Which VHF-Hi ONLY antenna or other solution?
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fracarro
why do the pics for the "high performance band III wideband", BLV6F, in the "instruction", vs the "photo" links differ, they appear as different antennas??
is this enough to model on?
http://www.fracarro.com/international/index.php?option=com_content&task=view&id=258&Itemid=340
why do the pics for the "high performance band III wideband", BLV6F, in the "instruction", vs the "photo" links differ, they appear as different antennas??
is this enough to model on?
http://www.fracarro.com/international/index.php?option=com_content&task=view&id=258&Itemid=340
model BLV6F
when i modeled the BLV6F, the far field gain pattern runs out the backside, instead of the front, is this just a lack of info in the model, or does it take a lot more optimizing to find the correct dimensions, or am i using NEC wrong?
when i modeled the BLV6F, the far field gain pattern runs out the backside, instead of the front, is this just a lack of info in the model, or does it take a lot more optimizing to find the correct dimensions, or am i using NEC wrong?
swept back
can you explain in basic terms why/how the swept back active element in these yagis (K6STI) help improve gain and f/b, intuitively i would have thought sweeping it forward would help?, and can this swept back be applied to all different types of yagis?
http://imageevent.com/holl_ands/yagis/k6sti
can you explain in basic terms why/how the swept back active element in these yagis (K6STI) help improve gain and f/b, intuitively i would have thought sweeping it forward would help?
, and can this swept back be applied to all different types of yagis?http://imageevent.com/holl_ands/yagis/k6sti
The gain and the f/b come from the interaction of the directors and reflectors to the driven element.
Sweeping back the DE normally broadens the beamwidth, which in this case it looks like it does.
Also sweeping back normally results in some loss of gain, but if done correctly its minimal.
Sweeping forward does the opposite, narrows the beam and increases gain, but if swept forward too much, undesirable sidelobes will appear.
Sweeping back the DE normally broadens the beamwidth, which in this case it looks like it does.
Also sweeping back normally results in some loss of gain, but if done correctly its minimal.
Sweeping forward does the opposite, narrows the beam and increases gain, but if swept forward too much, undesirable sidelobes will appear.
Yes, but the trick is to do so with a minimum loss of gain. In the above example, the directors and reflectors are carefully placed to minimize the loss.
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.
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.
Choclab, stay away from plastics as booms - they're too flexible:
ABS, PVC, other plastics and Rubber for structural parts
ABS, PVC, other plastics and Rubber for structural parts
Holl_ands has some VHF-Hi bowties here:
http://imageevent.com/holl_ands/multibay;jsessionid=w78o10bb81.frog_s
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.
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.....
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.....
Just saw this for some reason, but thanks, 300 ohm and holl_ands... I was talking with holl_ands on the avs forum, and I'm going to try one of the VHF-hi bowties from his site. I may make it from wood at first just for ease of construction, then convert it to PVC if it works well enough to make it more permanent. (Or maybe even waterproof the wood -- I have a big can of polyurethane sitting around.)
I might try another yagi some time, and take my time with it for better precision. But first I want to try the bowtie design, partly for the wider bandwidth. (If I can get a reflector on the big thing, it has high FM gain as well.)
And 300 ohm, it's 2-edge stuff... Just a fun DXing thing I do on some stations 125 miles away when conditions are favorable.
I need to go read that link Stampeder provided on the building materials... Looks like some great ideas. Thanks for that!
I might try another yagi some time, and take my time with it for better precision. But first I want to try the bowtie design, partly for the wider bandwidth. (If I can get a reflector on the big thing, it has high FM gain as well.)
And 300 ohm, it's 2-edge stuff... Just a fun DXing thing I do on some stations 125 miles away when conditions are favorable.
I need to go read that link Stampeder provided on the building materials... Looks like some great ideas. Thanks for that!
K7MEM On-Line Calculator comes up with 51-in 6-Element and 66.5-in 7-Element designs:
http://www.k7mem.150m.com/Electronic_Notebook/antennas/yagi_vhf.html
He provides guidance for either a 300-ohm Folded Dipole or 75-ohm Straight Dipole design.
51.0-in, 6-Element Yagi: 8.9 dBd = 11.1 dBi
66.5-in, 7-Element Yagi: 9.8 dBd = 12.0 dBi
These would need to be modeled to determine F/B and F/R Ratios...but is probably not quite
as high as K6STI's Optimized 5-Element (31-in) Yagi with 9.5 dBi Gain and 22+ dB F/B & F/R on Ch13:
http://imageevent.com/holl_ands/yagis/k6sti
K6STI developed his own Yagi Optimizer program, the results of which you see above.....
Note charts for K7MEM's (non-optimized) 4-Element (29-in) and 8-Element (100-in) Yagi designs.
