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[Articles Home]  [Add Article]  

Antennas for QRP

Norman Sullivan (NZ5L) on December 12, 2001
View comments about this article!

As a confirmed QRPer, I have given a lot of thought to the subject of antennas. 

My conclusions should be of interest to those planning QRP operations, as well as those of us on limited budgets. 

In the first place, despite the obvious advantages, I am going to rule out expensive beam and tower combinations. If you are seeking to save money by building a kit you probably aren't going to spend thousands on a 50' Tri-ex tower and TH7-DXX combo with heavy-duty rotator! That leaves two basic choices - vertical types and wire types. 

To me, the first requirement of a good QRP antenna is efficiency, i.e., most of the RF fed to the antenna should be radiated. Unfortunately, most verticals are not renowned for their efficiency. Their short physical length, as opposed to the desired quarter-wave electrical length, almost guarantees a low radiation resistance, which, in conjunction with typical ground losses, adds up to net efficiencies of 10-40%. Not a big deal if you are operating 150 to 500 Watts but not satisfactory for the QRPer. A very extensive radial system or an above-ground counterpoise would improve things, but the best that can be obtained is about 60-65%. (Some alternative designs - mainly some GAP models - theoretically exceed these limitations. If you can afford their entry price - then try it, by all means. My solutions tend to cater to the less well munificently endowed.) 

This leaves wire antennas, a field in itself. The operator who puts up a five band trap dipole at twenty feet and then laments about the poor performance will think: "Oh, I've tried that - it was a bummer", or some such sentiment. In fact, even a standard dipole will give a good account of itself if situated in the clear and at least a half-wavelength high at the operating frequency. (65' or more for 40 Meters, 35' for 20, etc.) One way to increase the gain somewhat is to go to a full-wavelength dipole. Use the standard formula, and place the center insulator 1/4 wavelength from one end. The center conductor of the co-ax should be connected to the 3/4 wavelength side. By measuring carefully, a very low SWR can be obtained so no tuner is necessary. Also, if erected as an inverted vee, the long leg can be oriented towards the area of interest. If the high point is your chimney, a short pole can be bracketed to it to give a typical height of 30' or so, excellent for 21 Mhz and above and useable on the 20 Meter band. Total length of the antenna for 15M is about 44', for 20M about 66'. 

Another favorite of mine is the Extended Double Zepp, or EDZ. This dipole is based on a 5/8 wavelength per side and gives an honest 3Db gain broadside over a standard dipole. (As such, setting it up as an inverted vee would negate the broadside gain and result in a more omni directional pattern.) An EDZ for 20 Meters would be about 84' long, and could be used on 80, 40, 20 and 10 Meters, if fed with balanced line and a tuner. Some feed line lengths work better than others; I've had good luck using a 42' length of 450 ohm ladder line going to coax via a good 1:1 balun. The performance on 20 justified the trouble of putting it up and gain on 10 (Cloverleaf-style at an angle to the wire) was also pronounced. On 80 and 40 it performed as a dipole. Try to put it up at least 40'. Trees make good supports and will not substabtially degrade the tuning or performance. Use insulated wire if it has to run thru any branches - the insulation won't affect the tuning greatly but direct contact with leaves would! 

Another favorite of mine is the Inverted "L". When discussing an inverted L, most hams think of 160 Meters, where it is a primary choice, but it also works very well on shorter wavelength bands, providing a good combination of vertical and horizontal polarization. I will suggest a length here of 165', which equates to 5/16 wavelength on 160, 5/8 on 80 (very effective - think 2 Mtrs!) 5/4 on 40, and 2 1/2 wavelengths on 20, performing as a long wire. It could also be used on 30 Meters. Ideally, an automatic wire tuner could be placed at the base of the wire and remotely tuned, but a common L network could conveniently be used. For operation from 80 and above I would recommend an inductance of 10 uH and a capacitance of 250 pF. A surplus roller inductor works very well and I've seen a few motorized inductors selling for $10-$12 at hamfests! MFJ has been selling a low priced L tuner for years and they are abundant on the used market (tip-if buying used check it out, it may need a repair). For Northeast winters, the tuner should be placed in a waterproof plastic box. Fine tuning at the feed point is really not necessary if you also have a tuner in the shack. The remote L could be thought of as a pre-tuner. You may well find (as I have) a setting that enables better than a 3:1 SWR on as many as three bands, the reactance can be tuned out from the comfort of your hamshack. As with any single ended antenna, a ground connection is required, but the radials (on or in ground) don't have to be resonant or straight and as few as 8 will give good results, as the radiation resistance will be much greater than ground resistance. A copper ground rod makes a convenient tie point, and copper braid can be run from there to the ground post on the pre tuner. 

At this point, it is typical to say something like "I busted a pile-up on 20 SSB for 7P8LO with 250 mW" or some such. Well, not exactly, but I can predict that you will be within 2 "S" units of the typical station and will be able to work 80-90% of all the stations you can copy. 

For me, it has made QRP operation enjoyable and fun. 

Try it, you'll like it. 

Good luck.

Member Comments:
This article has expired. No more comments may be added.
 
Antennas for QRP  
by NB6Z on December 12, 2001 Mail this to a friend!
Yes I completely agree with your observations on the EDZep design. I have used and modified this design for several years. You can see the details for construction and performance at: http://home.teleport.com/~nb6z/nb6zep.htm

I tried an inverted L on 160 meters supported by a couple trees. I could not get the vertical section long enough to be an efficient radiator. I had to load the horizontal section to acheive resonance. 160 meters is real tuff for low power... My best DX was KH6 from Oregon.


