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The Grand Illusion
28 February 2016 | by Five by Nine... QRP... How can it be?
What does an S-Unit really mean and how can a QRP station sound like a 500w station?
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| The real gain doesn't come from transmitter watts |
I rarely go up to the phone portion of the bands. Since I started doing QRP and CW last summer I think I've only made two SSB contacts just because my focus has been CW. But last night I was working on a bench project and tuned the Elecraft KX3 up to the phone portion of 40m for some entertainment.
A station in Rhode Island was testing his amp with a new antenna and was getting reports from various stateside operators. There was a lull where no one was answering his CQ so I thought I'd give him a call. He was peaking at S9 on my KX3's meter and he also sent me a signal report of S9 with some 10 over peaks. I then told him I was a QRP station running 10 watts and heard the usual surprised reaction from a QRO station.
I gave him reports as he switched back and forth from running barefoot ~75w to his amp ~500w. With his amp on he was an S9, running barefoot he was S8. So the amp gave him one additional S unit. In terms of hearing him I would have been hard pressed to tell much difference simply by volume. He was perfectly copyable without noise with the amp off.
We also did some tests with my station at reduced power (as if...) At 10w-12w output I received a S9 to S9+10. Reducing output to 5 watts netted me a S8 report and when I reduced to 1 watt (one watt) he was still able to comfortably copy me and I received an S5. So with my station at 1 watt and his running 500 watts we could still converse via SSB. Ladies and Gentlemen you don't need as much output wattage as you think you do.
He was running through a newly constructed homebrewed vertical while I was using my 80m OCF Dipole. We didn't discuss what sort of radial system he had installed, but the difference in antennas was likely the deciding difference in our stations. We were about 500 miles apart and his vertical probably had more low-takeoff gain than my dipole, or possibly more ground loss so I probably had better high angle gain on him for the short 500 mile skip. I think the take-away from this exercise is that the antenna is generally the key rather than transmitter power. If I can get 6 dB of gain from my antenna I have in essence quadrupled my effective radiated power. Quadrupled? Yes, Quadrupled effective output power.
Power and S-Units
You've probably heard it before but it's worth a refresher... Our radio's meter display a measurement in "S-Unit". To move the meter up one S-Unit the receiver must hear 6 more dB (decibels). So one S-Unit is 6 dB.
A decibel is:
- A Power Ratio: dB = 10 Log P2/P1
- A Voltage Ratio: dB = 20 Log V2/V1
You increase 3dB each time you DOUBLE your power
That's worth repeating...
You increase 3dB each time you DOUBLE your power. So to gain one S-Unit you must quadruple your power.
So if you are running 100 watts, to gain one S-Unit using the same antenna system you must increase your power to 400 watts. If you are running QRP SSB (10 watts) that is only 1.5 S-Units down from 100 watts. 100w / 2 (-3dB) = 50w / 2 (another -3dB or 1 S-Unit) = 25w... etc.
We have a great hobby, but there are so many aspects of it that sound like common sense when they really are not... like increase your power.
Increasing power gains you very little compared to a better antenna systems. Put that in your 811A amplifier tube and smoke it !
That's all for now.
So lower your power and raise your expectations (or your antennas)
72/73 (Note: 72 is a common substitute for 73 among QRPers... as in "not enough power for 73")
Richard, N4PBQ
Antennas offer the cheapest increase in dB
Note the statement above "using the same antenna system". That's the key then isn't it? It's easier to get 6 dB of gain from an antenna than from wattage. A 40m doublet can offer significant directional gain especially when operated on higher bands. Now unless it's rotatable you will be at the mercy of the directionality of its lobes but if you have trees or tall structures you can very cheaply string up a few dipoles oriented in different directions and for far less money that a 500 watt amp (6 dB). If you can only have one wire antenna you may miss out on some DX in the antenna's nulls but you will have some stellar gain in the direction of the lobes. Of course rotatable yagis and beams are the best but now we are talking about real money again. I'm talking bang for the penny. You don't have to buy a wire antenna. Some Dacron rope or weed-eater line and some surplus insulated wire is all you need. You can even make your own feedline cheaply from electric fence wire and insulators.We have a great hobby, but there are so many aspects of it that sound like common sense when they really are not... like increase your power.
Increasing power gains you very little compared to a better antenna systems. Put that in your 811A amplifier tube and smoke it !
That's all for now.
So lower your power and raise your expectations (or your antennas)
72/73 (Note: 72 is a common substitute for 73 among QRPers... as in "not enough power for 73")
Richard, N4PBQ
Richard Carpenter, AA4OO, is a regular contributor to AmateurRadio.com and writes from North Carolina, USA. Contact him at [email protected].
