HFU HF Underground
General Category => General Radio Discussion => Topic started by: Beam Tetrode on September 08, 2010, 0338 UTC
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Hey folks,
I'll be setting up my first Beverage sometime this week (when the wire spool finally arrives).
I've read through many resources, Including W8JI (http://"http://www.w8ji.com/beverages.htm")'s construction manual and the ARRL Low Band DXing book.
However, these books are written by Hams for Hams.
I am not interested in listening to bored retires talk about their grand kids
and their glaucoma medications ::), I want to use it to listen to Pirates.
Does anyone in the Pirate community have any piraty tips for me?
Would a jolly roger help?
Should I use discarded peg legs for supports?
Thanks in advance.
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Loop - have you tried building a loop? ... a 2' to maybe even a 4' diameter tuned loop ... you won't be disappointed ... ONLY if you've never tried one and seen how quiet they are compared to dipoles or verticals (not sure about a Beverage tho), if you have tried a loop, disregard this post :) :) :) . I tried a vertical about a month ago here at the QTH, full 1/4 Lamda vertical, 35' straight up cut/tuned for 6.93 MHz with ground radials ... and - MAN was that thing noisy!!! QRN out the wazoo ... worse, far worse than the dipole even ...
Technical/advanced hobbyists and theorists only - verifying/measuring vertical antenna resonance:
http://www.youtube.com/watch?v=OD2cslsbrQ0
Anyway -
This simple loop version worked pretty darn good, I've tried sizes from 1' diameter to 3' diameter:
http://www.mtmscientific.com/swloop.html
An article that is a little more technical; note also the coupling loop (to the receiver) is down low to the loop; this helps in coupling out a little more signal (real easy to try things; I used plastic clamps from home depot to 'mount' and move things like the coupling loop around for testing):
http://www.qsl.net/pa3hbb/magloop2.htm
Added:
You do realize, that this is not a good low-angle antenna, and for DX on HF you could have an incoming signal at 20 degrees elevation (from W8JI site; vertical omni included for comparison):
Antenna Type RDF (dB) 20-degree forward gain (dBi) Average Gain (dBi)
--------------- ----------- ---------------------------- ----------------------
1/2wl Beverage 4.52 -20.28 -24.8
Vertical Omni, 60
1/4wl radials 5.05 1.9 -3.15
Also - your link for W8KI site is broken
(Here's how a link should be embedded in text on a Simple Machines BB:
[ url=http://somesite/]Site Name[ /url ] <-- Note: No double quotes
Just take out the three spaces I added near the URLs!)
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As one that has low-band DX'd for just under 30 years, I will toss in my vote for a loop unless you live in a **very** quiet location.
Peace!
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So far the best low noise/high signal strength reception I've heard - judging from audio clips posted by various pirate DXers - has come from, in no particular order:
- Full wavelength HF loops (check with HFU logs for user ID "desmoface", located in Ohio)
- T2FD (hamsters love to gnaw this bone of contention to death as being inefficient for transmitting, but SWLs seem to report they're generally satisfied with the design)
- Exotic less-than-full-wavelength loops, flags and pennants (KAZ and others)
I use a smallish indoor magnetic loop (around 3' wide by 6' high) made from coaxial cable mostly to tame high suburban RFI. It's only the best compromise for my particular situation, and far from the best antenna. I got better reception with a cheap Radio Shack random wire kit in the rural area where I used to live, but you do what you have to for the conditions.
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Thanks for the replys guys.
I just moved onto a nice big property in the middle of the Yukon Wilderness.
There is little to know RFI neer me and everything I want to hear is to the South
so the beverage's directivity is a big plus.
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OK, first of all small loops are going to be more quiet than many other types of antennas. However, keep in mind that part of the reason is that small loops are also very inefficient.
Small loops are great if you can not put up a full sized antenna or if you want a second, directional, antenna that can null noise sources.
In general the physically larger the antenna the more signal you will pull in, it is simply about capture area or aperture. So a large antenna will get signals that a small loop cannot. Of course the noise floor will often come up also, but signal to noise is the key, not an absolute lack of noise or not. And very large antennas, even simple wire antennas, can exhibit directionality that must be taken into account. If the main lobes of an antenna are in directions you can not use, and nulls are in important directions, then it will seem the antenna is not working well, when the antenna is really just fine, but the installation is less than optimal.