 
Antennas for QRP  
by WB2WIK on December 12, 2001 Mail this to a friend!
Very nice article!

I disagree with the comment regarding efficiency of (simple) vertical antennas. The simple, low-cost Hustler 4BTV/5BTV for example, are indeed full-sized, quarter-wavelength verticals for their intended bands. The 10m radiator section is 8-1/4' long, that's a quarter-wave. The 15m radiator section is 11 feet long, that's a quarter-wave; and so forth. The elements are made just slightly shorter than quarter-wave, e.g., the overall radiator on 40m is 26' and not 33', due to the slight inductive loading created by the series traps; but 26/33 is 78.8%; and on the higher bands, the ratio is higher, as there's proportionately less inductive loading.

With a set of tuned, quarter-wave radials per band, this antenna considerably less than $200 to install and will offer omnidirectional performance rivaling, or better than, any of the wire antennas discussed.

Efficiency is a relative term of merit. Remember, that all power applied to _any_ antenna must be radiated or dissipated, it's got nowhere else to go. In the case of a trapped vertical, a slight amount of power is dissipated. I spent a lot of time making dissipation measurements on a 6BTV, and on 7 through 29 MHz, worst-case dissipation on any band was on 7 MHz, with cumulative dissipation of ~12W for 1000W power applied (Pdiss measured by thermal rise using bolometer). That's not much dissipated; everything else must, by basic principles of physics, be radiated.

(Note the efficiency falls dramatically if a good radial system is not used; however radials are just wire, insulators and rope, as are all the wire antennas discussed, and have little value, and occupy no greater space than the wire antennas discussed.)

As always, I invite any station to join me on a band of their choice between 7 and 29 MHz to do on-air antenna comparisons with distant stations. That's a lot more fun than postulating.

Having said all this, I enjoyed the article. Keep up the good work!

73 de Steve, WB2WIK/6
 
RE: Antennas for QRP  
by NZ5L on December 12, 2001 Mail this to a friend!
Nice to hear from you, Steve, and thanks for your comments. I'll stand by the statement that even a "full size" quarter wavelength antenna is relatively inefficient compared to even a simple dipole. The theoretical radiation resistance of a quarter wave antenna is a maximum of 35 ohms, half of a dipole's. "Loaded" or otherwise shortened versions are much less still. Even with a modest ground plane of 10 radials, ground resistance will be 30 to 35 ohms, translating to a maximum of 50% for the full quarter wave example. According to the ARRL Handbook, a 5/16 antenna (165' on 160)should have about 50 ohms of radiation resistance, with a resulting 58.8 % rad.efficiency. For typical verticals, things are much worse for the low bander. As I mentioned, at normal power levels, who'll miss a Db or two? That said, I will cut some slack for the new type asymetrical vertical dipoles (a.k.a. GAP Vertical). My Titan performed indistinguishably from a dipole from 40 on up. But my thrust here is efficiency - of $ as well as photon radiation.
 
RE: Antennas for QRP  
by WB2WIK on December 12, 2001 Mail this to a friend!
Hi Norm, nice to hear from you as well.

The radiation resistance figures you provided are based on a 1/4-wave over earth. When we discuss a 1/4-wave, elevated, over a tuned field of radials substantially above earth, a 1/4-wave vertical is in effect a 1/2-wave vertical dipole in terms of all relevant metrics. Since we're comparing elevated wire antennas, I don't think it's fair to assume a vertical will be ground-mounted (none of the wire antennas will work if laying on the ground). My HF6V, for example, measures 54 +j3 Ohms at 14.2 MHz, using a network analyzer plugged directly into the feedpoint at the base of the antenna. Hardly 35 Ohms.

The advantage of the elevated, 1/4-wave vertical with tuned radials over most wire antennas is its drastically lower rad angle.

Once again, it's fun to postulate but it's more fun to get on the air and do it. Up to a challenge?

73 & keep on experimenting. I'll never stop until I can't get out of bed anymore!

Steve, WB2WIK/6



 
Antennas for QRP  
by KA1EZE on December 12, 2001 Mail this to a friend!
I like my loop, something like 400 feet. The only antenna you can build with nearly 100% home depot supplies!

One reason is for receive. QRP is usually not a full powered dsp rig turned way down, but kits and less fancy radios.

The loop is almost magical in getting rid of qrm, and I have a bunch of dimmers in the house, a loop is deaf to them!

Rick
 
RE: Antennas for QRP  
by K0XU on December 12, 2001 Mail this to a friend!
Although I have never tried an inverted L for 160 meters, I did use one for a number of years on 2 meters. A real limited space antenna.

During this time frame I drove a big old pickup and parked in a ramp. The quarter wave vertical on the roof would clang away merrily as I drove into & around the ramp. So I did what any right thinking ham would, I converted it to an inverted L. About 10 inches on the vertical leg if I remember right. I could never tell the difference in performance as I rarely took the beast out of town anyway so it was used for repeaters & close in simplex anyway.
 
Antennas for QRP  
by KG4PYM on December 12, 2001 Mail this to a friend!
Hello. This looks like fun, I'm apologizing in advance as I tend to ramble on-

...I'm going to stay away from theory,
and next I'm going to remind myself that we're talking about antennas for QRP & QRPp, without having to go to the thousands of dollars solutions of elevated multi-element arrays, etc etc.

