Which VHF-Hi ONLY antenna or other solution?

[balm]

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?

[hkaye]

A custom yagi for channel 13 will do better than a broadband antenna designed for channels 7-13.

What's your tvfool?

Here is an article on stagger stacking that might be useful -

http://www.anarc.org/wtfda/stagger.pdf

You can do a google search on stagger stacking for more information. This will only work on one specific channel. Stagger stacking will increase gain but also eliminate multipath or ghosting for that channel.

[balm]

thanks hkaye,

guess im out of luck then, as so far a single yagi (7 elements, 94") would barely offer any movement on my signal meter, and thats with the Kitztezh amp....im assuming because its a 2nd edge channel, and probably much weaker than the 3 db NM TVFool indicates...also the higher I go the weaker the channels get

i think the longer the Yagi the more complex the stacking gets, especially using the schedule40 pvc as boom...mine was built quite precisely, using 1.25" boom PVC with all #10 copper wire elements (model from "Yagi Calculator")

TVFool:

http://www.tvfool.com/?option=com_wr...9fbe3eeb0522d1

[hkaye]

According to your tvfool you have another ch #13 almost 180 degrees in the opposite direction. I'm assuming you are trying to get WVNY. Can you get CJOH or atleast the audio of CJOH when you point the antenna at CJOH?

WVNY RF13 (22.1) @ -87.4db  118º
CJOH RF13 Analog @ -76.5db  291º

Looking at the power level rather than the NM in the tvfool chart and you'll see the analog station is actually stronger at your location by 10db. Noise Margins are calculated differently for analog stations than digital stations.

I would say that co-channel interference is your biggest problem and you'll need to get an antenna with a high f/b ratio to reject the CJOH signal. Your custom yagi with just one reflector might not be enough - a bigger reflector or more reflectors rods are probably required. Or stagger stacking two yagis to cancel out the other station.

But first I would use the tvfool interactive tools if you haven't already. Select the option to draw lines to the transmitters. Using Google satelite view follow the path to the transmitter and make sure there are no obstructions such as buildings in the way from your house to the transmitter. Follow the line carefully to WVNY for about 3km and do the same for CJOH. If there are more obstruction to WVNY than it just will get harder if not impossible to get that station.

[balm]

thanks hkaye, very informative,

i did not know about the power level relative to analogs....i never checked the reception of #13 analog with this antenna, and now unfortunately i dismantled the yagi, as it was constructed to "flimsy", ill try another one, but would like to avoid stacking as i dont have much room

what kind of reflector do you mean exactly, just add more reflector rods in the vertical plane, or like a screen behind the dipole...

ill check that on google earth, thanks

[hkaye]

The purpose of a better reflector would be to block signals coming from the reverse direction. For example, my tvfool indicates two stations at RF40-

CFTO RF40 (9.1)  @-89.4db 77º
CBLN RF40 analog @-77.5db 232º

Almost similar to your situation with an analog station with more strength opposite to the digital one I want to receive. Fortunately for me I live in a apartment building and the concrete walls of the building block the analog station so it doesn't interfere with the digital one I'm trying to receive.

If you have a big chimney or wall you could use to block the analog that might work also.

I haven't modeled any VHF antennas, but I do know when modeling UHF antennas that a screen reflector for my UHF antennas were too small and VHF signals would pass through them no problem. I'll try a couple of VHF models to see what it would take for a reflector to block the signals from the opposite direction.

