Plastic with the wires embedded in plastic at the edges. I've made
    a number of them from ribbon cable but none of those was providing as
    good reception as this one, which came with my Sony STRV55 receiver.
    Email: d plus musicant at pacbell dot net
     
  9. Dan_Musicant

    Dan_Musicant Guest

    :> I have a mini-stereo (5 year old Sony MHCMG110) and stations that it
    :> used to receive OK now are noisy (static, typical noise for a weak
    :> station). I almost always listen to low power stations (college radio),
    :> and their output is weak, of course. However, stations that used to come
    :> in OK now sound crumby. It varies from day to day, but overall it seems
    :> worse and I wonder if I can attribute this to some kind of deterioration
    :> in the system. The last week or so it seems worse than ever. Of course,
    :> it could just be that the 2-3 stations I listen to have changed their
    :> pattern of transmission or their transmitters are having problems.
    :>
    :> The antenna I use for this system is a dipole that I have mounted on a
    :> swiveling rabbit ears, and I've had that antenna since the mid-1970's. I
    :> have several dipole antennas, but I always got the best reception with
    :> this particular one, so I use it on the rabbit ears, which is just a
    :> homemade affair made from wood. The poles are in one straight line, and
    :> horizontal and I can rotate that line like a compass needle. I tested
    :> the leads yesterday with an ohmmeter and there's continuity between
    :> them. Cleaned the leads and reiniserted in the antenna input for the
    :> system, but there's no evident change.
    :>
    :> The dipole antenna is basically like this, and can rotate around that
    :> center point for best reception:
    :> ______________
    :> |
    :> |
    :> |
    :> |
    :> |
    :>
    :> I've been thinking of doing an additional split on one or both of my two
    :> rooftop TV antennas and running feeds to the ministereo. If two coaxial
    :> feeds, I'd have a switch. These two antennas point in different
    :> directions, basically 90 degrees apart, so I could get more stations
    :> that way. I know I'll have to use a balun if I use coaxial antenna
    :> inputs (I have some baluns).
    :>
    :> Any ideas? Thanks!
    :> Email: d plus musicant at pacbell dot net
    :
    :The answer is yes. The various componets can change values with age
    :and use. Depending on how much you want to spend, the price of a
    :replacment radio and senimentality of your existing unit you would
    :have to get a tech to test and or replace each componet. Also check
    :the output of power supply to make sure it is not giving low voltage.

    I wouldn't have it tested. I didn't expect it to last longer than it
    has, simply because I read a post by someone who's had a few of these
    ministereos and he said they last about 5 years. This one has a 60 CD
    changer, and I figured that would break first. However, nothing has
    broken on it except for two things:

    1. The volume control (spin knob) doesn't reliably advance or decrement
    the volume. You can spin it and nothing happens - very annoying. My
    workaround is to use the remote. People in this NG tell me I can buy a
    replacement control for $15 and I would except that folks say that
    taking the unit apart and replacing the control is apt to be pretty
    complicated.

    2. This reception problem, which as I say I am not sure is due to any
    deterioration of the unit. However, I figure there's a fair chance that
    it IS.

    :Re the antenna If you can afford it you are better off to use a
    :seperate FM antenna on a rotor so you can point it to specific
    :stations. You may receive stations that you cannot receive with an
    :indoor antenna.

    I really should do that. I should have a long time ago, actually.
    Email: d plus musicant at pacbell dot net
     
  10. It's in the shape of a T with the wires at the ends of the T arms soldered
    together?

    It's not impossible to add extra elements to one of these also made of
    ribbon, but it gets hard to handle and install. If the roof isn't metal you
    can put a TV FM antenna up in the attic.
     
  11. Dan_Musicant

    Dan_Musicant Guest

    :
    ::
    :> :Usually caused by a big lump of metal being moved close to the radio.
    :> Some
    :> :come with a dipole antenna made of ribbon cable - might be worth a try.
    :>
    :> I think mine is made of ribbon cable. It's cable almost 1/2 inch wide,
    :> IIRC. Plastic with the wires embedded in plastic at the edges. I've made
    :> a number of them from ribbon cable but none of those was providing as
    :> good reception as this one, which came with my Sony STRV55 receiver.
    :
    :It's in the shape of a T with the wires at the ends of the T arms soldered
    :together?

    Yes. In the case of this one, it's made in a factory and AFAIK solder
    wasn't involved. I checked the continuity to check the possibility that
    there was a discontinuity created by wear and tear over the years.
    Multimeter set on ohms says it's continuous.
    :
    :It's not impossible to add extra elements to one of these also made of
    :ribbon, but it gets hard to handle and install. If the roof isn't metal you
    :can put a TV FM antenna up in the attic.

    I actually have two rooftop TV antennas, one an anti-ghoster. I presume
    they also work for FM. They are on separate masts. I could maybe add
    another but not sure if I can have a 3rd mast. The attic is a
    possibility, I suppose. Not really headroom in there, but I suppose it's
    not necessary. Wouldn't such an antenna do better above the roof? The
    roof is pretty standard construction with composite shingles, plywood
    sheathing, felt, etc.

    Email: d plus musicant at pacbell dot net
     
  12. Dan_Musicant

    Dan_Musicant Guest

    I just got the idea that I can get ahold of a tuner somewhere, something
    better than what's in the ministereo and feed the line out (assuming
    they come with line out) into one of the inputs of the ministereo. For
    instance, the Video input.

    Dan
    Email: d plus musicant at pacbell dot net
     
  13. Should do. Sometimes it isn't worth the effort of outside mounting or there
    are rules against it. Assuming it isn't the radio, the antenna is the next
    logical thing to look at.





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  14. Dan_Musicant

    Dan_Musicant Guest

    :I just got the idea that I can get ahold of a tuner somewhere, something
    :better than what's in the ministereo and feed the line out (assuming
    :they come with line out) into one of the inputs of the ministereo. For
    :instance, the Video input.
    :
    :Dan

    I think I'm going to pursue this next. I have a receiver I don't use
    much that's not too big and will hook that up and see if it's signal is
    clearer. That's a lot less work than working out a different antenna
    system. Should tell me something.

    Dan

    Email: dmusicant at pacbell dot net
     
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