I've worked a few QRP stations in the last two weeks. I've tried to research antennas, and it seems, that when you read antenna books and articles, editorial comments and opinions are not included. Extended Double Zepps and other dipoles, seem too simple to be of such high value. There is the support thing to contend with, if you are so blessed with trees with the adequate spacing and height then all the battle is won.

I must say, the QRP stations that surprised me, were using Extended Double Zepps, or something very similar. They were loud enough for me to feel a need to rag-chew, even if the motivation was a selfish need to know more about their antennas.

Okay- South Africa was worked by cranking the DRIVE down to my best approximation of 5 watts, using a 200 foot in-shack end-fed at the tuner random wire that varies between 6feet and 30 feet in height, at least 100 feet of it being only between 10-20 feet above ground, and it sort of ends at 30 maybe 40 feet. Best I could do with a hand thrown rock+twine. BUT, the station on the other end was using a 2 element yagi @ 5 meters (and...4 watts). This was on 20 meters. Chalk it up to luck and favorable band conditions with the wire running along a north/south axis.

The last gent I worked who was QRPp (and I wasn't) was using a 10-160m 200' long, Ladder-Line fed Windom at 36' on 40 meters. We did chat, it was more than just call-sign, OP, QTH, and Power that we exchanged. He was running a quarter of a watt. He was loud enough that I wanted to rag chew a bit [all of this is on CW].

So steering clear of theory- it seems to me the Ext Double Zepps and other theoretically efficeint wire antennas fed with parallel feeds of one kind or another are a preferred choice by QRPers- given what I've heard on the air, whatever the reasons are, I want one of these wires... now if I can just convince my neighbor that it really won't be as obtrusive as his reluctance would suggest [he has the other required tree!].

I have thrown together one of those RFD's, the coaxial dipole, cut for 1/2 wave on 20- dangling beautifully from a tree branch that extends over my property [what luck I hope they don't cut the branch], I put red and green bows on the RF choke coil which is at 2' looking like a bizzare Christmas reath- oh I forgot to mention it's a Vertical Dipole. I have had moderate success with it on 20 to Europe and South America.

** However, I am surpised that more vertical users don't moan about the noise. I find it to be noisy compared to the random horizontal wire. I would never seriously consider a vertical for QRP work simply because of the noise- **unless I had no other choice.

This I have determined by keeping theory in mind, while hearing what seems to work best for me via experimentation.

Like I loaded the 20m vertical dipole on 40m in spite of theory which says don't do it. Indeed, the theory was confirmed, naturally, the long wire worked a whole lot better! ha ha.

I've tried it on 10m, theory confirmed, as a full wave dipole that X pattern in theory was true, yep- it has gain alright, but as a vertical dipole the gain is towards a Sewer man-hole cover, worms, and birds overhead, instead of at the horizon! hi hi. It loads, but it's virtually a reasonant dummy load on 10. Not really, I was heard, but no one was interested! hi hi.

In my lay-man's simplistic view of things, I find the QRP crowd, to be, well, different-

you know, you QRPers-making your own Altoid tin radios, competing in those crazy QSO per weight contests, pushing the envelope of the impossible every day... you're a Zany, friendly, eccentric, and really smart group in general.

I'm not out to re-invent the wheel, but I'm having fun fiddling with trying differently made wheels- And I'm gonna put up a Semi-Home Brew Windom/Off Center Fed Dipole as soon as I can.

If it works that good on 5 Watts or less just imagine how it'll work with 100 Watts. Simple as that.

And my next HF rig will be a QRP rig. In the mean time, I'll answer every "CQ CQ CQ DE /QRP-QRPp I hear!

I'll also turn down the power when I'm near the QRP calling frequencies, it seems many on the bands these days don't seem to care about that part of the band plan, something about fists- blasting away on xx.060.0 give or take a kc or two! :[

Ultimately, it's all good to me, and I'm having a blast on HF, and whatever antenna people decide to use, hey if it works for them I'm happy about that!

73

Darin.
 
RE: Antennas for QRP  
by NZ5L on December 13, 2001 Mail this to a friend!
To WB2WIK: I don't know the real "Z" but I'll readily grant you that elevated ground-plane verticals are a good way to go, having used such systems successfully in the Phillipines and San Antonio. I guess my bias against (simple, ground mounted) verticals stems from trying to work out of my backyard on the 80 Mtr Novice band in the late 50's with 15 Xtal controlled Watts and my Gotham "all band" vertical with no radials. I'm sure I warmed the worms. Come to think of it, the 5-band trap dipole (at 20 feet) wasn't all that much better except for close stations. And you're also right, wire antennas don't work all that well either when they're lying on the ground (Thank God for sling shots). Fortunately, we "higher primates" have the ability to learn from experience - and a few good antenna books!
 
RE: Antennas for QRP  
by WB2WIK on December 13, 2001 Mail this to a friend!
NZ5L: Good comments.

As a Novice in the mid-60's, my first antenna was a random wire but my second antenna was a base-fed vertical with a tapped loading coil, similar to a HyGain design but sold by Lafayette Radio for $18.95 brand new in 1965.

I also installed it on the ground. Horrible.

Per a local Elmer's suggestions, I started adding radials made from steel twisted-pair insulated wire originally used for crank-type "field phones" during WW2, and purchased from the local Army/Navy surplus store for $1.00. Wow.

Kept adding more radials. More wow.

Three months later, totally convinced that verticals are wonderful antennas. I probably could have loaded up the radials without the vertical and made a lot of contacts -- they were running everywhere.

