Fw: [Pskten] PSK Signals

[Jim's mail]

----- Original Message -----
From: "Jeff Steinkamp" <[hidden email]>
To: "Jim's mail" <[hidden email]>
Sent: Wednesday, December 19, 2007 1:44 AM
Subject: Re: [Pskten] PSK Signals

> No Problem. forward away.  I als0 have a few discussions on my web site
> about properly setting your transmiter and a discussion about IMD.
> http://www.n7yg.net
>
> Jeff N7YG
>
> ----- Original Message -----
> From: "Jim's mail" <[hidden email]>
> To: "Jeff Steinkamp" <[hidden email]>
> Sent: Tuesday, December 18, 2007 15:21
> Subject: Re: [Pskten] PSK Signals
>
>
>> Jeff,
>>
>> This information sound really good.  There is currently a discussion
>> on
>> another reflector I read on the topic of PSK and some of the settings
>> that
>> should be used for better signals.  Would you mind if I forwarded your
>> message to that group?
>>
>> 73,
>> Jim Good KD5VXH
>>
>>
>> ----- Original Message -----
>> From: "Jeff Steinkamp" <[hidden email]>
>> To: "PSK TenMeters" <[hidden email]>; "PropNet Online"
>> <[hidden email]>
>> Sent: Tuesday, December 18, 2007 2:44 PM
>> Subject: [Pskten] PSK Signals
>>
>>
>>> In the few days I've had the 30 meter antenna up, I have been able to
>>> spend some time watching the capture of signals in PropnetPSK (PNP).
>>> There
>>> has been some discussion in the past about PNP not acquiring a signal
>>> that
>>> was quite strong.  This discussion will also apply to YGPSK and just
>>> about
>>> every other PSK decoder that uses the PSKCORE.DLL as the Decoding
>>> element.
>>>
>>>
>>>
>>> PNP and the PSKCORE.DLL are quite finicky on signal quality and over
>>> the
>>> past few days I have observed a number of really terrible signals,
>>> either
>>> because they are completely overdriven or due to atmospheric
>>> conditions.
>>>
>>>
>>>
>>> If you look at a good PSK signal in the spectrum display instead of
>>> the
>>> waterfall and spread the display out, you will notice that a good PSK
>>> signal has two signal peaks, approximately 31 Hz apart with a small
>>> valley
>>> in the center.  A good signal lock-on will occur when the frequency
>>> line
>>> is between these two signal peaks.  Any third order harmonic
>>> distortion
>>> will be reduced by at least 60db.
>>>
>>>
>>>
>>> If the signal is overdriven, these third order products will be above
>>> the
>>> 60 db attenuation and this is where problem can start.  If you look
>>> very
>>> closely at an overdriven signal, you will see a mirror of the signal
>>> in
>>> the third order distortion product on either side of the main signal.
>>> There will be 2 smaller peaks along with a valley.   If this portion
>>> of
>>> the PSK signal is above the ambient noise floor, then the weak signal
>>> properties of PSK will lock on to this signal and start decoding
>>> because
>>> it thinks it is a qualified PSK signal.  Depending on the quality of
>>> the
>>> signal, it may or may not produce intelligence.
>>>
>>>
>>>
>>> This is why it is imperative that we make sure our transmitters are
>>> correctly adjusted for a good quality signal; rig power at something
>>> less
>>> than the 100% duty cycle rating of the radio and absolutely no ALC
>>> showing
>>> on the meter.  The last test will be to have someone locally have a
>>> listen
>>> to the signal for quality.  There are a couple of commercial 'PSK
>>> Meters'
>>> on the marker that will actually sample your transmitted signal and
>>> automatically adjust the sound card gain to keep you signal clean and
>>> pure.  I do not have one of these and therefore do not have any first
>>> hand
>>> knowledge of these devices, but from the reports I have read, this
>>> might
>>> be a very good addition to the shack for PSK or other sound card
>>> digital
>>> modes.
>>>
>>>
>>>
>>>
>>>
>>> Jeff Steinkamp - N7YG
>>> Tucson, AZ
>>> SCUD Missile Coordinates
>>> N32-13-55.01 W110-50-51.91
>>> http://n7yg.net
>>> http://home.earthlink.net/~jksteinkamp
>>> Linux User #420428
>>> Skype : jeff_steinkamp
>>> Yahoo Messenger: n7yg
>>> _______________________________________________________
>>>
>>> 'I'm not the one that misplaced the Deltivid asteroid belt!' - Q
>>>
>>>
>>> _______________________________________________
>>> Pskten mailing list
>>> [hidden email]
>>> http://www.nwlaweb.net/mailman/listinfo/pskten
>>>
>>>
>>
>>
>>
>
>
>
>

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