[TenTec] ORION II CW pile up readability

Thu Jan 31 20:34:16 EST 2008

I am grateful for this list, and now I only wish that the engineer who 
gave him the advice had bothered to put it in the manual.

Bob McGraw - K4TAX wrote:
> Glad that Jerry wrote this.  It is absolutely on the money.
>
> I"ve said it before and I had to learn this lesson.  Now we know that it is 
> difficult to train old dogs any new tricks, and I'm an old dog, 
> but............If you insist on operating the Orion and Orion II and the 
> Omni VII series they way you have operated radios of the past, AND if you 
> insist on operating these offerings from Tentec like the current breed of 
> radios from the "big three" let it be known and fact, you will not attain 
> the outstanding performance that the new Orion and Omni series has to offer.
>
> The gain structure of these radios is quite different and the AGC system is 
> quite different.  It does not and will not behave like the systems found in 
> "the big three".  Therefore, if you operate in the "old fashion" way you 
> will not be happy.
>
> The audio gain controls the audio level for comfortable listening be it with 
> internal speaker, external speaker or with your favorite headphones.  Best 
> is "set it and forget it".  The RF gain controls the levels inside the radio 
> for processing, AGC levels and such.  I've found that 90% of the "knob 
> turning" is now the RF gain and not the AF gain.  As to the NR and AN 
> functions, I have found that these should be applied to specific signals in 
> specific noise conditions.  They are not, in my opinion and findings,  for 
> "general use".  I operate with mine off 90% or more of the time.  Once I've 
> acquired a signal, adjusted the RF gain I then may {repeat may} activate the 
> NR or AN function.  I don't tune the bands with these functions on.  Most of 
> the time these functions are not needed if the RF gain and AGC is correctly 
> adjusted.
>
> I could go on and on with comments and suggestions and findings but Jerry 
> has done a fine job.  Now, go read again what he wrote.
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message ----- 
> From: "Jerry Volpe" <kg6tt at arrl.net>
> To: <tentec at contesting.com>
> Sent: Thursday, January 31, 2008 2:45 PM
> Subject: Re: [TenTec] ORION II CW pile up readability
>
>
>   
>> "OK, I brought this up before, and was specifically told that "low RF
>> gain and high AF gain," as is traditional in analog radios, does not
>> apply to the O2."
>>
>> I am going to get some flak here (which is why I read this reflector less 
>> and less these days) for what I am about to add... but here goes:
>>
>>
>> I must emphatically disagree with the comment quoted above. Why? I 
>> actually operated with the same thought for nearly two years and in that 
>> time I learned to hate my Orion a bit more each day.... much for the same 
>> comment regarding CW readability in a pile up, but also to weak signal 
>> audio distortion, extreme AGC compression and clicks in the speaker and 
>> headphones. Regarding this particular reflector thread....There is just 
>> too much AGC compression taking place in the Orion if the RF Gain is at 
>> maximum. However like most hams I had gotten use to not touching that 
>> control. Fact many transceivers don't even have an RF Gain control (and 
>> generally sorely missed).
>>
>> About three months ago I was talking (complaining) to one of my 
>> engineering friends at Ten-Tec regarding 'clicks' in the audio when I key. 
>> It was one of many things that continued to annoy me... and was really on 
>> my mind as I had just completed a CW contest and my ears were in pain. 
>> Anyway, I was hoping that there might finally be a 'fix' for this problem. 
>> At one point during our conversation he asked me how I set my RF GAIN, 
>> PREAMP, and ATTEN during normal operation. I explained that I normally 
>> didn't adjust down the RF Gain control unless maximum attenuation and no 
>> RF Preamp still resulted in too much signal (i.e. 40 or 80 meters at night 
>> with S7 or above noise floor). I could hear a 'frown' forming itself over 
>> the phone... and then he (a long time CW operator) explained what my 
>> engineering background had me consider a bunch of times but eventually 
>> ignored. Basically he said, to NOT use the attenuator unless I was in a 
>> genuine overload situation and that I actually would wa
>> nt to have the RF Preamp in under most conditions.... and that I should 
>> advance the audio output as high as possible and use the RF Gain to reduce 
>> the final audio level to what was pleasant to my ears. Sounded a lot like 
>> 'pre product detector days' to me. But frankly I was just about to give up 
>> on my Orion 565 (latest version 2.x) at that point.... already doing a lot 
>> of K3 research. So I decided to listen and maybe learn.
>>
>> We discussed the A-D converters in the Orion and that it was their 
>> practical sampling limit.... or max range of ability.... that made it 
>> important to keep the Preamp IN. The object there is to make sure that 
>> there is sufficient signal available to the A-D converters so that the 
>> conversion produced a better sampling overall (think of early audio CDs). 
>> If the RF energy applied to the A-D converters is too weak then the 
>> conversion process generates too few samplings... resulting in continual 
>> sampling errors which many of us experience as 'distorted' weak signal 
>> audio (I certainly had). Then it was explained (rather nicely) how the DSP 
>> derived AGC should be minimized.... even partially defeated by the Orion's 
>> RF GAIN control and that leaving the RF Gain MAX would result in extreme 
>> AGC compression and initial AGC overshoot.... even overdrive the following 
>> audio stages momentarily (resulting in the clicks and yet another 
>> situation of discernible audio distortion). The high AGC comp
>> ression on the CW signals coming through the same passband lessened my 
>> ability to sort through CW pile ups and created the ever present key 
>> clicks (especially in the headphones) as a side effect. Think about it.... 
>> to discern one CW signal from another you need audible 'markers' to help 
>> you separate them from each other. Since most of today's CW transmitters 
>> output essentially pure notes (no chirp, drift, hummm, etc.)so what we 
>> have left is separation in note... differing audio levels... and differing 
>> keying characteristics (speed, hand key, keyer, keyboard, dot-dash ratio, 
>> etc.). So eliminating differing audio levels (extreme AGC compression) 
>> eliminates one normally important factor that helps us separate. And if 
>> you further consider the eventual conversion back from digital to audio 
>> you can see the advent of more audio 'error' since the digital signal that 
>> is being converted is merely the sum of all digitized RF signals through 
>> the bandpass at any particular moment. No mat
>> ter how good the digital to audio conversion at this point it will 
>> generate more apparent error when compared to a well engineered, fully 
>> analog signal path. This apparent conversion error adds to the ear's 
>> confusion when working overtime to separate so many signals.... so closely 
>> spaced... during extreme reception conditions... i.e. CW contest.
>>
>> Finally.... learning to operate with the RF gain used to control the audio 
>> output (Audio GAIN at or near maximum) produces the best signal-to-noise 
>> ratio in the Orion's receiver. And isn't that what we usually want?
>>
>> So before you completely dismiss what I have written why not do what I 
>> did.... I turned off my automatic 'disbelief' button for a few weeks and 
>> started considering my Orion as a unique receiver that simply didn't 
>> provide its best performance when driven in a conventional manner. I began 
>> driving it as recommended and soon afterwards I began to develop a new 
>> respect for the Orion's abilities. And no more audio clicks... no more 
>> extreme AGC compression... no more weak signal distortion.... and I could 
>> more easily separate the piles of CW signals during a contest... or simply 
>> during the hunt for new DX.
>>
>> 73,
>> Jerry, KG6TT
>> Fairfield, CA
>>
>>
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>>     
>
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-- 
Larry  N8KU

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