Digitenna DUV-DF First Impressions

[holl_ands]

I also took another look at Ken Nist's doublebowa.ez file for R-S Double-Bow.
Trying to get the *.nec file anywhere near AGT=1.0 seems impossible....even
after I remove the long twin-lead feedline....but from what does run, the
SWR doesn't match ANYTHING very well....

Taking just one bowtie with 2.4-in SOURCE wire between the two halves,
the SWR is off the charts no matter what impedance is chosen.
Simulating a Balun with a 1-in SOURCE wire at the original Double-Bay
middle point (3.8-in below the Bowtie), the impedance improves, but
doesn't really match anything....although 800-ohm is better at high
freqs, 300-ohm is better at low freqs...

[holl_ands]

FWIW, here's my 4nec2 file for Just One Bowtie from Ken Nist's EZNEC file for R-S's Double Bowtie.
You can see effects of how it's fed by chosing either:
a) GW1 (End of TL=QWL feedline)....also enable GW8, GW24 & GW2 for other end of TL Card.
b) GW2 (Simulated Balun SOURCE)....disable TL Card, also enable GW8 & 24.
c) GW3 (Simulated Center SOURCE)....disable TL Card, also disable GW8 & 24.

Only the first one has AGT=1.0. For the others try running with AUTOSEG(11) turned ON.