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NI0L…. Happy Trails!
I have a new, bright, and shiny callsign!
When I made the decision back in 2013 to stay in Kansas after retiring from the military, I decided I would try to get a callsign for zero-land (or ten-land, if you like). It was time to leave my 7-land callsign and fully embrace being a citizen of the sunflower state. NI0L was available and I applied for it without much thought. After having the callsign for a while, I noticed many hams were confused with the 2×1 call. The most common mistake was flip flopping the zero and the “i”. Another common mistake was interpreting the “i” as one and then the zero would become an “o” (N1OL). All very confusing.
The hunt for a new callsign was on. I determined that a new callsign would still be from zero-land, thus greatly reducing the pool of available calls. In an effort to avoid callsign confusion, I further resolved that the call would be a 1×2 call. The good news was that the vanity callsign fee was no more. The bad news was that everybody and their brother was applying for vanity calls. For the last few months I kept at it – watching which calls became available and then submitting applications. Waiting. The odds where never in my favor. Often there would be 10 or twelve applying, all in competition.
Perseverance finally paid off. Last week the FCC said that I was now the proud holder of N0ZB. It is a 1×2 call, that should alleviate some confusion. The “zero” and the “zulu” may prove to be a bit of a tongue twister, but I think it will be far less of an issue and having the “zero” and an “i” next to one another.
Scott Hedberg, NØZB, is a regular contributor to AmateurRadio.com and writes from Kansas, USA. Contact him at [email protected].
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MFJ 1788 vs Weather
As like everywhere else it seems the weather up this way is as up and down as the solar conditions! Up this way we have been breaking records with both high and sometimes low temps. Along with this crazy weather comes conditions that can be very hard on our antenna systems. I have read on many blogs of fellow hams dealing with antenna damage due to wind, ice and heavy snow issues. My antenna foot print is a very small one and so I thought sheltered from many of the issues others have been dealing with. Here is my weather related antenna issue to add to the list of weather mishaps. On Wednesday this week Julie and I came home from work and she announced (as she was looking outside) “your not going to like this”. Not very comforting words as I had a look for myself and saw that the high winds had their way with my antenna! I have an MFJ 1788 mag loop antenna. It’s mounted on a tripod on our balcony of the condo. The wind had toppled it on it’s side and then tossed all around the balcony as well. I understand to most of the other hams out there with weather damaged antennas, mine is a walk in the park. In my humble opinion this is the only antenna I have, it’s not cheap to replace and I am very limited on my antenna choices. As a side note I usually place the antenna off to the side when not in use and that way it is totally sheltered from the elements. I admit I was lazy and figured it had been ok for a week with the antenna in that position………..WRONG! I stood the antenna back upright and there seemed to be no broken parts all was in tacked. I crossed my fingers turned on the K3 and gave the antenna a go, the lowest the SWR would go was 4.0:1 and higher on other bands……not good. Below are the steps I went through to eventually fixing the antenna:
In the above picture the 3rd fin from the left was perfect centre and all others had to match.
2 2. I then inspected the PL-259 connector just to make sure it was fine and not on it’s way out due to unforeseen damage. It was ok as well.
3 3. I then brought in the MFJ 1788 antenna into the house and first had a look over of the outside case, SO-259 and the antenna loop. All seemed good this way.
4 4. It was now time to open up the plastic housing and have a look inside, I have had the antenna apart on occasion for routine maintenance so I had an idea of how things should look. There was no obvious signs of damage to any of the major parts.
5 5. It was now time to connect the coax and run the internal variable capacitor to the end of each stop via the control box.
Here is where I noticed two problems:
· A.The spacing between the stationary fins and rotating fins was not equal at certain points along the variable capacitor.
· B. When the capacitor was fully seated in one direction both the stationary fins and rotating fins should sit flush with each other and some on the rotating section were sitting higher.
To fix the spacing problem (which I had to do then the antenna was shipped to me) I used a screw driver to manipulate the fins to even up all the air gap between fins. To repair the fins that were not sitting flush I was able to loosen a nut on the shaft that held all the moving capacitor fins in place. I then was able to adjust the fins that were sitting to high and make them all flush.
It's hard to see but from the left about 7 fins over the next five fins start to look odd, this is because these fins are not sitting flush with the other fins and they had to be adjusted so they were flush.
