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Author Topic: KX3 Kit is here - time to start learning antennas for QRP  (Read 10655 times)
KK6GNP
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Posts: 158




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« on: October 04, 2013, 03:54:08 PM »

Hey, Everyone.

I have a discussion going in the Antenna forum about QRO solutions for my home situation.  It has been a confusing ride so far, with more opinions than there are types of antennas, but I am thankful for the suggestions I've been getting.  I think it's going to take some time to work that out before I spend any money.

In the mean time, I realized today that I should start off where the KX3 is comfortable, with QRP.  Rather than agonize over permanent antennas for now, I think it would be wise to begin my journey by learning about some wire antennas.  I have some trees in my yard I can use.  They aren't super tall though, the tallest being 15-20ft or so.  I'm not opposed to getting some kind of mast either if my trees aren't going to cut it.

Kind of funny.. I've been so confused about what I was going to setup for QRO at home, I didn't bother getting the built-in ATU option for my KX3.  I figured I'd be buying a tuner anyway.  Well, I went ahead and ordered the option from Elecraft today....

My question to you QRP masters is, where do you think I should start?  I'm interested in learning to make my own wire antennas, but I also wouldn't mind buying a high quality one, if I can't make one as good or better myself.

Thanks in advance for your suggestions!  ~ 73's
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73 ~ Cory (JeepEscape)
KK6GNP
N3AEG
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Posts: 39




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« Reply #1 on: October 04, 2013, 04:00:06 PM »

Hey, Everyone.

I have a discussion going in the Antenna forum about QRO solutions for my home situation.  It has been a confusing ride so far, with more opinions than there are types of antennas, but I am thankful for the suggestions I've been getting.  I think it's going to take some time to work that out before I spend any money.

In the mean time, I realized today that I should start off where the KX3 is comfortable, with QRP.  Rather than agonize over permanent antennas for now, I think it would be wise to begin my journey by learning about some wire antennas.  I have some trees in my yard I can use.  They aren't super tall though, the tallest being 15-20ft or so.  I'm not opposed to getting some kind of mast either if my trees aren't going to cut it.

Kind of funny.. I've been so confused about what I was going to setup for QRO at home, I didn't bother getting the built-in ATU option for my KX3.  I figured I'd be buying a tuner anyway.  Well, I went ahead and ordered the option from Elecraft today....

My question to you QRP masters is, where do you think I should start?  I'm interested in learning to make my own wire antennas, but I also wouldn't mind buying a high quality one, if I can't make one as good or better myself.

Thanks in advance for your suggestions!  ~ 73's

I'm going to be ordering my KX3 next week and I have the same issue with antennas.  It might be more complicated since I live on a middle floor in a building that doesn't allow outside antennas.  I think I'm going to order the AlexLoop, but I also ordered one of these:

http://www.earchi.org/92011endfedfiles/Endfed6_40.pdf

I opted to buy one since I haven't been able to find a toroid for it.  The nice thing is they give you the design plans if you want to build one instead.

I am going to try and wrap it around my balcony and see what happens.  I figure the AlexLoop will be great either at home or on the road.

Good luck.
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W7ASA
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Posts: 255




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« Reply #2 on: October 04, 2013, 05:30:03 PM »

Congratulations!  The receiver on the KX3 is superb!
-...-

1.   I would highly recommend the built-in automatic antenna coupler ('tuner') for the KX3. It is excellent, quite efficient and allows you to experiment with antennas of many kinds. Many antennas do not cover entire bands, such as an 80 meter antenna cut for the CW portion might have an excessively high SWR at the high end of the band for voice.  The antenna coupler easily solves this. If you want to go portable (and with a KX3 you REALLY should.) the internal antenna coupler is worth it's weight in exotic QSL cards.   Wink  for being able to use simple antennas efficiently. 

