Muddy reception in VX-7r

Discussion in 'Radio Circuits, Repair & Performance' started by KJ6HZH, May 31, 2018.

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  1. KJ6HZH

    KJ6HZH Ham Member QRZ Page

    I've completed repair of my Yaesu VX-7, which was suffering from DC-induced damage to its ceramic filters. I followed http://pages.cs.wisc.edu/~timc/e/vx7r.html and the blocking capacitor notes at the bottom of the page. My results can be seen at https://www.flickr.com/photos/32548582@N02/albums/72157667529801877. The repair appears to have been a success.

    The next day, Wed May 30, I turned on both my VX-7 and FT-8800 to compare the reception. There was a net going on at 145.230 (w7bpd) transmitting from atop Sumas Mountain in northwest Washington, around 30 miles ENE from me. That repeater pegged both radios. The FT-8800 reception sounded very good. The VX-7 reception had bits of static and crunches. This was helped slightly by turning on the VX-7's attenuator and by using a rubber duck antenna. I also tried using the attenuator on the VX-7 and putting it on the FT-8800's antenna; an N9TAX slimjim hanging from a high ceiling. That was pretty good, but still not as good as what I got from the FT-8800.

    Other repeater and simplex reception doesn't provoke this response in my VX-7. Both radios put out audio of the same quality, albeit the VX-7 always sounds a bit tinny because of the speaker itself.

    What's going on here?
     
  2. G3YRO

    G3YRO Ham Member QRZ Page

    So you're saying that when you put your handheld on a PROPER antenna, and the signal is very strong, you're getting various distortion and noise problems?

    Well surely you know the answer . . . your handheld is being overloaded! (your mobile rig is obviously more sophistcated, and can cope with the very strong signal)

    At least you can HEAR the station . . . if you tried putting a Beofang handheld on a proper antenna, you wouldn't hear ANYTHING, as the front end would be swamped by all the signals between 100 and 500 MHz ! (although just on their small helical antenna, the Beofangs work as well as any expensive handheld)

    Roger G3YRO
     
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    The proper antenna for a Baofeng is the one that comes with it.

    There is no "Better" antenna, Just antennas that cost more than the radio.
     
  4. KJ6HZH

    KJ6HZH Ham Member QRZ Page

    I understand those points. I don't understand why I don't get similar distortion when transmitting 50 watts from my mobile to the handheld 40 or so feet away.
     
  5. G3YRO

    G3YRO Ham Member QRZ Page

    Probably because when the handheld has a decent antenna on it, it's a COMBINATION of the strong Repeater signal mixing with some other strong signal (like a Pager transmitter or other commercial out-of-band signal) that is causing the distortion you are hearing.

    So it's not JUST the fact that the signal is strong . . . it's the fact that the handheld will be picking up SEVERAL strong signals causing intermodulation products in the front end.

    Roger G3YRO
     
  6. W2WDX

    W2WDX Subscriber QRZ Page

    I've used a VX-7r for years. They are not that susceptible to overload as other HT's. I live in New York City where repeaters and other RF sources are everywhere nearby. The VX-7R is very good at dealing with things like IM issues.

    I would try doing the comparison between the two transceivers with a pair of headphones, this way you can truly judge if the differences are in the electronics, or just a problem with the respective speakers.
     
  7. VE1IC

    VE1IC Ham Member QRZ Page

    check the 455khz filter
     
  8. KX0Z

    KX0Z Ham Member QRZ Page


    he just replaced those, its a common fault with the VX7R, mine has a dead IF filter and is partially deaf..
     

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