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Author Topic: How much of a help is 6 DB?  (Read 4749 times)
KU3X
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Posts: 145




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« Reply #15 on: January 18, 2013, 01:37:12 PM »

All good information above. But to condense it: 6 DB = 1 S unit.
If you are an S 5 on the receive end of your transmission, adding 6 DB will make you an S 6.  If you're S 3, then you'll
be an S 4. Simple math.

The best advise someone gave you was to put the work into the antenna. The better the antenna the better the
ERP and the better the receive signal on your end.
Junk antenna = junk signal
Good antenna = good signal.
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WX2S
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Posts: 759




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« Reply #16 on: January 18, 2013, 02:07:34 PM »

Thanks, all, for your helpful replies.

My antenna situation is that I am not maxed out technologically, but probably with respect to what I can do and still keep the XYL. Smiley Towers and Yaagis or hexbeams are not an option. So I run a Hustler 6BTV with a radial system as recommended by DX Engineering. It's so far done the job; I've gotten some decent DX with 100w. Where I could use some improvement is in pileups.

73, -WX2S.


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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
KD0REQ
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Posts: 1050




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« Reply #17 on: January 18, 2013, 02:22:58 PM »

not every entrance panel is expandable, for the simple reason that breakers for some old crud are no longer availiable.  in the case of FPE and Zinser/Sylvania, there is a darn good reason, there are enough insulation, construction, and breaker flaws to rightly label them "arcwelders."

but if you're in for a dime and in for a dollar with non-disaster power distribution, heck, get some piggyback breakers if you can, double up some lighting circuits on them, and go for the pileup buster.
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K0OD
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Posts: 2591




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« Reply #18 on: January 18, 2013, 02:51:14 PM »

Quote
But to condense it: 6 DB = 1 S unit

That may have been true 60 years ago. On my TS-850 I came up with an S-unit being about 4.7 dB and only on the middle portion of the scale.  Difference between say S-2 and S-3 was much less. And I was only testing on 40 meters where I was trying to get an accurate determination of the performance of my array of phased verticals. S-meters can vary by band or even by frequency within a band according to one article.
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WB2WIK
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Posts: 20666




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« Reply #19 on: January 18, 2013, 03:11:25 PM »


500W to 1500W = 4.77dB
Being a "big gun" instead of a "little pistol" = priceless.


I got that much and more by changing antennas. Best antennas working the best they can first and then the power.

No point putting out 1.5kW if you can't hear anyone.

However, many already have the very best, biggest and highest antennas they can ever install so there's no potential for growth there.

Also, on HF (as opposed to VHF-UHF-SHF+), I've found adding antenna gain can result in not hearing anybody better unless the band and environment are very quiet (low noise).  Often a better "receiving" antenna is one that improves S/N but hasn't necessarily any gain at all.

On TX, the only things that count are power and antenna gain, and placement of that gain at a useful angle for the desired contact.  On RX, the only thing that counts is S/N and it doesn't matter how you achieve it.  Most big-gun DX stations on 160m and 80m don't use their "gain" transmitting antennas for receiving. Wink
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AA4PB
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« Reply #20 on: January 18, 2013, 03:13:37 PM »

Regardless of how inaccurate your "modern" S-meter may be, the point is still a good one. That is, 6dB makes only a "little" difference in the received signal. It isn't going to turn a weak signal at the noise level into a "booming" loud signal. It may get you through a pile up however if your signal is 6dB stronger than everyone else. But, you can sometimes get through the pile up with QRP if you get the timing right and/or have propogation on your side.
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W8JX
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Posts: 6683




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« Reply #21 on: January 18, 2013, 03:20:40 PM »

Regardless of how inaccurate your "modern" S-meter may be, the point is still a good one. That is, 6dB makes only a "little" difference in the received signal. It isn't going to turn a weak signal at the noise level into a "booming" loud signal. It may get you through a pile up however if your signal is 6dB stronger than everyone else. But, you can sometimes get through the pile up with QRP if you get the timing right and/or have propogation on your side.


