[ARC5] Lopsided modulation

[Richard Knoppow]

     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