The "noise" issue is a puzzlement. Sure, maybe some noise is more vertically polarized than horizontally, but my findings have always been that an efficient, resonant HF antenna receives lots of noise, and I'm very skeptical about any HF antenna that doesn't bring in a lot of noise; most of them don't work very well.

When I had several acres of property back east years ago, I put out a 5-wavelength Beverage receiving antenna to help my S/N on 1.8 MHz. That worked. Everybody was weak, but the noise was weaker, and it did improve copy. But it didn't transmit worth a darn.

73 de Steve WB2WIK/6
 
RE: Antennas for QRP  
by KG4PYM on December 13, 2001 Mail this to a friend!
Ahem, I did get that wrist rocket, a week after using that arm thrown rock. hi hi. I plan on excersizing the wrist rocket this weekend... for hanging, in the spirit of Christmas, the pretty G5RV I'll be pruning into a modified windom. [guess I like verticals aspects as well].

I think I've discovered one noise source the wood-working gent who has the wood shop in his garage behind me, running various power saws, drills, etc etc.

Then when it rains, the neighborhood power company pole transformers seem to stir up quite a ruckus for a while. In the case of the table saws, or transformer buzz- either antenna hears it for all practical purposes just the same, because its so LOUD- although the magnitude of those noises are- louder on the "vertical" (if you dare call what I'm using as a vertical at the time of this post- a vertical).

I would be skeptical of a tuner fed long random wire the way mine is configured like I might be skeptical of loading up the rain gutters on my house for an antenna, too. Well, not quite as skeptical. It did, after all reach South Africa on 4 watts. It was after all my first bonafide qrp contact ever.

I got my license November 5 1991... both my antennas, the 20m vertical 1/2 wave dipole and low long wire are at best marginal, my experience is limited. Perhaps a break for the bannana eating other primate is in order.

After this weekend my antenna will be Horizontal/Vertical of a specific sort.

May The Blessings Be.
 
Antennas for QRP  
by K4IA on December 14, 2001 Mail this to a friend!
My vote is for the inverted L but make it top fed in the middle. It becomes an upside down vertical with one radial. I have one that is 51 feet on a side with the center 60 feet high and fed with ladder line. It works great on 80-10 and even tunes up on 160. The length is not that critical but I don't think you'll get great performance if it is too short. You do get the best of both worlds, horizontal and vertical polarization and it is more omni directional.
 
RE: Antennas for QRP  
by KG4PYM on December 14, 2001 Mail this to a friend!
For K4IA,

Please pardon my ignorance...actually I got my license Nov. 5th, 2-0-0-1 :)

So your Inverted L is Center-Fed at the top w/Ladder-Line, and... does that mean you manage to run the feed line at about 45 degrees from vertical?

I know of a QRPer who is apartment bound but on an upper floor, so his is end-fed at the top... and it seems to work well. Fairly difficult to notice it's even there, too!
 
RE: Antennas for QRP  
by K4IA on December 14, 2001 Mail this to a friend!
Welcome to the world's greatest hobby.

Yes the ladder line is at a 45 degree angle coming up from the ground to the center. It is actually offset also. I am not sure how to describe it except to say the ladder line is not in the same plane as the two legs of the antenna. If the ladder line were run too close to one of the legs, it would become unbalanced.
 
Antennas for QRP  
by W7DAM on December 14, 2001 Mail this to a friend!
My main limitations are the neighborhood CC&R's. I'm on 40m with an MFJ monobander CW rig with 4 watts and I'm using their halfwave twinlead dipole. However, the highest I can get this antenna up in the air is only six feet because my back yard has only very small trees.

However, I'm having a fun time. Although I've yet to reach out of 6/7-land with this setup, and most of my contacts have been almost exactly in a straight line between Alaska and southern California, I enjoy every contact I make and most of the signal reports I get are about 579. I'm thinking about putting a wire up under the eaves of my house, but it's actually fun right now seeing what I can do with this setup just as it is.

Oddly enough, our silly CC&R's will have someone get written up for a violation if they see two weeds in your lawn, but they'll allow those ugly portable basketball hoop structures anywhere. I suppose I could get away with having a 133-foot basketball hoop in my driveway and using it as a 40m vertical :-)

-Dave
 
Antennas for QRP  
by WD4MFB on December 15, 2001 Mail this to a friend!
I was just reviewing an old log from 1982/83. I was using a Heathkit HW8 on 40/15 with an inverted V for 40. I had an add-on at each end to make the inverted V a 3/2 wavelength on 15. I lowered the antenna and used alligator clips for the extra length. That seemed to be the best antenna for QRP I used.

Now I am using a Elecraft K1 and a Cushcraft R8. Sometimes the noise level wipes out any hope of a contact, but until I find a permenant QTH, the R8 will have to do. I'm trying to get WAC on 40 now. Asia will be tough.

At my other QTH, I was building a 2 element inverted V
with phasing. I plan to go back to this again as it really seemed to be a winner.

One thing to keep in mind with QRP is buy good coax. It is a good investment. Use good insulating material, this can be inexpensive, just use good judgment.

Whatever you decide or use, enjoy. If you hear me, give a call.

Mike, WD4MFB
 
Antennas for QRP  
by KE3YO on December 18, 2001 Mail this to a friend!
Please correct me if I'm wrong on this. An extended double zepp is going to require a tuner, even for the band it is cut for and there is loss in a tuner, especially I understand the cheap one's made by a certain company in the southern United States. Something to keep in mind for QRP where every watt is important. I prefer half-wave dipoles. They require no tuner and I've always had very good results from them, even if they are not quite high enough off the ground. 73, Mark.
 