I disagree on 6db not making a difference. Granted if you have a strong signal another 6db is not going to do much but if you are in the noise and unreadable or barely readable, 6db can be a real game changer.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
WB2WIK
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Posts: 20666




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« Reply #22 on: January 18, 2013, 03:20:59 PM »

Depends on what kind of operating you do, also.

I work a lot of stuff on 10m that's right in the noise.  These are signals that are maybe "32" or so on SSB, or 329 or so on CW.  6 dB makes a hell of a difference; if those signals lost 6 dB, they'd be gone.

I work stuff on 160m that's weaker than that, pretty often.  CW signals that would "honestly" be 229 or 219.  But contacts can be made!  Again, -6 dB from those signals is "gone."

A lot has to do with how well you can hear, which in turn has a lot to do with what your local noise levels are like.  On a "quiet" night on 20m CW -- after 99% of the activity has dissipated and there's almost nobody on the band -- I work a lot of stuff that's literally right in the noise and somehow they hear me, so they must have quiet locations also.
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N3OX
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Posts: 8847


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« Reply #23 on: January 18, 2013, 04:53:44 PM »

Here are some files I made a while ago where I mixed steady noise recorded from my radio with the same recording of my voice over the radio

http://n3ox.net/files/6dB/

I mixed the "this is a test we'll keep 6dB higher" part of the voice recording to a level 6dB more than the first part using my recording software.

Then I adjusted the overall levels to different scenarios I've heard on the air.

75m_locals.mp3 is very loud like S9+10 signals.
dx_15m.mp3  is a signal-to-noise situation that reminds me of a decent but not very loud signal from Oceania...
brokencontact.mp3 was mixed down until I couldn't copy the first part at all.

You shouldn't take these too literally as the noise doesn't vary too much and there's no fading, but it might give you an idea.
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WB2WIK
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Posts: 20666




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« Reply #24 on: January 18, 2013, 07:15:28 PM »

When the going gets tough, 1 dB makes a difference.

When sigs are 1 dB over the noise, adding 1 dB to the TX power makes copy much more possible.
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K8AXW
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Posts: 4002




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« Reply #25 on: January 18, 2013, 08:47:19 PM »

Ed:

If push comes to shove, consider "piggy-backing" or extending the 240V line from your kitchen range or clothes drying to your amp.  It's just that you can't run both at the same time. 

If it's this or nothing..... then I'd try it.  No big deal.

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W8JX
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Posts: 6683




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« Reply #26 on: January 19, 2013, 05:16:56 AM »

You know 1000 watts is a excellent compromise between 500It can be done on 120 if need be and gives you 10db over 100 watts. going to 1500 is only about 1.5 db more.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
WX2S
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Posts: 759




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« Reply #27 on: January 21, 2013, 08:39:29 AM »

FYI: I finally got smart and ran some VOACAP predictions at 500 and 1500 watts. The short answer is that the extra 4.77 dB does buy some circuit reliability in DX areas, probably enough to be important. So I think I'll spend the extra shekels and get the big-gun linear to go with my popgun antenna.  Grin

73,
- WX2S
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
W8JX
Member

Posts: 6683




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« Reply #28 on: January 21, 2013, 08:57:51 AM »

FYI: I finally got smart and ran some VOACAP predictions at 500 and 1500 watts. The short answer is that the extra 4.77 dB does buy some circuit reliability in DX areas, probably enough to be important. So I think I'll spend the extra shekels and get the big-gun linear to go with my popgun antenna.  Grin

73,
- WX2S


And what about 1000 watts?  It does not have to only be 500 or 1500.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
WX2S
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Posts: 759




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« Reply #29 on: January 21, 2013, 01:45:57 PM »

And what about 1000 watts?  It does not have to only be 500 or 1500.
Selling one?  Grin

Seriously, I didn't check. I'll do so but would imagine that it's somewhere in the middle.

73,
- WX2S
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
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