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Author Topic: Sidetone Frequency  (Read 12035 times)
W6UV
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Posts: 540




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« on: November 08, 2010, 02:30:05 PM »

Have any studies been done on the optimum sidetone frequency for CW reception?

I've always used a high tone in the region of 900 Hz, but am beginning to think this isn't such a good idea for many reasons.

What do you prefer?
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NI0C
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« Reply #1 on: November 08, 2010, 03:09:32 PM »

I think what you mean by sidetone frequency is "pitch."  Most transceivers are aligned so that a signal at the passband center produces a pitch that is equal to the sidetone frequency during sending.

Pitch preferences vary among CW operators; however it is generally easier to discriminate among signals that are close together at the low end of the pitch scale.  For example, a 410 Hz tone is 2.5% higher than 400 Hz, while an 810 Hz tone is only 1.25% higher than 800 Hz.

Most transceivers have a variable pitch control that varies from about 400 to 800 or 1000 Hz, ususally in 50 Hz steps.  The Elecraft K3 can go as low as 300 Hz, and pitch is variable in 10 Hz steps.  My current preference is 360 Hz, but that's for listening to very weak signals on the low frequency bands.  For general ragchewing purposes, I might go as high as 440 Hz.

If you want to try different pitches, I'd recommend making small incremental changes, letting your ears adjust to each new pitch.  I made the QSY from 600 Hz to 360 Hz over a several year period.

73,
Chuck  NI0C 

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W6UV
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Posts: 540




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« Reply #2 on: November 08, 2010, 10:33:50 PM »

Yep, pitch is what I meant. Thanks for the clarification.
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KE7WAV
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« Reply #3 on: November 09, 2010, 02:41:01 PM »

One summer I helped an audiologist doing hearing tests.  Most people "lose" a little hearing at different frequencies.  for example at 300 Hz you may be down 25db but then right back up to only 5db down at 350-400 Hz.  The pitch you tune to as you listen to another CW op is probably going to be an area where your ear is stronger and is also comfortable.  After one summer I learned that no two ears are the same.  Most men do tend to lose higher frequencies first, in my observations.

The cochlea is worse than a drifty regenerative receiver-- your brain is always adjusting the controls to get the best reception.

73
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N2EY
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« Reply #4 on: November 11, 2010, 04:16:49 AM »

I've been studying it for 43 years. 900 Hz is too high, 700 to 750 Hz is about right.

The trick is to have the rig set up so that the center of the receiver passband is at the same frequency/pitch as the sidetone generated when you're sending. (Of course you need a narrow 400-500 Hz filter in the receiver).

73 de Jim, N2EY
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NI0C
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« Reply #5 on: November 11, 2010, 06:20:02 AM »

Quote
I've been studying it for 43 years. 900 Hz is too high, 700 to 750 Hz is about right.

What constitutes "studying it" ?  I think you're just giving us your personal preference.  The optimum choice depends on the individual and what they are trying to accomplish.  As a general rule, I find I prefer a higher pitch for high speed strong signals than for very slow and/or weak signals

Ten Tec found that not everyone agreed with their choice of a 750 Hz pitch, so they came up with a "low pitch" narrow CW filter centered at 500 Hz for their Omni 6. 

ON4UN's book on lowband DX'ing discusses the CW pitch preferences of lowband DX'ers, mentioning that some go as low as 200 Hz. 

Bill Tippett, W4ZV, has stated (in both the Ten Tec and Elecraft reflectors) that he uses CW pitch frequencies less than 450 Hz nearly all the time.  You may recall this eHam article about Bill from several years ago: http://www.eham.net/articles/10078 

In addition to setting the miles per watt record mentioned in the article, Bill appears at the top of the 160m DXCC list: http://www.arrl.org/system/dxcc/view/DXCC-160M-20101111-USLetter.pdf

Of course, as KE7WAV pointed out, we need to be guided by the frequency response of our own ears. 

