Posts Tagged ‘Elecraft KX3 QRP’

BLT+ Balanced line tuner at Excalibur

Another portable test of the BLT+ tuner

KX3 operating on internal battery.  What a fantastic portable rig.

I took the BLT+ balanced line tuner out to the Excalibur antenna site to try it out on the doublet antenna that we put up last Saturday.  This was the first test of that antenna (40m and 80m using a common feedpoint).

I didn't have much time today and after the first QSO it started to rain so I packed up and left before getting as much documented as I would have liked.  I apologize for not recording the actual tuning process and the subsequent QSO.

BLT+ connected to open wire line (under the gloves) going to ta 40m Doublet at 65ft
I had the KX3 operating using its internal batteries and outputting 2w. I was running 2 watts because that is the most efficient PA mode for the KX3.

I used the BLT+ to tune the 40m/80m doublet.  Balanced line antennas perform better with a tuner designed for balanced line and this was a good test for both the tuner and the new antenna. 

Portable shack, courtesy of three plastic chairs

I quickly matched the doublet using the BLT+ using the lowest impedance setting which is also the most efficient.  I was glad to see that the BLT SWR LED indicator is bright enough to be seen in direct sunlight.  I was wondering about that but you can definitely tell when it dims even in direct sunlight.


After quickly tuning up I sent my call two times and was promptly answered.  The other station was running a Flex 6500 into a KPA500 and a OCF Windom at 50 feet. 

He reported me as 559, while he was a 599.  He was running a new KPA500 amp at 500w so we were a bit mismatched on power.  

Interestingly the difference in 2w and 500w exactly matches the 4 S-Unit difference in our reports if you do the math (each increase in an S-unit requires quadruple the power). 

AA4OO sitting back and listening to the QSO

Paul AA4XX kindly snapped some pictures while I was listening to the other operator.  This is the Excalibur antenna site but the shack is outside the photo. 

The Doublet's feed line has not been brought to the shack yet so I was just sitting under the antenna.  The open feed line is running along the ground for a bit which certainly didn't help the signal but we haven't installed the posts to carry the feed line over to the shack and I was too lazy to move the chairs far enough away to keep the feed line in the air.

In the foreground is some saw-grass common on the NC coast.  I'm not sure why it's growing this far inland.

Portable shack at the Excalibur antenna site... The Doublet is 65 feet above my head
Waiting my turn in the QSO... holding the Palm Single Paddle.  BLT+ tuner in the chair to the right


Here is a brief video showing how the BLT+ is connected to the Doublet...


The little BLT+ performed great with both balanced line antennas I've tried.  It is easy to use and allows me to use my KX3 with balanced feed line antennas now.  I encourage you to build the kit from Pacific Antenna / .

That's all for now

So lower your power and raise your expectations

Richard, AA4OO

The Grand Illusion

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?

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.

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

Rock ‘N Radio — QRP Style

Operating QRP
Can mean operating from a "Quiet Restful Place"

I had the day off today and it was a beautiful morning.  I decided to spend part of it at Lake Wheeler Park in Raleigh, NC operating QRP from a stone bench under a tall oak tree.
rock 'n radio
I was operating the Elecraft KX3 from its internal AA batteries for the two hours I was there running 5 watts and it worked well.  I had brought an external battery but didn't need to connect it.

I threw a line over a tree using a throwing weight.  I hit my mark the first time, untied the weight, tied on the end of the antenna, and hoisted the 31 foot end-fed up exactly where I wanted it with the feed point a couple of feet off the ground.
31 feet of wire end-fed by a 9:1 balun.
A kite string winder holds the throwing line
A metal stake with a bit of rope anchors the balun and the other end of the rope

Another view of the end-fed with 9:1 balun, stake and coax
The 20 feet of coax serves as the counterpoise so hookups couldn't be simpler.  The KX3 simply has the coax attached to one side and the morse key and headphones in the other.
QRP operating position
The morning was very pleasant, if a bit windy, clear with a temperature of 55 F.

The KX3 will match the end-fed wire on about any band other than 160m but on 80m you could likely throw the radio farther than the signal travels.  The KX3 auto tuner is pretty amazing and I believe it could tune a piano if you hooked it up correctly.