2.   At you home, I REALLY recommend getting started with some kind of a dipole. 15 - 20 feet is not a huge limitation, especially for a new ham who is just getting started into HF.  A dipole -in general- is simple to make, efficient, and inexpensive. Do they work?  I am using a variant of the dipole now as my main antenna.  And example: I had a regular sked with a ham friend at Ft. Benning, Ga. all the way to my old cabin in Idaho. His antenna was strung-up each time, just before sked time, between barracks at roughly 10 feet. I had a G5RV (basically a doublet) at maybe 35 feet.  Power from him was 10-15 Watts or so and from me 20-25 Watts CW. Don't wait - get on the air and make improvements as you go.  This will keep your fun and interest HIGH. Antennas are one of the most fascinating aspects of ham radio for me, and for many other hams.

Example:  With the ATU, you could make a simple 'doublet' ( dipole ), fed with open wire line and use it to cover multiple ham bands, because the tuner will automatically transform the impedance that the transceiver sees from the antenna on bands where it does not present a perfect 50 Ohms(z).



Basically, what I am suggesting is to get on the air with a 'quick-up' antenna wherever you can safely put it at home and enjoy operating right away.  Next, you will probably improve you antenna set-up, for example, by adding a balun to the feed point of the open wire line on your doublet to see whether this will make a difference as it says in the antenna manuals. Later you might try wire loops and etc....  This way you can plan all kinds of antenna projects WHILE YOU ARE ON THE AIR and learn as you go.


73 de Ray
W7ASA ..._ ._

Ps. For anyone ordering a KX3, I HIGHLY recommend that you include the internal "ATU" (antenna tuning unit).  Elecraft did a TON of extensive engineering to make that accessory extremely efficient. Though incredibly small and they are very handy and likely perform as well or (likely much better) than many off-the-shelf tuner boxes.
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WX7G
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Posts: 6136




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« Reply #3 on: October 04, 2013, 06:26:12 PM »

The starting, and often the ending point, of wire antennas is the half wavelength dipole.

If you want multi-band coverage a fan dipole is good. Being that your KX3 will have the autotuner I would cut the dipoles per formula (length = 468/F) and let the autotuner do the rest. Balun or no balun the dipoles will work just fine.

I would be careful about using the KX3 autotuner on a dipole fed with ladder line to a balun. The VSWR on some bands will exceed the 10:1 VSWR spec of the KX3. It will tune but it might be inefficient.
« Last Edit: October 04, 2013, 06:28:16 PM by WX7G » Logged
WB6BYU
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Posts: 13339




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« Reply #4 on: October 04, 2013, 08:08:37 PM »

There really isn't any difference in antennas between QRP and QRO:  the same antennas
still work.  (Well, except those that can't handle the output power due to losses or voltage
breakdown in a trap or matching section.)

In either case, a dipole fed with coax is simple and can be pulled into place when you want
to operate, then removed when needed.  If you use thin wire it can be pretty difficult to
spot when you aren't looking for it.  You can build it for 40m or 20m to start, then add
more bands to a common feedpoint for convenience.  I've used such antennas backpacking
from several countries, for portable emergency operation, and from home - they are simple
and easy.  And cheap - you don't have to use the fanciest coax and wire.

I'd suggest starting with a length of coax and some sort of dipole center insulator that has
wing nuts to connect to the wires.  (I cut mine out of some scraps of outdoor PVC lattice.)
Now you can cut any sort of wire antenna you want, attach it to the insulator (tie it to the
holes/eye bolts for strain relief, then secure the stripped ends under the wing nut) and
try it out.  Makes antenna experimenting easy, and allows you to find what antenna seems
to work best for your situation.  For wire I use insulated hookup wire, perhaps as small
as #26 where light weight (or lack of visibility) is important, up to #16 or so for a more
rugged version.  I pick up spools at the local electronics surplus store for perhaps $1 per
hundred feet.  (At a hamfest I payed $5 for a spool with nearly a mile of insulated wire on it.)

Then you can use the same system at home or portable, with a wide range of antennas
that you want try out.


