Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: CW on modern rigs  (Read 2282 times)
WA2ASB
Member

Posts: 39




Ignore
« on: August 05, 2013, 04:43:21 PM »

I'm wondering how CW works on modern transceivers.  I thought I saw somewhere that a sideband was being used.  In the ole days, (note I didn't say "good ole days") AM had a carrier, a lower sideband and an upper sideband.  DSB was like AM w/o the carrier.  Of course SSB was w/o the carrier and one sideband.  CW was just turning the carrier on and off.  In order to hear it the receiver had to have a BFO turned on.

Is it still this way with modern transceivers or are they keying one of the sidebands on and off?

Logged
AA4PB
Member

Posts: 12766




Ignore
« Reply #1 on: August 05, 2013, 04:55:25 PM »

The vast majority turn the RF "carrier" on and off. The really modern ones do it in the digital signal processor (DSP) - the same place they do the modulation/demodulation for all of the other modes.

Logged
WB2WIK
Member

Posts: 20558




Ignore
« Reply #2 on: August 06, 2013, 10:06:20 AM »

Yes, in all the most "modern" rigs it's all done via DSP and it does turn the carrier on and off with keying.  No sidebands.  The only modulation is the 1/0 state of the carrier generated.

Logged
WB6BYU
Member

Posts: 13112




Ignore
« Reply #3 on: August 08, 2013, 07:03:32 PM »

Some of the early tube transceivers (including Collins, Heathkit, SBE, etc.) were really
designed for SSB, and CW was more of an afterthought accomplished by keying the
sidetone oscillator into the SSB input.  As long as the carrier suppression is good and
the audio waveshape is pretty clean, this produces something reasonably close to
keying a standard CW radio.  But most solid state rigs - even those that can by
no means be considered "modern" - do it by shifting and keying the carrier oscillator,
or the modern DSP equivalent of that.

The receiver still works in SSB mode, either upper or lower sideband, just as
would be the case on an old tube receiver where you could adjust the BFO knob
above or below the incoming carrier.  (And many modern rigs provide some way
to choose which sideband you want to use, though older Japanese solid state
rigs tended to always use USB.)
Logged
VE7BGP
Member

Posts: 80




Ignore
« Reply #4 on: August 16, 2013, 08:04:45 PM »

The Heathkit SB and HW-100, 101 and 102 series of tube type Transceivers  were designed better than most of the Tube era Transceivers for CW. CW was accomplished with an RF Carrier Oscillator and Grid Block Keying of the Final Amp. The Sidetone only activated the VOX to switch the rig to Transmit Mode and when you stopped sending the Delay turned the Rig back to Receive. The 101 and 102 versions in both SB and HW series had a switch to switch the CW Filter On and Off and the filter bracket had provisions for both Filters. An add on Kit was available for the SB-100 to add a CW Filter when the 101 came out. That Filter Kit could also be installed in the older HW-100. I had a British KW-2000B that had the CW as a afterthought like WB6BYU described I didn't enjoy operating CW on that rig at all no CW filter and annoying 1500 Hz sidetone. I was given an SB-101 a few years ago  that even had a CW Filter Installed and I do enjoy operating that rig on CW. It is a lot of fun operating it on Strait key New Years and Classic Exchange.  I just wanted to mention that those oldie Heathkit rigs were great on CW especially for fun QSO's 73 Gerry
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!