BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

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.

BFO, CW, sideband question
 

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.

BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

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

BFO, CW, sideband question
 

Hi!
Just to make things more complex (or simple). When you tune from LSB to USB
you also change the frequency of BFO, putting it on one side or another of
the IF filter. If you listen to LSB on USB position you can put the
simulated carrier frequency on the right place, but signal is out of IF
passband.
Sorry for my bad English. Hope you understand.
Damir 9A3IV

BFO, CW, sideband question
 

Actually, I think the convention is LSB below 9 MHz and USB above 9 MHz.
That comes from the fact that most old rigs used 9 MHz as the I.F.
Doesn't really matter though since our voice bands are 40M and 20M (CW
only on 30M), so by convention, we use LSB on 40M and below and USB on
20M and above. However, one can reverse this if one desires. It will
just confuse new people when they try to tune you in and wonder why they
can't get you tuned in...

Scott
N0EDV

Doug Smith W9WI wrote:
Jaggy Taggy wrote:



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.

BFO, CW, sideband question
 

Modern radios such as the FT1000MP Mk V automatically change the internal
local oscillator frequencies so that USB, LSB and CW appear on the same
indicated signal frequency, which is what we want. In CW we get a certain
pitch frequency such as 500 Hz (not zero beat) at the signal frequency. The
value of this pitch frequency can be changed from the front panel by the
operator to suit his preference.

In my homebrew rcvr I use the CW USB setting only. As I tune up the band I
hear the high pitch of a signal first and it then decreases pitch as I
continue to tune up the band (my preference). I use a single xtal filter
frequency for USB/LSB and a single xtal filter frequency for CW. The BFO
xtal frequency and the VFO frequency counter digital readout (not the actual
VFO frequency itself) are automatically changed to their correct values in
LSB, CW or USB mode. In CW mode I then have a 500 Hz beat note, which is
what I want, not zero beat, and the CW BFO xtal is then the correct value
for CW USB.

For a brief description of my homebrew rcvr see QRZ.COM, W0IYH.

Bill W0IYH

"Wor" wrote in message
...
Hi!
Just to make things more complex (or simple). When you tune from LSB to
USB
you also change the frequency of BFO, putting it on one side or another of
the IF filter. If you listen to LSB on USB position you can put the
simulated carrier frequency on the right place, but signal is out of IF
passband.
Sorry for my bad English. Hope you understand.
Damir 9A3IV

BFO, CW, sideband question
 

Scott wrote:
Actually, I think the convention is LSB below 9 MHz and USB above 9 MHz.
That comes from the fact that most old rigs used 9 MHz as the I.F.
Doesn't really matter though since our voice bands are 40M and 20M (CW
only on 30M), so by convention, we use LSB on 40M and below and USB on
20M and above. However, one can reverse this if one desires. It will
just confuse new people when they try to tune you in and wonder why they
can't get you tuned in...

Yeah, and more than once I've scratched my head about what type of voice
encryption someone was using in the middle of 20 meters before it dawned
on me to try listening on LSBgrin!

The 10MHz figure is somewhat arbitrary since indeed there are no amateur
voice frequencies between 7.3 and 14.1MHz - and commercial services
don't follow our LSB/USB convention.

As I understood it, the decision to use different sidebands in the two
spectrum areas came from the design of some early SSB equipment. If you
used a 9MHz IF and a 5.0-5.5MHz VFO, you could cover both 80 and 20
meters without having to mess with heterodyne oscillators. But since
you'd be using addition on 20 vs. subtraction on 80, the sidebands would
flip.

(there's GOT to be a better way to say that but it's too darned early in
the morning!)

At the time either there wasn't a phone band yet on 40 or phone
privileges there were very new & SSBers didn't care that much about it.
15 was also very new or non-existant, and I suspect most SSBers didn't
believe anyone had a receiver stable enough to receive SSB on 28MHz!
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

BFO, CW, sideband question
 

Yup, you've got it!

