How to build a UHF antenna... - Page 19

I found in a modeling different twists on the 4 bay UHF that the sharper twist seems to be superior to the long twist. It seems to negate the effects of the longer phase line somewhat better.

I would also note that the sharper twist is used by the commercial antenna builders like winegard and channel master.

I would think if the longer twist was superior that the commercial builders would build them that way because it should be easier to manufacture and cheaper because it would take slightly less wire.

Both ways were very close when modeled with only slight differences in gain and impedence.

The 2 bay bowtie for VHF-HI may also get the job done for uhf as well. The one I modeled and built showed decent gain on alot of the UHF channels and worked quite well. Also the 4 bay UHF bowtie without the reflector does an alright job on VHF-HI in fact very close in gain to a 2 bay VHF-HI with out the reflector.

Both antennas I built (VHF-HI 2 bay & UHF 4 bay) were able to get the local stations in my area which are now transmitting on ch's 7,8 & 42 digital and 12,34,40&46 analog and are about 35 -40 miles away.

The 2 bay VHF-HI has some wild receive patterns on UHF which could work either really well or really bad for someone looking to receive stations from different directions on different channels.

I meant a long spiral (or double helix) instead of a short one. But mclapp says the short one works better, so it is moot at least for that design.


Might be more than 3dB as the reflector may narrow the beam (simulating an end fired array) as well as fold it.


I don't remember what the beam width was on mclapps design and it takes a long time to rerun the simulation to check it. The beam may be that wide without the reflector but there is probably some gain loss that far off center.

It is a good idea to attach your TV fool results (before and after transition if different) along with notes about what stations you care about and don't when asking specific questions about your location. You may be better off with a different beam pattern. Best results in your situation may be achieved with a pattern that has a butterfly shaped radiation pattern with a null in the directly forward and backward direction.
Look, for example, at the link I posted recently for the army antenna manual. The look at figure 4-37 where it shows how the beam pattern for the V antenna is formed from the patterns of the individual wires. The pattern of a single wire looks close to what you want suggesting that some form of end fed long wire might work (you would have to do some research). You can probably also get that kind of pattern by taking an existing 8-bay (or side by side 2-bay) design and reversing the phase of one of the antennas. That will probably produce a null front and back and strong side lobes either side. You have to get the impedance right though, you can't just connect a phasing line between two antennas that were designed to produce 300 ohms individually or you will get 150 ohms.
But you can put a balun on each (with one connected backwards) and run a short coax to a good splitter/ combiner followed by a preamp so you don't add more coax weirdness. At least in theory. The two antennas must point in the same direction (between your stations); antennas which point in different directions tend to combine very poorly though they might work if the normal beam patterns overlap. Best to simulate this including the feed lines (adjusting for velocity factor) because there can be some weird transmission line effects.
Look at hdtvprimer's antenna pages.
http://www.hdtvprimer.com/ANTENNAS/ganging.html
http://www.hdtvprimer.com/ANTENNAS/silver.html
http://www.hdtvprimer.com/ANTENNAS/16bay.html (look at the "incorrect" pattern).
And before you try this, make sure the signals actually come from where you think they do by using a highly directional antenna and find the best direction for each and that the strongest signal doesn't come from a reflection or diffraction at an odd angle.

You situation may be a great application for a custom antenna but it can be tricky to do the design work. It illustrates the shortcomings of the mass market one size fits all approach. In many cases, if you aren't too close to the antennas, one weird antenna might serve many people in the same community. Thus there is a potential significant benefit to having a local antenna producer. Luckily, your case isn't too far from stock designs.

I also think there is potential for having a computerized system where you punch in your location and it looks at where the signals are and runs a custom antenna generator program using something like a genetic optimizer then feeds a CNC wire bender to make elements for a custom antenna using stock parts. I posted a link here, with text along the lines of "check out this weird antenna", to an example of where NASA did something similar only they were trying to duplicate the performance of an existing antenna in a smaller package. But you can optimize whatever qualities you want. Signal to noise on specific channels in specific directions given specific signal strengths is easy to make a figure of merit from. Some of the results might be very weird. Imagine, for example, having four "flower pots" at the corner of a 20"x20" square with weird metal "shrubs" growing out of them with elements sized, positioned, and shaped such that they not only exhibited significant gain on the right channels in the right direction but do so in a manner that the combined signals don't trample each other (the hard part). If you have never seen a CNC wire bender in action , there is a video of one on
youtube.