CM DoubleBow :  One Bowtie From R-S Double Bowtie, Ken Nist's EZNec converted with 4nec2
CM holl_ands mods: One vice Multiple "LD" Statements, Add FR/RP Statements, 28Jan2012
CM   Modify "EX" Statement for Positive Real & Zero Imaginary voltage.
CM   Round off to three decimals.  AGT finally will run, but AGT=0.44 (-3.5 dB).
CM   Replace Ken Nist's Twin-Lead Feedline (GW2-7) with 1.0-in SOURCE Balun + TL=QWL (5-in).
CM   JUST ONE BOWTIE: AUTOSEG(7) for AGT=1.0.  NO Errors, ignore FAT Wire Warnings.
CE
SY Rsrc=0.036		' Simulated SOURCE Wire Radius, Adjust for AGT=1.0: UHF=0.036
SY Zc=300    		' Impedance of Interconnecting Feedline (ohms)
SY Lc=0.127		' Length of Interconnecting Feedline (meters) [QWL(590MHz)=5-in]
GW	1	1	2.11	-0.5	-5	2.11	0.5	-5	Rsrc	' End of TL SOURCE
GW	2	1	2.11	-0.5	0	2.11	0.5	0	Rsrc	' Balun SOURCE
' GW	3	1	2.11	-1.2	3.8	2.11	1.2	3.8	Rsrc	' Center SOURCE
' Ken Nist's Original long twin-lead feedline (GW1-7):
' GW	1	1	-9.3	0.15	0	-9.3	-0.15	0	0.0545	' FL mod
' GW	2	33	-9.3	0.15	0	0.7	0.15	0	0.012
' GW	3	33	-9.3	-0.15	0	0.7	-0.15	0	0.012
' GW	4	2	0.7	0.15	0	1.3	0.5	0	0.025
' GW	5	2	0.7	-0.15	0	1.3	-0.5	0	0.025
' GW	6	3	1.3	0.5	0	2.12	1.2	0	0.05
' GW	7	3	1.3	-0.5	0	2.12	-1.2	0	0.05
GW	8	3	2.12	1.2	3.8	2.12	0.5	0	0.125	' Balun mod
GW	9	1	2.12	2	3.5	2.12	1.2	3.8	0.06
GW	10	1	2.12	2	4.8	2.12	1.2	3.8	0.06
GW	11	3	2.12	2	4.8	2.935	4.06	5.525	0.06
GW	12	3	2.12	2	3.5	2.935	4.06	2.875	0.06
GW	13	1	2.12	6.12	4.8	2.12	6.12	3.5	0.06
GW	14	3	2.935	4.06	5.525	3.75	6.12	6.25	0.06
GW	15	3	2.935	4.06	2.875	3.75	6.12	2.25	0.06
GW	16	3	2.12	2	4.8	2.12	6.12	4.8	0.06
GW	17	3	2.12	2	3.5	2.12	6.12	3.5	0.06
GW	18	1	2.12	6.12	4.8	2.935	6.12	5.525	0.06
GW	19	1	2.935	6.12	5.525	3.75	6.12	6.25	0.06
GW	20	1	2.935	4.06	5.525	2.935	6.12	5.525	0.06
GW	21	1	2.12	6.12	3.5	2.935	6.12	2.875	0.06
GW	22	1	2.935	6.12	2.875	3.75	6.12	2.25	0.06
GW	23	1	2.935	6.12	2.875	2.935	4.06	2.875	0.06
GW	24	3	2.12	-1.2	3.8	2.12	-0.5	0	0.125	' Balun mod
GW	25	1	2.12	-2	3.5	2.12	-1.2	3.8	0.06
GW	26	1	2.12	-2	4.8	2.12	-1.2	3.8	0.06
GW	27	3	2.12	-2	4.8	2.935	-4.06	5.525	0.06
GW	28	3	2.12	-2	3.5	2.935	-4.06	2.875	0.06
GW	29	1	2.12	-6.12	4.8	2.12	-6.12	3.5	0.06
GW	30	3	2.935	-4.06	5.525	3.75	-6.12	6.25	0.06
GW	31	3	2.935	-4.06	2.875	3.75	-6.12	2.25	0.06
GW	32	3	2.12	-2	4.8	2.12	-6.12	4.8	0.06
GW	33	3	2.12	-2	3.5	2.12	-6.12	3.5	0.06
GW	34	1	2.12	-6.12	4.8	2.935	-6.12	5.525	0.06
GW	35	1	2.935	-6.12	5.525	3.75	-6.12	6.25	0.06
GW	36	1	2.935	-4.06	5.525	2.935	-6.12	5.525	0.06
GW	37	1	2.12	-6.12	3.5	2.935	-6.12	2.875	0.06
GW	38	1	2.935	-6.12	2.875	3.75	-6.12	2.25	0.06
GW	39	1	2.935	-6.12	2.875	2.935	-4.06	2.875	0.06
GS	0	0	0.0254		' All in inches.
GE	0
EK
LD	5	0	0	0	1.66667e7	0
' EX 0 1 1 0 -1 1.22461e-16	' Original
EX 0 1 1 0 1 0			' GW1 is SOURCE wire - holl_ands mod
TL 1 1 2 1 Zc Lc 0. 0. 0. 0.	' Interconnecting Feedline, Zc=Impedance, Lc=Length
'
' FR Freq Sweep choices in order of increasing calculation time (fm holl_ands):
' FR 0 0 0 0 470 0		' Fixed Freq
' FR 0 29 0 0 470 12		' Freq Sweep 470-806 every 12 MHz - OLD UHF BAND
' FR 0 34 0 0 410 12		' Freq Sweep 410-806 every 12 MHz - Even Wider Sweep
' FR 0 39 0 0 470 6		' Freq Sweep 470-698 every 6 MHz - PREFERRED FOR UHF
' FR 0 77 0 0 470 3		' Freq Sweep 470-698 every 3 MHz
' FR 0 153 0 0 470 1.5		' Freq Sweep 470-698 every 1.5 MHz
FR 0 71 0 0 300 10		' Freq Sweep 300-1000 every 10 MHz - WIDEBAND SWEEP
' FR Hi-VHF choices:
' FR 0 15 0 0 174 3		' Freq Sweep 174-216 every 3 MHz
' FR 0 29 0 0 174 1.5		' Freq Sweep 174-216 every 1.5 MHz - PREFERRED
' FR 0 43 0 0 174 1		' Freq Sweep 174-216 every 1 MHz - Hi-Rez
' FR 0 26 0 0 150 6		' Freq Sweep 150-300 every 6 MHz - WIDEBAND SWEEP
' FR Lo-VHF choices:
' FR 0 19 0 0 54 3		' Frequency Sweep every 3 MHz for Ch2-6 + FM
' FR 0 35 0 0 54 1		' Frequency Sweep every 1 MHz for Ch2-6
' FR 0 36 0 0 75 1		' Frequency Sweep every 1 MHz for Ch5 + Ch6 + FM
' FR 0 28 0 0 54 6		' Wide Freq Sweep every 6 MHz for Ch2-13
' FR 0 64 0 0 54 12		' Super Wide Freq Sweep 54-810 every 12 MHz
' RP choices in order of increasing calculation time:
' RP 0 1 1 1510 90 90 1 1 0 0	' 1D Gain toward 0-deg Azimuth - SIDE GAIN
' RP 0 1 1 1510 90 0 1 1 0 0	 ' 1D Gain toward 90-deg Azimuth - FORWARD GAIN
' RP 0 1 1 1510 90 180 1 1 0 0	' 1D Gain toward 270-deg Azimuth - REVERSE GAIN
' RP 0 1 37 1510 90 0 1 5 0 0 	' 2D (Left only) Azimuthal Gain Slice
RP 0 1 73 1510 90 0 1 5 0 0 	 ' 2D Azimuthal Gain Slice - PREFERRED
' RP 0 73 1 1510 90 0 5 1 0 0 	' 2D Elevation Gain Slice
' RP 0 73 73 1510 90 0 5 5 0 0 	' 3D Lower Hemisphere reveals antenna (Fixed Freq)
' RP 0 285 73 1510 90 0 5 5 0 0	' 3D Full Coverage obscures antenna (Fixed Freq)
EN