Now for the $64,000 question (which will only buy about 21,000 gallons
of gas these days!)...With these modern rigs, if I want to answer
someone calling CQ on CW, how do I adjust my radio to be on exactly the
same frequency as they are calling on (to conserve spectrum for other
operators)??? My "old" TS-520 has a "Tune" position, which sets the bfo
frequency exactly to the I.F. frequency (I don't have the service manual
in front of me, but follow the logic here). As I tune the radio (with
the VFO) in this TUNE position, when I have the VFO set to provide zero
beat, I will be right on his frequency since my BFO is running at the
I.F. frequency (9 MHz) and the combination of the far end transmitter
frequency and MY VFO frequency gives an I.F. output at 9 Mhz, so the
difference in frequency is zero. Whent I then return my switch from the
"Tune" position to the CW position, it shifts the BFO 800 Hz in SOME
direction (up or down, I can't remember and I don't really care!). Now
his signal mixed with my VFO and my now shifted BFO (which is now
running at 9.0008 MHz, for example) provides a tone of 800 Hz. Easy!

My "new" TS-690S doesn't have a TUNE position. The manual says to tune
for a tone frequency of 800 Hz (or whatever you have the "CW Tone"
frequency programmed into the radio). My question is how the $#@% do I
know when I have an 800 Hz tone coming out of my radio? Do they really
expect me to have a freq. counter hooked up to the speaker? I have
overcome this by setting the RIT to display either 800 Hz up or down
(can't remember which right now), turn on the RIT, zero beat they guy,
turn off the RIT and then I will be on his frequency. I find it's
easier to CALL CQ and let the other guy worry about getting on MY
frequency ;)

Scott
N0EDV


Doug Smith W9WI wrote:



As I understood it, the decision to use different sidebands in the two
spectrum areas came from the design of some early SSB equipment. If you
used a 9MHz IF and a 5.0-5.5MHz VFO, you could cover both 80 and 20
meters without having to mess with heterodyne oscillators. But since
you'd be using addition on 20 vs. subtraction on 80, the sidebands would
flip.

(there's GOT to be a better way to say that but it's too darned early in
the morning!)

BFO, CW, sideband question
 

Scott wrote:
Now for the $64,000 question (which will only buy about 21,000 gallons
of gas these days!)...With these modern rigs, if I want to answer
someone calling CQ on CW, how do I adjust my radio to be on exactly the
same frequency as they are calling on (to conserve spectrum for other
operators)???

Newer rigs tie the sidetone to the offset, so that if you zero-beat the
sidetone with received signals you're transmitting on the same frequency
as the other guy. In most rigs if you close the key without putting the
rig in transmit (i.e., break-in is off) you'll get a sidetone without
muting the receiver, allowing you to zero-beat the sidetone.

Older rigs often had a "SPOT" button which keyed up low-power
transmitter stages to allow you to zero-beat the transmitter against
received signals. My FT1000MP also has such a button - I'm sure the
electronics behind it are very different but its purpose and function
are the same as in the old rigs.

To be honest I don't worry about it. After 30 years of CW operating I'm
pretty good at getting it right!
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

BFO, CW, sideband question
 

Scott wrote:
My "new" TS-690S doesn't have a TUNE position. The manual says to tune
for a tone frequency of 800 Hz (or whatever you have the "CW Tone"
frequency programmed into the radio). My question is how the $#@% do I
know when I have an 800 Hz tone coming out of my radio?

The sidetone you hear when you key down is going to be pretty close
to the 800Hz offset you need. So just tune the other guy until he
sounds roughly the same note.

Do they really
expect me to have a freq. counter hooked up to the speaker?

Gees, give guys a 8-digit frequency counter and they think they
have to be tuned to 1Hz to work somebody else. Most of my rigs
had more than 800Hz of chirp when I bought them :-).

Tim.