A good, low noise, large antenna is a full wave sky loop. One cut for 80 meters and about 20 to 30 feet off the ground will work very well for receive applications from AM BCB to about 20 MHz. It works above that freq, but will be best below 20. This antenna would be laid out in a square about 64 feet on a side. Actually, it should be a circle, but a square is a good compromise between support simplicity and performance, it could even be an equilateral triangle, but you would start to get some pretty noticeable nulls in the coverage.
The Beverage is a fine antenna, but if built as a true Beverage it will also have some directionality, so keep this in mind during your planning stage.
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A bev antenna is used for LW and AM BCB bands because signals approach it at very low angles. If you use a bev for 7 megs, the signals will be coming in from a much higher angle, and you will actually have negative 'gain' compared to a dipole at the high angles.
However, this is a good time to point out that experimentation is what it's all about. So, if you want to find out for yourself, go for it!
The best antennas I have used for 7 MHz. area SWLing are-
Large inverted L (over lots of ground wires, fed with 9:1 balun)
T2FD (horizontal, flat config.)
1/2 wave wire dipole (with 1:1 balun feed)
Verticals are OK, if you have LOTS of ground radials and are in a quiet location (I am). But, even the simplest dipoles outperform a vertical for SWLing, hands down.
Seriously, I know the 'expert hams' hate T2FD antennas, we hashed it out a little here not too long ago. However, for SWLing, they are really quiet, and really pull in the signals! Sometimes, I can hear things on the T2FD that I cannot hear on the other 5 antennas. I don't care how they transmit, just talking about SWL applications here.
73!
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Verticals are OK, if you have LOTS of ground radials and are in a quiet location (I am). But, even the simplest dipoles outperform a vertical for SWLing, hands down.
Ground radials can be elevated (located several feet above physical earth)* along with the antenna feed point ... if you are going to actually mount the vertical at __ground__ level (at the level of local physical earth) then the requirement for 'LOTS' of ground radials arises ... for receive, I am going to state that this is not nearly as critical, it makes a BIG difference on the GROUND losses during transmit for sure, but on receive you are 'working' with a signal to noise level already establish by the local and ionospheric environment (as in "QRN" vis-a-vis lighting 'static' discharges) in a similar manner that a small tuned loop works (physically small, but working with a S/N ratio established by 'outside factors').
And AS noted above, the vertical _was_ the nosiest antenna I have ever used ... I cannot emphasize how noisy it was, and this was with direct comparison against 3' receive tuned loop and the dipole ... so I make this statement quite beyond simply repeating the experiences of others ;) ;) ;) :) :) :)
*Reference:
Found it - "HF vertical ground systems experiments"
http://www.antennasbyn6lf.com/2008/08/hf-vertical-gro.html
"Beginning about a year ago I set up a test range in my pasture and began a series of careful experiments on HF verticals with various ground systems including some with elevated radials. Two results stand out. First the NEC prediction that a few elevated radials can be as efficient as a large number of ground radials seems to be correct at least at my site with the test antennas I used."
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I'll second (or third) loop antennas in general. I put up a 132 ft T2FD about 2 years ago, and was quite pleased with the results. Lower signal levels than my various dipoles, but much lower noise levels, so an overall improvement in the SNR.
A few months ago I put up a roughly 635 ft horizontal loop antenna, which is about 20 to 40 ft above the ground, in a roughly rectangular shape. The goal was to have something with better MW reception than the T2FD. So far, it seems to be working well for that, also for HF. I am anxious to try it on LW this winter.
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Just a few more comments concerning your beverage antenna possibility.
From where you are a beverage erected in the proper direction should work very well.
If you terminate the beverage properly it becomes a wonder antenna for frequencies with a minimum of one 1 wavelength of wire or more up to around 10 Mhz where other antennas usually take over as a better choice. I have heard them personally demonstrated on several occasions and instantly became green with envy when a beverage was compared to almost any other antenna, again for stations in the design direction and at the lower frequencies. From your distance reception (beam width) will widen out appropriately to cover most of the lower forty I would think.