I had a somewhat similar idea, on a smaller scale, when I started working on these antennas. The idea was to optimize an antenna for my city. Turns out when I look at the post transition configuration that there isn't as much room for optimization as I originally thought, post transition requirements are somewhat similar to the one-size-fits-all solution, but there is still some room for optimization.

There is a significant risk that wind blowing trees, annual changes in foliage, or new construction will change the needed antenna pattern.

You situation is also a potential application for a rotator. Reportedly, though people aren't terribly happy with rotators on digital stations because they are hard to tune. And I have yet to see a rotator controller with a smart antenna inteface so it knows what station you are trying to watch. Rotators can be pretty sloppy about their aim, as well.
But a rotator (at least a good one) lets you use maximum possible gain in the direction of the station you are watching (assuming you are only watching one).

Yep, those paints and varnishes arent long lasting outside. But in an attic out of the sunlight, theyll last a good long time.

Actually the easiest solution for attic use is to use what I used on my old closed end 4 bay bowtie. (pictured earlier in the thread) Bolt (screwing is a weaker joint) the whiskers and feedline onto a length of 1/4 inch plexiglass and mount to a wood frame so that no metal part of the elements or bolts touches the wood. 1/4 inch plexiglass (or polycarbonate) can be recycled from a surprising large variety of things, and cut and lap glued (a piece over another piece on the back) together to make a long piece. The extra thickness also helps with increasing the reflector to element spacing on a typical 2 x 4 piece of lumber (3 1/2" - 3 9/16" typical).


Yep, and at 1 rpm, they are painfully slowwwwwwwww. Especially when 2 stations are at 180 degrees apart. That gets old quick. If you only want 2 positions, try the poor mans rotor. Two antenna sets, two downleads connected to one A-B box near the TV. Radio Shack even sells a remote controlled A-B switch.

I buy that it works better in that case. Particularly since it was optimized to work with the other style of phasing array.



That argument doesn't fly. Commercial outfits, in any field of endeavour, often do things wrong. The products are often abysmal. The long twist might be trickier to make, either manually or automatically. If you look at the feed lines on the commercial antennas, they look like something you might produce in a single stamping operation on a small machine. A longer spiral might have a tendancy to stick in the alignment grooves of the die. The cost of a few inches of wire may not be a significant motivating factor.

Your argument is similar to arguing that a curved reflector doesn't make sense because they use essentially flat ones. Yet you found a curved reflector worked better. We both seem to have come up with antennas that outperform the commercial ones. The fact that two companies do the same thing just suggests that they copy from a common source - or each other. I have already posted a couple quotes about a history of this behavior in the antenna field. They may also be copying some of their own behavior from 15 years ago when running simulation.

Incidently, the first recorded mention of the CM-4221 on usenet seems to be in 2000. It wasn't mentioned again for almost 7 years. It was then mentioned one year ago today by someone referencing the work at hdtvprimer. It has been mentioned ten times since then, each time using hdtvprimer's CM-4221 designation rather than the companies 4221 designation. In other words, the buzz rate (mentions per year) on the internet has increased about 70 fold as a direct result of hdtvprimer posting the specs that the company neglected to post all those years.
I learned this trying to figure out how old the CM-4221 was.

Computers then were ten times slower and had considerably less memory than today. Consider the implications of that for antenna modelling which is still painful today. Consider how many little details of antenna design were not fully explored.

Thanks Whitis for the report on wood in post#544. I saved that report.

Anyone know of any other remote controlled A-B switch?

All my search attempts give lots of results because of how vendors have their pages and the search engine methods but no other switch for antennas.

If all the (RF) channels are higher than ch 6 and 180° off-axis, try removing the screen on a 4221 or 4228 bowtie to make it bi-directional, eliminating the need for a rotor. It doesn't always work, but it often works great. Several people in my area, including myself have no-screen 4228s that receive two markets ~170 to 180° apart and 45 to 70 mi away.

There is one exception - scaling. Change all dimensions and you get easily predictable results.
http://www.avsforum.com/avs-vb/showt...1#post13296851

What I find amazing is the expansion of this thread; it took 15 months to get to page 2, and 4 months later we're pushing 20 pages with a huge increase in the quantity and quality of the information presented.

Way to go!
Frank

Thanks everyone for their inputs.

I have attached my TVFool.com for 2009.

I'll list the channels I'm interested in but as a summary;
I am interested in the channels; 11 North, 35 North West, 7 South, and a bunch of UHFs South.

