Search found 63 matches

by k6sti
07 Jul 2016 22:11
Forum: Antennas
Topic: Ten-Element Yagi
Replies: 6
Views: 3708

Re: Ten-Element Yagi

I called it a T-match because that's what it looks like. But it's primarily a convenient way to place a short radiating conductor where it enhances the pattern. The T-match must be located between the driven element and first director. Other orientations don't work as intended.

Brian
by k6sti
07 Jul 2016 03:43
Forum: Antennas
Topic: Ten-Element Yagi
Replies: 6
Views: 3708

Re: Ten-Element Yagi

I've just discovered that a horizontal T-matched dipole can mimic the pattern-enhancing qualities of a horizontal folded dipole. I've updated the ten-element Yagi writeup with the new design, which offers slightly higher forward gain: http://ham-radio.com/k6sti/ten.htm The T-match permits 75-ohm fee...
by k6sti
24 Jun 2016 00:06
Forum: Antennas
Topic: Stacked DAB Yagis
Replies: 0
Views: 1625

Stacked DAB Yagis

Image

I've added a 22-element stacked array to my DAB Yagi writeup. The reflectors have unequal but symmetrical lengths and offsets.

http://ham-radio.com/k6sti/dab.htm#stk

Brian
by k6sti
15 Jun 2016 13:05
Forum: Antennas
Topic: Körner 19.4
Replies: 1
Views: 2336

Körner 19.4

Peter Körner has revised his 19.3 Yagi design. The 19.4 further reduces backlobes over the rear quarter-plane. The boom is 0.44 meters longer and forward gain is slightly lower above 98 MHz. I've added the 19.4 to my 19.3 writeup. I include several performance comparison plots and graphs. http://ham...
by k6sti
23 Apr 2016 14:49
Forum: Antennas
Topic: Wanted Supplier of Band 2 Beam Antennas
Replies: 18
Views: 7230

Re: Wanted Supplier of Band 2 Beam Antennas

http://ham-radio.com/k6sti/ly5a.gif I added a design optimized at 20 feet above ground to the 5-element log-Yagi writeup. At practical installation heights it provides a better pattern than does the free-space design. http://ham-radio.com/k6sti/ly6a.gif I did the same thing at 30 feet for the stack...
by k6sti
22 Apr 2016 23:11
Forum: Antennas
Topic: Wanted Supplier of Band 2 Beam Antennas
Replies: 18
Views: 7230

Re: Wanted Supplier of Band 2 Beam Antennas

Dave, what I had in mind for the phasing lines was the 1/8" soft aluminum wire I used to find in 25- or 50-foot rolls at hardware stores. I've used it for all kinds of antenna projects over the years including inductors. You can seal coax with goop if you can't build an enclosure. Don't use anything...
by k6sti
21 Apr 2016 02:26
Forum: Antennas
Topic: Antennas in a mixed polarisation environment
Replies: 4
Views: 2254

Re: Antennas in a mixed polarisation environment

Now, the value of a horizontal antenna with narrow beamwidth and deep nulls off the sides is of remarkably little use in the pursuit of weak signals from outside the area because each and every HP ae will show a peak off the sides for VP signals. This isn't true in free space unless the antenna has...
by k6sti
21 Apr 2016 00:47
Forum: Antennas
Topic: Wanted Supplier of Band 2 Beam Antennas
Replies: 18
Views: 7230

Re: Wanted Supplier of Band 2 Beam Antennas

...but I am surprised you seem to be dismissing this as a useful antenna for dx-ing. I did no such thing. I simply don't agree that it "clearly offers the highest performance/size ratio of any Band II antenna." I think it's a nice starter design. I would never recommend it to someone who is serious...
by k6sti
20 Apr 2016 01:02
Forum: Antennas
Topic: Wanted Supplier of Band 2 Beam Antennas
Replies: 18
Views: 7230