Look on an amateur radio website W8JI.com for some realistic comments and installation hints. My own advice would include;
1) Static dissipation with a dc ground must be provided lest your receiver front end go quiet without a whimper. I’ve seen snow static light up florescent bulbs in my own shack when living up north. Beware!
2) Beverages work best (and must be) very close to the ground, however up there make sure the moose population can get underneath or it may not last long. It may need to be 15 feet or more off the ground and they work fine if covered with snow.
The advice given by others which includes using a loop of proper design is quite valid and I would build a loop even if you do erect a beverage. You always need more than one antenna and especially in your case where cold wire comes down in the middle of winter. You may also want to erect a long insulated wire on ground as they also provide low noise reception. I used to have a full wave of wire for 40 meter transmission while receiving on a quarter wave of wire on the ground. Great s/n ratio!
The very best to you and keep us informed how you make out.
Many hours of good listening to you sir!
One note- I just noticed that you had read the articles on W8JI's site. Believe me his advice and experience on low band reception can be used to your advantage. Not all of us blab and whine about our number of or the effects of our medications but some may just be in a position to help and assist from a technological standpoint.
Stay warm ;D
weaksigs
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Rhombic - I'm surprised no one mentioned the Rhombic (including me :) :) ). I thought of it about a week after my first response ...
If you have the room (real estate), the Rhombic can do what I think you want the Beverage to do: directionality.
The Rhombic will give you directionality, but also doesn't have the limitation of a 'low angle of reception'.
A little more info:
http://www.tpub.com/neets/book10/42o.htm
Some interesting history on/of Rhombics:
http://web.archive.org/web/20011116030212/users.neca.com/cummings/rhombic.html
Edit: Spelling!
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Thanks for the link!
I've wanted to learn more about rhombics :)
Peace!
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Beverage demo on 1.816 Mhz
Here is a link that demonstrates the reception between an inverted "L"
antenna and a 720 ft beverage. The beverage is oriented at 55 degrees
from a site in Massachusetts and the demo is performed at 4:00 pm local.
The guy talks a lot but you can hear the signal difference when the
antennas are switched for an "A" - "B" antenna comparison.
Lets us know your beverage plans and please share your experiences.
Have you also investigated "pennant" and "flag" antennas?
Cheers- weaksigs
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Rhombic - I'm surprised no one mentioned the Rhombic (including me :) :) ). I thought of it about a weak after my first response ...
If you have the room (real estate), the Rhombic can do what I think you want the Beverage to do: directionality.
The Rhombic will give you directionality, but also doesn't have the limitation of a 'low angle of reception'.
I did not mention the Rhombic because I was not aware he was looking for directionality. In fact that was why I mentioned beware the directionality of the Beverage, or plan for it.
I have three Rhombics myself, and absolutely love them. One is a 450 footer pointed 270 deg true (South Pacific, Malaysia area, and Australia for me), another 450 footer pointed 035 deg true (Europe, Middle East, and N Africa for me), and the last is a 300 footer pointed 310 deg true (China).
Each of mine has a switched 800 Ohm termination (600 Watt non-inductive, but for receive only use a 1 Watt carbon resistor would be fine) that can be controlled from the listening desk. This means with the termination selected the antenna is directional along its primary axis, but when I switch the termination out the antenna becomes bi-directional, along the axis and reciprocal. This gives me directions of 270 and 090 on one, 310 and 130 on another, and 035 and 215 on the other.
When terminated the Rhombics are also fairly low noise antennas.
The 450 footers are about 240 feet per leg length, which means at 20 MHz the gain is roughly 12 dBd, at 10 MHz the gain is roughly 9 dBd, and at 6 MHz it is roughly 7 dBd. The 300 footer has legs about 168 feet long, meaning about 10 dBd at 20 MHz, 7 dBd at 10 MHz, and 5 dBd at 6 MHz. Those are calculations, not measurements. In the bi-directional mode subtract 3 dB from each of those numbers.