The Channels are: 30, 19, 20, 32, 31, 43, 35, 47, 41, 39, 7, and 11.

The difference between 2009 and now is that the PBS on channel 11 is presently broadcasting on channel 57. NBC on channel 7 is presently broadcasting on 42. The received power of many of the channels is also presently lower then they will be in 2009.

Many map programs like mapquest and google earth put my house at the other end of my street which is a lot lower in altitude. For example, my first floor is about the same elevation as my next door neighbor's second floor.

I have to use my latitude/longitude for tvfool because I think they are also using the wrong end of the street because I do not have LOS and the power a lot lower when I use my address.

A little history of my antenna may also help understand my location.
I have RS double-bowtie antennas. Back in 2001 when I got my HDTV, only the PBS north and CBS south had HD, the other digital stations were only SD at that time. I could get the PBS north of me when I put it in the first floor window facing north. I could get the digital stations south of me just pointing the antenna south. I ended up with two RS double bowtie antennas in the attic. One pointing North, the other South with a A/B switch near the TV.

I am presently using one of the RS double bowtie connect to a DTV converter box, and the other for the HDTV. Both are facing south. I can presently get the PBS north of me on analog 11. This is strange because it is clearer then cable 11 and from the back side of a cheap UHF antenna. However, analog 7 South does not come in clear with the same antenna which is pointing south.

Ganging Antennas is magic to me and I'm hoping I'm be able to get the interested channels on one antenna or on a UHF and a VHF antenna combined together as I talked aboutin post 549. I also plan to split the antenna(s) between 2 or 3 TVs. If worst comes to worst, I'll continue to give up channel 35 (MyN) NW of me.

You may be right but I've worked in a manufacturing environment for 25+ years and usually anything they can do to save a 1/2 cent they will find a way to do it.

Mclapp, thanks again for posting the gain pattern of your VHF Hi bow ties antenna. http://www.avsforum.com/avs-vb/showt...8#post14245728 To me, it shows this antenna is very wide. Do you have a similar plot for your UHF antenna (without a reflector)?


This information is probably spread over several threads and posts. But I cannot find it.

Are their any good public domain (free) programs for antenna simulation which will run on Windows?

I'm pretty sure the a 4 bay without the reflector mounted outside will get you all of the stations that you are getting now and more including the VHF-HI ones. A 4 bay without the reflector should have the gain to match what you have now with the plus of a bi directional pattern and mounting it outside will greatly improve things.
I'll attach the estimated reception patterns for the one I posted the plans for, no reflector and flat elements. You may have to consider an amp somewhere in you line if you start splitting off to multiple TV's.

 

CH30 UHF 4 bay no reflector plot.pdf 16.0078125k . file

 

CH9 UHF 4 bay no reflector plot.pdf 15.9521484375k . file

4nec2 seems to be pretty good I've used it some and it has alot of nice features. http://home.ict.nl/~arivoors/

I'm sure there are others

One amp and one antenna is better then multiple antennas and no amp, IMO.

Basic Question:
How do I relate the Signal Rx(dBm) in TvFool.com to the gain of the antenna?

Ditto mclapp on both antenna recommendation and 4nec2 recommendation.

The only issue with the antenna will be multipath, so the quality of your receiver will matter. In my case, the well-reviewed 6th-gen LG SoC in my CECB isn't nearly as good as my Sony CRT, but your mileage may vary.

If you get a strong signal and poor reception, you have multiple signal paths reaching your receiver and it can't decypher the signal. In an analog signal, it causes ghosting. Bi-directional antennas like a 4-bay without reflector pull in signals from many directions. If you have a strong multipath source, you may find a better solution is to retain two antennas, make them both 4-bay with reflector, and use a combiner or switch as you do now.

I strongly suspect, based on your TVFool plot, that multipath is your only worry. All the stations you want are far stonger than the ones I get indoors with a reflectorless 4-bay. At least it's a cheap thing to test!

Frank

Signal Rx is a P(99,99) prediction of signal strength at your location - 99% confidence that the stated level is exceeded 99% of the time, based on the Longley-Rice propagation model and local topology. Actual signal is 5-15dB higher, depending on distance and diffraction. holl_ands has posted links to the details Alan Lee used in creating TVFool. But that's just raw EM wave amplitude.