RE: Antennas for QRP  
by NZ5L on December 18, 2001 Mail this to a friend!
KE3YO: OK, you asked for it. 1). I don't know why a tuner should be thought of as a lossy device any more than some other stage of a radio, but it ain't necessarily so. I'm sure some are better than others, but a typical tuner would have much less than 1 Db of loss. If ladder line is used to feed a multi-band antenna with a tuner, the savings in line loss over a coax run usually turns out to be a net gain. 2). No, the EDZ design needn't require a tuner at all if fed with the right length ladder line, a balun, and coax. This antenna article was intended as more of an idea piece than a point-by-point construction article, but a 20 Mtr EDZ (3Dbd - i.e., over a dipole) can be made to have a very low SWR on parts of 80, 40, 17, and about 2:1 on 10 withOUT a tuner. To each his own, of course, but don't knock it 'till you've tried it.
 
RE: Antennas for QRP  
by KG4PYM on December 18, 2001 Mail this to a friend!
Perhaps someone would care to chime in-

I was wondering, there's a section in the ARRL Antenna Book, concerning TUNERS, and according to my interpretation, the article seems to imply that Loss in a tuner was more a function of CIRCUIT CONFIGURATION- more so than the make and model of a given tuner.

Please correct me if I misunderstood.

I'm also thinking, variable air capacitors are basically the same as any other- plates are metal-air is well- AIR. Then there are the inductors...basically, windings, on air or iron- I've seen those expensive roller inductors- and I can understand specific gripes with makes of anything, shoddy sheet-metal, fits, etc etc. Poor mechanical alignments...but moving on-

Next I was wondering, my BASIC understanding given the principles of physics, concerning loss and tuners, Pi, L, or other- I'm thinking, depends on the mismatch- reactive/resistive. In other words if the mismatch is without the tuner say, 8:1 sure- more loss in the tuner, but if it's tuning a mismatch of 2-3:1 the loss is much less if the antenna system it is tuning is close to resonance.

Am I missing something on that?

Anyway- trade-offs abound, many hams QRP or not, are limited and may not be able to put up 5 perfectly resonant dipoles, and if so, may want to work SSB plus CW.

And back to Verticals vs Horizontal dipoles, we all work people all the time on Verticals, and I've noticed (perhaps it's my blessing or my curse) that- anytime I say, think, or write anything that may be construed as negative about verticals, then my next 3 QSOs turn out to be people on verticals, and the chap with the loudest signal on 40 is a guy on a vertical! LOL! One guy had a LOUD signal, of course he was on a farm, and when I asked about radials, he said- they had two large tractors and two small tractors, and the vertical was ground mounted over wire fencing. hi hi.

As a final case-in-point, last night, I answered a CQ on 40 - I thought surely this person was running "normal" 80-100W "high power" and to a great antenna- he's 599 to me in Atlanta. I'm 579 to him near Chicago. I'm running basically 5W. Ted, near Chicago is doing a fine job avoiding rig/antenna issues, talking about the wx, how he should be in bed now, etc etc. Unable to stand it anylonger, I cave-

I send that rig here is 5 watts, antenna is home-brew Windom. He replies how good a job my set up is doing (very nice of him, I sure appreciated it! I was afraid and still am afraid my antenna might not be working like I hoped) and then he drops the bomb- HE'S RUNNING A K2 AT 5W ANT IS 200' ZEPP. I didn't ask how high- it was high enough, and all I could do was grin and bear it!

I have found myself asking why I bothered cutting the G5RV in the first place- then I remembered- because of where the trees are placed in relation to the transceiver- otherwise the feedpoint would have been over my kids' sand-boxes and too close the the swing-set.

Best to All.

Darin.
 
RE: Antennas for QRP  
by KE3YO on December 19, 2001 Mail this to a friend!
You don't have to put up 5 resonant diploles to work 5 bands. Its easy to build a multiband dipole that is resonant in each band. Look in your ARRL antenna book.
 
RE: Antennas for QRP  
by KG4PYM on December 19, 2001 Mail this to a friend!
KE3YO DE KG4PYM

TNX OM...TRULY=

Yes, I got distracted, after I posted it I thought, Darin where did you get that 5 dipole thing?!?

Glad someone's paying attention, hi hi.

Anyway- I guess we're getting nit picky here, hihi. To me an EDZ is basically a dipole fed w/parallel line cut to a defining length. Loss via coax, Loss via tuner... hmmmm.... gain via lobes, what about coverage for areas in the nulls... trade offs trade offs...

I really intended to made a point that it's one thing when a manufacturer makes a product and holds it's out to be something better than it really is... my impression of certain mentioned company down here in the southern region is that they don't do that. Perhaps Hy Gain antennas are marketed as such but those are good from all reports I hear- and the Patriots [back to verticals again] aren't "cheap" nor are they inexpensive- but this company you mentioned makes those less expensive alternatives also- while the the quality is still good even for the lower cost. That company makes a lot of stuff...and I for one am appreciative of the fact they do- I mean one can't expect Lexus quality and performance from a Hyndai. But for those that are limited to the Hyndai equivalent market, it's a good thing there's something available. Personally I'm using, a used small Ten Tec Tuner- great heavy duty cabinet. But I did get a nifty, inexpensive, Indoor/Outdoor Thermometer/Clock that works good- and I got it from that place over down yonder in Missisippi. I'm sure some of their products are worse than others. From an economic stand-point I'm glad they exist- it's a market driven economy where competition is a good thing for the consumer market place.

tah tah for now,

D.
 