73,
Chuck  NI0C



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KV1E
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Posts: 10




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« Reply #6 on: November 17, 2010, 09:23:42 AM »

As has already been pointed out, everyone has a favorite side tone frequency.  I've found my ears respond to around 450 Hz best, but for weak signals right at the rx noise level I find 300 Hz is best for me (with the most narrow filter in).  During a QSO I'm usually listening at around 450 and will vary it with the pitch control quite often, but never go above 600 Hz.  When listening to QRQ transmissions for extended periods I find that varying the pitch when I start to get too far behind in copying helps.  So, you can see that there is no perfect, universal pitch.
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WB2WIK
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« Reply #7 on: November 17, 2010, 04:04:17 PM »

I change both the sidetone frequency I'm using and also the pitch of received CW signals pretty often to suit myself.  I might leave my sidetone set at 600 or 700 Hz, but use the R.I.T. to tune in a signal at 300 Hz, or even at 1 kHz, depending on conditions.  Noise levels, QRM, etc. can dictate what "sounds" easiest to copy, from contact to contact.

Nothing stays adjusted the same way long here!
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AB2T
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« Reply #8 on: November 18, 2010, 05:43:11 AM »

Some people are good at listening to a signal and then zero-beating without having to use a "help" like a sidetone.  I can't.

One of the things I value in a rig is a steady and easy to hear 600 Hz tone that I can easily superimpose over a CQ.  Then I adjust the RIT to about 400 Hz. 

I find it very hard to "spot" signals with newer rigs, as I don't know how to generate the sidetone easily.  Sometimes I'll have to press a few buttons to get a non-transmittable tone.  I invariably find myself off the mark quite a bit with the new rigs since I don't have time to RTFM or don't understand the manual instructions.  Sometimes other people don't know what I'm talking about.

That's just me, however.  I think that most operators have an easier time zero-beating than I do.  However it's crucial that I at least ask the rig's owner or someone in the shack how to properly match my signal so that I might reduce interference.  Makes it easier to copy me as well!

73, Jordan
« Last Edit: November 18, 2010, 05:45:08 AM by Jordan » Logged
N3QE
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Posts: 2341




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« Reply #9 on: November 18, 2010, 06:38:38 AM »

I don't have absolute pitch or whatever musical skill, but I do know that within minutes of starting a contest, I have figured out how to zero beat (+/- 150Hz) by ear the station I want to work, using that particular rig. I can do this whether the filter is wide or narrow for several different rigs. But there is a short period, probably several minutes (which can mean 5 or more QSO's at the start of a contest!) where I haven't really gotten my sea legs.

For most contesting the +/- 200 Hz is about right - there are exceptions.

Every so often there's some Nimrod out there on the bands with a filter that's only 25Hz wide and it's a mixture of funny and frustrating to hear them miss a lot of QSO's because they're using such a narrow filter. What's especially hilarious is when he tells the other op that they are on the wrong frequency as if he never heard of RIT and thinks that CW is channelized or something.
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NI0C
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« Reply #10 on: November 18, 2010, 07:26:04 AM »

There's nothing wrong with using narrow CW filters.  They help improve the s/n ratio on weak signals and allow efficient use of our CW band space. 

For S & P contesting and general DX'ing, the ability to accurately (+/- 10 Hz, yes that's ten) know where your signal is with respect to others will improve your ability to get through.  If you are running stations, yes, you will need a wider filter in order to pick up those stations who don't know how to zero beat.  Field Day is the worst contest in this regard-- I am planning on purchasing a 700 Hz filter-- 500 Hz seems too narrow for FD.

For general ragchew type QSO's, it is considerate to accurately zero-beat the station you are working-- it minimizes the space your QSO occupies.  For three and four way CW QSO's, it is obviously even more important that everyone be on the same frequency. 

73,
Chuck  NI0C
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N3QE
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Posts: 2341




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« Reply #11 on: November 18, 2010, 07:55:10 AM »

There's nothing wrong with using narrow CW filters.  They help improve the s/n ratio on weak signals and allow efficient use of our CW band space. 

For S & P contesting and general DX'ing, the ability to accurately (+/- 10 Hz, yes that's ten) know where your signal is with respect to others will improve your ability to get through.  If you are running stations, yes, you will need a wider filter in order to pick up those stations who don't know how to zero beat.  Field Day is the worst contest in this regard-- I am planning on purchasing a 700 Hz filter-- 500 Hz seems too narrow for FD.