Start simple - but get started!
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WA9UAA
Member

Posts: 319




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« Reply #5 on: October 05, 2013, 02:52:43 AM »

Any successful QRP work is going to require the absolute best in an antenna. A ladder line fed antenna is going to have the lowest loss over several bands. For single bands the PAR Endfedz have a very good reputation.
73,
Rob
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KB1GMX
Member

Posts: 782




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« Reply #6 on: October 05, 2013, 11:14:16 AM »

For QRP QRO antennas work but you cannot use power to make up for inefficiency.  So the antenna
must be effective and efficient.  The definition of efficient being at least a full size dipole at sufficient
height (1/2 wave or higher).  Or a beam of some sort... Wink

I'd add for QRP the PAR end fed monobanders are very good and I use for a lot of variable
uses the PAR EF 40/20/10.  The PAR/LNR endfeds are the same performance as a similar sized
dipole at the same height with the convenience of feedpoint at the end.  This means verticals, slopers inverted V and inverted L configurations are easy to do depending on supports (trees or poles).

The tribander (the EF 40/20/10) is only 40ft long so the 40M performace is only a small amount
down from a 66 foot long dipole and on 20 and 10 is equivalent to a dipole for those bands.
But being end fed and shorter than 66ft its very convenient for small lots and portable ops. 
That antenna unlike the monobanders only can take 25 watts continuous.  The monobanders
are good for 100W and some to 300W.

The latter (PAR/LNR) EF 40/10/10  is very portable and if you use an alternate wire cut for a specific band
(length in feet = 468/Fmhz) its useful from 5 to 30mhz.   It can also be hung all the possible ways.

I have a EF-40/20/10 here at home and I use it all the time with the various radios throttled
to QRP and 25-35W with good results. I have a spare for things like park ops and Field Day. 
Though I have other wires that antenna happens to be oriented best for a lot of uses.

I don't work for PAR/LNR just a user of a product I've used, abused, tested and find very useful.

The EARCHI 6-40M antenna is not a resonant antenna and is a short antenna below typically 20M
and does need a ground radial/counterpoise for best results though in some case the COAX will
provide that if it is long enough.  Performance of that antenna is typically 1 to 2 S-units down from
the PAR verified by my own A/B testing where the height and location was controlled.   This antenna
was designed for portable/emergency work and operates on many bands with a minimal tuner(internal).
As to 6M its a poor substitute as a 6M dipole is better and only 115 inches (SSB 115", FM about 108")
long plus operating on 6M SSB really wants a horizontally polarized antenna and the FM part of the band wants vertical making it a very bad compromise for both.  Its a different antenna from the half wave
end fed and offers lower performance but some operating convenience. 


Allison
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KK6GNP
Member

Posts: 158




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« Reply #7 on: October 06, 2013, 08:43:11 AM »

Thanks for the advice, everyone.

I went ahead and ordered the multiband End Fedz wire so I can set it up here at home and get things running.  Ultimately, I may end up using wire regularly here, since I don't have a lot of room for  a vertical with radials, and pretty much everything else other than a mag loop is out of the question.

I'll be getting the 100W amp for the KX3 in December, and I will be operating portable a bunch this Winter, so using wire makes sense for me in general.

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73 ~ Cory (JeepEscape)
KK6GNP
KK6GNP
Member

Posts: 158




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« Reply #8 on: October 11, 2013, 05:55:50 PM »

I put my KX3 together today, and put a Par End Fedz (10-20-40) up between a tree and my house, and everything is working great.  Of course, I can't really transmit until I get my next license test done, but it feels amazing just getting this all put together and listening to the bands for the first time with my own rig.  The wire is only about 20ft off the ground, because that's all the tree I have, but I was still amazed to be hearing signals from all over the country. 

A station calling CQ had a great pileup, including some ops from Japan, but they were in the mud for me.  The furthest I heard today was Chicago so far, but I've only been listening about an hour.

You know, I can appreciate people who have the real estate and capability to put up a tower and an elaborate shack, but I have to say it was a pleasure being able to set up this KX3 with such a minimal amount of technology.  Hearing a nice loud signal from Chicago with my little wire antenna was like magic to me today! hahaha

Thanks to everyone for the suggestions.  I feel like a load is off of me after months of reading, learning and anticipating.  Can't wait to take my General and Extra tests.
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73 ~ Cory (JeepEscape)
KK6GNP
W1JKA
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Posts: 1771




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« Reply #9 on: October 11, 2013, 07:47:14 PM »