The antenna gain is a geometric attribute telling you how much of the aerial signal is received, relative to an isotropic or dipole antenna.0 It just tells you how much better it does than the reference. (Amplifiers have no role here as their gain amplifies the noise, too.)

The third piece is the receiver sensitivity. I recall numbers in the -70 to -80dBm. With an isotropic antenna (gain = 1), you need a signal strength equal to the receiver sensitivity plus any transmission losses.

A high-gain antenna just gathers more signal than the reference, and so lowers the minimum EM amplitude needed to exceed receiver sensitivity requirements.

I hope this helps,
Frank

Not as basic as I expected.

Let see if I understand by me giving an example.

Assume the following:
My receiver sensitivity = -75 dBm.
My Coax lost = -2 dBm
My attic lost = -4 dBm
The TVFool Signal Rx(dBm) = - 72 dBm.

My total signal strength at the receiver will be the following or above 99% of the time:
TvFool Signal Rx + coax lost + attic lost
-72 + (-2) + (-4) = -78 dBm
But my receiver sensitivity is only -75 dBm.
So I need an antenna gain of at least 3 dBm to be able to view DTv 99% of the time.

Is this correct?

A little tricky. The relationship between the fore and aft stations is a little different than I thought. Not symetrical.

Here is a crazy idea. Take a model of a 4 bay antenna without reflector. Ask mclapp to send you his or download one (such as the PM-8800) from hdtvprimer (4nec2 can read the eznec files found there). Then add a refector on the east side. Try something like 3 feet high by 6 feet long 2x4 mesh (with the 4" dimension on the same axis as the 6 foot one) broken down into 1" segments. The simulation will be very slow. Eliminating the vertical wires from the mesh may speed things up considerably. The result, if you are lucky, is that the front and rear lobes will be bent westward. Your side signals are pretty strong so you might not shift the lobes sideways too far - keep a little more gain 4 and aft. You can also use two properly combined 4 bays (out of phase) which have a butterfly shaped curve.

The theory here, by analogy. When you erect an antenna with horizontal gain lobes over the earth, those gain lobes are bent upward (called the take off angle). We are trying something similar but sideways. The USMC Field Antenna Handbook focuses a lot on take off angles.
http://www.armymars.net/ArmyMARS/Ant...antenna-hb.pdf


If your house is angled correctly and you have aluminum siding on the side of the attic you might be able to use it as your reflector and save some wind load (but you lose signal due to lower elevation).

If channel 35 is the only off axis channel you are really interested in,
you might want to set up a separate antenna for that one (don't forget to space it away from your main antenna, and use a jointenna. It will hurt the channels either side of channel 35. 34 and 36 are toast possibly 33 and 37. Cost is $32. The device presumably puts a narrow band reject filter centered at channel 35 (in this case) on your main antenna and a narrow band pass filter on your extra antenna and combines the signals. That way, you can maximize your gain fore and aft.
http://www.warrenelectronics.com/ant...Jointennas.htm

As far as windows modelling programs, I second mclapp's suggestion of 4nec2. The eznec demos are available but they are crippleware; you have to upgrade to one of the paid versions to get the same level of capability as 4nec2 will give you for free.

If the reflectorless antenna doesn't give you enough gain, you might put elements on both the front and back of your reflector and use your a/b switch. That way, you get two antennas at a lower price and a lower wind load since they share a reflector.

TVfool uses 20dB as a rule of thumb for attic losses. Also, you should drop the "m" in dBm when you are talking about loses. It applies when you are talking about actual signal levels. I.E.

My receiver sensitivity = -75 dBm.
My Coax lost = -2 dB
My attic lost = -4 dB
The TVFool Signal Rx(dBm) = - 72 dBm.
-72dBm - 2dB - 4dB = -78dBm
Looks a little funny but two of the numbers are absolute numbers and two are relative ones. Kinda like:
25 degrees celsius + 10 celsius degrees = 35 degrees celsius.
25°C + 10C° = 35°C

Yeah, though that can be mixed with a penny wise/pound foolishness and short term thinking, too. Suppose the feedline is 30 inches long and one feed line arrangement uses 34 inches of wire and the other 32. Now suppose the rods that you feed your machines are 10' long (120 inches) (it is hard to take the curl out of roll fed wire). Either way, you get 3 pieces out of one rod. Also, suppose that switching requires a new die that costs $3000 to make. At $0.12 per antenna saving (at retail prices, not bulk), you have to make 25,000 antennas to pay it off and you take a hit on this quarter's report.

