What gives !!!!!!!

Why are so many Amateur Radio Operators so Scared of Running Low Frequencies in there Audio?
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What gives !!!!!!!

Post by k5kab »

I’m kinda embarrassed to ask this question, but another hammie who I really look up to staggered me with a question on ESSB. The 756 Pro II will only give about 3.0 kHz on audio, so what is the purpose of running a behringer rack.( mic amp, compressor, virtualizer, eq) The band pass will only allow the 3 khz so why all the equipment?

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Post by Voodoo Guru »


That is an easy question answer, not to mention a great one to ask.

You do not have to be 4kc, 6kc, or 10kc (I wish!) to sound terrific.
You can sound like a million bucks with just 2.9kc of bandwidth.
Granted, it will not sound as full and open as the wider bandwidths, but nevertheless less, you can get it to sound superb.

This can be done by using the Rack equipment.
You can tweak and set the Rack equipment to give you the best sounding Audio in the 2.9Kc bandwidth that just a microphone alone could never do.

The thing to be the most careful with about using a narrow bandwidth is that you CANNOT push allot of lows!
This is what allot of people get in trouble with, you have to have the extra bandwidth on the high frequencies to offset the amount of lows you add.
Its a fine 'BALANCE' that cannot be circumvented.

If your running at 2.9Kc, you must balance the High Frequencies of the audio for a well defined presence, against the low frequencies for a rich and robust low end, but not boomy or muddy.

It can be done, and is being done.
Hope this helps,
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Voodoo Guru
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Post by w5cul »

Here is some technical junk to think about in relation to your question as well.

Given a stock radio, what are some of things that would hinder you from producing a well rounded, efficiently utilized band-pass, such that your highs and lows are well balanced with one another? Two things come to my mind immediately, the stock IF Filters, and the Mic Input circuitry; not too mention a stock Mic ;-) So how do IF Filters affect your audio? Well, most ham gear right off the manufacturing floor are shipped with mediocre IF Filters; ceramic Murata’s come to mind. Their filter slopes are not as sharp as we would like them, and they exhibit quite a bit of band-pass ripple. Because the filters slopes are not sharp, this forces the manufacture to offset the filter's position from the carrier injection point such that you do not produce enough lows, yet quite a bit of highs; they don’t want their gear to be accused of poor opposite sideband suppression. The inherent ripple in the stock OEM ceramic filter will attenuate groups of frequencies in your audio, while bringing out other frequencies into the forefront. Unfortunately, this ripple is not selective, thus does not choose which frequencies are best suited for the operator's voice. You couple this with a suedo designed Mic input circuit that has been carried over from one product line to the next, despite inherent design flaws that produce a less than flat response (Mark V starts its downward slope at 1.8Khz, just like the FT-1000 & 1000D), and then add a stock Mic which has it’s own band-pass and ripple issues to that smorgasbord, and your left with some pretty rough sounding audio.

So how do you adjust for that? Well, you can take the extremist route; trade out the OEM IF Filters for some nice crystal Inrads with a wider band-pass, move the -6db point of the IF Filter closer to the carrier injection point because you now have sharper slopes, thus picking up more lows. Then tap the balanced modulator thus bypassing the 1960’s Mic input circuit, and add some audio rack gear, ultimately giving you an over-the-air signal that sounds like you’re sitting right in my study. Or, the easier route would be to keep the same stock IF Filters (thus >3Khz xmit band-pass), maybe adjust the carrier offset a little to gain a few more lows, add some audio rack gear (particularly EQ) to abate the ripple and mic input circuit anomalies, and sound better than the plain stock radio ever could. W2IHY is making a killing offering audio gear just for that purpose. Chances are, if you hear someone on the band that is less than 3Khz and has well balanced audio, he has either added some audio gear to his mix, and or adjusted his carrier offset, and may be using a professional Mic over that of the stock Mic. In any case, his rig is not stock, whether internal or external.

I hope this helps in answering your question.



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Why ask Why

Post by w5udx »

Its like running it up the flagpole and saluting it. Or, like taking a fat girl home cause you think, "yea, I think I can ride her"
Put a big ole rack in front of that Icon radio and piss off some of the norms on Hammy radio. :lol: :prayer:
Don't give me that sissy ass audio, put some lows in it!


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Post by Bow »


I'm only running at 3.3kHz on my IC-718...

W5UDX says it sounds pretty good, and that's good enough for me

Quite possibilly the only 3.3 Khz wide Icom IC-718 in the world...

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