Filter out CW station identifiers while scanning?

Status
Not open for further replies.

dimab

Member
Joined
Dec 19, 2002
Messages
364
Location
CT
I stream a scanner feed online and really hate it when when the station ID breaks through in CW. Is there any solution to filtering out the CW audio from the audio output of the scanner? I realize there might be some cobbled software solutions, but I'm hoping someone knows of a hardware solution that I can apply to my other radios.

Sent from my Nexus 5 using Tapatalk
 

902

Member
Joined
Nov 7, 2003
Messages
2,433
Location
Downsouthsomewhere
Well... there are a couple of things that might be happening. First is that this is a modern, commercially produced base station or repeater and the ID is programmed in to go off in between traffic. Sometimes (but not all times) this ID goes off without CTCSS. If this is the case, if your scanner or radio supports CTCSS, program the channel with the CTCSS tone and most of the time this will go away. In some cases it won't.

If this is a ham creation or an older repeater with an add-on identifier, it probably sends CTCSS or may actually be only carrier squelch. Then there is no simple way of doing this. You can STILL filter it out using a deep audio notch filter that's tuned to the right frequency for the CW tone. You can build one using precision LC components.

Or you can use a digital signal processor add-on unit sold by many ham stores and set the frequency on that. Properly tuned you won't hear any CWID.
 

N8IAA

Member
Joined
Dec 19, 2002
Messages
7,047
Location
Fortunately, GA
Since both frequencies have either CTCSS, or, DCS, no. Using those won't solve the problem unless you aren't using the tones. The CW ID will still be heard.
Larry
 

dimab

Member
Joined
Dec 19, 2002
Messages
364
Location
CT
In my case, its a public safety feed that does use tones for the identifier.

Sent from my Nexus 5 using Tapatalk
 

dimab

Member
Joined
Dec 19, 2002
Messages
364
Location
CT
Or you can use a digital signal processor add-on unit sold by many ham stores and set the frequency on that. Properly tuned you won't hear any CWID.
I've tried to Google some DSP filters, but apparently my google skills are not so great. All I'm getting is filters to improve CW reception. Any help would be appreciated.
 

XTS3000

Member
Joined
Nov 4, 2005
Messages
1,082
Long ago, Radio Shack sold a powered external speaker with DSP. This speaker did NOT clean up static, but almost completely removed any tones broadcast. I noticed the speaker would quiet down CW signals by 80-90%.

The DSP speaker had a headphone out port, so it would work with online streaming via sound card.

Pretty sure you could pick up one used for a decent price. Maybe someone here has one they are not using and would sell to you. I have one, but won't sell it because CW ID's drive me nuts.

The item your looking for is the Radio Shack "DSP 40". It's catalog number is: 21-543. It specifically has a CW filter setting along with a SSB and NR. Also has bandwidth settings for narrow, med, and wide.

To get rid of the CW ID's, you'd run the SSB filter. Sounds strange, but trust me on that.
 
Last edited:

phask

Member
Premium Subscriber
Joined
Dec 19, 2002
Messages
3,303
Location
KZZV - SE Ohio
My idea might be the same as the post below - but what about some audio filtering equipment where you filter out that audio freq.? It should be a pretty consistent freq. I know there are sophisticated audio filers/processors, but cost might be prohibitive.

Good luck.


Long ago, Radio Shack sold a powered external speaker with DSP. This speaker did NOT clean up static, but almost completely removed any tones broadcast. I noticed the speaker would quiet down CW signals by 80-90%.

The DSP speaker had a headphone out port, so it would work with online streaming via sound card.

Pretty sure you could pick up one used for a decent price. Maybe someone here has one they are not using and would sell to you. I have one, but won't sell it because CW ID's drive me nuts.

The item your looking for is the Radio Shack "DSP 40". It's catalog number is: 21-543. It specifically has a CW filter setting along with a SSB and NR. Also has bandwidth settings for narrow, med, and wide.

To get rid of the CW ID's, you'd run the SSB filter. Sounds strange, but trust me on that.
 

902

Member
Joined
Nov 7, 2003
Messages
2,433
Location
Downsouthsomewhere
I've tried to Google some DSP filters, but apparently my google skills are not so great. All I'm getting is filters to improve CW reception. Any help would be appreciated.
Your google skills are fine. There's just a lot of junk out there and I didn't explain it as I should have.

This is the thing I'm talking about. Click on the picture and you can see the controls on it. If you push the Auto Notch button, virtually every tone you get will be notched out and all you'll hear is speech. If you want to hear all tones except one (the tone frequency of the CW identifier being transmitted), you can adjust the knobs to notch just that one frequency out.

