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Directional 75M DX Receiving Antenna




 
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« Reply #25 on: February 25, 2009, 02:16:45 PM »

Steve, do tree trunks ruin the pattern on either of these antennas.     The only place I have is full of tall pine trees,  the type that has about 80 ft of trunk with the rest of the tree up high.    One of them ought to be a good center support for the K9AY type.    I was thinking of putting up a simple terminated one for 75M aimed NE.   That would be good for the New England and east coast AM'ers in the day and the SSB DX window at night.    I don't have much for 160M to transmit and just PW on the power for 160M.
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« Reply #26 on: February 25, 2009, 02:31:55 PM »

Steve, you posted some good info on beverage construction.

How about some links to K9AY construction info.  I haven't done a search lately, but in the past, most of  my searches took me to discussion forums about K9AY loops, but I couldn't find much on construction details.

I built a non-directional low-noise horizontal loop per the K6STI article in Sept 95 QST, but the results were disappointing.  It is supposed to be insensitive to ground wave signals but respond  well to sky waves, and he even published computer modelling data to demonstrate, but mine never worked any better than a random length piece of wire tossed out the shack window.

Isn't it supposed to be relatively easy to construct the K9AY so that it uses a single pole, and configure it so that it can be physically rotated by hand to null out noise or local QRM, kind of like manoeuvring the sail on a sail boat?
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« Reply #27 on: February 25, 2009, 02:36:30 PM »

I can easily hear 1-land AM stations, even those in Maine during the day, at least during the winter months. In December, I could hear these stations as early as 1300 local time. But that was only on the K9AY. With the dipole, many stations were in the noise. I don't see much improvement on most AM signals at night, except for longer distance ones, like the Midwest and West coast.


I notice the same thing in the day when signals are at least 300 miles away.  The optimum angle during the day on 75M is usually LOW cuz of the absorption.  I find the Tron (300 miles away) is usually MUCH louder on the high NE quads during the day. When he uses his wire array also, we can talk at 1PM, no problem. But when we each use a low dipole, it's very noisy.  However, at night, the difference is small and even sometimes in favor of the dipoles cuz the optimum vertical angle is much higher between us at night.



BTW, Bob, the trees won't bother your 75M antennas. I know guys with full blown 4-squares made of wire hanging from trees in the woods and they are some of the best ears and loudest into Europe. My bevs run thru the woods and work really FB as well as many thousands of others around the world.

However, on 6 meters I have done some tests while tuning Yagis. When I suspend a Yagi from a tree limb to tune to 1:1, I can rotate it so that the elements are within a few inches of leaves and tree branches - the swr will move up to over 2:1 or more. So there is a limit in frequency - maybe 28 mhz or so when foliage can have a meaningful effect.

I was told to be above the tree forest when beaming on 6M, or expect attenuation. Since then I always place my lowest Yagi in a 6 meters stack at least 70' high to clear any trees in the area.

T
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« Reply #28 on: February 25, 2009, 02:45:31 PM »

The Beverage is a section of transmission line (single line over ground plane)terminated in its characteristic impedance.  The ground plane is lossy and so the resulting radiation pattern, as opposed to a perfect ground plane/transmission line and no radiation coupled in or out.

Tom,

To add to your comments....  I understand some guys have said that their Bevs worked poorly when run over highly conductive ground like swamp land.  I would be interested in seeing the relative patterns of a Beverage over standard rocky soil (like here) and over something like super good soil OR even over ocean salt water.  That shud shed light on this idea even more.

I would model it myself, but my old MiniNec DOS program from the 80's is good only for wire arrays and Yagis, and does poorly over ground dependant systems. I would also lose hundreds of old antenna models I've developed over the years by using the  new format... sigh   (But I really need to upgrade it... :-))

T
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« Reply #29 on: February 25, 2009, 03:00:50 PM »

The Beverage is a section of transmission line (single line over ground plane)terminated in its characteristic impedance.  The ground plane is lossy and so the resulting radiation pattern, as opposed to a perfect ground plane/transmission line and no radiation coupled in or out.


I would model it myself, but my old MiniNec DOS program from the 80's is good only for wire arrays and Yagis, and does poorly over ground dependant systems. I would also lose hundreds of old antenna models I've developed over the years by using the  new format... sigh   (But I really need to upgrade it... :-))

T


Give mmana-gal a shot.  It's somewhat freeware, does a GREAT job, and has NEC plugins.

