Who decides to which side of the carrier the BFO will heterodyne a CW
signal.
I mean there must be convention, otherwise we would have to find out on an
individual basis, but what is this convention???

Uwe

Jaggy Taggy wrote:
Who decides to which side of the carrier the BFO will heterodyne a CW
signal.
I mean there must be convention, otherwise we would have to find out on an
individual basis, but what is this convention???

A BFO will heterodyne a signal on *both* sides of the carrier. Most
modern receivers are designed to filter out the heterodyne on one side.
For CW signals, which side depends on the manufacturer. (i.e. there
is no convention!)
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

My FT1000MP mark V allows either USB or LSB CW reception, according to front
panel push buttons.

Bill W0IYH

"Doug Smith W9WI" wrote in message
...
Jaggy Taggy wrote:
Who decides to which side of the carrier the BFO will heterodyne a CW
signal.
I mean there must be convention, otherwise we would have to find out on
an
individual basis, but what is this convention???

A BFO will heterodyne a signal on *both* sides of the carrier. Most
modern receivers are designed to filter out the heterodyne on one side.
For CW signals, which side depends on the manufacturer. (i.e. there is no
convention!)
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

When in the CW mode, My Kenwood TS-870 defaults to the USB, by pushing CW
REV, it goes to LSB
Handy when in a DX pileup, the split is a few KHz up and the big guns are
obliterating the weak DX station

--
CL -- I doubt, therefore I might be !






"Jaggy Taggy" wrote in message
...
Who decides to which side of the carrier the BFO will heterodyne a CW
signal.
I mean there must be convention, otherwise we would have to find out on an
individual basis, but what is this convention???

Uwe

Who decides to which side of the carrier the BFO will
heterodyne a CW signal.

For many SSB+CW transceivers, the maker of the transceiver decided on a
default sideband at manufacture time. Usually USB for rigs that are
capable of both sidebands.

For the oldest SSB equipment you don't get a choice of sideband:
14MHz and above comes out on USB, 7MHz and below come out on LSB, due
to the 9MHz IF + 5MHz VFO scheme.

I mean there must be convention, otherwise
we would have to find out on an individual basis

It doesn't matter as long as you're consistent between your TX and RX,
AND you make sure you're inside your band.

With most (all?) modern synthesized transceivers the frequency on the
display is that of the CW transmission in CW mode, but on older SSB+CW
rigs there was an offset (between a few hundred Hz and a few kHz)
between the dial and the actual CW transmission frequency (which was in
the sideband - the dial was calibrated to the suppressed carrier
frequency in USB/LSB). The offset was usually mentioned in the manual
(or in fancier rigs with RIT/XIT could be dialed in).

Tim.

I started this thread because there is a bit of confusion in my head
regarding where the signal is, where the carrier is and what is indicated on
my radio dial.

And by the way, I do have an older radio, a Kenwood TS 830, not a modern
radio. My radio-display shifts on transmit to a frequency 800 Hz higher than
what was displayed on receive.

So I assume it displays the carrier frequency on transmit, while on receive
it displays the heterodyned frequency, which on my radio happens to be
lower, but as some indicated in this group, this is an arbitrary choice made
by the people at Kenwood.


The ARRL CW transmissions frequencies, for example, seem to be given for the
carrier which is not what my radio displays (my radio displays 800HZ lower
on receive) and therefore I need to adjust my radio to a different frequency
than what is advertised.

This is confusing to me.


It is also confusing me that I can't receive SSB on the lower bands using
USB (and a slight retune), I need to use LSB.
I don't know why since I learned that the two sidebands contain the same
info.


And the more I think about it the more I realize that I don't really
understand this whole topic very well...

Uwe





On 10/28/05 9:45 AM, in article
, "Tim Shoppa"
wrote:

Who decides to which side of the carrier the BFO will
heterodyne a CW signal.

For many SSB+CW transceivers, the maker of the transceiver decided on a
default sideband at manufacture time. Usually USB for rigs that are
capable of both sidebands.

For the oldest SSB equipment you don't get a choice of sideband:
14MHz and above comes out on USB, 7MHz and below come out on LSB, due
to the 9MHz IF + 5MHz VFO scheme.

I mean there must be convention, otherwise
we would have to find out on an individual basis

It doesn't matter as long as you're consistent between your TX and RX,
AND you make sure you're inside your band.