For general ragchew type QSO's, it is considerate to accurately zero-beat the station you are working-- it minimizes the space your QSO occupies.  For three and four way CW QSO's, it is obviously even more important that everyone be on the same frequency. 

I know that most modern equipment has display resolution and stability, and possibly even accuracy (especially with TCXO) that you are proposing as the gold standard (ten Hz). But having spent decades on the CW bands, overlapping with the era when novices were rock-bound, I have a hard time seeing how I could ever expect the general population to zero beat to better than a few hundred Hz, and I still often work with mismatches of a kHz or more.

I do accept that the "listening +/- 5 or 10 kHz" common from the rock bound days probably isn't really necessary anymore but I can't make the leap to expecting +/- 10 Hz spotting. For one thing the CW keying sidebands will extend out much further than that.

And personally for me with nets, having each participant identifiable by an audible offset is actually desirable. Of course I'm not one one of the guys with a 25 Hz filter. Just my two cents.

Maybe there's a community of CW operators out there that really do expect 10Hz zero beats but I've never worked any of them because of my lax standards. Twisting the motto of the SOC "second class operators's club"... zero beating is tolerated but not encouraged :-)

Tim N3QE
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NI0C
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Posts: 2418




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« Reply #12 on: November 18, 2010, 08:36:19 AM »

Tim,
I was a rock bound Novice in 1959, using a receiver that probably had a 5-10 Khz bandwidth.  As you pointed out, times have changed, radios are better-- more stable and accurate, and narrow crystal and DSP filters are routinely available. 

I was talking more about results than expectations.  People who have trained themselves to place their frequency accurately in a DX pileup will run circles around those who don't really know where they are transmitting.  People who can zero beat each other in a round table CW ragchew are taking up less space than those who are a couple of hundred Hertz apart.   

73,
Chuck  NI0C 
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WB2WIK
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Posts: 20629




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« Reply #13 on: November 18, 2010, 01:33:15 PM »

 


I know that most modern equipment has display resolution and stability, and possibly even accuracy (especially with TCXO) that you are proposing as the gold standard (ten Hz). But having spent decades on the CW bands, overlapping with the era when novices were rock-bound, I have a hard time seeing how I could ever expect the general population to zero beat to better than a few hundred Hz, and I still often work with mismatches of a kHz or more.

Whaaaaat?

For CW I normally operate with 150 Hz IF bandwidth (and sometimes 80 Hz), using brick-wall DSP: At 151 Hz off frequency, the received signal doesn't get weaker, it completely disappears:  No matter how strong it is.

I can zero-beat stations by ear within 20 Hz very easily...when it gets down to this note, you can hear the warble of the beat and it's close to zero.  You need headphones to get that close, as speakers won't usually reproduce such low frequencies; but I don't know any serious CW operator who uses a speaker. Tongue

To me, a 100 Hz difference in signal frequency is enormous and often outside my passband altogether.

I sure wouldn't want anyone operating any of my contest stations who can't do this without even thinking about it; they'd waste too much time calling stations who aren't going to hear them, because they're 200 Hz off. Cheesy



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N3QE
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Posts: 2341




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« Reply #14 on: November 19, 2010, 02:22:54 AM »


For CW I normally operate with 150 Hz IF bandwidth (and sometimes 80 Hz), using brick-wall DSP: At 151 Hz off frequency, the received signal doesn't get weaker, it completely disappears:  No matter how strong it is.

[...]

To me, a 100 Hz difference in signal frequency is enormous and often outside my passband altogether.


I think we've had this discussion before :-). I prefer, if at all possible, to run my bandwidth as wide as possible in CW. If I can hear a couple stations above me and below me in a contest, then I start to feel that I have a broad awareness.

I also have a very strong distaste for brick wall filters because they have abysmal group delay properties. I think our previous discussions were over filter bandwidths.

I check my logs for WB2WIK and NI0C in the past couple years and I don't see either of you guys in there. I suspect my lax tolerances and non-insistence that the other guy zero-beat me, excludes us from QSO'ing. Probably like when I was a kid and I never got to hang around with the cool groups at school - mutually exclusive groups.

Tim.
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