Again, You'd not so much lose your old stuff, but would be starting over from scratch.

I've used it on Win XP 32 bit as well as X64 Vista.  No problems, and comes with a WEALTH of "off the shelf" antennas in it's library..  Both commercial and 'homebrew'.

I even found quite a few beverages on it, just need to figure out how to add the loading constants into it..  It WILL accept loading coils, I just haven't figured out HOW to model them myself.

Not in any way shape or form affiliated with them, just a happy freeware customer (they  also make a commercial version that's supposed to be more accurate, etc....  It pretty much matches what I've seen other places for accuracy, though).

I even figured out how to GRAPHICALLY enter antennas, makes things LOADS easier than having to graph paper it out (which is why I DON'T antenna model on NEC style proggies).

--Shane
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« Reply #30 on: February 25, 2009, 04:52:24 PM »

Anyone have any experience with phased loops or with the (expensive) DX Engineering phaser?

I use a small tuned loop to squash the big noise from somewhere.  It makes a huge difference, a night and day difference.  I aim the loop null at the noise and get a huge S/N difference.  I forgot the dB difference but it's amazing.

I'm pondering two of these phased.  Anyone doing that?
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KL7OF
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« Reply #31 on: February 25, 2009, 05:50:15 PM »

I agree with K1JJ on the effect of trees on low band antennas...I live in the tall trees and my experience is that the RF doesn't even "know or see" those trees until around 10 megs...My advice (from my experience) on beverage antennas is to put up whatever length you can, even if it is only as short as 60 ft...because in some situations it WILL receive better than your tx antenna...
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Steve - WB3HUZ
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« Reply #32 on: February 25, 2009, 05:53:08 PM »

As Tom said, no. Trees won't be a problem. Remember, you only need a 25-30 foot high support for the K9AY. You could run a a rope from any tree to the ground at the right angle and get the 25 foot support. Or a single pole made of PVC or other light mast material. The loop can make up part of the guy assembly, if needed.


Steve, do tree trunks ruin the pattern on either of these antennas.     The only place I have is full of tall pine trees,  the type that has about 80 ft of trunk with the rest of the tree up high.    One of them ought to be a good center support for the K9AY type.    I was thinking of putting up a simple terminated one for 75M aimed NE.   That would be good for the New England and east coast AM'ers in the day and the SSB DX window at night.    I don't have much for 160M to transmit and just PW on the power for 160M.
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Steve - WB3HUZ
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« Reply #33 on: February 25, 2009, 05:55:47 PM »

Attached is the original article by Gary Breed.




Steve, you posted some good info on beverage construction.

How about some links to K9AY construction info.  I haven't done a search lately, but in the past, most of  my searches took me to discussion forums about K9AY loops, but I couldn't find much on construction details.

I built a non-directional low-noise horizontal loop per the K6STI article in Sept 95 QST, but the results were disappointing.  It is supposed to be insensitive to ground wave signals but respond  well to sky waves, and he even published computer modelling data to demonstrate, but mine never worked any better than a random length piece of wire tossed out the shack window.

Isn't it supposed to be relatively easy to construct the K9AY so that it uses a single pole, and configure it so that it can be physically rotated by hand to null out noise or local QRM, kind of like manoeuvring the sail on a sail boat?

* k9ayarticle.pdf (159.2 KB - downloaded 293 times.)
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KD6VXI
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« Reply #34 on: February 25, 2009, 08:42:13 PM »

As Tom said, no. Trees won't be a problem. Remember, you only need a 25-30 foot high support for the K9AY. You could run a a rope from any tree to the ground at the right angle and get the 25 foot support. Or a single pole made of PVC or other light mast material. The loop can make up part of the guy assembly, if needed.

I wouldn't bet on the PVC...  Nuke it in the microwave first.

I learned the hard way at 1750 meters, PVC DOES interact with RF.

If it warms in the nuke, it will interact.

I seem to remember it was pigment / dye specific, not MFG...  Some colors where worse than others.