                     Now that you have your Par end fed antenna and if you haven't done so all ready try experimenting with different configurations. Depending on your QTH ground conditions you may have better signals with an inverted L or a sloper,20 ft. ht. is good for both. Some get better results with a sloper if they put the matching unit on the high end, of course this means a longer coax feed line.
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KK6GNP
Member

Posts: 158




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« Reply #10 on: October 11, 2013, 08:09:29 PM »

                     Now that you have your Par end fed antenna and if you haven't done so all ready try experimenting with different configurations. Depending on your QTH ground conditions you may have better signals with an inverted L or a sloper,20 ft. ht. is good for both. Some get better results with a sloper if they put the matching unit on the high end, of course this means a longer coax feed line.

I'll need 50-60 feet of feed line to do that.  Will I see a lot of loss at that length?
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73 ~ Cory (JeepEscape)
KK6GNP
W1JKA
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Posts: 1771




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« Reply #11 on: October 12, 2013, 06:07:52 AM »

 Re: KK6GNP reply #10

   For practical QRP operating, you will not notice any loss, my longest end fed fixed feed line is 72 ft. and my two portable feed lines are 25 and 40 ft. As you know there is always some loss in any length of feed line (length, velocity factor, free space test results etc.) but again I'm talking practical use. I'm sure others will chime in with perfect ENZAC? results for 60 ft. depending on your type of coax. Also it's relatively easy to experiment with directional headings with an end fed antenna but keep in mind that your strongest signals are not always from the direction that you have your antenna set up for due to average propagation and ground/structural conditions at YOUR particular QTH.
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KK6GNP
Member

Posts: 158




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« Reply #12 on: October 12, 2013, 09:45:31 AM »

Re: KK6GNP reply #10

   For practical QRP operating, you will not notice any loss, my longest end fed fixed feed line is 72 ft. and my two portable feed lines are 25 and 40 ft. As you know there is always some loss in any length of feed line (length, velocity factor, free space test results etc.) but again I'm talking practical use. I'm sure others will chime in with perfect ENZAC? results for 60 ft. depending on your type of coax. Also it's relatively easy to experiment with directional headings with an end fed antenna but keep in mind that your strongest signals are not always from the direction that you have your antenna set up for due to average propagation and ground/structural conditions at YOUR particular QTH.

Thanks for the help.  Just getting on the air finally has made me want to try all kinds of things.
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73 ~ Cory (JeepEscape)
KK6GNP
K5TED
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Posts: 747




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« Reply #13 on: October 12, 2013, 06:50:32 PM »

With only 10w, and a very tight lot, you will have your work cut out for you working SSB.



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KB1GMX
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Posts: 782




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« Reply #14 on: October 12, 2013, 07:47:00 PM »

K5ted: With only 10w, and a very tight lot, you will have your work cut out for you working SSB.

I'd bet based on experience he can assuming he isn't doing anything wrong to sabotage the effort.
What can be done wrong?  Antennas not tuned, bad cables or connectors, incorrect radio setup
are the top three.

I've run QRP enough to say you are likely half right.  Today I worked a Rover runnning 40M form
PA in the PA QSO party.  My station was a KNQ7a SSB in the mobile running a 7ft loaded whip in NH.
That's 10W into an antenna that is typically less than 10% the performance of a halfwave anything.
I do this often enough that its normal to me.

I've worked many countries at 4W using a Par EF40/20/10 and it's doable using SSB on those bands.
You are not going to be the king of the heap but contacts are not rare either.

As to the tight lot, a PAR EF40/20/10 is 40 ft long and if installed 20ft of it vertical and the remaining
part horizontal you only need a 20ft garden for that inverted L.  Sounds doable to me. 

To KK6GNP, as a tech and if so you do have SSB and CW privileges on 10M.  Also any reasonable
feed line (RG8x, RG8, RG213 or equivilent) has relatively low loss at HF and if the antenna is
tuned for a reasonable match (anything under 2:1) the loss will be trivial out to 50-100FT.   
Note the PAR EF40/20/10 does not have the wire tuned to length as supplied as every location
is a bit different (read the fine but small manual) its on the long side so the user can tweak it for
their uses.

Allison

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