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Which VHF-Hi ONLY antenna or other solution?

81K views 360 replies 32 participants last post by  300ohm 
#1 ·
There are so many threads, but i would like to know what VHF-Hi only antenna, specifically #13, would give the maximum gain, commercial or DIY


the antenna chart mentions wade WL-7-13, winegard YA-17-13, antennacraft Y10-7-13,

and in the smaller ones, antennas direct C5, antennacraft Y5-7-13

how do these compare to VHF-Hi gain on the larger combo antennas, and GH w/ NARODS models?

so far my DIY #13 YAGI designed for 13 dbi didnt help me, so i was thinking of stacking 2 of them or 2 of the commercial antennas?
 
#54 ·
No disrespect intended, but I'm not sure I see a conclusion here as to what antenna design is best for VHF-HI. I'm guessing it's a yagi, but that's just a guess.
I haven't seen many Yagi VHF antenna designs, except for single channel cut ones. Log periodic designs are more common (they are often mistaken to be "Yagi" antennas).

For maximum gain, I would recommend a large log periodic model.
 
#55 ·
It is impossible to declare any particular Hi-VHF antenna "best" without knowing the "criteria":
1) Most Gain (or F/B) DIY irrespective of size (do you have room for a 20-element Yagi or Log-Yagi???),
2) Most Gain (or F/B) in a commercial antenna for a "typical" attic installation (100-inch boom Log-Yagi???)
3) Most Gain (or F/B) DIY for a given H, W and/or D (e.g. even smaller, such as K6STI's 5-Element Yagi):
http://www.imageevent.com/holl_ands/yagis
4) Easiest (and/or least expensive) DIY with High Gain (perhaps Zig-Zag Log Periodic or LPDA).
5) Easiest (and/or least expensive) DIY with Moderate Gain (2-Bay or Circular Loop, with or w/o a Reflector).
6) Least expensive commercial antenna with Moderate Gain (perhaps Antennacraft 60-in boom Y5-7-13)
7) Compact commercial antenna with Moderate Gain (perhaps A-D C5).

Very few Yagi designs provide good Gain, SWR and F/B Ratio across the ENTIRE Hi-VHF Band,
with the exception of K6STI's 5-Element Yagi (7.5-9.5 dBi Gain). Commercial Log-Yagi's, such as
W-G YA-1713 (100-in) and Antennacraft Y10-7-13 (120-in) provide about 10 dBi Gain and so-so
F/B Ratio....or about the same as a 100-inch long Zig-Zag Log Periodic Wedge or a DIY LPDA with
a 100-inch Boom length constraint.

A Hi-VHF antenna with more than 10 dBi of Gain will likely NOT cover the ENTIRE band and might
only cover a single channel, such as the following Ch7 12-Element Yagi, which is 4.7-meters long:
http://imageevent.com/holl_ands/yagis/12elyagi
 
#57 ·
Holl ands, I'd just say max gain within reasonable constraints on size, outdoor, F/B not significant, both DIY and commercial.

A major component of my job is "dumbing down" complex technical issues for non-technical people so I can get their agreement on how to move forward. I suppose I view the conclusion of this thread in the same light.
 
#58 ·
I'd just say max gain within reasonable constraints on size, outdoor,
Max gain is not always what you want. Generally, the higher the antenna gain, the narrower the beamwidth. Beamwidth can be very important. Say you have two transmitting towers 35 degrees apart. A high gain antenna will probably only catch one well without a rotor. A lower gain antenna may do both well without a rotor.
TVFool data and the FCC coverage charts provide a wealth of info to determine what you need. The FCC coverage charts assume 4 db for vhf-low and 6 db for vhf-hi. Outside of the FCC coverage area, youre heading into DXing area.
 
#60 ·
Again, that's not always the desired outcome. I can think of many areas in the DC/Baltimore metro that would need broader beamwidth to catch the VHFs from both markets. Your solution would work for me, since the two markets are nearly on the same azimuth from my location.

However, I have VHF DX opportunities 180 degress from Baltimore, so that implies yet a different solution. A table of options is probably the best outcome for this thread.
 
#61 ·
new model VHF #13

Can anyone squeeze more gain out of this, on #13, so far its about 1 dbi better than a yagi calculator, i havent got it over 11 dbi without losing the desired high f/b?