[lithOTA]

Originally Posted by 300ohm

I dont think you have to do anything that drastic, heh.
Just take close ups of it and measure one half of the driven element since its symmetrical to the other half. Measure the center to each tip point and center to each fold point, and then do the same for the height. Then measure the total length of the driven element as mounted, and the air space in between.

Thanks 300, I did take a look at doing that and impedance isn't the only problem. The DUV module would have to be attached to the top of the XG's boom, just like the X-directors are. But the DUV module is so big that I would have to remove the 2 rearmost X-directors to make it fit. And I'm not sure how I would handle the tiny metal director that is rivetted just in front of the XG's module. Oh well, I can procure a longer director boom- appearantly, Digitenna makes them for specialized applications.
I did take the Digitenna down in order to attempt measurement, but the weather was going downhill and I had to get the rotator back up and running. I decided that measuring would have to wait until I have a better weather day. I will try the measuring technique you suggested.
But I was able to get the rotator back up spinning the Digitenna. This gives me a better idea of how it does on stations in other directions.
What I said about VHF response seems to be correct- above NM +20, it delivers SNRs of 27:1 and even 28:1. With NMs in the teens, it's okay but not great, and below that it's pretty much useless. I was also able to get some weak reception on an analog RF 6 (it's actually a radio station on 87.7, with a traffic map).
On UHF, it really rocks on the low end, up to about RF 30. The beamwidth on these freqs is quite wide, I'd say as much as 60 degrees of usable gain. On higher channels, it is much more laser-beam, but not nearly as much as the 91XG. UHF response from the rear is very strong, especially above RF 40.
I was able to lock in to an extremely weak low-power (43 miles LOS) that has a full-power co-channel (70 miles 2-edge) at 100 degrees off-center. Usually, the full-power will wipe out any chance at the low-power, but the Digitenna has been able to grab it. I am even able to switch between the Digitenna on the low-power, and a ClearStream 4 on the full-power, so flipping the switch causes the tuner to "change channels" on the same frequency. This seems to me like quite a feat- the ability to get 2 stations in different directions but on the same frequency, from the same location at the same time, with 2 different antennas.

[lithOTA]

Okay, here are the dims on the DUV-DF. I was going to use Metrics (since this is a Canadian site), but the unit was built in inches, so it made sense to just use old-fashioned inches.
The director and reflector parts were easy, but the DE was a real bear. There is a small variability between the two elements of the DUV module, so my measurements are within that margin of error. Just trying to convey the shape of the thing is pretty tough.
I should note that you can also build a model of the DUV-XF (13 directors) or the DUV-F (6 directors). Everything else is the same.
If you have any questions, or need me to get another photo or measurement, please let me know. The antenna is in my attic now, so I can get to it easily.