--Shane
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Steve - WB3HUZ
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« Reply #35 on: February 25, 2009, 10:37:14 PM »

Remember, this is a receive antenna, so I don't think PVC would be a problem. And it's a center mast, the antenna only comes near it at one point. Also, years ago, I built a small receiving loop (about 3-4 feet across) using PVC as the spreaders and it worked FB.
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« Reply #36 on: February 26, 2009, 09:55:52 AM »

The 4th Edition of ON4UN's Low Band Dxing book has extensive details on just about any receiving antenna that has been described in print.

The problem with phased Beverages is that they are monobanders wheras I find the single wire usefull thru 30M and have even used on 20M when snow static wiped out a DXpedition.

With 7 Beverages covering the compass I find that I can hear just fine, its the other end that often cant. Especially if he is in the tropics or in a building in downtown Hong Kong.

Its really hard to take a computer model and compare to real world performance with a Beverage (and many other antennas). A Beverage works best with a poor ground and is a dud over salt marshes, just ask W1KM and others who have tried them. When I operate from our cottage on the Maine coast a rotatable shielded loop is used. At home Im on top of a granite rock pile hilltop that slopes off nicely in all directions; its a location that has proven to work from 160 to microwaves.

The only help there is 10dB+ in the TX department at my end but I dont think 12KW is the way to go. Im already maxed out in antenna gain.

As far as angles are concerned it always helps to have low and high available. Ive worked some of my longest haul DX on 160 at this QTH using an inverted vee with the apex at 50'. I won a 160M contest in the late 80's at another QTH with the xcvr feeding 2 amps with one feeding a vertical and the other a horizontal at 120'. Earlier testing on SSB reported a stronger and steadier signal to W6/7 and Europe as well as full coverage closer in.

Carl
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Steve - WB3HUZ
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« Reply #37 on: February 26, 2009, 10:01:32 AM »

Quote
Its really hard to take a computer model and compare to real world performance with a Beverage (and many other antennas).


To some extent, but it's done all the time. It largely depends on the quality of the model and the power of the modeling program The FCC is even allowing some AM broadcasters to using modeling to do their proofs. The better modeling programs consider ground. I can model a beverage over a salt marsh and see its diminished performance.


You are a lucky man with all those Beverages ove rocky soil!  Grin
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« Reply #38 on: February 26, 2009, 10:21:43 AM »

Anyone have any experience with phased loops or with the (expensive) DX Engineering phaser?

I use a small tuned loop to squash the big noise from somewhere.  It makes a huge difference, a night and day difference.  I aim the loop null at the noise and get a huge S/N difference.  I forgot the dB difference but it's amazing.

I'm pondering two of these phased.  Anyone doing that?
Here are some field test results from noted MW DXer Mark Connelly, WA1ION, who compared phased loops with phased whips and something new to me, floating the feedline and intentionally using it as a separate antenna to phase against the real antenna.   This was for AM broadcast band DX-ing.

http://www.qsl.net/wa1ion/coupler/phased_spaced_antennas.htm

Maybe I'll try something today because it's raining and it is a well known fact that antennas erected in the rain work better than ones constructed during pleasant weather. 
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« Reply #39 on: February 26, 2009, 11:28:03 AM »

The problem with phased Beverages is that they are monobanders wheras I find the single wire usefull thru 30M and have even used on 20M when snow static wiped out a DXpedition.




Yep, phasing Bevs does create a monobander. That's what optimization for one band is all about - a small advantage and a give-up - no free lunches.... Grin

Though it would be easy enuff to disconnect one Bev with the coax jumper and be back to a single system for all bands. But 75M is my main band and I don't even bother.


re: Broadcash band tests for Bevs and K9AY loops: 

We find that the f-b and side rejection works more dramatically on the BC band vs: 75M.  It may be because the BC signals come in at lower angles. Both Steve and I have noticed this big performance on the BC band whereas, switching to the higher angles common to 75M, the performance was reduced somewhat.

That's not to say Bevs don't kick ass on 75M, it's just that the opportunities for lower angle incoming signals seems more domiiant on the BC band.  If we look at the vertical pattern of a Bev or K9AY, we see that the high angle discrimination is poor, whereas the low angle pattern is well defined and sharp.  A high angle view of most DX antennas looks more like an omni-directional affair.

I once put up a rotatable Adcock DFing antenna. I found on 75M, it DFed only signals that were at least 300 miles away and more. The local, high-angles signals made it useless for DFing unless it was mid-daytime when the optimum angle was much lower and liking to the Adcock vertical pattern.

