Topics

QRPp Antennas #u3s #antenna

TrueBlue
 

OK, so in these dismal periods of propagation, ~0.15W and an "antenna" that's merely a piece of wire strung up in the hallway with staples, what should show up on aprsinfo but an hour and twenty minutes of my 20m WSPR spots (4) from ZL1RS at a distance of 6569 miles, which is well over twice my U3S distance record.

I naturally assume he's on vacation in Las Vegas or somewhere, which would be about a typical signal, and has just failed to update his coordinates.  I asked him just in case and he informs me that, no, these are real New Zealand catches.  Well.

So,  it was enough to get me thinking about getting a proper antenna up again for a few minutes.

Frankly, I had just given up on ever getting an actual antenna design sorted out as it didn't look like anyone really knew what he was talking about.  The books are full of imaginary science and contradictions from amateur hobbyists ("Mr. Dunning, meet Mr. Kruger!").

Here's the latest physical argument that never reached a point of resolution:  Do QRPp devices substantially lose power from antenna tuners and other peripheral whatnot beyond the concerns of a more QRO system?  At least one position in this low-power efficiency debate is wrong.

This is but a small sample of what I'm up against.

Alan G4ZFQ
 

an hour and twenty minutes of my 20m WSPR spots (4) from ZL1RS at a distance of 6569 miles, which is well over twice my U3S distance record.
Bob has a really good RX location and Beverages...

Do QRPp devices substantially lose power from antenna tuners and other peripheral whatnot beyond the concerns of a more QRO system?
The same amount. But QRO + losses is still more effective than QRP + the same losses.
The most effective QRP station has the biggest antenna with low losses. The best QRO station has....

73 Alan G4ZFQ

TrueBlue
 

On Thu, Sep 6, 2018 at 02:10 PM, Alan G4ZFQ wrote:
QRO + losses is still more effective than QRP + the same losses.
So, yes.

That was my understanding of the logic.  I thought it must have been a trick question.

(EME people seem to view this efficiency quite fanatically.)

M Lu
 

It will be interesting to see the responses from others.  Answers vary because there are many variables, as you know.

 

And I echo Alan, and add “The best QRO station has…the biggest antenna with low losses, just like the QRPp station”  Remember when Clinton used to say “It’s the economy, Stupid?”  My Elmer used to say “It’s the antenna, Dummy!”

 

In this case, you answered a very specific question…good on ya OM.  I will provide a very specific answer.

 

You asked: Do QRPp devices substantially lose power from antenna tuners and other peripheral whatnot beyond the concerns of a more QRO system?

 

My response: BEYOND the concerns of a more QRO system?  No.  The concerns are the same.  We must look at the entire system to see total efficiency, QRO or QRP or QRPp.  One footnote: as you already know, with QRO the concern is for the ability of the components in the tuner to handle higher voltages from more *power* contained in the mismatch.  But that is the one difference.

 

If I was in your shoes, and I was asking the questions, my next question would be “OK, Mr. Dunning, do I need to be concerned about the losses in my coupler in absolute terms, then, rather than relative to QRO?”

 

My typical answer, because I am an engineer, is “it depends” and “it’s all relative”

 

We need to viewing the entire setup as a complete system, from rig to antenna, we must consider several factors:

 

1.       What is the SWR mismatch?  Coax losses could be higher than the tuner losses depending on length and type of coax.

2.       What are the components used in the tuner at your QTH?  Higher SWR at the tuner will be accompanied by higher loss across the components, but “better” (higher quality, better design) parts will have less loss.

 

Of course, the goal is maximum radiated power. Best to illustrate with my example (feel free to stop reading if this is boring, I apologize but it’s my nature).

 

Also keep in mind these are guesstimate numbers, not measured.  And for the purists on this board, please don’t flame me if you disagree.  I’m 54, not 24, and I never claimed to be a PhD.  The only thing I ever did claim was for the punks in the neighborhood to get off my lawn.  Feel free to comment/add your observations.

