Home |
Search |
Today's Posts |
#1
![]() |
|||
|
|||
![]()
I was looking for a graphic of the US Ham Bands that included the ARRL
band plan to replace the out of date posters in the club's shack. I went to looking around and found a few neat looking PDF files but I couldn't find a poster that has both the Part 97.301 and the ARRL band plan in graphical form. I couldn't find what I wanted, so in true ham radio style I started to develop one of my own. While I was digging though part 97.301 and the ITU band plans I came up with an unanswered question. In Part 97.301, only 60 Meters is specified to be USB. The rest of the bands can legally be used with either USB or LSB when using SSB phone. I figured that the ARRL's band plan would specify USB or LSB for the band, but they don't, at least in the tables I found. I understand that there is a convention born of convenience when SSB was just getting started. Apparently it was easier to build multi- band rigs for SSB that did upper and lower side band on various bands when this all got started but most of us don't build our rigs today. Where can I find out what the convention here is for 160, 80, 40, 20, 17, 15, 12, 10, 6, 2 (and up) SSB phone operation? Thanks! -= bob =- |
#2
![]() |
|||
|
|||
![]() "KC4UAI" wrote in message ... I was looking for a graphic of the US Ham Bands that included the ARRL band plan to replace the out of date posters in the club's shack. I went to looking around and found a few neat looking PDF files but I couldn't find a poster that has both the Part 97.301 and the ARRL band plan in graphical form. I couldn't find what I wanted, so in true ham radio style I started to develop one of my own. While I was digging though part 97.301 and the ITU band plans I came up with an unanswered question. In Part 97.301, only 60 Meters is specified to be USB. The rest of the bands can legally be used with either USB or LSB when using SSB phone. I figured that the ARRL's band plan would specify USB or LSB for the band, but they don't, at least in the tables I found. I understand that there is a convention born of convenience when SSB was just getting started. Apparently it was easier to build multi- band rigs for SSB that did upper and lower side band on various bands when this all got started but most of us don't build our rigs today. Where can I find out what the convention here is for 160, 80, 40, 20, 17, 15, 12, 10, 6, 2 (and up) SSB phone operation? Thanks! -= bob =- Extracted from the fcc question pool -- see google for "usb lsb convention" get a pdf file "Technician Study Sheet" sez Radio Modes The simplest radio signal is just a single frequency. By turning that radio wave on and off, it's possible to send morse code (CW). Amplitude Modulation is the simplest voice modulation scheme but it's not very efficient because it has two identical (redundant) sidebands with the voice information and the radio carrier that doesn't contain any information. Amateur radios often use Single Sideband (SSB) transmissions that are spectrally (space) and power efficient by removing one of the AM sidebands and the carrier before transmission. This leaves either the upper or lower sideband (USB/LSB). Convention dictates that lower sideband (LSB) signals are used below 10MHz and upper sideband (USB) is used above 10MHz. 60M as you pointed out is USB Lamont |
#3
![]() |
|||
|
|||
![]()
In article ,
KC4UAI wrote: I understand that there is a convention born of convenience when SSB was just getting started. Apparently it was easier to build multi- band rigs for SSB that did upper and lower side band on various bands when this all got started but most of us don't build our rigs today. The story I heard is that this started because Collins radios had an IF of 9MHz and only needed one set of (expensive) sideband filters to have LSB below 9 and USB above. Mixing to get the final output: F1+F2 gives same sideband you start with, F1-F2 inverts. That's what I was told. |
#4
![]() |
|||
|
|||
![]()
On Dec 13, 8:27�pm, (Mark Kramer) wrote:
In article om, The story I heard is that this started because Collins radios had an IF of 9 MHz and only needed one set of (expensive) sideband filters to have LSB below 9 and USB above. Mixing to get the final output: F1+F2 gives same sideband you start with, F1-F2 inverts. That's what I was told. You were told wrong. That mixing scheme does not invert the sideband. This amateur radio urban legend has been around a while, but that's the first time I heard it attributed to Collins. Here's what really happened: A few hams were using SSB in the 1930s. W6DEI, Ray Moore, was on the ham bands with SSB in 1934 or earlier, and the use of SSB is promoted in "200 Meters And Down", first published in 1936. But it wasn't until after WW2 (late 1940s) that SSB began to become really popular with hams. The HF ham bands in those days were just 80, 40, 20, 11 and 10 meters. US hams didn't get 15 meters until 1953 or 54, and didn't get 30, 17 and 12 meters until after 1979. 