T



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« Reply #40 on: February 26, 2009, 11:28:35 AM »

Phased loop arrays are used by some hams with great results. They've been used in the government/military world for decades in DF operations. You can phase an array of any antenna type, so you don't need to use loops. Loops are nice in that they can be small and are relatively ground independent. And if you choose to remotely tune them, they can make a great hi-Q preselector for your receiver.
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« Reply #41 on: February 26, 2009, 12:09:33 PM »

If the neighbors are OK with it  FB OM...There are stealth beverage extensions as well..I know a fellow that stapled his beverage along the wooden fence that runs the length of the alley behind his house.....and then there is the BOG (beverage on ground)   I have used a BOG before (insulated wire) with very good results...


The K9AY is even wider on the front lobe  - 130 degrees at the 3 dB points compared to about 90 degrees for the Beverage , so I'm hoping to see some improvement with the Beverage.

I'm still trying to figure how I can add some more wire to the Beverage (think neighbor's yard).  Wink
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Steve - WB3HUZ
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« Reply #42 on: February 26, 2009, 12:20:35 PM »

Quote
We find that the f-b and side rejection works more dramatically on the BC band vs: 75M.  It may be because the BC signals come in at lower angles. Both Steve and I have noticed this big performance on the BC band whereas, switching to the higher angles common to 75M, the performance was reduced somewhat.


For sure. The propagation is much more constant during the day on the BC band. It seems the angle of arrival (AO) varies little. Such is not the case on 80/75 meters at night.

There was a very good example of this during my QSO with Don - K4KYV on 3685 kHz last night. We both saw what looked like fairly major changes in the AO several times during the QSO.

He was receiving on either a Beverage or a dipole. I was receiving on either a K9AY or a dipole. At times Don was much stronger on the K9AY. Other times he was much stronger on the dipole. I saw differences of 10-20 dB. Don was seeing much the same on his end. When I was hearing him best on the K9AY, he was hearing me best on the Beverage. When he was hearing me best on his dipole, I was hearing him best on my dipole. We both used dipoles on transmit throughout.

Don is about 550-600 miles from me. The QSO was from about 9-10 PM ET. We both noted that we should set up a diversity system using both antennas simultaneously. Fading would probably be a thing of the past. Cheesy
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« Reply #43 on: February 26, 2009, 12:52:05 PM »

Quote
We find that the f-b and side rejection works more dramatically on the BC band vs: 75M.  It may be because the BC signals come in at lower angles. Both Steve and I have noticed this big performance on the BC band whereas, switching to the higher angles common to 75M, the performance was reduced somewhat.


For sure. The propagation is much more constant during the day on the BC band. It seems the angle of arrival (AO) varies little. Such is not the case on 80/75 meters at night.

Don is about 550-600 miles from me. The QSO was from about 9-10 PM ET. We both noted that we should set up a diversity system  Fading would probably be a thing of the past. Cheesy


"using both antennas simultaneously."

That's how my Bev / quads diversity receiving system works now.

Though, a true "voting" diversity system would be neat to try too.  This would pick the strongest antenna and use it until the other took over. This is in contrast to the dual diversity system I use that keeps the two antennas on line all the time - and continuosly fed to each ear in a divided dual stereo receiver system that is sync locked.

Since the quads and Bevs are separated by more than a wavelength, I see different fading characteristics on each. When a real weak one is at the threshold, I find myslef favoring one ear or the other as the signal comes in and out. Many times I can get enuff info from the two broken up signals to put together the meaning.  Many times it makes the difference between getting the name, QTH and signal report or not. This is cuz fading on 75M can be slow, like 5 seconds at a time and much is lost in 5 seconds with one antenna.

I hear a lot of talk about "voting" systems on the HF bands, but never ran across someone using one... :-)    I know the regional police repeater systems used to use them, (and probably cell phone sites now) but have not seen a simple circuit that is easily constructed for 75M.

Though, I wonder if the brain integrating two sync'd receivers (using stereo headphones) is as good or better than a digital switch going from only A or B ?

I think the brain can be trained to be very good at integrating the two signals together vs: using just the strongest of the two - as long as the two signals are within a cycle of each other in frequency phase.

