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  Topic: PSK Tones (3 replies)
#1     Sun Nov 26, 2006 1:50 am
W0SDG
Apple Valley MN
 
Join Date: Oct 2006
Posts: 101
Subject: PSK Tones

It seems as though 1500 Hz is not the best tone to use with PSK using CQ100 and the internet. I was chatting with Satoru, JA1ZCW today and noticed he was using 1000 HZ tone instead of 1500. We worked with different tones then and he demonstrated to me the difference of noise levels between lower tones and higher tones. Lower tones also generate a little wider signal which improves copy of text. Actually if we went lower then 1000 hz it improved more.

So why 1000 Hz? It is simply a comprimize of tones that are more pleasing to the ear. I listened to a QSO a few days ago at about 450 Hz and I could not listen for very long as it was unpleasant to listen to for me. It seems the same was true for Satoru. So it seems that when we use CQ100 and VoIP channels, that the standard 1500 Hz tone was designed for HF software and doesn't apply here on the internet. Since we are not sharing band space, it doesn't matter here and lower tones seem to work better.

1000 Hz is the standard Television test tone and it appears to be better for copying PSK text. Probably 800 Hz would even be better. The most impressive result was in the noise reduction. Very little foldovers and shadows, etc., were the result. So, it seems that maybe a standard, lower then 1500 Hz, be set here as we grow in numbers. For me it is a matter of toleration. CW is commonly sent using 700 to 800 Hz tones. Which sounds the best is probably the question, and I just happen to like 1000 Hz. It probably doesn't really matter other then to just set some sort of standard so we are all working together.

If you are interested, find someone on PSK and do the same tests with tones we did and you should find some interesting results. Bottom line is that we just need to be on the same tone to work the other station. Would a standard be practical? Probably. My suggestion is 1000 Hz if a standard is sensible.

Steve - W0SDG
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#2     Sun Nov 26, 2006 9:45 am
VE3EFC
 
Join Date: Aug 2006
Posts: 724
Subject:

Very interesting Steve.

The GSM 6.10 codec is optimized for human voice, so there must be a best tone to use for digital modes. I wonder if its optimized for male or female voice. Maybe a google search on this codec will turn up more information.

73 Doug
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#3     Sun Nov 26, 2006 4:06 pm
W0NBP
Ottumwa, Iowa
 
Join Date: Nov 2006
Posts: 22
Subject:

Hello Steve,

I agree 1000Hz is easier on the ears. Last night my 5 year old grandson came into the shack and asked me "are you squealing Grandpa?" I reduced the volume on the PSK31 qso in progress and had to laugh at his discomfort with the sound.

I also agree that a standard should be used in this mode on CQ100. Not all the tried and true methods from HF will trnspose to this virtual radio. As with any new mode, we will by experimentation and sampling, find what works best and soon all will using it second nature.

Thx fer ur comments.... good idea.

Bill

de W0NBP
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#4     Sun Nov 26, 2006 11:16 pm
JA1SCW
Atsugi, Japan
 
Join Date: Nov 2006
Posts: 10
Subject: Re: PSK Tones

Hi Steve, thank you for the QSO in PSK31 yesterday.
This is Satoru, JA1SCW in Atsugi, Japan. During the last a couple of weeks, I made 18 QSOs with 11 entities in PSK31, 63 or MFSK16. I am pleased to know digi-modes do work well even on CQ100 over internet.

I am sure that eveyone will easily recognise that IMD for PSK31 over VoIP like CQ100 is inversely proportional to the frequency. Although signal level is almost identical in any frequency within the 3Khz band width. It looks me that this phenomenon is a kind of aliasing generated by packeting and carrier of PSK31 and it is naturally resulted to a subject of Someya-Shannon's Sampling Theory (maybe pre-post filter issue!?).

There might be differences of aliasing degree due to variation of characterlistic of sound card and/or software for PSK31 to be used for...

Any comments are highly appreciated.. Best 73s, de JA1SCW
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