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TX shift of 100Hz to 3,000Hz (MENU item #20)!

Posted: Mon Apr 14, 2014 9:09 am
by JJ2013
I know I probably should leave this well enough alone, but I am still puzzled as to where I need to set MENU item #20 on my TS870? Up until recently, I had the TX shift set to 0Hz-3,000Hz, but have been told that if I want to get a little wider in TX bandwidth, I need to set it to 100Hz-3,000Hz. I guess I am dim-witted as I don't get this.....Why would you first get rid of the first 100Hz and then EQ it back in?

Also, I remember from some postings on this forum that using 100-3,000 may render the audio a little more balanced and also help get rid of "mud." I don't seem to have the muddy problem though so I am still wanting to use 0-3,000

Cap mod is done and I am feeding audio in through ACC2.

Sure would appreciate some clarity on this..... :lol:

:? :?



Posted: Mon Apr 14, 2014 8:12 pm
by KC7OV
Go to Point over to the TX Setup, click the Audio Response Tutorial. Hopefully, this should help you understand the difference between TX bandwidth and audio bandwidth.

Posted: Thu Apr 17, 2014 7:04 pm
by JJ2013
Hi Mike,

I appreciate the reminder, but I guess I should've formulated my original question better.

Isn't it true though that regardless of which kind of rack and EQ etc. one has it is impossible to EQ frequencies in if the TX IF filtering, DSP impose a "brickwall" limit to your RF TX bandwidth? Say the brickwall is at 3.5kHz then how would one be able to transmit SSB that had audio components around 4kHz, 5kHz? Wouldn't those frequencies be "lost" after all?

The above seems like a really simple question and given that I have been reading up (perhaps I didn't absorb what I read.... :roll: ) on ESSB over a period of many months.......At any rate, perhaps someone can put this into common sensical language :wink:



Posted: Fri Apr 18, 2014 12:05 am
by KC7OV
Yes, you are correct in regards to radios that brickwall the TX audio, especially Icom rigs. The 870 can be manipulated via certain upper end eq frequencies to push it. I am not sure exactly what the proper term is for it, but it is like cascading or layering them. For instance, using an eq frequency of 4khz, then 5khz. then 4 kHz again. !Kant posted awhile back using the DSP1124 with that scheme. I have tried it and it works.

Posted: Fri Apr 18, 2014 8:48 am
by JJ2013

"Cascading," OK.......that's something that I'd not thought about at all. Perhaps that is a way to add boost without making the audio sound tinny, say EQ two separate times at 5kHz and using a 15/60 or 20/60 octave bandwidth ("BW") or something......

Audio engineers talk about "feathering," but that is different in that (I forget if this applies equally to high end and low end frequencies?) they may boos/cut in "increments," like say, +2dB at 4kHz (15/60 BW), +2 at 4.5kHz at 15/60 BW, but the problem seems to be that the latter +2dB is actually within the former +2dB still..........

I know iKANT and will email him about his posting.....perhaps I find it using the "Search" function here on the Forum.



Posted: Fri Apr 18, 2014 11:14 am
by KC7OV
These are the the frequencies he posted:
50hz: b/w 60, fine 0, gain +8
80hz: b/w 60, fine 0, gain +2
200hz: b/w 75, fine +7, gain -12
630hz: b/w 110, fine +3, gain -9
3.2khz: b/w 15, fine -3, gain +3
4.0khz: b/w 12, fine +3, gain +10
5.0khz b/w 12, fine -8, gain +13
4.0khz: b/w 12, fine +6, gain +11
A big thank you to those who came before us and after for making their information available.

Posted: Fri Apr 18, 2014 11:23 am
by JJ2013