(sorry about the unsequenced tag and element numbering)



Code:
CM
CE
SY rad=.125
SY GAP=1
SY GAPRAD=.13
SY L1=10.93359
SY H1=2.005327
SY T1F=0.8
SY T1=T1F*H1
SY L1T=L1+T1
SY H1T=H1-T1
SY L1BGAP=1.333645
SY L1TGAP=0.962769
SY H1TGAP=0.33274
SY X1=0
SY S1=9.553982
SY L2=11.41533
SY T2F=0.8
SY H2=1.927319
SY T2=T2F*H2
SY L2T=L2+T2
SY H2T=H2-T2
SY X2=X1+S1
SY S2=2.20615
SY L3=12.3898
SY X3=X2+S2
SY S3=15.91353
SY T4F=0.797669
SY H4=2.526827
SY T4=T4F*H4
SY H4T=H4-T4
SY L5=8.803471
SY L5T=L5+T4
SY X5=X3+S3
SY S5=11.98839
SY L6=8.711446
SY L6T=L6+T4
SY X6=X5+S5
CM	'reflector
GW	1	7	X1	-L1	H1	X1	0	H1	rad
GW	12	3	X1	-L1T	H1T	X1	-L1	H1	rad
GW	11	1	X1	-L1T	-H1T	X1	-L1T	H1T	rad
GW	10	3	X1	-L1	-H1	X1	-L1T	-H1T	rad
GW	9	7	X1	-L1BGAP	-H1	X1	-L1	-H1	rad
GW	8	3	X1	-L1TGAP	H1TGAP	X1	-L1BGAP	-H1	rad
GW	200	1	X1	0	H1TGAP	X1	-L1TGAP	H1TGAP	rad
GW	201	7	X1	0	H1	X1	L1	H1	rad
GW	2	3	X1	L1	H1	X1	L1T	H1T	rad
GW	3	1	X1	L1T	H1T	X1	L1T	-H1T	rad
GW	4	3	X1	L1T	-H1T	X1	L1	-H1	rad
GW	5	7	X1	L1	-H1	X1	L1BGAP	-H1	rad
GW	6	3	X1	L1BGAP	-H1	X1	L1TGAP	H1TGAP	rad
GW	7	1	X1	L1TGAP	H1TGAP	X1	0	H1TGAP	rad
CM	'active
GW	13	8	X2	-L2	H2	X2	-GAP	H2	rad
GW	74	1	X2	-GAP	H2	X2	GAP	H2	GAPRAD
GW	75	8	X2	GAP	H2	X2	L2	H2	rad
GW	14	3	X2	L2	H2	X2	L2T	H2T	rad
GW	15	1	X2	L2T	H2T	X2	L2T	-H2T	rad
GW	16	3	X2	L2T	-H2T	X2	L2	-H2	rad
GW	17	5	X2	L2	-H2	X2	L1BGAP	-H2	rad
GW	18	3	X2	L1BGAP	-H2	X2	L1TGAP	H1TGAP	rad
GW	19	1	X2	L1TGAP	H1TGAP	X2	-L1TGAP	H1TGAP	rad
GW	20	3	X2	-L1TGAP	H1TGAP	X2	-L1BGAP	-H2	rad
GW	21	5	X2	-L1BGAP	-H2	X2	-L2	-H2	rad
GW	22	3	X2	-L2	-H2	X2	-L2T	-H2T	rad
GW	23	1	X2	-L2T	-H2T	X2	-L2T	H2T	rad
GW	24	3	X2	-L2T	H2T	X2	-L2	H2	rad
CM	'bar
GW	25	11	X3	-L3	0	X3	L3	0	rad
CM	'dir2
GW	38	9	X5	-L5	H4	X5	L5	H4	rad
GW	39	3	X5	L5	H4	X5	L5T	H4T	rad
GW	40	1	X5	L5T	H4T	X5	L5T	-H4T	rad
GW	41	3	X5	L5T	-H4T	X5	L5	-H4	rad
GW	42	3	X5	L5	-H4	X5	L1BGAP	-H4	rad
GW	43	3	X5	L1BGAP	-H4	X5	L1TGAP	H1TGAP	rad
GW	44	1	X5	L1TGAP	H1TGAP	X5	-L1TGAP	H1TGAP	rad
GW	45	3	X5	-L1TGAP	H1TGAP	X5	-L1BGAP	-H4	rad
GW	46	3	X5	-L1BGAP	-H4	X5	-L5	-H4	rad
GW	47	3	X5	-L5	-H4	X5	-L5T	-H4T	rad
GW	48	1	X5	-L5T	-H4T	X5	-L5T	H4T	rad
GW	49	3	X5	-L5T	H4T	X5	-L5	H4	rad
CM	'dir3
GW	50	9	X6	-L6	H4	X6	L6	H4	rad
GW	51	3	X6	L6	H4	X6	L6T	H4T	rad
GW	52	1	X6	L6T	H4T	X6	L6T	-H4T	rad
GW	53	3	X6	L6T	-H4T	X6	L6	-H4	rad
GW	54	3	X6	L6	-H4	X6	L1BGAP	-H4	rad
GW	55	3	X6	L1BGAP	-H4	X6	L1TGAP	H1TGAP	rad
GW	56	1	X6	L1TGAP	H1TGAP	X6	-L1TGAP	H1TGAP	rad
GW	57	3	X6	-L1TGAP	H1TGAP	X6	-L1BGAP	-H4	rad
GW	58	3	X6	-L1BGAP	-H4	X6	-L6	-H4	rad
GW	59	3	X6	-L6	-H4	X6	-L6T	-H4T	rad
GW	60	1	X6	-L6T	-H4T	X6	-L6T	H4T	rad
GW	61	3	X6	-L6T	H4T	X6	-L6	H4	rad
GS	0	0	.0254
GE 0
EK
LD	5	0	0	0	58000000
EX	0	74	1	0	1	0
GN	-1
FR,0,1,0,0,213
EN
 