My Rhombics are not really optimized, I built them more to my property constraints than anything else. So, the enclosed angles are not quiet as good as they should be, but pretty close. For example, the 270 deg antenna is 450 feet long and 190 feet across the wide part, it really should be more like 220. Also, they really should be higher. Here I have them at about 30 feet, they would work better if I had them more like 50 feet. But, as we clock winds of 100 MPH about once a year in the region (although I have not seen that at the house) I keep them fairly low and survivable.
I also have a couple of wire V-beams that work well and are again directional. The nice thing about a V-beam is that you only need one tall support (at the apex), but the supports at the far ends can be low, say 8 feet.
I still say that if I for some reason I could only have one antenna, and I need it to be for general use and omni directional, it would be a horizontal sky loop, made as large as I could get away with. I would want at least 60 feet per side, and a height of 25 feet or more. I am, however, very glad I am not limited to one antenna.
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I did not mention the Rhombic because I was not aware he was looking for directionality. In fact that was why I mentioned beware the directionality of the Beverage, or plan for it.
I put two and two together and deduced from his location ('Yukon wilderness') and his inclination towards a beverage that he might be desiring some directionality and gain back into the states ... the original suggestion towards a loop was made before Beam revealed he had 'nice big property' :) :) so ... he could build something with some nice gain *and* directionality too, sounds like a prescription written for a Rhombic!
Token, Beam's original query was about construction details, poles/suppots (peg legs :) :) ) and such - what did you use to hoist/hold your Rhombics up?
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So the Beverage is up, about 1 Meter above ground and 80 Meters Long.
Even at that short a length it is working wonderfully ;D. On 160 and 80 meters
signals are around S2 quieter then my G5RV at 40 Feet, but they are much easier
to hear as the antenna is much quieter.
On the funny bands it works just like Tube Shortwave said, in fact I have not been able
to hear anything above 5 megs on it aside from local CW :-\.
I had never really considered a Loop or a Rhombic, but I have been convinced.
I've decided on a terminated Rhombic as my next antenna project.
I'll keep you all informed, and thanks again for all the tips and information.
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On the funny bands it works just like Tube Shortwave said, in fact I have not been able
to hear anything above 5 megs on it aside from local CW :-\.
So ... numerical result data wasn't convincing?
(copied from the first response - data from chart on W8JI website at the link found in the first post)
http://www.w8ji.com/receiving.htm )
Antenna Type RDF (dB) 20-degree forward gain (dBi)
--------------- ----------- ----------------------------
1/2wl Beverage 4.52 -20.28
Vertical Omni, 60
1/4wl radials 5.05 1.9
Gee, willya look at the "forward gain" at the 20 degree incoming angle ... much signal at 20 dB down *? :) :) :)
Prior to seeing W8JI's chart I had not realized such a big difference existed (btw a beverage and 'sensitivity' related to elevation angle), and tend to be 'skeptical' of off-handed claims unless I can see some numerical data since there are so many old-wives -er- ham tales out there ...
Nice to see some confirmation of what W8JI saw too :) :)
* Relative to a 0 or 1 degree elevation angle
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So ... numerical result data wasn't convincing?
Sorry SW-J, nothing personal against you old bean, I just cant bring myself to trust numbers.
You see, they killed my father...
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Do you detect any significant directivity?
I could use a good antenna for the 4Mhz desert beacons and have the land... depending on the oriientation
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Do you detect any significant directivity?
Yes, there is significant directivity with proper termination.
I used a potentiometer for my terminating resistor because I have no way of
measuring the feed point impedance. The get the proper setting I did the following.
On 80 meters I found a Ham behind me in Alaska talking to someone in the lower 48.
I hooked the output from my rig into a CB, walked down to the end of the beverage,
tuned in the CB on a handheld and then I adjusted the termination resistance to whatever
made the Alaskan's signal fade the most.
Interesting note, the Zo of my Beverage is around 800 Ohms.
Does that seem high?
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On the funny bands it works just like Tube Shortwave said, in fact I have not been able
to hear anything above 5 megs on it aside from local CW :-\.
So ... numerical result data wasn't convincing?