 

My setup:

·         I am sending 500 milliwatts of WSPR from my rig to an end-fed wire, 100 foot vertical and 32 foot horizontal.  I am transmitting on 80 meters, that’s a half wave long wire.

·         I have a remote coupler at the base of the wire, a CG-3000 unit, rated for 300 watts.  Because of this, I can pretty much ignore SWR losses on the coax.

·         I am using LMR-400 coax for the 300 feet from my shack to the coupler.  (Yes, that’s extreme, but it’s what I had at the time).  That gives me about 0.5 dB loss at 3.5 MHz, if I remember correctly.

·         The CG-3000 is a fancy design that has been tested and found to be fairly lossless (we can assume 95% efficiency with this high impedance load on 80 meters).

·         I have 24 radials, 16 x 32 feet and 8 x 64 feet.  Although it is a half wave wire, it does still need a counterpoise.  Not as much as a quarter-wave, but it does have to be there.  With high impedance feed-point, we can neglect the losses at ground in this case and assume a radiation efficiency that is pretty high, like 90%. 

·         And no gain at low angles for a vertical wire, so let’s consider that factor of unity

 

So in my example above, the tuner losses can be ignored.

 

But what happens if we cut the wire down to 16 feet, we jump to 20 meters, move it indoors, use a small length of coax, and use a tuner at the rig?

 

1.       The wire will have a low impedance (quarter wave at 20 meters is 16 feet), so the tuner will have a harder time to make a match, and our efficiency will go down.  Let’s say 75%.

2.       The coax losses will be small, let’s assume 8 feet of coax from tuner to wire.

3.       No counterpoise, so the rig and the tuner and the human and nearby objects become the counterpoise.  The radiation efficiency goes WAY down, like to 25% or less.

4.       And what about the attenuation of the structure?  That could be minor (5-10%), or it could be huge (up to 50%).

 

In this second example, the losses from reduced antenna efficiency and the attenuation from the structure are way bigger than the losses of the tuner.  I would be more concerned about those losses and trying to improve those if possible.

 

Hopefully this helps. 

 

Oh, and congrats on that WSPR report.  Well done!  Who says there is no propagation? 

 

 

 

Mark Lunday, WD4ELG

Greensboro, NC  FM06be

wd4elg@...

http://wd4elg.blogspot.com

SKCC #16439  FISTS #17972  QRP ARCI #16497

ajparent1/KB1GMX
 

Trueblue..  (IBMer?) ;)

Anyhow.  There are many ways to look at this.
LEts review the three rules:

1. For a bigger signal put the wire higher.  Altitude always helps.
2. If you cannot put the wire higher, put up more wire.  Longer wire,
a half wave to tune easier using a weak ground, add a counterpoise
on the floor for examples.
3.  Any wire you put up is still better than a bucket of wire in storage.
The position there is try something anything see if with all the constraints
if you can make it better.

That is a practical and pragmatic approach.  Minimaize losses where
it applies, get the best match to transfer as much of the power as possible.
Add grounds or counterpoises to insure the coax and radio are not the inefficient 
half of an antenna.

A dipole for 20M is 33ft and some inches out in the wind shorter indoors.
It can be bent in three dimensions as needed (L, V, C, W or Z!).  

Tuners, um rather, antenna matching units of decent design cost little in terms
of power loss unless your trying to load a very short antenna for a given frequency.
A dipole tuned to the right length has no need of one for example.  The best place
to do that tuning is at the antenna (less feedline loss) or better yet experiment
with loops or self contained antennas like tuned Loops.  Experiment, wire is cheap
and can be re-used.

