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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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4th Apr 2019, 7:19 pm | #1 |
Retired Dormant Member
Join Date: Apr 2019
Location: Livorno, Italy
Posts: 3
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Yupiteru MVT-9000 malfunctioning: help required
Hi all, I'm Daniele, I'm from Italy and I'm new to this forum. Recently I bought a second-hand Yupiteru MVT-9000 in very nice conditions, which works good apart from a strange malfunctioning that it shows when operating in LSB mode:
https://www.youtube.com/watch?v=7uudxHNB-N0 I performed an informal test with a friend of mine, by connecting an AM generator to the antenna input @7150 kHz and trying to zero-beat the AM carrier, both in USB and LSB. Results of this simple test seemed to indicate that there was no real difference in LSB vs USB. My friend suggested a possible programming error in the firmware of the unit. Any information about a similar problem that occurred to someone with this receiver? Thank you very much in advance for your feedback. |
5th Apr 2019, 12:25 am | #2 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,526
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Re: Yupiteru MVT-9000 malfunctioning: help required
Don't quite understand the problem..... the zero beat tuning point for an AM carrier or indeed a CW signal should be at the same tuning setting regardless of whether USB or LSB operation is selected.
Unless the receiver cuts corners by having only one 3kHz filter requiring the LO to be offset one way or the other to resolve USB/LSB? After looking at the video, could the receiver simply have a problem with USB/LSB filter selection?
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5th Apr 2019, 9:03 am | #3 |
Moderator
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Location: Ipswich, Suffolk, IP4, UK.
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Re: Yupiteru MVT-9000 malfunctioning: help required
I'm not familiar with this particular receiver. Some receivers, when set to SSB, show the frequency of the missing carrier, whilst others show the centre frequency of the received sideband. My JRC NRD-525 can be configured to do either. I wonder if something similar applies to the OP's receiver?
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5th Apr 2019, 3:27 pm | #4 |
Retired Dormant Member
Join Date: Apr 2019
Location: Livorno, Italy
Posts: 3
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Re: Yupiteru MVT-9000 malfunctioning: help required
First of all, thank you very much for your replies.
In fact, the zero beat with the AM carrier occurs a couple of kHz away from the nominal frequency of the AM signal, thus my hypothesis was that the display was showing the center frequency of the LSB/USB passband filter. Another hypothesis is the the display shows the LO frequency with an error of a couple of kHz. Not sure what is true, honestly. Anyway, it looks like there is no switch between LSB and USB actually. Could be due to a component failure or even an error in the firmware. The schematic diagram is a bit too complex for me to understand where to look to resolve the issue, so I wondered if someone had experienced the same problem just to share his/her findings. |
7th Apr 2019, 7:55 am | #5 |
Tetrode
Join Date: Aug 2013
Location: Monterey, California USA
Posts: 51
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Re: Yupiteru MVT-9000 malfunctioning: help required
Looks like it is stuck in USB to me.
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20th Apr 2019, 7:31 am | #6 |
Retired Dormant Member
Join Date: Apr 2019
Location: Livorno, Italy
Posts: 3
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Re: Yupiteru MVT-9000 malfunctioning: help required
New test yesterday in the evening on 20 metres. It looks like the radio is able to properly demodulate the same signal both in LSB and in USB, with a difference in the tuned frequency of about 2.85 kHz (for example LSB freq = 14175.15, USB freq = 14172.30) which matches quite well with the expected width of the passband filter. This behaviour could be regarded as normal, I think; whilst in 40 meters (LSB) apparently there is no way to demodulate the received signal, irrespective from how far I move the tuning knob up and down.
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