RE: Antennas for QRP  
by NZ5L on December 19, 2001 Mail this to a friend!
Loss in a tuner is a matter of construction as well as circuit chosen. An inductor made of #28 enameled wire is going to have more loss than one of 1/4" copper tubing no matter what the circuit in use. That said, tuners are still relatively low loss devices (variable capacitors are theoretically lossless) and pay dividends in operating flexibility and, in some cases, harmonic reduction. In a simple circuit (as many QRP units tend to be) they add an extra tuned circuit that aids on receive as well. I'll be the first to admit that no single antenna is right for everybody, but that doesn't mean there is nothing much to choose between a simple dipole or vertical and a multi-element beam. (If you don't think 3Db is worthwhile, operate for a month at half your normal power with your usual antenna and see how it goes.) The point is that most QRP signals can get a significant boost without making a significant investment if you have the desire (and/or space) to try out something new. I always read antenna articles and have tried several over the years. If you have a good idea please share it. Ham radio is an activity where everybody can win.
 
Antennas for QRP  
by KD6JLS on December 21, 2001 Mail this to a friend!
I'd be interested to know what you guys think about J-pole antennas for QRP. I'm going to be buying an FT-817, and will need an antenna to use on 10m SSB (I'm a Tech Plus). I have very little space, so a vertical antenna is a given. I'm just trying to decide between a "standard" 1/4 wave vertical with radials, or a "copper cactus" type J-pole. I've been holding on to an article on how to build a copper cactus for years, so I thought I'd give it a try. Is a j-pole made from copper tubing efficient enough for low power operations? Any thoughts would be appreciated. Thanks.

Mark KD6JLS
 
RE: Antennas for QRP  
by K4IA on December 21, 2001 Mail this to a friend!
Check out http://www.geocities.com/aa5tb/efha.html for more info on J Poles and end fed half wave length antennas.
 
Antennas for QRP  
by N3FG on December 27, 2001 Mail this to a friend!
I have a dipole at 35 feet, a full wave loop (top at 35 ft.), and a vertical with radials at 20 feet. More often than not the vertical & the loop outperform the dipole for DX.
 
Antennas for QRP  
by K7UGQ on December 28, 2001 Mail this to a friend!
Obviously you prefer wire antennas. Nothing wrong with them unless you preport to write an article about "Antenna for QRP" and fail to address all or most of the other very very good antennas for QRP. Additionally you failed to appreciate that very few hams have the real estate to errect full wave dipoles for the popular low band qrp activity.

Although I am not a fan of vertical antennas you were not totally correct in your effeciency statements about them. Several companies (Not only Gap) have pretty efficient verticals albeit as long a good ground system is in place. One even has taken the dipole and turned it 90 degrees to the vertical!

I use magnetic loops and large electrical loops for my qrp operation. They perform very well, consume little real estate and compare or exceed the basic diople antenna.

 
RE: Antennas for QRP  
by KG4PYM on December 28, 2001 Mail this to a friend!
So, I have a Windom now up at 33' [trees didn't allow flat-top "full" 1/2wave 40m placement]. It's a Van Gordon (I think, really it looks like one but was HRO generic) G5RV pruned to 66' overall for coverage on 40m up. It even came with the RF 1:1 choke balun where the twin-lead [300 ohm] terminates to the RG8X. Seems to work great especially on 20 and above. My suspicion is that most of my 40m DX is attributable to the *31' twinlead* "vertical" section. Although the "dipole" part is 1/2 wave overall- OCF 14%, it's only 1/4 wave above ground, so from what I could find it makes any take-off angles fairly much too high for good DX work. (I guess).

I was going to trim the vertical radiator thinking it might enhance DX performance on the higher frequencies; I really modeled it after Radio-Works' Carolina Windom but hoped to gain more efficiency by not using coax for the vertical and not using a top-side balun- but keeping the "line isolator."

However I find no other radiation patterns for Windoms, and the effects on performance of this antenna given varying lengths of vertical radiating sections seem elusive... perhaps given the combination of polarizations...who knows? Might anyone have any data/info- theoretical or other on the subject of Windoms?

It seems to work very well on 10 and 20, okay on 40, but it has shined on qrp on 20. It's gotten through it's fair share of recent 10m CW pile-ups with 80-100watts...so I'm reluctant to mess with it now that it's hung. I was going to shorten the 31' "vertical radiator" but now wonder if the difference would be appreciable enough to warrant the trouble...and if I did trim it, would 40meter DX performance suffer because of it?

A current 40m commercially available model has the vertical section at about 10' and probably or maybe this was chosen via field-test data and taking into account other variables such as velocity factor.

Comments/Ideas? Anyone? Good bad or other?
Even any theory on the matter would be greatly appreciated!

Best to All,

Darin.
 
RE: Antennas for QRP  
by KG4PYM on December 28, 2001 Mail this to a friend!
BTW i think QRP with-

- magnetic loops is- awsome. Are those indoor loops? Are they very directional? If they are I'd say perhaps it makes up for any bother concerning bandwidth... and if they are like little beam antennas you could steer them as needed- whereas a real kicker of a EDZ at a 1/2 outside may not have that option [no coverage in the nulls]. Fairly bi-directional I heard [so there's a hoorah for the verticals! hi hi hi].

Which could become a disadvantage if you're say, the FOX.

It's all good to me! This just shows the wonderful resourcefullness of hams in general.

QRP magnetic loops- wow, I think that's really cool.