Allison

Braden Glett
 

I'm certainly no expert, but I'll tell you my experience. I run QRPp whenever it's possible given summer QRN and poor propagation. I don't like the "listen and pounce" approach one bit, so I always call CQ. I will run as low as 100 mW which is as low as my radio can be dialed down to. If I can't get a reply within one or two CQ calls at 100 mW, I start dialing the power up until I do get a response. Depending on conditions, that can go as high as 5W which of course isn't QRPp but then reality is that QRPp isn't always practical in all conditions.
I use a 600 foot delta loop, that is up 35 feet at the feedpoint, and up 50 feet elsewhere. It is fed with balanced feedline (400 ohm from MFJ) which of course virtually eliminates all feedline losses. I'm sure a much smaller loop would work pretty well, too, but obviously not as well as 600 feet does. This antenna is always used with an automatic antenna tuner.
Summer QRN makes QRPp more difficult on the one or two bands that are reliably open at this point in the sunspot cycle, 40 and 30. Last winter, 100 mW worked very well most of the time, even for rag chewing. Now granted, I wasn't making contacts with NZ, but instead contacts in the eastern US and Canada, from SW Ohio. I think my furthest contact was Puerto Rico for QRPp. If I can't get at least a 57 report, I dial up the power a little, as I'm not trying to torture the person on the other end.
Of course, I am working CW since it is really the only thing that works well with QRPp, at least in these conditions.
Just my 2 cents worth, for what it's worth. 
Ciao and 73,
Brady KD8ZM

 

Hello, what does mean (QRPp)?
Tnx Juan HK6J

Juan Herrera
Enviado desde mi iPhone

El 7/09/2018, a la(s) 8:34 a. m., Braden Glett <bradenglett@...> escribió:

I'm certainly no expert, but I'll tell you my experience. I run QRPp whenever it's possible given summer QRN and poor propagation. I don't like the "listen and pounce" approach one bit, so I always call CQ. I will run as low as 100 mW which is as low as my radio can be dialed down to. If I can't get a reply within one or two CQ calls at 100 mW, I start dialing the power up until I do get a response. Depending on conditions, that can go as high as 5W which of course isn't QRPp but then reality is that QRPp isn't always practical in all conditions.
I use a 600 foot delta loop, that is up 35 feet at the feedpoint, and up 50 feet elsewhere. It is fed with balanced feedline (400 ohm from MFJ) which of course virtually eliminates all feedline losses. I'm sure a much smaller loop would work pretty well, too, but obviously not as well as 600 feet does. This antenna is always used with an automatic antenna tuner.
Summer QRN makes QRPp more difficult on the one or two bands that are reliably open at this point in the sunspot cycle, 40 and 30. Last winter, 100 mW worked very well most of the time, even for rag chewing. Now granted, I wasn't making contacts with NZ, but instead contacts in the eastern US and Canada, from SW Ohio. I think my furthest contact was Puerto Rico for QRPp. If I can't get at least a 57 report, I dial up the power a little, as I'm not trying to torture the person on the other end.
Of course, I am working CW since it is really the only thing that works well with QRPp, at least in these conditions.
Just my 2 cents worth, for what it's worth. 
Ciao and 73,
Brady KD8ZM

M0RON
 

Hi Juan,
QRPp is transmitting with less than 1 watt.
Andy

Rick, DJ0IP
 

Mark's reply was very good.  I'd like to add a bit if I may.

Asking if a matchbox (not tuner) has a lot of loss can only be answered with "it depends".
All matchboxes have sweetspots (frequency and impedance ranges) where the loss is so low that it is negligible.
I have a drawing showing this, here:  http://www.dj0ip.de/antenna-matchboxes/perfect-matchbox/ 

The ARRL defines this to be less than 10% loss.
So the answer to whether or not the matchbox has noticeable loss is, it depends on whether it is operating within its sweetspot or not.

In addition, the ARRL has tested a couple dozen matchboxes over the past 20 years.
I have summarized their findings into a single, MONSTER Excel spreadsheet.
It clearly shows the sweetspots of each matchbox model tested.

Unfortunately, you need to know the impedance of your antenna system where it connects to the matchbox, not just the SWR.
A 3:1 SWR can be either 150 Ohms or 33 Ohms.
150 Ohms is within the sweetspot of most matchboxes.
33 Ohms is often not within the sweetspot.  
So just knowing the SWR (alone) does not always give us the right answer.

