ARRL

Forum Home - Rules - Help - Login - Forgot Password
Members can access, post and reply to the forums below. Before you do, please first read the RULES.

CWL and CWU

Feb 25th, 02:55

VA3ABN

Joined: Feb 24th 2012, 11:21
Total Topics: 0
Total Posts: 0
I have read and heard aboutCWL/CWU, but I am unable to find any information on what it is exactly? I know what CW is, but never knew there was a lower/upper side like in SSB.

Ken VA3ABN
Feb 25th, 04:32

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Ken,

CWL/CWU is similar to LSB/USB. CW reception is almost the same as SSB, except the IF passband is narrower. If you're set for a 700 Hz tone, the inserted carrier can be 700 Hz higher or lower and you still get the same CW audio out. The main difference is how the signal tone changes as you tune your main dial (VFO). If it's CWL (LSB), the tone frequency increases as you tune upward. It decreases in the CWU mode.

Sometimes QRM might be rejected better if you use one mode or the other, depending on your radio and the specific interference situation. But mostly it's a question of personal preference.

73 Martin AA6E
Feb 25th, 10:39

VA3ABN

Joined: Feb 24th 2012, 11:21
Total Topics: 0
Total Posts: 0
Thank you Martin. Can I assume that on 7 MHZ (40M) and lower is for CWL and CWU for above 7 MHZ, like as in SSB?

73 Ken VA3ABN
Feb 25th, 14:32

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Based on a quick Google search:

Icom does it that way, but Kenwood and Yaesu default to USB on all bands. The Elecraft K2 is similar, but not quite, and the K3 defaults to LSB on all bands. I suggest studying the instruction manual of your rig, then tuning with your radio to verify that the information you read is accurate.

Zack W1VT
ARRL Senior Lab Engineer
Feb 26th, 02:04

VA3ABN

Joined: Feb 24th 2012, 11:21
Total Topics: 0
Total Posts: 0
Thanks Zack

My question isn't in regards to a rig that I may have. I built a QRP SSB rig and was investigating the possibility of adding CW. In my research I came across CWL/CWU and was wondering if this is something I should be looking at.

Ken VA3ABN
Apr 5th, 18:07

W0IS

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Different manufacturers display it differently, and I think Yaesu is the one who uses the CW-U and CW-L terminology.

Basically, the transmitted signal is identical either way. Some manufacturers may differ, but in general, the frequency displayed on the transceiver's VFO will be the transmitted carrier frequency.

The CW-L or CW-U setting means what you will be receiving. On CW-L, you'll be receiving LSB. On CW-U, you'll be receiving USB. The only time I can think of where this would make any difference is if you are working cross-mode with an SSB station. So if you want to work a station running LSB, you'll need to switch to CW-L. To work a USB station, you'll need to set it to CW-U.

Again, actually working CW, it will make no difference. However, depending on how you have it set, the VFO will seem to work "backwards" in one of the settings. For example, if you have it on CW-L, you are receiving LSB. Therefore, as you tune up in frequency with it set to CW-L, the pitch of the received CW signal will get higher and higher. On CW-U, the pitch of the received signal will get lower and lower as you tune up in frequency.

73,
W0IS

Back to Top