[ARC5] Lopsided modulation

[AKLDGUY .]

FM does not seem to be present in either his signal or mine. The carriers
are straight lines on the waterfall display. Actually, there is one
operator on the net whose carrier is a fuzzy line when he speaks, but his
sidebands are symmetrical. I'm stumped.

Neil ZL1ANM

On 25/02/2018 10:30 AM, "Richard Knoppow" <1oldlens1 at ix.netcom.com> wrote:

>     That affects the upward vs downward modulation but not the strength of
> the sidebands. A frequent cause of asymetrical sidebands is incidental FM.
> If the oscillator is being affected by the modulation it can be the cause.
>     The scope display will not show assymetry of the upper vs lower
> sidebands although it will certainly show assymetry of upward vs downward
> modulation.
>
> On 2/24/2018 1:18 PM, Jim Wiley wrote:
>
>> One reason could be that your voice in itself is non-symmetrical.  If you
>> can do so easily, try reversing the "polarity" if the modulation
>> transformer, and see if that helps.  If it does, your can leave it set the
>> way that works best for you. Monitoring the modulation envelope with an
>> oscilloscope is always  the best way.
>>
>> - Jim, KL7CC
>>
>>
>>
>> On 2/24/2018 11:38 AM, AKLDGUY . wrote:
>>
>>> A friend and I are running Command transmitters on the local 75 meter AM
>>> net, with full plate and screen modulation. We monitor our transmissions on
>>> the local SDR receiver site which has a waterfall display. In both cases,
>>> the lower sideband shows as considerably stronger than the upper, and this
>>> has us perplexed. Our stations are the only ones affected.
>>>
>>> I have never seen anything in the literature to explain this. Downward
>>> modulation is a problem with AM, but articles do not indicate whether
>>> lopsided modulation results.
>>>
>>> My transmitter is the AN/ARC-5, absolutely unmodified and running 40W
>>> input due to dynamotor constraint. His is the SCR-274 modified for plate &
>>> screen modulation and running twice that.
>>>
>>> Anyone suggest a reason for the unequal sidebands?
>>>
>>> Neil ZL1ANM
>>>
>>
>
> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
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