Thanks Mike...just a bit of humor in a technical world...
Cecil
Sent from my iPad
On Aug 30, 2013, at 8:15 PM, Mike Chatfield <mikechat@embarqmail.com> wrote:
> I very rarely write a response, but Cecil, what a great explanation of how
> this technology works. I love analogies and your's was RIGHT ON......
>
> Mike
> W0BBC
>
> On 8/30/2013 10:46 AM, chacuff@cableone.net wrote:
>> Ok, here goes with an analogy...
>>
>>
>> I’ve been up in the Smokey Mountains many times and they have some of these
>> beautiful short tunnels through rocky hillsides for the roads to pass.
>>
>>
>> Lets say you were standing in the middle of the road at one end of one of
>> these short, straight tunnels looking through to the other side. At the
>> other end of the tunnel you see a very nice looking young lady just to the
>> left of center and a really ugly old lady just to the right. Of course the
>> desirable view at this point is the nice looking young lady but it’s really
>> difficult to get a good look because of the really ugly lady...so. Say you
>> had a knob that would allow you to move the end of the tunnel left or right
>> just enough to block out the view of the really ugly lady leaving only the
>> view of the very nice looking young lady...there you have IF Shift....also
>> called PBT by other manufacturers.
>>
>>
>> Now re-center the knob where you have both ladies in view. Hold up the
>> index finger of your right hand out at arms length. Close one eye and place
>> that finger over the really ugly lady blocking the view of her and leaving
>> only the view of the nice looking younger lady...there you have the Notch
>> Filter. It may not cover the whole view of the ugly lady but it does enough
>> to allow a better view of the nice looking young lady.
>>
>>
>> The others are a bit more difficult to explain...
>>
>>
>> RIT is really not a filter at all...just another way to tune the frequency
>> of the receiver a small amount without changing your transmitter frequency.
>> Say you are having a short SSB QSO after calling CQ with a fellow who
>> doesn’t seem to be tuned properly to your frequency and he sounds like he
>> has been snorting helium so you need to tune your VFO to make him sound more
>> natural. If you tune your main VFO you are not only tuning your receiver
>> but also your transmitter...which will result in a change in how you sound
>> in his receiver. Well on the next over he may retune his VFO to make you
>> sound normal in his speaker and it’s an endless chase up and down the band.
>> (this can be caused by radio alignment issues) Better choice would be to
>> engage RIT and just move your receiver until he sounds natural to you which
>> will not change your transmit frequency only your receiver frequency leaving
>> you sounding the same in his receiver and less likely causing him to
>> retune...ending the chase.
>>
>>
>> DSP Noise reduction...well this being a software feature is implemented
>> differently in every manufacturers radios and sometimes even between models
>> in the same manufacturers radios.
>>
>> The goal of all is to reduce random noise as much as possible while
>> identifying the desirable young lady...um...signal and bringing it out of
>> the noise. All this is done using math inside the computer. Some work
>> better than others. The Icom system works well at reducing background noise
>> without adding too much digital artifact noise as long as you don’t over use
>> it. Seems some think if a little is good then a lot is better...it’s a
>> balance. Turning the knob full clockwise will result in digital noise and
>> not help at all. The DSP system on my Orion II is different and I’m not
>> sure exactly how to explain it..except the way Ten-Tec does that advancing
>> to a higher number increases the length of time sampling is done before the
>> digital filter is built. Which results in a better built filter in software
>> but it takes longer to get there. Of course the desirable signal needs to
>> be there for the duration of the sample or it probably will have a hard time
>> doing it’s job. None of them are magic...and most work well some times and
>> not so well others...it’s just another tool.
>>
>>
>> Noise Blankers. Most are designed to work on repetitive noise pulses like
>> old auto ignition system noise or electric fence pulses. Some works well on
>> power line noise some not so much. I’m surprised sometimes at how well some
>> work and how poorly others don’t...and it doesn’t seem to matter how much
>> the radio cost. Some of the older cheap radios noise blankers do wonders on
>> power line noise and a high dollar radio won’t touch it...go figure. Won’t
>> do much on atmospheric static crashes because they don’t happen on a timed
>> repetitive timeline which noise blankers are designed to sense.
>>
>>
>> Well that’s about all I got...my apologies to any of the ladies out there
>> with my analogy...it was the first vision that popped into my head this
>> morning when envisioning an answer to the question. No harm intended...
>>
>>
>> I’m sure others will have more insightful answers and between the group of
>> us we should answer your questions.
>>
>>
>> Best of the Labor Day weekend....
>>
>>
>>
>> Cecil Acuff
>> Gulfport MS
>> K5DL
>>
>>
>> From: Will Jones
>> Sent: August 30, 2013 9:33 AM
>> To: tentec@contesting.com
>> Subject: [TenTec] Explanations of the Different Types of Filtering on Radios
>>
>>
>> There are a few of us who meet together every Wed. morning at a local
>> restaurant to talk about ham radio and stuff.
>> Some are new hams. One asked this week a question which I think would be an
>> interesting study in comments.
>> He asked, "I have an I.F. shift on my radio and I have read about what it
>> does but don't really understand "what" it does. Also how does it compare to
>> the other features I see on radios such as PBT, notch filters, RIT, DSP
>> noise reduction and noise blankers. Without having a radio with these
>> features on them it is hard to explain just what your signal will sound like
>> when these devices are used.
>> So can anyone give us some ideas how to explain these different types and
>> why we would want one and not another and why radios don't have them all on
>> one radio.
>> Bill, N4LB in TN
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