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@arrl.net>
> To: <tentec@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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>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>>
>>
>
>
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>
>
--
Larry N8KU
l o n g w i r e . c o m
HF - DX - CW - Digital
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