Re: Wanted Supplier of Band 2 Beam Antennas

Peter Körner optimised some small Yagis and designed the very large multi-reflector antennas with from 9 to 19 elements, which offer unprecedented performance but really need a large lattice tower with a heavy-duty rotator... Take a look at the 13 photos of Körner 19.3 installations here: http://ha...
by k6sti
22 Mar 2016 19:58
Forum: Antennas
Topic: Coax for a balun
Replies: 2
Views: 2063

Re: Coax for a balun

Glenn, I don't know where you can get a short length of RG-6 with complete specs, especially with a copper shield. I'm not sure RG-6 is made except with an aluminum shield. But note that you don't need to restrict your search to 75-ohm cable. The optimum impedance for a halfwave coaxial balun is 150...
by k6sti
15 Mar 2016 16:48
Forum: Antennas
Topic: Help to buy antenna...
Replies: 9
Views: 3224

Re: Help to buy antenna...

Sven Jacobson, who owned the VHF Teknik AB antenna manufacturing company in Sweden for many years, has one of the Antennenland LPDAs. He does not recommend it because of the way the elements are mounted. They have ribbed ends and are simply pushed through holes in the booms. You can see this if you ...
by k6sti
14 Mar 2016 11:44
Forum: Antennas
Topic: Help to buy antenna...
Replies: 9
Views: 3224

Re: Help to buy antenna...

I believe the gain figure for the Antennenland log-periodic is overstated by about 2.5 dB. Here's a DAB antenna of similar size you can build yourself that goes to 240 MHz, has 50Ω impedance, and has higher real gain: http://ham-radio.com/k6sti/dab.htm Note that gain in dBi = gain in dBd + 2.15 dB. ...
by k6sti
05 Mar 2016 18:11
Forum: Antennas
Topic: Stacked 6-Element Log-Yagis
Replies: 4
Views: 2902

Re: Stacked 6-Element Log-Yagis

Yes, that looks like PVC near the Yagis. Without it, the crossboom would affect the element currents. One of the disadvantages of horizontal stacking is the need to use a nonconductive crossboom, at least in the vicinity of the antennas. I just redesigned the vertical stack using my latest optimizer...
by k6sti
05 Mar 2016 14:34
Forum: Antennas
Topic: Stacked 6-Element Log-Yagis
Replies: 4
Views: 2902

Re: Stacked 6-Element Log-Yagis

Image

The azimuth pattern is more sensitive than usual to ground proximity. To improve it at practical installation heights, I added a design optimized at 30 feet over ground.

Brian
by k6sti
03 Mar 2016 16:38
Forum: Antennas
Topic: Stacked 6-Element Log-Yagis
Replies: 4
Views: 2902

Re: Stacked 6-Element Log-Yagis

Image
by k6sti
28 Feb 2016 14:50
Forum: Antennas
Topic: Stacked 6-Element Log-Yagis
Replies: 4
Views: 2902

Stacked 6-Element Log-Yagis

http://ham-radio.com/k6sti/ly6f.gif To obtain a narrow main beam along with low backlobes, I optimized a stacked pair of 6-element log-Yagis. The booms are 114" long and spaced 78". Forward gain is 8.8-10.2 dBd, and secondary forward lobes and rear lobes are down 30 dB. http://ham-radio.com/k6sti/d...
by k6sti
21 Feb 2016 13:59
Forum: Antennas
Topic: Korner 9.2 build
Replies: 4
Views: 2181

Re: Korner 9.2 build

I like those simple element mounts, Glenn. Loss for baluns similar to the one you're using is about 0.75 dB. Loss for a halfwave coaxial balun is 0.05 dB midband and 0.12 dB at the band edges. This data might help you decide whether it's worth the trouble to replace that balun.

Brian
by k6sti
17 Feb 2016 13:30
Forum: Antennas
Topic: K6STI 5 element Yagi available from HS Publications
Replies: 29
Views: 7600

Re: K6STI 5 element Yagi available from HS Publications

As a G0KSC fanboy, you'd do well to take my warning seriously. If you e-mail me, I'll explain the basis for it.

Brian

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