Good info from Ken.
Do you hear a similar asymmetry on ssb receive? If it's bfo freq or
filter, you should also hear this difference on receive. I would also
expect that one SSB mode should sound "bassy" and one SSB mode should
sound "trebly". I wouldn't expect one mode to sound correct and the other
mode to sound thin.
An easy thing to do that would help would be to tune the receiver to an
empty part of the band and run the audio through a soundcard spectrum
analyzer on both modes and compare to see the difference in passband
response. If you can receive ssb through multiple filters, repeat the
spectrum analysis with the other filters.
73, Barry N1EU
On Sun, Apr 6, 2014 at 4:13 AM, Ken Brown <ken.d.brown@hawaiiantel.net>wrote:
> The LSB or USB transmit signal is produced in the balanced modulator, and
> then filtered to remove the unwanted sideband. The DSB signal that is
> eventually run through the filter, to remove the unwanted sideband is
> generated by combining the voice audio with the BFO. The signal produced by
> the balanced modulator is supposed to be a clean double sideband signal,
> with very little carrier. The carrier balance adjustment nulls the carrier,
> and any residual carrier is further attenuated by the SSB filter. What is
> left of that DSB signal after passing through the 2.4 kHz filter is
> dependent on the BFO frequency and the shape of the filter. If it sounds
> real good using one sideband, and not good using the other, they are really
> only two possible causes either 1) the BFO frequency is wrong or 2) the
> filter has poor symmetry. (This assumes there is not something else
> changing, that should not change, when you change sidebands, such as some
> control signal which should be identical for both sidebands, but somehow
> changes. For instance, the balanced modulator gets unbalanced to produce
> CW. It the logic that controls that is messed up, and unbalancing the
> modulator in one SSB mode, that could be a problem. A leaky diode or bad
> gate in the control logic might do that.) The only things that should
> change between operation on LSB versus USB is the BFO frequency, and some
> correction to the frequency readout, or shift of some other oscillator to
> make the frequency display correct. There should be no change in the audio
> level or frequency response feeding the balanced modulator, and no change
> in the way the balanced modulator works.
>
> Most SSB filters are not perfectly symmetrical, and there will be some
> minor difference in the sound of your transmitted signal when switching
> sidebands. The difference should be something you really have to listen
> carefully to notice. It should not be such a big difference that it sounds
> "bad" on one sideband and "great" on the other.
>
> How have you confirmed the BFO frequencies are correct?
>
> DE N6KB
>
>
>
>
>
> On 4/5/2014 4:34 PM, Mark Kenward wrote:
>
>> i have set Reference oscillator , and the BFO's on the rig.
>>
>> Rig is on frequency as discussed a week or so ago.
>>
>> My issue is this.
>>
>> USB sounds great on transmit.
>>
>> LSB, however, is thin. Narrow, like you are talking through a 1.8-2.1 kHz
>> filter.
>>
>> I tried another 2.4 filter in 9mHz slot, with no change.
>>
>> Can someone tell me what to adjust to move the USB and LSB transmits more
>> to the center of their respective ranges.
>>
>> I am happy with the rig so far, but it is obvious that LSB needs an
>> adjustment, and of course, it is not the BFO.
>>
>> I have a friend who wants the rig, and I would like to make it perfect
>> for him.
>>
>>
>> Thanks for any help.
>>
>> Mark
>> K8VF
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>
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