It's a little on the expensive side, but I do have one of these. I bought it (personally) a while back when I was in charge of technical services at a communications center. Before I hooked it up at home, I was playing with sending the fire base station traffic, transmit and receive, through the telephone system's hold feature. I used it to strip all of the tones but pass the voice. Worked pretty well, but we ultimately went in another direction.
 

wa1nic

Member
Premium Subscriber
Joined
May 28, 2012
Messages
263
Location
Westfield, Ma
The CW ID on my Part 90 base station transmits with the TSQ turned off.

Some may do that, others may not. It takes a bit of effort to do it.

I did it to make sure that the automatic ID isn't sent out in rolling tone scrambled mode.

If someone left the scrambler function turned on, the ID box would key the radio when it is supposed to and transmit in whatever mode it was left in, which would not be legal if it was scrambled.

There were multiple possible solutions to making sure that wouldn't happen, but the easiest solution on my particular radio (ICOM F5021) one was to simply have it transmit the ID on a different programmed channel from the "normal channel".

The "different channel" is actually the same frequency as the "normal channel", but the extra settings are different. Scrambling is disabled on the "ID Channel", and I chose to turn off TSQ Receive in the process of making sure it wouldn't transmit while the channel was active with another user who was using a different or no tone (that is actually a legal requirement - "listen before you transmit" - very few commercial base stations or repeaters actually do that though).

While I was in there, I turned off TSQ transmit in the "ID Channel" as well, so no one running TSQ receive will be bothered by the ID.
 
D

DaveNF2G

Guest
I'm a little surprised that even ham operators, who should know better, refer to Morse Code base station IDs as "CW." They are not CW, they are FM modulated with audio tones in a Morse Code pattern. Calling it CW only confuses the issue when discussing such things as filtering out the identifier audio, which has nothing to do with "CW filters."
 

k9rzz

Member
Joined
Dec 12, 2005
Messages
3,164
Location
Milwaukee, WI
Sounds like an engineer talking. Typical hams who -operate- CW will call any morse code CW, even if you're using your car horn. =:^] Personally, I've got no problem with that, I know what's being talked about. "CW" refers to the mode, e.g. Phone vs CW.
 

wa1nic

Member
Premium Subscriber
Joined
May 28, 2012
Messages
263
Location
Westfield, Ma
11F2 then if it makes it clearer,...

I don't recall anyone referring to a Morse ID on a repeater as something other than the "CW ID". Not in my recollection anyway.

I believe that it is accepted jargon in ham radio to refer to it as "CW ID", even if it isn't interrupted continuous wave.

To each his own though. I can handle either.
 
Last edited:

902

Member
Joined
Nov 7, 2003
Messages
2,433
Location
Downsouthsomewhere
I saw CWID and pretty much knew what it was right there. I guess it's a regional thing. We use the term downstate and in NJ, in the Midwest, and Down South, too. Either way, I guess it's bugging him.

I had a P25 conventional system that used to transmit CWID. When the system was busy, the ID was programmed so slow (less than 15 WPM) that a transmission on the system would reset the ID. Some times it would reset just about 20 times until there was a break between the traffic to send the whole thing. It got very annoying to listen to on a scanner (maybe why it was left that way...). It didn't come through my mobile or portable radios, though, so she-s a no matter.
 

wa1nic

Member
Premium Subscriber
Joined
May 28, 2012
Messages
263
Location
Westfield, Ma
47 CFR §97.3(c)(4)

MCW. Tone-modulated international Morse code telegraphy emissions having designators with A, C, D, F, G, H or R as the first symbol; 2 as the second symbol; A or B as the third symbol.


So, I guess it is MCWID, or F2AID if one wants to be precise.

However, in "§97.119 Station identification",

paragraph (b) The call sign must be transmitted with an emission authorized for the transmitting channel in one of the following ways:

(1) By a CW emission. When keyed by an automatic device used only for identification, the speed must not exceed 20 words per minute;
-----


It does not specifically refer to A1 or F2 or CW or MCW anywhere else in the identification section. When they say "CW", they do not say "Morse Code" either. CW doesn't technically even mean "Morse Code" ... it means a "Dead Key". As soon as you interrupt it, it is not continuous, so apparently the FCC takes some liberties with meanings based on historical usage of ham "lingo".

So, even the FCC uses the abbreviation "CW" with the intent of it meaning "Morse Code", and they don't use it specifically for only A1 when they use the phrase.

DE WA1NIC AR
 
Status
Not open for further replies.
Top