#63 ·
heres my latest version, simpler, but cannot beat 10.9 dbi, for f/b=27

it uses 1" fat bars and 1/4" tubing driven

Code:
CM
CE
SY rad=.125
SY radbar=.125
SY GAP=1
SY GAPRAD=.13
SY refrad=.5
SY L1=13.1565
SY S1=7.809403
SY L2=12.54095
SY H2=1.215604
SY X2=S1
SY S2=1.606957
SY L3=12.42174
SY X3=X2+S2
SY S3=15.86488
SY L4=11.43866
SY X4=X3+S3
SY S4=13.70802
SY L5=11.38477
SY X5=X4+S4
CM	'reflector
GW	1	7	0	-L1	0	0	L1	0	refrad
CM	'active
GW	2	8	X2	-L2	H2	X2	-GAP	H2	rad
GW	3	1	X2	-GAP	H2	X2	GAP	H2	GAPRAD
GW	4	8	X2	GAP	H2	X2	L2	H2	rad
GW	5	3	X2	L2	H2	X2	L2	-H2	rad
GW	6	5	X2	L2	-H2	X2	-L2	-H2	rad
GW	7	3	X2	-L2	-H2	X2	-L2	H2	rad
CM	'dir1
GW	8	11	X3	-L3	0	X3	L3	0	radbar
CM	'dir2
GW	9	7	X4	-L4	0	X4	L4	0	refrad
CM	'dir3
GW	10	7	X5	-L5	0	X5	L5	0	refrad
GS	0	0	.0254
GE 0
EK
LD	5	0	0	0	58000000
EX	0	3	1	0	1	0
GN	-1
FR,0,1,0,0,213
EN
 
#65 ·
encouraged

built this compact 5 element #13 yagi, using old parts
(gain above 11 dbi net, f/b above 30 db)

in early testing at my difficult location, #13 wvny 2nd edge, this is getting a lock around 60% on tv meter with attenuated amping, i had to put it higher in the antenna farm, at about 20 ft, sandwiched between an M4 facing opposite direction, and an M4 at 90 degrees... not too sure why generally my 2nd egde channels need lower heigth, and yet with #13 needs to be higher (at lower height i receive it but with constant pixel)


i was originally thinking to put it lower, where the unwanted co-channel #13 wouldnt be as strong from the back, but no it seemd to need the heigth...









if i can reliably receive this channels, i would be receiving all available channels, although some are not consistent, with a total of 4 antennas :eek:
 
#67 ·
thanks

for this prototype i used all grey pvc electrical conduit for structure/stubs, and PVC nibco T fittings

i also modeled it with a steel boom and no diff, however if the elements touch the metal boom i beleive you need corrections to element lengths (you can see the other thread about this, personally i wanted to avoid metal boom)

Notes:

- make sure to keep your element LENGTHS to within 1/16"-1/32" accuracy or else!

-try to use 1" bars for front 2 directors, and reflector,

- i used 3/8" bars for driven and 1st director because thats what i had on hand, but 1/4" bars give better numers (all dimensions would need to be reoptimized)

-also if you dont need the high f/b, you can easily get gains over 12 dbi with a slighlty longer boom
 
#70 ·
Stagger Stacking explained

On pages 186-187 of TV Antennas and Signal Distribution Systems by M. J. Salvati, you will find a good description of stagger stacking.



I quote:
"Stagger stacking is a special variation of vertical stacking in which one antenna is mounted one quarter wavelength ahead of the other (Fig. 8-8). The cable section connecting the forward antenna to the signal combiner is made an electrical quarter wavelength longer than the other so the signals from the front are combined in phase. Signals arriving from the back, however, are 180 degrees out of phase and thus cancel. This results in a very high front-to-back ratio, even if the front-to-back ratio of the antennas is very poor. When this technique is used on antennas having a high front-to-back ratio to begin with, the rearward pickup of the array is virtually zero."

More info if you want to try it.

Will the situation improve after the transition?
 
#72 ·
balm:

Good find on the Bill Thompson article, thanks.

Yes, a hybrid combiner is the conventional splitter/combiner that we use. It usually uses toroids for wide bandwidth.