[holl_ands]

F/B and F/R Ratio specs for Commercial Hi-VHF antennas are only so-so (dBi = dBd + 2.15 dB):
W-G HD-7082P, F/B Ratio > 20 dB on Ch13 with 12.2 dBi Gain (111-in boom)
W-G HD-7080P, F/B Ratio > 18 dB on Ch13 with 13.2 dBi Gain (90-in boom)
W-G HD-8200U, F/B Ratio = 18 dB on Ch13 with 14.2 dBi Gain (168-in boom)
W-G HD-7084P, F/B Ratio = 17 dB on Ch13 with 13.0 dBi Gain (131-in boom)
W-G HD-5030, F/B Ratio = 15 dB on Ch13 with 10.3 dBi Gain (120-in boom)
W-G YA-1713, F/B Ratio = 14 dB on Ch13 with 12.5 dBi Gain (100-in boom)
W-G HD-769xP, F/B Ratio = 14 dB on Ch13 (for any size in the series)
Antennacraft Y10-7-13, F/B Ratio = 16.5 dBi with 11.6 dBi Gain in Hi-VHF band "somewhere" (120-in boom)
Unfortunately, most of the other manufacturers don't bother providing specs anymore.....

Pricey Professional Hi-VHF antennas are quite a bit better:
Wade WL7-13/S, F/B Ratio > 25 dB with 11.5 dBi Gain (96-in boom)

I modeled and compared several DIY Hi-VHF Antennas here:
http://imageevent.com/holl_ands/yagis
Comparison charts are included in K6STI results:
http://imageevent.com/holl_ands/yagis/k6sti

DIY K6STI's 5-ELEMENT YAGI:
Optimized for best F/R Ratio on Ch7-13, and has a F/B Ratio that is even higher than
the charted F/R Ratio (see chart below).
Shrinking all sizes by a factor of about 0.94 (seat of pants guestimate, not modeled)
would move the F/R Ratio peak so that it falls on top of Ch13.

DIY 13-ELEMENT YAGI WITH 2 REFLECTORS: User <kgb> posted a UHF Yagi design, which
has been rescaled for Ch13. However, I was unimpressed by either Gain or F/B numbers:
http://imageevent.com/holl_ands/yagis/hivhf13elyagikgb
Perhaps it needs an additional Reflector between the other two to improve F/B Ratio......

DIY ZS6BTE's 14-ELEMENT LPDA:
Exhibited an even higher F/B Ratio (equal to F/R Ratio) on Ch13:
http://imageevent.com/holl_ands/zigzaglpa/lpda/lpda14el

My DIY WEDGE ZIG-ZAG LPDA:
Simple DIY design for attic use also had high F/B and F/R Ratios:
http://imageevent.com/holl_ands/zigzaglpa/zigzagnoboom

STAGGER STACKING:
Can null out an undesired channel when it is in nearly the opposite direction
as the desired direction....which is the case for your two Ch13 stations:
http://www.tesc.com.au/stagger.htm
http://www.anarc.org/wtfda/stagger.pdf
http://www.simplicitytool.com/PDFs/O...gger_stack.pdf
I haven't seen any good numbers on how effective this is.
It would be a simple, interesting project for 4nec2 modeling.....

[balm]

can you tell me why this model i( the one i built) isnt giving the designed (as per YAGI CALCULATOR) 13 dbi...