(copied from the first response - data from chart on W8JI website at the link found in the first post)
http://www.w8ji.com/receiving.htm )
Antenna Type RDF (dB) 20-degree forward gain (dBi)
--------------- ----------- ----------------------------
1/2wl Beverage 4.52 -20.28
Vertical Omni, 60
1/4wl radials 5.05 1.9
Gee, willya look at the "forward gain" at the 20 degree incoming angle ... much signal at 20 dB down *? :) :) :)
Prior to seeing W8JI's chart I had not realized such a big difference existed (btw a beverage and 'sensitivity' related to elevation angle), and tend to be 'skeptical' of off-handed claims unless I can see some numerical data since there are so many old-wives -er- ham tales out there ...
Nice to see some confirmation of what W8JI saw too :) :)
* Relative to a 0 or 1 degree elevation angle
A couple of issues here.
The W8JI data quoted does not really explain why Beam Tetrode is not getting better performance, and, a pet peeve of mine, when is a Beverage a Beverage?
First, the W8JI data does not explain why Beam Tetrode is not getting the performance he should from the Beverage. The quoted numbers, for a half wave Beverage, are not applicable to the areas he is having problems with.
Beam Tetrode has a Beverage that is 80 meters long. He specifically states it works with better signal to noise than his G5RV on 160 and 80 meters but is not working well above 5 MHz. At 5 MHz the antenna is near 2 wavelengths and the 20 degree gain performance from the W8JI chart should be within 6 dB of the vertical. 6 dB is 1 or 2 S units, depending on how your radio is calibrated. 1 or 2 S units are important, don’t get me wrong, but should not equal “I have not been able to hear anything above 5 megs on it aside from local CW”.
The next section is a minor rant from me, feel free to ignore it, but I am agonna say it ;) A half wave Beverage just is not a Beverage, I tell ya! By the way, it is presented here for discussions sake, not arguments sake, if it comes off confrontational that is accidental.
What makes a Beverage a Beverage? The original patent (1381089, filed June 7 1921) claims that the operational affects of the Beverage start at “over” 1/2 wavelength and increases in performance from that point. More recent definitions of the length of a Beverage (and all known real-world applications of the Beverage by it’s inventor, Harold Beverage) are “more than one wavelength”. While this does not mean a Beverage or Beverage like antenna cannot be only half a wavelength it would be a strong indicator that if you want one to work, as a Beverage instead of as a random low wire, they should be “long” in relationship to the wavelength, ie, a full wave or longer.
With this in mind it becomes pretty clear why the W8JI data shows such a high main lobe for a 1/2 WL “Beverage”. A 1/2 wave antenna that is unterminated will display a main lobe somewhat perpendicular to the wire axis in free space. In close proximity to the ground the primary lobe energy towards the ground will be reflected up, adding to and remaining in plane with the perpendicular to wire axis lobe, OK, it can become somewhat more pronouncedly double lobed at this point. Terminating the wire at the far end will “bend” the lobe towards the termination. The velocity of the signal in the conductor is slower than the velocity of the signal in free space, so the longer the wire, the more the lobe will be “bent” towards the termination end.
So, a halfwave Beverage will have a high angle cone in the direction of the termination. The longer the length of the Beverage the lower the included angle of this cone, and the greater the gain in the primary lobe. At a half wave the main beam is pointed up so the gain towards the horizon, relative to a “no gain” (some verticals do have gain, lets assume none for this) omni directional vertical, is down significantly, just over 20 dB if the W8JI data is correct (and there is no reason to believe it is not). The main lobe itself of the Beverage may have more gain than the vertical (probably around 3 dB if the vertical is 1/4 wave), but it is pointed more up in relationship to the vertical.
As I said above, the longer the Beverage the more this main lobe comes down towards the horizon and, at the same time, the more gain the main lobe has. And thus the gain delta at 20 degrees between the vertical and Beverage is down to about –6 dB by the time the Beverage is 2 wavelengths long. However, the gain in the main lobe is now up around +4 dBi or more. So, the longer the better, but also the more directional.
