Re: [TenTec] New Sherwood Presentation - Powerpoint & Audio

["Bob McGraw - K4TAX" <RMcGraw@Blomand.net>]

The Sherwood Presentation and data is only one set of parameters for judging 
a receiver performance.  Truly there are others that are more or less 
important to each of us.
Just this morning, in a SSB QSO on 75M, the other fellows in the group 
complained that a QSO some 3 kHz downband on USB was clobbering them.  I did 
a SWP and indeed saw the signals downband as well as those on the frequency 
of which I was in the QSO.  On my Omni VII I tuned VFO B downband 3 kHz and 
switched to USB.  Sure enough there was a QSO in progress. Signals were 
running about S-5 to maybe S-9 in that QSO.  Switching back to VFO A and LSB 
the signals in the QSO there were running S-9 +10 to 20 dB.  The end result, 
I had no problem copying the stations in my QSO and was not bothered the 
least  by the QSO on USB some 3 kHz downband.  I find it interesting that 
some radios seem to have a problem with this condition while others do not. 
Yes, there's more to receiver performance than 2 kHz dynamic range 
performance.
73
Bob, K4TAX




----- Original Message ----- 
From: "Alfred Lorona" <w6wqc@dslextreme.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Tuesday, March 18, 2008 12:51 PM
Subject: Re: [TenTec] New Sherwood Presentation - Powerpoint & Audio


> Terry, N4TZ/9  has touched on an important point that has long been a
> priority on my list of receiver specifications that are relevant and those
> that are less relevant. Two tone IMD is not at the top on my list. A 
> related
> parameter which is similar but not identical is receiver desensitization.
> This requires only one off freqeuncy signal, not two. And there is not a
> precise frequency requirement as with two tone IMD. In adddition, I have
> also noticed that often a still more pernicious phenomena is transmitted
> broadband phase noise. Several field day operations have been ruined
> primarily by these two types of interference and not two tone IMD. I also
> wish to add that two tone IMD is more serious on CW becaue both signals 
> are
> always transmitted at full power. On the other hand, with SSB, both
> transmittiers must hit peak power simultaneoulsy for a third order product
> to be generated in the receiver. Due to the instantaneous peaks of speech
> that occur at a sporatic manner, the probability of this happening is
> greatly lessened and when it does happen, the interference is an extremely
> short spurt.
>
> 73, AL, w6wqc
>
>
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