[CQ-Contest] CQ-Contest] Impressive demonstration of one dB of signal strength improvement

Fri Aug 23 18:42:47 EDT 2019

A comment about amps: Doug is right on the 10:1 bang for the buck ratio, but there are other advantages to state-of-the-art autotune amps. For example, you don’t have to take the time to retune when changing bands or moving up the band doing S&P. It only takes a few seconds to manually retune, but that might cost a QSO or two. And when you’re bleary-eyed after 35 hours of contesting tuning mistakes and amp faults are a lot more common (been there, done that.) Finally, if you run Assisted, an autotune amp and antenna switching system can let you do rapid-fire point-and-shoot, jumping from band to band or all around band like 160 where tuning is narrow. Not possible with a manual tune amp. Lastly, most autotune amps can be located remotely (mine are in basement closet under the shack), reducing heat and noise in the shack, and the resulting fatigue.

Worth the cost? Depends on the op and how you operate. I don’t think you can justify the cost differential with score improvement, but it might make the whole contesting experience more pleasant, which may keep you in the chair longer. 

73, Dick WC1M

From: Doug Grant <dougk1dg at gmail.com> 
Sent: Friday, August 23, 2019 5:48 PM
To: John Geiger <af5cc2 at gmail.com>
Cc: Dick Green WC1M <wc1m73 at gmail.com>; CQ Contest <cq-contest at contesting.com>
Subject: Re: [CQ-Contest] CQ-Contest] Impressive demonstration of one dB of signal strength improvement

The answer is 42. You just need to ask the right question. (arcane reference to Hitchhiker's Guide to the Galaxy").

This is really too broad a question to answer easily. But maybe I can help a bit for your particular situation.

Your QRZ.COM <http://QRZ.COM>  entry says you are in Lawton, OK, and that your antennas are: 

   "6 band miniquad around 16 feet high, a homebrew G5RV type antenna at 25 feet". 

The miniquad model you are using has a 4.5-foot boom and loaded elements about 11 feet long. During high-sunspot years, it probably works great, especially on 10 meters. At this point in the cycle, I'm sure it is frustrating with 10 rarely open and 15 not much better. And a 16-foot high antenna really isn't very effective on 20.

Focus first on improving your antenna. There is a huge "bang for the buck" going from a miniquad at 16 feet to the same antenna (or bigger) at 50-60 feet. That is probably the biggest ROI. Towers can be expensive You'll have to do the math on the cost and determine if it is worth it.

If a tower is not an option, try some kind of push-up mast to get the antenna up in the air.

A better antenna (like a 25-foot boom tribander like the Bencher SkyHawk) will help some, but at 16 feet, you may not notice a big improvement.

I see on your QRZ page that you have worked 8BDXCC and over 300 DXCC with this (or similar) setups. Congratulations! You have accomplished a lot more than many guys with lots more hardware.

Looking further into your QRZ.COM <http://QRZ.COM>  page, it seems that the houses on NW Liberty Ave in Lawton are pretty closer together and the lots are pretty small. Putting up a tower (or firing up an amplifier) may not go over well with your neighbors. 

Your QRZ bio says you were licensed in 1980 at age 13, so you are now 52 years old and a Professor at Cameron University. They appear to have an Engineering department there. There are lots of good-sized buildings, so maybe it is time to start a ham club there. Put some antennas

a up on the roof. Do contests from there.

You won't like this suggestion, but the biggest bang for the buck may involve moving out of town. Now is the time to look for your retirement QTH. Find some acreage out of town...a hilltop, long sloping foreground, rural enough to minimize noise sources like power lines and neighbors. Maybe with some big trees to hold wire arrays. Buy the land now, do some portable operating with a pushup mast and the miniquad, build a house (with tower) later. 

As far as amplifiers go...nobody on the other end can tell the difference between the 1500W that comes out of a used SB220 with a dented cabinet that cost you $500 at a flea market and the 1500W out of a $5,000 state-of-the art solid-state autotune amp. That is a 10:1 difference in "bang for the buck".

But there's a big difference between a 500W amp and a 1500W amp....that's almost 5 dB.

However, in your current QTH, I would not suggest either a 500W or 1500W amp. Way too many possibilities for RFI problems. 

73 and good luck!