T

We be doing the Funky Electric Slide down the band, caw mawn.
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« Reply #44 on: February 26, 2009, 01:35:33 PM »

I use a small, tuned receive loop so I can point the null at the local HNG (Horrendous Noise Generator).  I suppose I should take a run at the local power company instead but the loop really works well.  I'm hoping to use two, space them, point each at the HNG and try phasing them for some directivity. 

A Beverage running under a power line would be overwhelmed by noise, wouldn't it?  I could maybe squeeze in a 400' NE Beverage but I have never tried it because I supposed it would be hopelessly noisy.


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« Reply #45 on: February 26, 2009, 04:43:16 PM »

A terminated Beverage is a transmission line that exhibits a velocity factor dependent upon the ground conductivity; that VF affects the tilt of the arriving wave. With a good termination it is pretty immune to coupling from other conductors, especially if crossed at 45 to 90* angles. I cross Beverages at about 2-3' spacing and have one that terminates 10' from the street power lines and another that starts at the lines. If there is noise pickup or directivity skewing I dont notice it.

Ive been considering installing a 3 el 160M wire yagi around 10' above ground aimed at the deep Southern polar regions. It should be an interesting experiment as thats a particular area that Ive found high angles to predominate when Im many hours into darkness. I spend less time on 80 but there are parallel similarities.

Carl
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« Reply #46 on: February 26, 2009, 06:31:19 PM »

 
My east/west beverage runs under a 3 phase power line at 90 degrees to the power line.....When the insulators are dusty/dirty I hear some buzz but the antenna is very usable......I had a bev than ran almost parallel to the power line and it WAS unusable...... I took it down because I never used it..


Quote-.-.-.-.-.

A Beverage running under a power line would be overwhelmed by noise, wouldn't it?  I could maybe squeeze in a 400' NE Beverage but I have never tried it because I supposed it would be hopelessly noisy.



[/quote]
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Steve - WB3HUZ
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« Reply #47 on: February 28, 2009, 09:24:01 PM »

Posted earlier about the K9AY improving reception of some AM signals on 75 meters during the day. Attached is a good example. It is Ken-K8TV on 3875 at 2PM ET. Reception is rather noisy on the dipole (you'll hear it first) but much less so on the K9AY. Ken is about 390 miles northwest of my location.

* k8tv28feb091902z3875.mp3 (426.22 KB - downloaded 385 times.)
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« Reply #48 on: March 01, 2009, 09:28:36 AM »

Tom,
Voting systems are actually fairly easy to do for hams with all the receivers in 1 spot. I studied the motorola system when I worked for them. There are a couple ways to do it. First rectify the audio from each radio after filtering out the noise and send the two DC signals to a comparator. The stronger RX has its audio passed to the speaker or headphones. My Racal has another method. Ive never tried it but the hardware is in the AGC to do the voting.
Another method you need two of the same type receiver. Then take the two AGC voltages and vote on the stronger one. The Cubic R3030 receivers have both receivers driving a stereo jack so you hear 1 RX in each ear to let the brain sort it out.
Happy Snow storm
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« Reply #49 on: March 01, 2009, 12:31:07 PM »

Tom,
Voting systems are actually fairly easy to do for hams with all the receivers in 1 spot. I studied the motorola system when I worked for them. There are a couple ways to do it. First rectify the audio from each radio after filtering out the noise and send the two DC signals to a comparator. The stronger RX has its audio passed to the speaker or headphones. My Racal has another method. Ive never tried it but the hardware is in the AGC to do the voting.
Another method you need two of the same type receiver. Then take the two AGC voltages and vote on the stronger one. The Cubic R3030 receivers have both receivers driving a stereo jack so you hear 1 RX in each ear to let the brain sort it out.
Happy Snow storm

Hi Frank,

Thanks for the info. They sound like good methods. It would be pretty cool for moderate to strong signals like when working AM signals during the day.. 

The problem is when signals are near the noise floor, like when the voting system might be very useful, the noise dominates the agc (or audio) that is used for voting selection. I imagine it would become quite unstable.

I think the dual diversity system using continuous signals into stereo headphones for the brain to integrate and decide which is best is the preferred method for weaker signals. 

We were on last night working Eur and even though one antenna was louder than the other, I STILL found the info coming from the weaker antenna (in diversity) to be helpful when filling in the QSB gaps.

T
 

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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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There's nothing like an old dog.
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