[Elecraft] LSB on 75 Meters

[Gregg W6IZT]

I think that this is a waste of energy, and a bit pissy. I am going to
stretch out on the couch, pour a glass of good CA Cab, and listen to the
rain on the tin roof.

73 ya 'll

w6izt/4
(sorry eric)
-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bob Nielsen
Sent: Tuesday, November 22, 2011 7:16 PM
To: Elecraft List
Subject: Re: [Elecraft] LSB on 75 Meters

Is this some sort of "new math"?  As I see it, 9.003 minus 5.000 equals
4.003 and 5.000 minus 9.003 equals -4.003.

Bob, N7XY
On Nov 22, 2011, at 3:44 PM, Joe Subich, W4TV wrote:

> 
>> Working the sideband part into it with a 9 MHz USB signal and a 5 MHz
>> LO - Suppressed carrier freq: 9.000 minus 5.000 = 4.000 3 kHz
>> modulation tone: 9.003 minus 5.000 = 4.003
> 
> No, it's 5.000 - 9.000 = -4.000 and 5.000 - 9.003 = 3.997
> and it's 5.500 - 9.000 = -3.500 and 5.500 - 9.003 = 3.497
> 
> The VFO does not need to be the LO ... the IF can just as easily be
> connected to the LO port.
> 
>> Just as a sanity check, take another look at your own negative
>> number example, Joe, and 'splain to me how 5.000 minus 9.003 gives
>> minus 3.987. OK,I'll grant you a typo and assume you meant minus
>> 3.997, but you're still wrong. It's minus 4.003.
> 
> You're correct it's a typo *BUT* there is no error in the inversion
> when the 9 MHz USB signal is applied to the LO port of the mixer.
> All you need to do is spend some time with the historical record.
> 
> 73,
> 
>    ... Joe, W4TV
> 
> 
> On 11/22/2011 6:22 PM, KU4AF wrote:
>> First, let's dispense with the red herring of backward tuning. The VFO
does
>> tune backward on 75 but it has nothing to do with sideband inversion. The
>> USB/LSB business works the same way with a fixed LO as with a VFO, and it
>> works as I described.
>> 
>> When you mix a 5 MHz signal with a 9 MHz signal, there's no need to stand
on
>> your head and pretend that you're subtracting 9 from 5 to get minus 4.
>> Instead, you go back to second grade and subtract 5 from 9 and get 4.
>> 
>> Working the sideband part into it with a 9 MHz USB signal and a 5 MHz LO
-
>> Suppressed carrier freq: 9.000 minus 5.000 = 4.000
>> 3 kHz modulation tone: 9.003 minus 5.000 = 4.003
>> 
>> Just as a sanity check, take another look at your own negative number
>> example, Joe, and 'splain to me how 5.000 minus 9.003 gives minus 3.987.
OK,
>> I'll grant you a typo and assume you meant minus 3.997, but you're still
>> wrong. It's minus 4.003.
>> 
>> John, KU4AF
>> Pittsboro, NC
>> 
>> 
>> On 11/22/2011 4:04 PM, KU4AF wrote:
>>> Whatever the genesis of the LSB/USB convention on the ham bands,
>>> this conversion scheme wasn't it. Mixing a 9 MHz USB signal with a 5
>>> MHz VFO will produce a USB output on either 4 MHz or 14 Mhz. The
>>> sidebands only get inverted in a mixer when you subtract the SSB
>>> signal from a higher frequency
>> 
>> Try the math again ...
>> 
>> If you have a 5.0 - 5.5 MHz VFO and subtract a 9 MHz USB signal from
>> that VFO you end up with a LSB output that tunes from 4.0 - 3.5 MHz
>> in reverse.  Start at 5.0 and subtract the 9 MHz carrier frequency you
>> get *minus* 4.0 MHz (carrier frequency) when the highest modulating
>> frequency (3 KHz or 9.003 MHz) is used you end up with *minus* 3.987
>> MHz - *lower sideband*!  Do the same with the VFO at 5.5 MHz and you
>> will find LSB at *minus* 3.497 to 3.500 MHz.
>> 
>> A mixer can produce F2 +/- F1 just as easily as it produces outputs
>> at F1 +/- F2.  If you don't believe this ... spend some time reviewing
>> the early SSB transmitter and receiver articles in QST from the 1950s
>> or borrow a Drake 1A/2A/2B and learn why some bands "tune backward."
>> 
>> 73,
>> 
>>     ... Joe, W4TV
>> 
>> 
>> --
>> View this message in context:
http://elecraft.365791.n2.nabble.com/US-60-Meter-Band-Changes-Approved-by-FC
C-tp7011949p7022509.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
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_____
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