160 had been a popular band before WW2 but it was reallocated to LORAN during the war and we got it back a little at a time over many years, with all sorts of restrictions, until LORAN was finally phased out. 40 meters had no 'phone segment until 1953/54, either. 11 and 10 were great as long as there were sunspots. So the two most popular 'phone bands were 20 and 75, which were much narrower then than today. For some reason, the 75 meter SSB folks chose LSB, while the 20 meter gang went for USB. Most rigs of the time could do either sideband on either band, but the convention took hold early on and never changed. When US hams got 15 meters, it seemed natural for 15 to be USB, and when 40 got a 'phone band, it was equally natural for 40 to be LSB. It had nothing to do with Collins or 9 MHz IFs. Now about the mixing scheme: None of the early Collins ham rigs had a 9 MHz IF. Collins made mechanical filters, which were only practical up to about 500 kHz or so, and sideband choice with them was a simple matter of switching a BFO crystal. Some early SSB transmitters did indeed generate SSB at 9 MHz, and then heterodyned it to 75 or 20 by mixing with a VFO in the 5 MHz range. But that mixing scheme *does not* invert the sideband! If you take a 9 MHz SSB signal and mix it with a 5 MHz VFO signal, you'll get the same sideband out of the mixer as you put in, regardless of whether you add for 20 or subtract for 75. The VFO will tune backwards on 75, but the sideband will not invert. Those early rigs all had USB/LSB switches in order to match the convention. The only way to get sideband inversion by mixing is if the local oscillator frequency is higher than both the input and output signal frequencies. The 9 MHz-IF story isn't just an urban legend - it flat out doesn't work. It *is* true that if you generate SSB in the 5 MHz region and mix it with a ~9 MHz VFO, you'll get the desired sideband inversion. Some 1960s SSB rigs used that scheme - but they were long after the convention was in place. And the urban legend doesn't mention those rigs. If you want to see the math on how all this works, I can post it. 73 de Jim, N2EY |
#5
![]() |
|||
|
|||
![]() |
#6
![]() |
|||
|
|||
![]()
On Dec 14, 6:43�am, Bill Horne wrote
: ISTR that early Swan transceivers offered only USB for 20, 15, and 10, and only LSB for 80 and 40. You are correct, sir! But they were not the only ones to do that - National and some others did too. The early Heath monobanders had no sideband switch, for example. Swans used IFs in the 5 MHz range. They say the memory is the second thing to go, but perhaps that was where this convention got started. The problem is that by the time Swan showed up in the early 1960s, the standard was already in place. And later Swans let you use either sideband. The 9 MHz IF/ 5 MHz VFO system was popular in the 1950s. The Central Electronics 10A, 10B and 20A exciters all used it, as did the popular W2EWL SSB rig featured in the article "Cheap and Easy SSB". You'd think those popular rigs would have caused the standard to be that the same sideband would be used on both 20 and 75, because they don't invert the sideband. Swan would then have been bucking an established trend. Yet the opposite is true. I suspect that Swan chose their heterodyne scheme to save a little money by not needing a second BFO xtal nor a switch. BTW, given a choice between LSB and USB, the military's preference is for Upper sideband, since using USB makes it easy to talk another station on to a net frequency: if his voice sounds high, then so is his frequency. IMHO, there's also the simplicity. If everyone is on USB, regardless of band, you don't have to think about which one to use, or even provide a choice. 73 de Jim, N2EY |
#7
![]() |
|||
|
|||
![]()
In article ,
wrote: On Dec 13, 8:27�pm, (Mark Kramer) wrote: and we got it back a little at a time over many years, with all sorts of restrictions, until LORAN was finally phased out. LORAN is still active, at least according to the Coast Guard. |
#8
![]() |
|||
|
|||
![]() |
#9
![]() |
|||
|
|||
![]() |
#10
![]() |
|||
|
|||
![]()
On Fri, 14 Dec 2007 06:43:35 EST, Bill Horne
wrote: BTW, given a choice between LSB and USB, the military's preference is for Upper sideband, since using USB makes it easy to talk another station on to a net frequency: if his voice sounds high, then so is his frequency. USB was the commercial standard for the 50 years or so that I've been in that business. Even with ISB (Independent SideBand) where each sideband has different information, the "lower" sideband(s) are not inverted relative to the "upper" sideband(s). -- 73 de K2ASP - Phil Kane From a Clearing in the Silicon Forest Beaverton (Washington County) Oregon e-mail: k2asp [at] arrl [dot] net |
Reply |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Forum | |||
Rig Identification | Swap | |||
Antenna Identification question... | Scanner | |||
BK-100 Bug Identification | Equipment | |||
BK-100 Bug Identification | Equipment |