Doug K1DG

On Fri, Aug 23, 2019 at 6:58 PM John Geiger <af5cc2 at gmail.com <mailto:af5cc2 at gmail.com> > wrote:

I really enjoyed the powerpoint presentation as well.  In terms of return on investment, what would be the best sized antenna to get, at what height, and which power level linear would be best?  I mean this by getting the most bang for the buck.  I know larger and higher is better for antennas, but there gets to be a point where going to a larger antenna gets really expensive, compared with the improvement it will probably give you.

73 John W5TD

On Fri, Aug 23, 2019 at 12:55 PM <wc1m73 at gmail.com <mailto:wc1m73 at gmail.com> > wrote:

Terrific presentation, Doug. Wish I'd seen something like this when I got serious about contesting 20 years ago!

A few comments:

- 6% per dB is a lot! That would compensate for my UBN losses in most contests. In the big DX contests with close scores, 1dB or 2dB could make the difference between winning and coming in second or third.

- One of the most compelling slides for me was "Feedline Improvements". I've worked on that in my station over the years, but have never seen a treatment of just how much bang for the buck it can offer.

- I think it's implied in a couple of slides, but ther are also cost/dB equations related to tower height/capacity, namely how much bang for the buck you get by increasing antenna height and/or installing stacks, both of which require taller and/or beefier towers (lots of $$$$, not to mention the cost of longer low-loss feedlines, stack-switching gear, ring rotors, cables, etc.). Yet another item that adds to cost is getting (or fighting for) zoning permission to build more/higher towers. It's tough to quantify these improvements because more effective signal angles don't translate directly to an overall increase in dB.

- There are other improvements that are hard to quantify with a cost/dB formula, particularly improvements on receive. For example, a 4-square on 40 will be many dB below even a modest, low short-forty on transmit, but will have superior F/B that enables better copy of weak stations. Then there's the hard-to-quantify advantage of being able to switch to a vertical array on receive when snowstorm static is wiping out receive on the beam. And with the right transceiver (at more cost) there's the advantage of being able to use antennas with different polarization for diversity reception. That one has definitely boosted my QSO totals on 40. And the cost of improvements like these isn't always in dollars. A 4-quare on 40 is relatively inexpensive to build, but a major amount of work if you install a full-size ground radial system.

- Finally, I'd add one more item to "There is no secret!": Increase your time in the chair. For most of us, more time in the chair translates directly to higher contest scores and there's no dollar cost. While improvement may include getting/staying healthier, eating right, regulating caffeine, getting enough rest before the contest, plotting an off-time strategy, and so on, my own experience is that hours in the chair increase with enthusiasm, grit and determination. Also, I suspect a study might show that the more on-the-air practice you get between major contests, and the more time you spend preparing for a given contest, the more hours you're likely to put in.

73, Dick WC1M

-----Original Message-----
From: Doug Grant <dougk1dg at gmail.com <mailto:dougk1dg at gmail.com> > 
Sent: Thursday, August 22, 2019 1:03 PM
To: cq-contest at contesting.com <mailto:cq-contest at contesting.com> 
Subject: Re: [CQ-Contest] CQ-Contest] Impressive demonstration of one dB of signal strength improvement

On Thu, Aug 22, 2019 at 4:00 PM W3LPL wrote:

These recordings are an impressive demonstration of the benefit of
> one dB of signal strength improvement in a weak signal situation.
> Click on the links on this website:
>
> www.ab7e.com/weak_signal/mdd.html <http://www.ab7e.com/weak_signal/mdd.html> 
>
>
Many years ago, Clarke Greene, K1JX, casually mentioned that he had determined adding 1dB to your signal strength would result in a 6% increase in your contest score (mostly applied to DX contests). I filed that away for future reference.

Test cases are hard to find, but I found one in 2014 when N1UR switched from Low Power to High Power in the CQWW. Same op, same QTH, same antennas, and very comparable propagation near the top of the cycle.

My conclusion: the K1JX "6% per dB" rule was about right.

The exercise for the reader is to figure out how to add dB at the best "dB per dollar" ratio. Not all dB cost the same!

You can find some hints in a presentation I did a while back at CTU:

https://www.contestuniversity.com/wp-content/uploads/2017/06/K1DG_CTU_2015_Ten_Ways_to_Improve_your_Contest_Score.pptx

Slides 5-22 cover this topic.

73,

Doug K1DG

.

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