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Author Topic: Hammarlund HQ129 X Freq. harmonics?  (Read 1868 times)
KD0ACY
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Posts: 91




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« on: June 03, 2011, 05:28:32 PM »

I have a Hammarlund HQ 129X that works well, however I pick up AM transmission at two frequencies. One on 10 mega hertz and at 1.33 mega hertz.
The 1.33 is duplicated at 1.49mh, the 10.1 which is wwv shows up again at 11.0. I am not familiar with this rig and haven't fussed with it much. Hope someone can save me a lot of time and point me in the correct direction.
Mike 
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W6OU
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Posts: 192




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« Reply #1 on: June 03, 2011, 06:12:49 PM »

The HQ-129X is a single-conversion receiver with an intermediate frequency of 455 kHz. It will receive an image of the received signal when the receiver is tuned to a frequency which is 2 X 455 kHz = 910 kHz higher. This could happen on all frequencies on all bands although it is worse at the higher frequencies. This is one of the reasons better receivers of that era went to double-conversion. This explains your observation of WWV received at approximately 11 MHz. I don't know about the problem at 1.3 vs 1.49 MHz. That might be an intermodulation problem.
« Last Edit: June 03, 2011, 06:17:41 PM by W6OU » Logged
KD0ACY
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Posts: 91




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« Reply #2 on: June 04, 2011, 05:02:48 AM »


Do you know how I can cure this problem?
Also ---  the 1.33MHz is a local Am station with a lot of power.
Mike
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KE3WD
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Posts: 5689




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« Reply #3 on: June 04, 2011, 06:20:53 AM »


Do you know how I can cure this problem?
Also ---  the 1.33MHz is a local Am station with a lot of power.
Mike

You could try placing a well-designed broadcast frequency trap in front of the antenna input.  I'd look into designing one that could be tuned to that frequency of interest rather than a broadbanded type. 

http://www.dxing.com/tnotes/tnote06.pdf

Don't count on being ale to make the thing perform like something it isn't, though. 

73
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KD0ACY
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Posts: 91




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« Reply #4 on: June 05, 2011, 10:33:08 AM »

Tnx to all! I am off to the races, looking for ,how and why.
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