The other type is a stripline combiner that uses discrete lengths of transmission lines in a shielded housing with multiple ports. The lengths of the transmission lines are related to the design frequency that will be used. It is said to have a lower loss than the hybrid type, but I have no proof of that claim. Stripline combiners are hard to find, expensive, and would usually be a custom job for TV reception.

Stripline Power Dividers
•Using Waveguide•
Ron Whitsel WA3AXV
http://www.packratvhf.com/power_di.pdf
 
#73 ·
stagger stacking #13

Rabbit73,

thank you, but someone else originally found me that B. Thompson article, i believe 300ohm and holl_ands...

I have read thru it and attempted a stagger stack using his calculations. I built 2 identical 5 element K6STI yagis (swept back) optimized for my #13 situation (using 4nec2).

I placed them at 12 ft off the ground, 6" in front of my tower, vertical separation is 33", horizontal stagger is 13.86". They were built to within 1-2 mm accuracy, however stacking and alignment on the mast pole is VERY difficult to do accurately (but i think i came close)

And the good news is i had almost a full day of uninterrupted digital reception of #13 (WVNY) for the first time :) reception registered a mere 50% on the tv meter. Again it came in with 20 db attenuation on the kitztech amp.

Bad news is in the early evening i lost reception, then I had to leave the house so couldnt continue testing. I did seem to lose reception when #13 analogue from the opposite side would reappear (although very snowy).

Acording to theory this is supposed to nullify the backside co-channel, but when I modeled the pair staggered in 4nec2, i'm not clear on the result, especially given the forward gain appears skewed (this would mean tilting the antenna to compensate and even then undesired #13 would probably still come in, and the f/b ratio doesnt seem to improve much.

That said, Im not sure how to model the combined antennas correctly. Maybe some of the modelers can comment. Or maybe some other design is better suited. But there is now more reason for optimism. Im also unclear on the advantage of going to this trouble as compared to designing a specific single yagi with very high f/b ratio.

Thanks

Here is the nec file:

Code:
CM Hi-VHF, 5-El Yagi w Swept Driver, 4nec2 file by holl_ands, 19Jun2009.
CM Rev A to Brian Beezley (K6STI) design using AO 8.06 Antenna Optimizer.  
CM All elements Aluminum with O.D.=3/8".  SOURCE: Elem#2 middle segment.
CM Char Imp = 75-ohm.  Boom Correction: Metal Boom, Insulated top mounts.
CM ALL MEASUREMENTS ARE IN INCHES.  Segments per AutoSegmenter.
CE
GW	1	13	0	-13.25	0	0	13.25	0	0.1875
GW	2	13	11.625	-12.5	0	11.625	12.5	0	0.1875
GW	3	11	24	-12.25	0	24	12.25	0	0.1875
GW	4	11	40	-11.75	0	40	11.75	0	0.1875
GW	5	7	3	-15.25	0	7.875	-1	0	0.1875
GW	6	7	7.875	1	0	3	15.25	0	0.1875
GW	7	1	7.875	-1	0	7.875	1	0	0.1875
GW	8	13	13.86	-13.25	33	13.86	13.25	33	0.1875
GW	9	13	25.485	-12.5	33	25.485	12.5	33	0.1875
GW	10	11	37.86	-12.25	33	37.86	12.25	33	0.1875
GW	11	11	53.86	-11.75	33	53.86	11.75	33	0.1875
GW	12	7	16.86	-15.25	33	21.735	-1	33	0.1875
GW	13	7	21.735	1	33	16.86	15.25	33	0.1875
GW	14	1	21.735	-1	33	21.735	1	33	0.1875
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	3.08e7	0
EX	0	7	1	0	1	0
EX	0	14	1	0	1	0
GN	-1
FR	0	1	0	0	213	0
RP 0 1 73 1511 90 0 1 5 0 0
PS :
Rabbit73: could you provide me a link on the Salvati article also. Thank you.

Stampeder, perhaps our last few posts should be subject of a new thread or addded to the old thread of last year ("Which VHF-Hi only antenna?"), thanks ;)
 
#74 ·
#76 ·
balm:

Your stagger-stacking experiments are encouraging. The extra 1/4 wavelength of coax measured for that particular channel (allowing for the velocity factor of your type of coax) for the forward antenna is very critical.

Rabbit73: could you provide me a link on the Salvati article also.
Sorry, there is no link. You would need to borrow the book from your library thru interlibrary loan, buy a used copy of the book (it's worth the trouble), or have someone send a copy of the pages to you.
Im also unclear on the advantage of going to this trouble as compared to designing a specific single yagi with very high f/b ratio.
I don't think it is possible to design a single yagi with as high a ratio as you can get with stagger stacking.

The technique that majortom gave a link for is very useful, but it is not the same as stagger stacking.
 
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