D.
 
Great portable, mobile, or fixed 6m antenna.  
by W8KQE on December 29, 2001 Mail this to a friend!
For those six meter fans who prefer a portable, smaller footprint, broadband antenna, the horizontally polarized PAR Electronics OA-50 omniangle loop antenna (or similar design) just may be your ticket. I work almost everything I hear with this thing while running low power, and it comes 90 % constructed already (for those of us with time constraints)! It is also stackable of course. I cannot say enough good things about the PAR OA-50!!! It has been a godsend for me lately!
 
RE: Antennas for QRP  
by AA2IZ on December 30, 2001 Mail this to a friend!
Well, I'm going to add my 2 cents worth to the tuner loss part of this discussion. In my view, often tuners are asked to operate under conditions in which they become very lossy.

The first such condition is when matching up to an antenna that presents a large SWR. For instance, a doublet antenna, being operated well away from resonance. It is not at all unusual to have ratios of 8 or 9 to 1 in such cases. This gives rise to VERY large circulating currents in the tuner. An amazing large number of amperes can be circulating in the coil. This leads to the obvious I squared R losses in the coil. This is one of the main reasons that some expensive tuners are made with edgewound coils constructed from bar stock or tubing.

The second such condition is when using a tuner with a built-in Balun, to feed a balanced antenna with a high SWR situation. Loops and doublets fed with 450 ohm ladder line are obvious examples. In addition to the coil losses mentioned above, there will be large eddy current losses in the balun. Ever wonder why they wind these baluns with expensive tapes and other insulators ? It's cause of the losses, which make them HOT.

Of course, proper design helps.

But, I think we have to say that tuners are indeed very lossey under some circumstances.

73 de Gary
 
RE: Antennas for QRP  
by NZ5L on December 30, 2001 Mail this to a friend!
K7UGO ; In my 40+ years of active hamming, I have used a large variety of antennas: several verticals, 4 commercial yagis and a few homebuilt ones, a 2 el. homebrew multi-band quad (the most effective) delta loops and the aforementioned wire antennas. I don't mean to shortchange any design, as all have their merits. However, the thrust of my article was two-fold: 1. effective (efficient) antennas for QRP use and, 2. low cost designs. Now that I am a retiree, $ outlay has assumed more precedence than it had formerly. Some hams have some real estate (I have only 1 1/4 Ac., enough for the examples mentioned) and using that resource and wire is presently the most efficient for me performance wise and esp., COST wise. Personally, the beam and tower route is great for QRP, as are phased vertical antennas. Both take more effort and money than the examples I gave. Actually, I believe whatever works for you is the best antenna. For me, from San Antonio, my phased Butternut HF-2Vs did the trick. From DU-land, the cubical quad and rhombic. As the situation changes, we have to change with it, there are no absolute right or wrong antennas - only what you can afford and how you deploy it. This article was intended as a thought provoker. Evidently it worked.
 
Antennas for QRP  
by PHINEAS on January 4, 2002 Mail this to a friend!
I made a portable ground plane vertical antenna made from the bottom part of a mic stand, a modified 3/8x24 mirror mount(The kind that truckers use for CB antenna), some of that aluminum ground wire from radioshack, 2 u-bolts, and some old junk CB antennas. All I did was drill some holes for the GPs. I am using 50 ft of RG58, and a cut CB antenna for 10 meters, and a 54" piece of pipe for 6, and 2 meters. This setup rocks. all I have to do is change the antenna if I want to change the band. I am using 8 GP radials @ 27" long made from the aluminum ground wire.

Took me 30 minutes to build, and sets up in 5 minutes or less. I get good reception, A little gain(at least 3db from my measure according to my measurements, and a good radiation angle. Talked to Japan on 25 watts on 10 meter with the antenna just 10 feet off of the ground.

Not a pretty antenna, but works great...cant wait till spring to try it out by a lake!!!!

Phineas
KC0LSC
 
Antennas for QRP  
by N0TONE on January 6, 2002 Mail this to a friend!
WB2WIK, I am fascinated by your bolometer measurements of the vertical antennas. It is so rare to see someone actually performing scientific investigations instead of gut feel.

I have a few questions for you.

First, how did you prevent the vertical radiator from transferrring its heat to the air? I would think that without putting the vertical in a vacuum, you would most likely underestimate how much power was being turned into heat by a factor of about 10. Or did you mathematically compensate?

Also, how did you measure the heating of the earth? I can measure some very strong electromagnetic fields underneath a ground plane, therefore it is obvious that the earth is being heated by RF.

My own experiences with verticals suggest to me that for restricted lots, they are best avoided. You need a ground plane, which will occupy the same horizontal distance as a half wave dipole at the same frequency. But, if you end-load or trap the dipole, you make it shorter. My measurements with end-loaded or trapped ground plane wires suggests that although you can achieve resonance by doing that, you have radically increased the amount of earth you expose to the RF fields.

This all becomes irrelevant if you can get the vertical system, including ground plane, elevated a half wavelength or so, then the RF fields impinging on the earth will be notably weaker, and thus won't be so effectively converted to heat.

Curious about your measurements....

AM
 
Antennas for QRP  
by KE0VH on May 16, 2002 Mail this to a friend!
OR QRO. The small EH antenna design works and works very well. I have written an article that should appear soon here at EHam with details. Check out the links to www.eh-antenna.com or www.qsl.net/w0kph. These antenna's are 2% of hertz antenna size and extremely efficient (sometimes near %100). At least check them out. They do work as I have proven to myself (I am a broadcast engineer and work with antennas alot)with the 20 meter version of the pole EH antenna. It is only 14 inches long and 2 inches in diameter. This could revolutionize apartment dwelling and covenant restrictive neighborhood operation, plus be a dream for field day or portable.

