[AMRadio] Re: Carrier with one sideband


jeremy-ca km1h at jeremy.mv.com
Thu Feb 7 19:10:25 EST 2008


----- Original Message ----- 
From: "D. Chester" <k4kyv at charter.net>
To: <amradio at mailman.qth.net>
Sent: Thursday, February 07, 2008 6:22 PM
Subject: [AMRadio] Re: Carrier with one sideband


>
>> From: Peter Markavage <manualman at juno.com>
>
>> A number of the early phasing type transmitters/exciters and SSB adapters
>> allowed you to operate on "AM" with just one sideband. So, only operating
>> DSB AM would really be an issue.
>
>
>>> From: "Bob Macklin" <macklinbob at msn.com>
>
>> Any of the Heath SSB rigs (SB-100/101, SB-400/401, HW-100/101) could be
>> modified to Vestigial SB. SSB with carrier reinserted.
>>
>> Bob Macklin
>> K5MYJ
>
>
> SSB with the carrier re-inserted is not the same thing as what we know as 
> AM.  It is nothing more than SSB with poor carrier suppression.  Reception 
> with an envelope detector inherently generates severe distortion at 
> modulation levels beyond about 20%.  This mode is useful only with a 
> receiver with BFO that locks onto the "pilot carrier" to eliminate 
> frequency error in SSB reception, a technique that has in fact long been 
> used in commercial services, with the carrier level reduced to about 20 dB 
> below p.e.p.  At modulation levels low enough to avert this distortion, 
> known as "quadrature distortion" it is very wasteful of power since the 
> sideband power becomes a very small percentage of total radiated power. 
> Those amateur SSB rigs that transmit "AM" with carrier and one sideband 
> sound like CRAP.  Unless the receiving station is equipped with a proper 
> receiver with PLL carrier reinsertion, which includes very few amateur 
> receivers, it is a totally useless mode beyond simply getting someone's 
> attention when they are receiving in AM mode, in order that they may 
> switch the receiver over to SSB to receive the signal in normal SSB 
> fashion.
>
> This problem is inherent to the principles of modulation, and has nothing 
> to do with the quality of the equipment used.  Transmitting AM with one 
> sideband is NOT a solution to the problem nor is it even a satisfactory 
> option.
>
> 73,
>
> Don k4kyv


I agree with Bob that the phasing rigs sounded great on AM. Ive owned all 
the CE's from the 10A to 200V, a Lakeshore Phasemaster, and a HT-37. However 
I always ran them in the DSB position except for the 200V which was a 
cheapend up 100V.

Ive been keeping a lookout for another 100V these days to keep company with 
the 75A4 and NCL-2000 Ive had since 1964. Worked a lot of DX and contests 
with that setup. Sold the 100V in the late 80's and been kicking myself 
since.

Carl
KM1H




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