If this interests you and you have a bit of time, you may download my MATCHBOX SHOOTOUT  at the bottom of this page:
http://www.dj0ip.de/antenna-matchboxes/matchbox-shoot-out/ 

Remember guys, a dB is a dB, whether we're running 500 Watts or 50 mW.
If my signal happens to be 55(9) with 100mW, one dB of loss is meaningless - unless the guy's noise level is also 55 (hi).

73 - Rick, DJ0IP
May the Sunspots be with us!

 

Tnx Andy, my QCX/20 comes out with 2,8 watts
HK6J 
Juan Herrera
Enviado desde mi iPhone

El 7/09/2018, a la(s) 9:33 a. m., Rick, DJ0IP <Rick@...> escribió:

Mark's reply was very good.  I'd like to add a bit if I may.

Asking if a matchbox (not tuner) has a lot of loss can only be answered with "it depends".
All matchboxes have sweetspots (frequency and impedance ranges) where the loss is so low that it is negligible.
I have a drawing showing this, here:  http://www.dj0ip.de/antenna-matchboxes/perfect-matchbox/ 

The ARRL defines this to be less than 10% loss.
So the answer to whether or not the matchbox has noticeable loss is, it depends on whether it is operating within its sweetspot or not.

In addition, the ARRL has tested a couple dozen matchboxes over the past 20 years.
I have summarized their findings into a single, MONSTER Excel spreadsheet.
It clearly shows the sweetspots of each matchbox model tested.

Unfortunately, you need to know the impedance of your antenna system where it connects to the matchbox, not just the SWR.
A 3:1 SWR can be either 150 Ohms or 33 Ohms.
150 Ohms is within the sweetspot of most matchboxes.
33 Ohms is often not within the sweetspot.  
So just knowing the SWR (alone) does not always give us the right answer.

If this interests you and you have a bit of time, you may download my MATCHBOX SHOOTOUT  at the bottom of this page:
http://www.dj0ip.de/antenna-matchboxes/matchbox-shoot-out/ 

Remember guys, a dB is a dB, whether we're running 500 Watts or 50 mW.
If my signal happens to be 55(9) with 100mW, one dB of loss is meaningless - unless the guy's noise level is also 55 (hi).

73 - Rick, DJ0IP
May the Sunspots be with us!

Arv Evans
 

Juan HK6J

QRP is usually seen as 10 watts or less.
QRPp is usually seen as 1 watt or less.

Arv  K7HKL
_._


On Fri, Sep 7, 2018 at 7:51 AM Juano <juano9876@...> wrote:
Hello, what does mean (QRPp)?
Tnx Juan HK6J

Juan Herrera
Enviado desde mi iPhone

El 7/09/2018, a la(s) 8:34 a. m., Braden Glett <bradenglett@...> escribió:

I'm certainly no expert, but I'll tell you my experience. I run QRPp whenever it's possible given summer QRN and poor propagation. I don't like the "listen and pounce" approach one bit, so I always call CQ. I will run as low as 100 mW which is as low as my radio can be dialed down to. If I can't get a reply within one or two CQ calls at 100 mW, I start dialing the power up until I do get a response. Depending on conditions, that can go as high as 5W which of course isn't QRPp but then reality is that QRPp isn't always practical in all conditions.
I use a 600 foot delta loop, that is up 35 feet at the feedpoint, and up 50 feet elsewhere. It is fed with balanced feedline (400 ohm from MFJ) which of course virtually eliminates all feedline losses. I'm sure a much smaller loop would work pretty well, too, but obviously not as well as 600 feet does. This antenna is always used with an automatic antenna tuner.
Summer QRN makes QRPp more difficult on the one or two bands that are reliably open at this point in the sunspot cycle, 40 and 30. Last winter, 100 mW worked very well most of the time, even for rag chewing. Now granted, I wasn't making contacts with NZ, but instead contacts in the eastern US and Canada, from SW Ohio. I think my furthest contact was Puerto Rico for QRPp. If I can't get at least a 57 report, I dial up the power a little, as I'm not trying to torture the person on the other end.
Of course, I am working CW since it is really the only thing that works well with QRPp, at least in these conditions.
Just my 2 cents worth, for what it's worth. 
Ciao and 73,
Brady KD8ZM