With most (all?) modern synthesized transceivers the frequency on the
display is that of the CW transmission in CW mode, but on older SSB+CW
rigs there was an offset (between a few hundred Hz and a few kHz)
between the dial and the actual CW transmission frequency (which was in
the sideband - the dial was calibrated to the suppressed carrier
frequency in USB/LSB). The offset was usually mentioned in the manual
(or in fancier rigs with RIT/XIT could be dialed in).

Tim.

Jaggy Taggy wrote:


And by the way, I do have an older radio, a Kenwood TS 830, not a modern
radio. My radio-display shifts on transmit to a frequency 800 Hz higher than
what was displayed on receive.

The 'true' CW frequency would be that of zero-beat as opposed to where
you 'hear' the signal. The rig assumes that you are listening to a beat
note offset by about 800 Hz and compensates accordingly on transmit.

So I assume it displays the carrier frequency on transmit, while on receive
it displays the heterodyned frequency, which on my radio happens to be
lower, but as some indicated in this group, this is an arbitrary choice made
by the people at Kenwood.

I think we're saying the same thing.


It is also confusing me that I can't receive SSB on the lower bands using
USB (and a slight retune), I need to use LSB.
I don't know why since I learned that the two sidebands contain the same
info.

Alas, a SSB station is only transmitting one of the sidebands! This by
convention is LSB on 40 and below and USB on 20 or above. If a station
WERE to xmt USB on 75 meters, for instance, you would have to use the
USB position and would not be able to detect it in LSB.

-Bill

Jaggy Taggy wrote:
I started this thread because there is a bit of confusion in my head
regarding where the signal is, where the carrier is and what is indicated on
my radio dial.

Join the crowdgrin...

It is also confusing me that I can't receive SSB on the lower bands using
USB (and a slight retune), I need to use LSB.
I don't know why since I learned that the two sidebands contain the same
info.

Ah. What you learned about was DSB, not SSB.

In a regular AM (Dual Sideband) transmission the two sidebands indeed
contain the same info and you can tune either one. (or in most cases, both)

But what hams use is SSB, Single Sideband. One of the two sidebands is
filtered out, only one is transmitted.

It is traditional for amateurs to transmit the lower sideband below
10MHz and the upper sideband above 10MHz. Hence, you need to use LSB to
receive SSB signals on the low bands -- the upper sideband simply
doesn't exist on these signals. And vice-versa on the higher bands.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Alas, a SSB station is only transmitting one of the sidebands! This by
convention is LSB on 40 and below and USB on 20 or above. If a station
WERE to xmt USB on 75 meters, for instance, you would have to use the
USB position and would not be able to detect it in LSB.

-Bill


Right Bill, but why. Could I not retune my receiver so that I would catch
the transmitted sideband with my "LSB window"?

I guess from experience the answer is no, and that is also what you said,
but what is the reason??

Uwe

Jaggy Taggy wrote:

Alas, a SSB station is only transmitting one of the sidebands! This by
convention is LSB on 40 and below and USB on 20 or above. If a station
WERE to xmt USB on 75 meters, for instance, you would have to use the
USB position and would not be able to detect it in LSB.

-Bill



Right Bill, but why. Could I not retune my receiver so that I would catch
the transmitted sideband with my "LSB window"?

I guess from experience the answer is no, and that is also what you said,
but what is the reason??

Uwe


Visualize a LSB signal as having the carrier frequency at 7000 kcs (or
more precisely, phantom carrier). The audio sidebands tune down to
6997. A USB signal on the same freq has the audio sidebands from 7000
to 7003.

To tune to an SSB signal (and have it intelligible) you have to tune to
the phantom carrier freq. You can't fool the rcvr by going 3kc hi or
low and switching sidebands. Yes, the signal is there - to wit you can
hear it - but you can't detect it.

Why? Think about how BFO injection works. Take a fixed freq BFO of
7000 in this case for simplicity. 7000 beating against an USB audio
sideband at 7001 gives you a bit of 1 kc audio information. Repeat the
same with an audio sideband at 7002...you get the 2kc audio information.
If you try to fool the radio by tuning to 7003 and selecting LSB, yes
you have duplicated the bandpass from 7003-7000 but all that audio
information is now inverted.

In most rigs nowadays there's a single filter of about 2-3kc width that
is used for both sidebands. When you select USB or LSB you're simply
moving the bfo freq from one edge to the other.

Thats all an oversimplification but does it make sense?

-Bill