Unfortunately, the formula driven Yagi designs are NOT OPTIMIZED for much of ANYTHING, including
an impedance targeted for Amateur Radio use rather than TV coax.
Hi-VHF 2-Bay with Screen Reflector has 12.5 dBi Gain on Ch13 and F/B & F/R in 15 dB region
(which I would expect to be similar to what modeling would reveal for the K7MEM 6 & 7-Element Yagi's):
http://imageevent.com/holl_ands/multibay/hivhf2bayrefl
Note that it is 56-in high, 72-in wide and 16-in deep.
Reflector Rods, rather than a Screen Reflector should be able to improve the F/B & F/R Ratios,
but would have to be modeled (full width vs split in middle).....hmmm, need to add to my TO-DO list...
http://www.k7mem.150m.com/Electronic_Notebook/antennas/yagi_vhf.html
He provides guidance for either a 300-ohm Folded Dipole or 75-ohm Straight Dipole design.
51.0-in, 6-Element Yagi: 8.9 dBd = 11.1 dBi
66.5-in, 7-Element Yagi: 9.8 dBd = 12.0 dBi
These would need to be modeled to determine F/B and F/R Ratios...but is probably not quite
as high as K6STI's Optimized 5-Element (31-in) Yagi with 9.5 dBi Gain and 22+ dB F/B & F/R on Ch13:
http://imageevent.com/holl_ands/yagis/k6sti
K6STI developed his own Yagi Optimizer program, the results of which you see above.....
Note charts for K7MEM's (non-optimized) 4-Element (29-in) and 8-Element (100-in) Yagi designs.
Unfortunately, the formula driven Yagi designs are NOT OPTIMIZED for much of ANYTHING, including
an impedance targeted for Amateur Radio use rather than TV coax.
Hi-VHF 2-Bay with Screen Reflector has 12.5 dBi Gain on Ch13 and F/B & F/R in 15 dB region
(which I would expect to be similar to what modeling would reveal for the K7MEM 6 & 7-Element Yagi's):
http://imageevent.com/holl_ands/multibay/hivhf2bayrefl
Note that it is 56-in high, 72-in wide and 16-in deep.
Reflector Rods, rather than a Screen Reflector should be able to improve the F/B & F/R Ratios,
but would have to be modeled (full width vs split in middle).....hmmm, need to add to my TO-DO list...
this is the model I was talking about.
did not quite match the claims, since I was originaly wrongly optimizing for the channel above 13...
still 10.5+ dBi gain on ch13, 18+ dB F/B,F/R
did not quite match the claims, since I was originaly wrongly optimizing for the channel above 13...
still 10.5+ dBi gain on ch13, 18+ dB F/B,F/R
Code:
CM
CM biquad for VHF-hi
CM optimized by nikiml
CE
SY radius=0.003175
SY feed=0.03231829 '0.01, 0.07
SY y1=0.3184432 '0.1, 0.6
SY z1=0.5801599 '0.1, 0.65
SY z2=0.163965 '0.05, 0.6
SY drz0=0.1151976 '0.02, 0.2
SY rz1 = 0 +drz0
SY drz1=0.1865335 '0.02, 0.25
SY rz2 = rz1 +drz1
SY l1=0.6272845 '0.01, 0.65
SY l2=0.6169326 '0.01, 0.65
SY drz2=0.2077309 '0.02, 0.25
SY rz3 = rz2 +drz2
SY l3=0.5884499 '0.01, 0.65
SY drz3=0.2019844 '0.02, 0.25
SY rz4 = rz3 +drz3
SY l4=0.3359146 '0.01, 0.6
SY x=0.3356441 '0.01, 0.4
GW 1 35 0 feed 0 0 y1 z1 radius
GW 2 19 0 y1 z1 0 0 z1+z2 radius
GX 10 010
GW 3 67 -x -l1 rz1 -x l1 rz1 radius
GW 4 66 -x -l2 rz2 -x l2 rz2 radius
GW 5 63 -x -l3 rz3 -x l3 rz3 radius
GW 6 36 -x -l4 rz4 -x l4 rz4 radius
GX 20 001
GW 100 5 0 feed 0 0 -feed 0 radius*1.1
GE 0
LD 5 0 0 0 24900000
GN -1
EK
EX 0 100 3 0 1 0 0
FR 0 0 0 0 213 0
ENim trying to model an added corner reflector to a vhf style yagi, but not sure the minimum criteria, any ideas
so far my attempts have not increased either gain, or directionality, or f/b...
i read that 90 degrees and 60 degrees are typical apex angles, and the grid area should be at least 2 x the target wavelength
so far my attempts have not increased either gain, or directionality, or f/b...
i read that 90 degrees and 60 degrees are typical apex angles, and the grid area should be at least 2 x the target wavelength
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