I worked stations on 20m, 40m and 30m.

I called CQ on the 20m QRP calling frequency (14.060) and had a brief QSO with a lot of QSB (fading).  I didn't hear much activity that early in the morning on 20m so I dropped down to 40m and worked the QRP calling frequency (7.030) and had my call answered right away.  After that QSO another station jumped in there calling for a specific station so I moved on.  40m was busy.  Every time I thought I'd found an open frequency someone would jump back in or if I called QRL? I'd get an R R.

So I went up to 30m, and had a very nice long ragchew that lasted nearly an hour.  The internal AA batteries on the KX3 were getting a workout operating at 5w for that entire time but I never saw the transmit wattage drop below 5w and when I finished up the internal batteries still showed 9.8 V  The cutoff is 8.5 V so there was plenty of juice left.  I may just stop carrying the external battery on these brief jaunts.

My long ragchew was with a station in GA about 400 miles away and he gave me a report of 599 so I was thrilled with 30m this morning. Coincidentally, this end-fed antenna, balun, coax-counterpoise combo is nearly resonant on 30m and I've had some of my best reports when operating this portable antenna on 30m. 

Key wise, I was using the Palm Single Paddle.  It is a great little key when you don't have a table to operate from and you don't want to strap something to your leg.  I get strange enough looks from passer-by's without them wondering why I have some mechanism strapped to my thigh and the Palm Single is very inconspicuous.

The Palm key has a clip-on, magnetic base which I use to temporarily attach it to my clipboard when I'm not sending.  When I'm ready to send I simply pull it off the clipboard and hold it in my left hand. As I noted in an earlier review of the Palm Single Paddle it can be used as a straight key if you turn it on its side.  The long ragchew I had on 30m was with a gentlemen who sent me his SKCC number in the first exchange so I quickly turned off the electronic keyer in the KX3's and turned the Palm Single on its side.  That station sent me a nice compliment on my straight key FIST; so the little Palm Single key can serve duty as a paddle into a keyer or (in a pinch) as a straight key.  I far prefer to use my Kent Hand Key if I'm operating manual key but it's too big to bring along for portable operations and I can't quite picture myself trying to hold onto the giant Kent Hand Key with one hand whilst operating it with the other like I can the Palm Single.

The Palm Single Paddle works great in portable operating positions
I made a silly little video of my trip to the park...

So enjoy some nice fall weather if you still have it and have a Rock 'N Radio adventure.
What could be finer than to be in Carolina in the Mooo-oor-ning

Enjoying the last nice days of our Fall... birds singing and morse code beeping
That's all for now...

So Lower your power and raise your expectations

Richard N4PBQ

The Perception of Power

Power... or lack thereof

I had a good afternoon playing radio on 40m, 30m, 20m and 17m

I like 30m because that band seems to be more laid back and I seem to have some of the longest ragchews there.  One of the QSOs began with a fellow in CT using a K2 at 80w while I was running 5w.  

As the QSO progressed he was surprised by how well he could hear a QRP station.  This seems to be repeated often enough to me that I asked him to lower his power and see how it goes.  

He lowered his power from 80w to 50w and I gave him a signal report that didn't differ from his original.  Then he came down to 20w and I dropped him a point. Eventually he lowered his power down to 5w while I went to about 1w.  We continued to have our QSO although QSB started to make copy difficult but the main thing was that he was very surprised that he could come down to 5w and have me hear him and that he could still copy me at 1w.  We were both using wire antennas and he was about 500 miles north of me.  Solar Flux was only 107 today so it wasn't particularly stellar (pun intended) and it wasn't grey line by any means.

I think QRP operators should encourage QRO operators to try lowering their power just as an experiment.  After all we are supposed to use just enough power for communication, rather than all that we can generate.  I generally start at 5w and if a station is having difficulty or gives me a 339 I'll turn it up to my scorching 12w.

Save power, save the planet.  Maybe we can design a CW key that generates enough power to run our milliwatt rigs.

So lower your power and raise your expectations

73 es 72

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