But all of this is plotted along the wire axis. The main lobe at the horizon and some angle (angle depends on antenna length and other factors) off the axis of the wire in the horizontal plane will be many dB up from the vertical omni performance. These main lobes on the horizon still will not have as much gain as the main lobe up does, but it is closer to the theoretical.
Placement of a Beverage, or any other fixed directional antenna, is important because once placed they are going to work well in a specific direction and, by design, not so well in others. With a Beverage think about where you are placing the lobes, not just the wire axis, a long enough Beverage (say over 3 Lambda) should start to blur the lobes with the wire axis. With a Rhombic the central axis is the lobe axis.
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I put two and two together and deduced from his location ('Yukon wilderness') and his inclination towards a beverage that he might be desiring some directionality and gain back into the states ... the original suggestion towards a loop was made before Beam revealed he had 'nice big property' :) :) so ... he could build something with some nice gain *and* directionality too, sounds like a prescription written for a Rhombic!
Token, Beam's original query was about construction details, poles/suppots (peg legs :) :) ) and such - what did you use to hoist/hold your Rhombics up?
Yep, I missed the post he made about location and did not see a need for directionality, I do see it now and agree.
My Rhombics are pretty simple, and light duty. Around here we have high winds, but nothing like ice loading to worry about. Because of the high winds I keep my antennas a bit lower than is optimal and accept the performance hit for the ease of maintenance and lower install cost.
Each of my three Rhombics are built slightly differently from the others, but the basics are all the same.
Each are supported by 4 metal poles, one at each of the four points of the “diamond”, feedpoint end, termination end, and across the middle. If I was going higher or was building a bit more heavy duty I would use telephone poles. Each antenna is about 30 feet above the ground. As I said before two are 450 feet along the long axis and 190 feet across the width, one is 300 feet along the long axis and about 130 feet in width (I don’t have the exact width handy).
At the feed end the antenna the balun is mounted directly to the pole and the pole is hinged at the base so that I can lay it over to work on the feed point. Each of the other three support points use a pulley mounted to the top of the pole, and nylon rope through the pulley so that I can lower the antenna to the ground for work. The apex points across the middle are simple antenna insulators and the wire is allowed to float in the insulator. I have even used ¾ inch sched 40 PVC pipe to make these insulators in the past. At the termination end is a plexiglass plate with eye bolts to accept the antenna wire, and (on 2 antennas) an 600 Watt 800 Ohm non-inductive load, that is slight overkill, mounted on the plate. A 600 Watt termination means I can key down 1200 Watts CW indefinitely, and legal limit for extended periods. In reality a 300 Watt termination should be able to handle legal limit transmissions on SSB with reasonable duty cycles. The third antenna has only a 200 Watt term resistor, it has handled legal limit power, but I try to remember to not push that antenna as hard. Included on the plate is a relay so that I can select the termination or deselect it. With the termination selected the antenna is monodirectional, lower noise, and broader banded. With the termination deselected the antenna is biderectional, but much more peaky in performance as it becomes more resonance limited.
The feedline is 50 Ohm coax, either LMR400 or RG-214, depending on which antenna. I have tried both 9:1 and 16:1 baluns, I saw little receive performance difference between them and I think all three are currently using 9:1. For transmit use I use a tuner at all times, but the raw SWR is not too bad in several bands.
The wire used is not all that important, unless you are running high power, and for receive or lower power (say 400 W or less) transmit applications I have run #18 stranded copper ground wire that can be gotten at places like Home Depot for about $30 for 500 feet.
If you have the land and can orient a Rhombic in a “good” reception direction for you then a Rhombic is a decent choice. But, if you are unsure of your primary reception directions, or want omni performance, than a large sky loop would be my selection.
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A half wave Beverage just is not a Beverage
Agreed, I cut my Bevy to be 2λ at 6.925 (86.6 meters to be exact).
I was on the ball in that regard, however comically futile my precision was.
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Less ice, more liquor.
That's my advice and I'm sticking to it
:D
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Less ice, more liquor.
That's my advice and I'm sticking to it
:D
I was dying to say something similar this whole thread.
Thank you! ;D
Peace!
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It took me entirely to long to realize what you were talking about.