Shaving a couple inches off all 4 sides of the reflector, on the other hand, saves a lot of wire.

It is also very possible that they never even realized that the second geometry exists and that it saves wire.

Now, my estimates of the effect are at band center. That is a good starting point and often minimizes the effect at one band edge or the other. But sometimes you use one wrong value to correct for an error elsewhere or stagger parts of the design. For example, you might optimize the whisker length at one frequency, the reflector spacing at another, and the phasing line for another to broaden the bandwidth a little.

So, I am not saying it is necessarily wrong to have a short twist. But if you deviate from the theoretical optimum you should have a justification other than carelessness. On your antenna, you appear to. It could turn out, however, that because your reflector spacing and your whisker length are shorter than appropriate for the center of the band that you have some impedance effects and an odd length on the transmission line helps transform it. It could even be that those dimensions seemed to do better in the first place because of the phasing line irregularities. Also, since you are using a program that apparently doesn't calculate net gain directly, you might have been optimizing VSWR and feedline irregularities might improve apparent VSWR (but not actually improve net gain) because the mismatch reflects energy before VSWR is measured at the feed point.

Also, while we are on VSWR and impedance, be wary of NEC2/4 results there. The impedance values go awry before the raw gain values do.
http://www.cebik.com/content/a10/model/conv.html
I think we are avoiding most of the things that confuse NEC2/4 though something as simple as using a different diameter wire for the phasing lines and the whiskers could very well excite the bugs in both.

I agree about scaling, though that isn't really an exception to what I was saying since you are changing other dimensions to compensate. But it is the easy way to change an antenna design. Unfortunately, antennas often include both parts that can be scaled easily and others that can't (off the shelf hardware).

Having a computer go through and take particular designs and scaling the parts that do scale and keeping the ones that are less practical to scale and then optimizing and repeating this at every octave or so to produce a table of dimensions at various frequencies would be handy. You could then linearly interpolate various dimensions. Other parameters could be changed but have a limited selection of sizes, such as wire gauges, bolt sizes, PVC pipe fittings, and standard insulators (which sadly are very hard to find).

Good point about the meta analysis on the thread. Here is a graph of number of cumulative number of posts (or post number), vs time. Looks rougly exponential.
Attachment 115135
Produced using the following in gnuplot:
There were 62 authors. # of posts followed by name. I added first post # for top 10.
There is far more information on N-bay bowtie antennas with or without reflectors on this thread than 5 antenna books combined.

You made some good points. But using a splitter/combiner with two antennas pointed different directions tends not to work so well. With a 1dB splitter/combiner loss, you lose 4dB in the combiner unless they are pointed in the same direction (in which case you gain 2dB). The reason is simple: half your signal is retransmitted out the other antenna. Thus you need more than 4dB of gain difference over a bidirectional antenna for this to work better than a bidirectional antenna. Which is possible. If you have strong signals, this may not matter and can be worth it for the convenience. It is not unusual for multipath to come from behind, though.

Thanks.

Wood is an interesting material. It has low embodied energy, low embodied CO2, is renewable, biodegradable, recyclable, strong, easy to work with, often comes from close by reducing transportation impact and can be inexpensive. It is a composite material composed primarily of 3 polymers, cellulose, hemicellulose, and Lignin. But it succumbs to weather and becomes part of the food chain or a habitat outdoors. Termites, wasps, and other insects are a problem as are fungai. Probably some bacteria. Some birds. Even cows can eat it. Thus it is tricky to use outdoors and many preservatives negate or reduce the environmental benefits of using wood. The more environmentally friendly ones tend to need more frequent maintenance. And some have almost been forgotten.

It is good stuff, use it when you can. And try to use it in ways that preserve its environmental benefits. Antennas, particularly outdoor ones, though, are not the best application.

I did a quick search and came up with these :

http://www.mcmelectronics.com/product/32-4425

http://www.tinlee.com/RF_Switches.php?active=6

Hmmm, the infrared models are much cheaper, but an rf model remote with decent range would mean it could be put closer to the two antennas.


