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Author Topic: Audio tone difference LSB and USB Drake TR4-C  (Read 1027 times)
ZS5WC
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« on: September 18, 2018, 04:54:34 AM »

 ???I recently restored and aligned my old Drake TR4-C, what a great rig!.
Only minor complaint is that I cannot get the audio on the 'X' bands to sound full.
i.e. on 80m the audio is great, on 40 still on LSB, the audio sounds thin and nasal.

Obviously this is due to the mixing scheme and selection of another filter, but no amount of moving of the carrier point can correct it.
How can I improve it, filter matching ?.

73 de William
ZS4L / ZS5WC
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WD0GOF
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« Reply #1 on: September 26, 2018, 09:15:42 AM »


First insure that all the oscillators are dead on.
Then: do the 9Meg alignment (page 34 in my manual).

If that doesn't help then you have some trouble-shooting to do.


73 WD0GOF



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KB7TT
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« Reply #2 on: September 27, 2018, 10:28:29 AM »

The TR4's have two SSB filters one for LSB one for USB.  I think there is only one oscillator and you have to balance the frequency between the two filters for them to both sound good.  If the alignment procedure does not work you may have one aged/bad filter.  I sold a set of those filters to a guy with a similar problem several years ago.
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WD0GOF
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« Reply #3 on: September 27, 2018, 12:20:09 PM »

The 9meg alignment is where you adjust for zero-beat between the usb and lsb.
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ZS5WC
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« Reply #4 on: September 28, 2018, 10:45:54 PM »

 :)I did do all the alignments as per the manual, I think your suggestion of the filter might be spot on.
I recall years ago I had a similar issue with a new looking TR4-C, and installed Inrad filters into it.
Problem solved.. Might do same again some time.

73 de William
Zs4L / ZS5WC
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