[300ohm]

I was going to use Metrics (since this is a Canadian site), but the unit was built in inches, so it made sense to just use old-fashioned inches.

Dont ever let that stop anyone from posting dimensions. With 4nec2, metric, inches or feet is just a 1 click setting.

You pretty much have the 3D drawing. You have the top view, the side view and the end view as is taught is mechanical draughting classes. One problem is, the light lettering of the numbers. I cant make out some of them.

[lithOTA]

That's funny, I did take Mechanical Drawing back in high school- HAND drawing, with a T-square and triangles! AutoCAD came out just a few years later, so I'm self-taught on that.

I will try to produce a better scan on my hand drawing, and post it a little later.

Ok, it's later...



I used an auto-correct tool to improve the contrast. Let me know if you can read it.

[300ohm]

Yeah, I can read it now. I also noticed that IE 10 has a new neat zoom feature in the lower right hand corner which makes it even easier.

Whats the feedgap on that folded bowtie, ie the shortest air space between the two bow/whisker sections ? Plastic is covering it up, but it looks like it may be 1/2" ?

[300ohm]

Also, regarding the folded bowtie, what's the thickness of the material ?

[lithOTA]

The feed gap between the driven elements is 2.75", essentially the same width as the DUV module.
As for the thickness of the metal, I sure wish I had a micrometer, but I don't. Using a very precise ruler, I get a thickness of 1/32". This might be off by a few thousandths, but I had a second pair of eyes that agreed.
One thing I was curious about was the director spacing. After finding the spacing at a nice even 4", I checked the spacing on my Antennacraft HBU-33 and found the exact same 4" spacing. An old CM 3016 has a tighter spacing, about 3.25".
What's the ideal spacings for antennas that are designed to go up to 51, 69, and 83?

[lithOTA]

I tried another experiment with the DUV this weekend. I removed the reflector and director booms, so it's just the DUV module with the oragami-like elements. I built a little mount so that I could attach it to my mast, and installed it up there. Essentially, in this configuration, it's a DUV-IN.
The UHF reception results are very good in two directions, similar to when using a reflectorless SBGH or M4, and on VHF it's almost as good as when the booms are attached.
The reason I tried this is that there is a guy on eBay who has a couple of hundred DUV-INs new in box, and he's selling them dirt cheap. I was thinking of buying 4 of them and using them as driven elements on an M4, with a 4-way splitter as a combiner and a wide reflector to improve VHF.
Before I do that though, I will wait to see if one of you has been able to model the DUV module with Nec4.

[mrvanwinkles]

Yes ...

Interesing "Origami" bow-tie like elements. Folded of thin sheet.

I wanted to play around and experiment with 3-D conical "cone shaped" elements in another thread ... but I have a million other projects I am working on.

But Yes ... the road to improved antennas and receive elements may be going to some sort of 3-D shapes and designs.

Reading with great interest.

All the best.

[stampeder]

In antenna theory the cone is the ideal element for certain uses, but flat, triangular elements or else the two prongs of a bowtie have the effect of representing a cone element, with the bowtie prongs having the great advantage of much lower wind/snow load. It would be interesting to see the actual performance difference in numbers between cone/flat/bowtie elements, but it is not much.

[lithOTA]

The eBay seller who had the DUV-INs listed dirt cheap has changed his strategy- he's now selling a lot of 40 for about 400 bucks. He may not have had any takers on the single-unit listing.

Although the DUV element works well by itself, I changed it a little by re-installing the director boom (but NOT the corner reflector boom). So in this configuration, it works as a bi-directional with a bias towards one side.
If you listen to the Digitenna President on his YouTube video, he talks a lot about how his module is better than others at getting the signal from the elements into the cable. I'd love to see what's in there, but it's all covered in black goo, and you would have to destroy it in order to get a peek.

[PoppaDigital]

http://www.google.com/patents?id=R1H...615005&f=false

http://www.google.com/patents?id=nvp...page&q&f=false