Theres a trick to that. After downloading the .ez files, right click on them, > open with > choose program and browse to the 4nec2X.exe program. Also download the patches to give more segments.
The 4nec2x program also takes advantage of both processors in a dual core system. (not sure if it takes advantage of all four processors in a quad core system)

Thanks, and yes, I know about combiner losses, but his question is in the context of an A-B switch as I recall. Looking at his TVFool plot, combiner losses look minor compared with getting a clean, mainly single path signal, and become moot with a switch.
Frank

That is the basic idea, but your numbers are off, as whitis noted, especially for attic loss. I've never seen a loss quoted from TVFool, but I have seen data comparing indoor and attic performance, and -15 to -20dB loss is typical. I also gave a fictitious receiver sensitivity; a broadcast engineer would do this right, but it at least gives you a feel for what you need.

CAVEAT: With DTV, be aware that multipath trumps signal strength. In the analog world, sensitivity is all you need because the display is just an amplified version of the signal received - crappy signal, crappy image. DTV is all or nothing - perfect or unwatchable - because the signal requires digital signal processing before you get an image. If the DSP can't lock on the digital signal, sensitivity and strength don't matter anymore!

Frank

... with a break in early March, right after the government coupon program began delivering, and people started buying DTV converter boxes and found out they needed an antenna upgrade, or in my case (and yours I trust), found something that was terribly interesting and actually somewhat practical.

I see another break in early May which started the current phase of daily posts, rough about the time mclapp started reporting on modeling results, and that aspect took off.

Thanks for taking a look!
Frank

Yeah, Ive seen numbers like -6 to -20db loss too. But with a loss like -4 to -8db thru the attic would mean a very very dry and cheaply built roof, that may fall in with a good snow. (hmmm, my polycarbonite greenhouse roof may have a -4 db loss or less, heh.) Ive also noticed fine iron pieces (I had gotten iron splinters in my hand, heh) imbedded in the shingles Ive bought recently.


Very true. Ive been playing with building uhf antennas (because theyre small) for many years. Im glad to see more people involved.

That doesn't do much for you unless you are trying to share an amplifier (or the switch has a built in one) and then the switch would need to be outdoor rated. You save a few $ on coax but less than you probably spend on the RF remote. The cable losses are the same whether you switch them near the antenna or near the tv.

RF remote is handy if you watch TV in more than one room. An IR remote extender, however, may let you control the switch and other devices as well. If you try to use more than one TV tuned to different channels by using more than one switch, the RF remote can be handy in eliminating the need to run two coaxes to each room but make sure you can use two or more remotes and switches in the same house (i.e. separate remote codes for each unit). Most remote controlled devices are crippled in this respect.

There are some sophisticated channel combining methods that can be used but they tend to be expensive. You could have an amplifier on the signal from each antenna (probably in addition to the one on the mast since there are some high losses) feeding a splitter. Connected to the splitter are a bunch of single channel filters. The outputs of the single channel filters go into a combiner. www.tinlee.com has single channel filters for around $30 each. Alternatively, a jointenna for each channel fed from the splitters might be used. Adjacent channels can be a problem. Single channel amplifiers can be used. This is more practical for an apartment building than a single residence.

One trick that may work in some cases is to combine two antennas using a splitter/combiner AFTER they have been amplified. That avoids the reradiation problem. You get more noise this way as you as you get the noise in both antenna directions (1.5dB) plus the noise of both amplifiers (1.5dB). Simply combining two antennas without amplifiying first you get the noise in both antenna directions (1.5dB) plus you lose about 3dB of signal to reradiation.


You can open them directly from within 4nec2/4nec2X open file menu dialog. A little more detail on the "patches" (actually missing programs) is in message 436.

I got a chance to try my vertical stack 6 bay Friday and it didn't work any better than the 4 bay. It only showed 1 db over the 4 bay on paper and even though I tried to be sure that I measured everything correctly any small error in the phasing line length or twists could eat up that 1 db real fast.

I'm still exploring the vertical stack 2 bay arrangement. I'm thinking the 2 bay horizontal stack could be a nice little antenna for multipath issues, narrow beamwidth with the gain of a single vertical stack 4 bay.

I also explored the longer feedline idea that whitis mentioned in an earlier post to eliminate the twist and also thought that it would give the freedom to move the element bays further apart. My inital modeling has shown that there is some gain to be had there but at the cost of bandwidth similar to the larger reflector spacing, but unlike the larger reflector spacing it kills the VHF-HI gain. Just scratching the surface on that though.

In the field tests I've done I haven't been able to build anything better than the curved reflector 4 bay, except maybe the 8 bay 450 ohm ladder line fed. I'm thinking of taking down the 8 bay from my mount a taking it to my test site (my friends house) and see how it compares there where I have a larger selection of stations at different signal levels in multiple directions.