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Author Topic: Which Sideband and Why  (Read 3909 times)
AC5WA
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Posts: 35




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« on: July 13, 2000, 11:08:58 AM »

I guess originally the SSB signal was created at a single frequency for ease of generation and then mixed to the band of interest.  The reason the higher ones are upper and the lower ones are lower sideband is that is the signal was mixed to generate the frequency of interest and the higher bands used the sum product and the lower bands used the difference product of the mixer.  Just a guess but if it's easier thats how I would do it. I believe the early SSB generators used a phasing scheme to cancel the undesired sideband and it would seem to be much more difficult to change the generator output from upper to lower than with the filter method now used.
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W0PEA
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Posts: 3




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« Reply #1 on: July 12, 2000, 11:35:13 PM »

Who and what set the precedence of operating LSB  on 40M, 75M, 160 M, and USB on all bands 20 M and up??  Post your answer, I will give the true and correct answer in a few days.
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AC5WA
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« Reply #2 on: July 14, 2000, 12:50:05 AM »

I'll be doggone if I know how I got to be the top of this issue!
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K0CBA
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Posts: 304




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« Reply #3 on: July 14, 2000, 08:16:01 PM »

SSB was 'generated' starting with an AM signal and brute force phasing out the carrier and unwanted sideband.   The main osc.s used  in these phasing units was 9 megacycles (yes, back then we had cycles!).

Because of "how things work out" signals ABOVE 9 Mhz left the upper sideband while signals originating BELOW 9 Mhz. left the lower sideband for final amplification.

And dat's how the 'tradition' started.  
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K0CBA
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« Reply #4 on: July 15, 2000, 11:29:52 AM »

P.S.   You also asked 'who'.  I suspect it was Art Collins.
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K4DPK
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« Reply #5 on: July 16, 2000, 06:04:50 PM »

Digging 'way back, it seems to me that the first filters might have been ladders, and since it is easier to make a symmetrical LSB filter, the first ones were.  Then a scheme was arranged to generate signals on two bands without changing carrier or VFO frequencies, and the method of 9 mc carrier +/- 5 mc VFO yielded outputs on both 4 and 14 mcs. simply by switching the mixer tuned circuit. Because of this mixing scheme, sideband reversal gave USB on 20 m.  It was probably either Joe Bachelor or Art Collins that hit on this method.

I don't think the phasing system played a part in setting this precedent, because with that method SSB can be, and usually was generated on the VFO frequency, which was also the output frequency.  Later sideband phasing adapters like the Heathkit SB-10 took advantage of this and were inserted between the low and higher level RF stages in am/cw rigs of the time.

Phil Chambley, Sr.
K4DPK
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N2MG
Administrator

Posts: 0



« Reply #6 on: July 17, 2000, 01:05:33 PM »

AC5WA made it to the "top of this issue" because of a bug in eham's software.  There, I said it. Smiley

Mike
N2MG
webmaster@eham.net
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AC5WA
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Posts: 35




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« Reply #7 on: July 18, 2000, 12:44:54 AM »

Well, at least THAT mystery is solved!
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N2MG
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« Reply #8 on: July 25, 2000, 02:17:55 PM »

Yeah, where is the answer?
It's been a "few days". Smiley
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W0PEA
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Posts: 3




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« Reply #9 on: August 20, 2000, 12:12:55 AM »

The answer is as follows:

In an early 1950's CQ,  an article called Cheap and Easy SSB was written by Tony Vitali (W2EUQ, I believe) that used a 5 Mhz ARC-5 as the VFO and Final with a 9 Mhz phasing SSB Generator.  With phasing generators, it was difficult to get good  unwanted sideband suppression on both sidebands, so the generator was setup for optimum operation on USB.  

Since sum mixing of 9 Mhz and 5 Mhz produces a 20 Meter USB signal and difference mixing of  9 Mhz and 5 Mhz produces an 80/75 Meter LSB signal.

Many early SSB operators used this design and thus set a precedent.

Later design changes added other bands.
Any band that was sum mixing was USB.
Any band that was difference mixing was LSB.  
That made 80/75 and 40 be on LSB, and 20, 15, & 10 be on USB.

Thus was set the precedence of our use of the current sidebands on HF>

This design  was later used by Central in designing the model 10A, 10B, and 20A sideband exciters.

Thanks to everyone for their answers.  Several were very close.  

Sorry to be late posting the answer, but I have been on vacation.

Don,

W0PEA

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W0PEA
Member

Posts: 3




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« Reply #10 on: August 20, 2000, 12:39:37 AM »

The corrected answer is as follows:   I goofed on Tony's Call

                   In an early 1950's CQ, an article called Cheap and Easy SSB was written by Tony Vitali, W2EWL                         that used a 5 Mhz ARC-5 as the VFO and Final with a 9 Mhz phasing SSB Generator. With
                   phasing generators, it was difficult to get good unwanted sideband suppression on both sidebands, so
                   the generator was setup for optimum operation on USB.

                   Since sum mixing of 9 Mhz and 5 Mhz produces a 20 Meter USB signal and difference mixing of 9
                   Mhz and 5 Mhz produces an 80/75 Meter LSB signal.

                   Many early SSB operators used this design and thus set a precedent.

                   Later design changes added other bands.
                   Any band that was sum mixing was USB.
                   Any band that was difference mixing was LSB.
                   That made 80/75 and 40 be on LSB, and 20, 15, & 10 be on USB.

                   Thus was set the precedence of our use of the current sidebands on HF>

                   This design was later used by Central Electronics in designing the model 10A, 10B, and 20A                    sideband exciters.

                   Thanks to everyone for their answers. Several were very close.

                   Sorry to be late posting the answer, but I have been on vacation.

                   Don,

                   W0PEA
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