73' AT LEAST CHECK IT OUT!! :) KE0VH
www.geocities.com/ke0vh
 
Antennas for QRP  
by VE3DDY on August 27, 2002 Mail this to a friend!
Hi Guys,
I'm new to this group but QRP antennas is my passion.
The absolute best Antenna that I have used for QRP is a folded monopole vertical on 40 meters.
This vertical has greatly increased radiation efficiency and is easy to build and deploy. The antenna radiating element consists of 2 parallel 34 ft long wires , spaced by 8 to 12 inches with plastic strips every 24 to 30 inches or so. The top end that is hauled up into a tree is shorted together. The bottom end is connected to either side of an insulator.
Connect your balun across the insulator and connect the other wire at the bottom of the insulator to ground. The 50 ohm coax connects to the antenna via a 4:1 balun.
Ground is a short 2 ft length of copper pipe thrust into the dirt and it has 2 -36 ft radials connected there as well. Occasionally I'll pour some salt down the pipe followed by some water to assist the ground conductivity. I don't know if this wetting action has any merit but I feel good about it.

Now, the radiator can be "enhanced" by suspending a close spaced director or a full wave loop director in front of the vertical. My loop that I used was made from a loaded shortened 80 meter dipole and was hung in a delta 30 ft per side . As a closed loop it was a director on 40 meters as it was a loaded full wave (minus 5 %)at that frequency.
The loop was within 24 inches of the antenna at the top
but the base was pulled away from the radiator to about 20 ft.
You don't have to have the delta element but it gives great directivity and is easily moved around the base of the vertical to change direction. You just have to pull up 2 stakes and run around to the selected direction and poke them into the ground again.
I don't know how much gain The system gives but you should consider the gain of a driven element and a close spaced director in the antenna literature. Theoretically this can be as high as 5 db.
If you don't have a convienent tree to sling a line over, consider the vertical fiberglass masts by MFJ.
(Don't use the top thinnest section but tie the mast bottom to a vertical 4 ft piece of wood planted firmly in the ground adjacent to the ground pipe.
Somebody else try this antenna. It works.
A word to tuning.
To tune for 7 Mhz use the MFJ antennalizer at the 3 rd harmonic (21 MHz) You won't get a decent reading at 7 mHz. Can anyone explain why?
With a 4 :1 balun, tis antenna will operate (using a tuner) on all bands 80 thru 10M but the gain will be evident on 40 meters for which it is primarily built.
72/73
Jim
VE3DDY
 
Antennas for QRP  
by VE3DDY on August 27, 2002 Mail this to a friend!
Hi Guys,
I'm new to this group but QRP antennas is my passion.
The absolute best Antenna that I have used for QRP is a folded monopole vertical on 40 meters.
This vertical has greatly increased radiation efficiency and is easy to build and deploy. The antenna radiating element consists of 2 parallel 34 ft long wires , spaced by 8 to 12 inches with plastic strips every 24 to 30 inches or so. The top end that is hauled up into a tree is shorted together. The bottom end is connected to either side of an insulator.
Connect your balun across the insulator and connect the other wire at the bottom of the insulator to ground. The 50 ohm coax connects to the antenna via a 4:1 balun.
Ground is a short 2 ft length of copper pipe thrust into the dirt and it has 2 -36 ft radials connected there as well. Occasionally I'll pour some salt down the pipe followed by some water to assist the ground conductivity. I don't know if this wetting action has any merit but I feel good about it.

Now, the radiator can be "enhanced" by suspending a close spaced director or a full wave loop director in front of the vertical. My loop that I used was made from a loaded shortened 80 meter dipole and was hung in a delta 30 ft per side . As a closed loop it was a director on 40 meters as it was a loaded full wave (minus 5 %)at that frequency.
The loop was within 24 inches of the antenna at the top
but the base was pulled away from the radiator to about 20 ft.
You don't have to have the delta element but it gives great directivity and is easily moved around the base of the vertical to change direction. You just have to pull up 2 stakes and run around to the selected direction and poke them into the ground again.
I don't know how much gain The system gives but you should consider the gain of a driven element and a close spaced director in the antenna literature. Theoretically this can be as high as 5 db.
If you don't have a convienent tree to sling a line over, consider the vertical fiberglass masts by MFJ.
(Don't use the top thinnest section but tie the mast bottom to a vertical 4 ft piece of wood planted firmly in the ground adjacent to the ground pipe.
Somebody else try this antenna. It works.
A word to tuning.
To tune for 7 Mhz use the MFJ antennalizer at the 3 rd harmonic (21 MHz) You won't get a decent reading at 7 mHz. Can anyone explain why?
With a 4 :1 balun, tis antenna will operate (using a tuner) on all bands 80 thru 10M but the gain will be evident on 40 meters for which it is primarily built.
72/73
Jim
VE3DDY
 
RE: Antennas for QRP  
by KD2JC on December 7, 2002 Mail this to a friend!
I agree with Rick, the Loop has been a performer for me on QRP over the years. I have a 40 meter loop (in the vertical position) and have been using it with great results with an old Heathkit HW-9, several homebrew projects and more recently with the K-1. The K-1, with the ATU has handled the Loop well on 80, 40 30 and 20 meters.
73/Joe?KD2JC
 
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