CE
GW	1	9	0.311	0.3165	-0.025	0.311	0.02	-0.025	1.29e-3
GW	2	11	0.417	0.32	0	0.417	0	0	1.29e-3
GW	3	11	0.67	0.3175	0	0.67	0	0	1.29e-3
GW	4	11	0.973	0.315	0	0.973	0	0	1.29e-3
GW	5	11	1.325	0.3125	0	1.325	0	0	1.29e-3
GW	6	11	1.719	0.3105	0	1.719	0	0	1.29e-3
GW	7	11	2.141	0.308	0	2.141	0	0	1.29e-3
GW	8	11	2.585	0.3065	0	2.585	0	0	1.29e-3
GW	9	9	0.311	-0.3165	-0.025	0.311	-0.02	-0.025	1.29e-3
GW	10	11	0.417	-0.32	0	0.417	0	0	1.29e-3
GW	11	11	0.67	-0.3175	0	0.67	0	0	1.29e-3
GW	12	11	0.973	-0.315	0	0.973	0	0	1.29e-3
GW	13	11	1.325	-0.3125	0	1.325	0	0	1.29e-3
GW	14	11	1.719	-0.3105	0	1.719	0	0	1.29e-3
GW	15	11	2.141	-0.308	0	2.141	0	0	1.29e-3
GW	16	11	2.585	-0.3065	0	2.585	0	0	1.29e-3
GW	17	11	0.03	0.345	0	0.03	0	0	1.29e-3
GW	18	11	0.03	0	0	0.03	-0.345	0	1.29e-3
GW	19	19	0.311	-0.3165	0.025	0.311	0.3165	0.025	1.29e-3
GW	20	1	0.311	0.3165	0.025	0.311	0.34	0.0125	1.29e-3
GW	21	1	0.311	0.3165	-0.025	0.311	0.34	-0.0125	1.29e-3
GW	22	1	0.311	0.34	0.0125	0.311	0.34	-0.0125	1.29e-3
GW	23	1	0.311	-0.3165	0.025	0.311	-0.34	0.0125	1.29e-3
GW	24	1	0.311	-0.3165	-0.025	0.311	-0.34	-0.0125	1.29e-3
GW	25	1	0.311	-0.34	0.0125	0.311	-0.34	-0.0125	1.29e-3
GE	0
EK
LD	5	0	0	0	5.8e7	0
EX	0	19	10	0	1	0
GN	-1
FR	0	1	0	0	213	0
RP 0 1 73 1511 90 0 1 5

[hkaye]

Unfortunately the software I use to model doesn't seem to be able to run card decks from other programs.

[300ohm]

(as per YAGI CALCULATOR)

Which Yagi Calculator, K7MEMs or the stand alone desktop Yagi Calculator ?

[balm]

300ohm,

the standalone calculator gives me 13 dbi (i assume this is RAW)

My nec file gives me 5 dbi, SWR =130...


im not sure where the modeling error is, the element dimensions are identical to those used in the calculator...

[Choclab]

Hey, everyone. First post here, although I've read for years. I have to say, the Hoverman work is phenomenal, and many of you are outstanding craftsmen with your builds! I have an Antennacraft version that I bought a couple months ago, and I'm surprised at how well it works. But I'm sure it's satisfying to DIY one instead.

Was looking around because I have two VHF channels (8 and 9) that I'd love to get, and the K7MEM scaled for 8-10 that holl_ands posted looks perfect. I'm a little skittish because I threw together a yagi a couple of years ago, and it was a dismal failure. I didn't put the proper effort into it, most likely.

Any ideas for the boom on one of these other than wood? I see that the sim was run for a wood boom, but PVC would be so much lighter. Not sure how I'd attach the elements to the top of the round conduit, though... And after last time, I think it's important to be absolutely precise.

Maybe even better, has anyone build a mclapp or other bay-type scaled to VHF-Hi? I know it would be big, but this is just a fun DX-type project and at my location space isn't a concern.

Thanks.

[stampeder]

Choclab, stay away from plastics as booms - they're too flexible:

ABS, PVC, other plastics and Rubber for structural parts

[300ohm]

Maybe even better, has anyone build a mclapp or other bay-type scaled to VHF-Hi?

Holl_ands has some VHF-Hi bowties here:
http://imageevent.com/holl_ands/mult...o10bb81.frog_s

I have an Antennacraft version that I bought a couple months ago, and I'm surprised at how well it works. But I'm sure it's satisfying to DIY one instead.

Was looking around because I have two VHF channels (8 and 9) that I'd love to get

If you have the Antennacraft G1483, you could put NARODs and NAROD reflectors on it to get VHF-Hi.
Post your TVFool image or link so we can see what kind of gain channels 8 and 9 would need.

[holl_ands]

Non-metallic materials, such as PVC and Wood do NOT require any Boom Corrections.

If you decide to use a metal boom, recalculate using K7MEM on-line calculator.
But you'll find that at Hi-VHF frequencies, the differences are small enough to ignore.....