M Lu
 

Rick/DJ0IP
 
Thank you very much for:
 
  1. Taking the time to perform extensive research
  2. Share this highly valuable information with the rest of us
 
Mark Lunday, WD4ELG
Greensboro, NC  FM06be
wd4elg@...
SKCC #16439  FISTS #17972  QRP ARCI #16497
 
 
 

TrueBlue
 

On Fri, Sep 7, 2018 at 07:33 AM, Rick, DJ0IP wrote:
If this interests you and you have a bit of time, you may download my MATCHBOX SHOOTOUT  at the bottom of this page:
http://www.dj0ip.de/antenna-matchboxes/matchbox-shoot-out/ 
Even more interesting was:

WHEN SHOULD YOU USE A MATCHBOX ?

ANSWER:  Hopefully Never!  . . . because ALL matchboxes add unwanted losses!

...and your following points which were sort of my objects in a very simplified, single-frequency dipole antenna design that will work and (hopefully) do this one thing with high efficiency.

TrueBlue
 

On Thu, Sep 6, 2018 at 02:10 PM, Alan G4ZFQ wrote:
Bob has a really good RX location and Beverages...
This guy picked me up a few minutes ago:

https://youtu.be/IBChwkjzliw

Shouldn't present any problem!

Alan G4ZFQ
 

Crazy!
That chap does not have the fun of experimenting to see what can be done on a tiny plot.
But he does have the capability of deceiving us that our bits of wire work well:-)

73 Alan G4ZFQ

Bob has a really good RX location and Beverages...
This guy picked me up a few minutes ago:
https://youtu.be/IBChwkjzliw

Rick, DJ0IP
 

Sorry about my poor math, guys.
50 / 3 = 17 Ohms, (not 33).
17 Ohms is definitely below the sweet spot of most antenna matchboxes.
 - Rick

Rick, DJ0IP
 

There's a lot to be said for using monoband dipoles, but they also have their downsides.
Say we hike to the top of a mountain with a dipole for our favorite band and find that band is mostly dead.

It is nice to have alternatives.  Basically the coax fed dipole only works on its fundamental and 3rd harmonic.
Thus I prefer taking multi-band solutions with me such as the Aerial-51 Model 404-UL.
This gives me the possibility to work on most bands, 40m and above; in most cases without a matchbox.
- 73 Rick, DJ0IP

TrueBlue
 

On Sat, Sep 8, 2018 at 07:54 AM, Rick, DJ0IP wrote:
There's a lot to be said for using monoband dipoles, but they also have their downsides.
Say we hike to the top of a mountain with a dipole for our favorite band and find that band is mostly dead...
I think you misunderstand me.  I don't want to tune to one band, I really did mean one frequency, hopefully the sole 20m FT8 one shortly after Hans issues the U3S firmware upgrade.  I have no interest in CW or 'phone.  This is a pure beacon.  That should simplify construction, yes?

John VA7JBE
 

You'd think so, but it's basically the same as any other monoband dipole.  Every dipole has a design frequency, but usually they're broadband enough to cover most of the band with an acceptable SWR.  If you're looking for an online calculator, this one will help you keep track of things like apex angle, height above ground, and wire/tubing/insulating effects (it's labeled Linked Antenna Designer, but you can set it to one frequency) https://www.sotamaps.org/extras.php.  If you're looking for antennas with a higher Q (and a narrower usable bandwidth) then you might check out the antennas group https://groups.io/g/antennas/topics

Good luck,
John VA7JBE

Rick, DJ0IP
 

Oh, sorry.  YES, I did misunderstand you.  I'm not really into FT8 and I work multiple bands and multiple modes when in the field... so we were on different pages.   As always, it's horses for courses!  73 - Rick, DJ0IP