1 6. It was not time to cross my fingers and try the antenna (with plastic cover off) and see if this was in fact the problem. I was able to turn the antenna to 1.1:1- 1.1:4 on all bands and this was with the antenna sitting on a table in my living room. It seems the problem was fixed!
2
7. I then put the plastic cover back on and again check the SWR on all bands, I wanted to make sure nothing changed……. nothing did change and all was still good.
7. I then put the plastic cover back on and again check the SWR on all bands, I wanted to make sure nothing changed……. nothing did change and all was still good.
3 8. I then re-mounted the antenna on the tripod and covered it with my canvas patio table cover….so it does not “look” like an antenna. I then tested the SWR again…it was now 8:1!!
4 9. I then removed the canvas cover and the SWR was fine again…..seems canvas was damp do to the rain that accompanied the wind that day. I put the cover in the dryer and then back on the antenna and all was well. I am now going to purchase some waterproofing spray for the canvas to keep the antenna dry.
Below is one section of the fins that have been adjusted and are back to normal position.
Below is one section of the fins that have been adjusted and are back to normal position.
Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].
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RSGB grants permission to use images of book covers.
It has been sometime since I wrote the short review of the RSGB Radio Communication Handbook 12th edition:
At the time of writing I didn't have permission from the RSGB to include images from their books.. However I have recently been in touch with the RSGB and have been granted permission to include them on my blog, subject to asking at the time I require.
Thank you
That particular blog has now been updated with the cover image, see link above.
Steve, G1KQH, is a regular contributor to AmateurRadio.com and writes from England. Contact him at [email protected].
Cover courtesy RSGB
At the time of writing I didn't have permission from the RSGB to include images from their books.. However I have recently been in touch with the RSGB and have been granted permission to include them on my blog, subject to asking at the time I require.
Thank you
Mark Allgar, M1MPA
RSGB Commercial & Membership Manager
RSGB Commercial & Membership Manager
That particular blog has now been updated with the cover image, see link above.
Steve, G1KQH, is a regular contributor to AmateurRadio.com and writes from England. Contact him at [email protected].
» Leave a Comment (0)
RSGB grants permission to use images of book covers.
It has been sometime since I wrote the short review of the RSGB Radio Communication Handbook 12th edition:
At the time of writing I didn't have permission from the RSGB to include images from their books.. However I have recently been in touch with the RSGB and have been granted permission to include them on my blog, subject to asking at the time I require.
Thank you
That particular blog has now been updated with the cover image, see link above.
Steve, G1KQH, is a regular contributor to AmateurRadio.com and writes from England. Contact him at [email protected].
Cover courtesy RSGB
At the time of writing I didn't have permission from the RSGB to include images from their books.. However I have recently been in touch with the RSGB and have been granted permission to include them on my blog, subject to asking at the time I require.
Thank you
Mark Allgar, M1MPA
RSGB Commercial & Membership Manager
RSGB Commercial & Membership Manager
That particular blog has now been updated with the cover image, see link above.
Steve, G1KQH, is a regular contributor to AmateurRadio.com and writes from England. Contact him at [email protected].
» Leave a Comment (0)
How to organize your RF connectors
Kenneth, W6KWF, used to dump all of his N, BNC, and PL-259 RF adapters in two quart-sized Ziploc bags. Now all of his connectors are organized by rows in this Plano 1258 tackle box from Bass Pro Shops.
He mentioned a great old trick for keeping track of your connectors at group events. He paints a little dot of nail polish on each one. Now he always gets them back! 🙂
Check out the video below and lots more at his blog, The Life of Kenneth.
How do you organize all of your RF adapters and connectors?
Matt Thomas, W1MST, is the managing editor of AmateurRadio.com. Contact him at [email protected].
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Teeth marks in the K3
DX-expeditions love their K3s. And I love my K3. But look closely at the MENU button and you will find the marks of someone who literally have put the K3 on their menu as well.
Neither has the BAND button escaped this. Judging from the size of the teeth marks it is perhaps not so hard to guess who did this.
This is our club station’s K3 and off weekends the only inhabitants there are mice, who seem to have taken their fancy on the soft buttons of the K3. They let every other piece of equipment alone, such as the Yaesu FT-1000MP, so there is definitely something special about the K3. I would guess that this was not part of the original Elecraft design specifications for these buttons.
The remedy is shown here: A custom-designed acrylic cover that is fitted on the K3 whenever it is not in use.
This article originally appeared on the LA3ZA Radio & Electronics blog.
Sverre Holm, LA3ZA, is a regular contributor to AmateurRadio.com and writes from Norway. Contact him at [email protected].
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