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Discussion Starter #1
At some point this winter, say January/February timeframe, I'm thinking of building some yagis.

Here, I want one for UHF 60,65,66, and so do a couple of my mates.

I imagine there might be others in the Ottawa region who would want a custom yagi, for some particular channel or group of channels.



So, come this winter, I hope to again open the workshop for a day (really, only a day needed for these!), and set up a small custom production line for a few yagis.

They don't even have to be for the same channel(s) -- the time savings come from using common materials and constructions. The element lengths (different for each yagi) shouldn't really affect the time required by much.

Depending upon numbers, we might even include coax-loop baluns for each yagi as part of the build.

So.. if you're reading this, and within reach of us here in West Ottawa, then bookmark this thread. Come winter, I'll post again here, with a pointer to a new thread for the Ottawa Yagi Build Party.

Assuming there might be a couple of others interested.

Posting your interest here now won't reserve a spot for you, but it will help motivate me to actually make this happen in a few months time. ;)
 

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That's great news, Mlord! I'm only wishing a trek across Canada wouldn't be required for me to attend :). I'll be one of the many who will follow the progress from afar, but suspect you're going to have a full house. Looking forward to this one!

A Yagi is actually going to be my next project in the next couple weeks...
 

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Key words to meditate on

I know that mlord wants to keep this small and local, but if you're from a warmer climate and thinking of attending, here are some things to consider:
  • Ottawa
  • Winter
  • January
  • February
  • cold
  • bitter
  • numbing
  • wind chill
  • ice
Ottawa is beautiful in the winter but just be aware of what to expect. :D

There are a few hotels/motels in the Nepean area too, although mlord and other Ottawans can make better recommendations.
 

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Ottawa Yagi Build Party

You may have gathered that I'm from Florida. January/February are months we look forward to here. Those are the months I will be most comfortable messing around with my OTA stuff in my ATTIC !!!. Maybe the day of the party, I'll take a jump into my pool.

Hey, I'm originally from Michigan, so I know (intimately) what all those Key Words are. One you forgot :

- Shoveling

But really, this sounds like fun. I do hope you all have a good time and I'm looking forward to posts that I know will be coming.
 

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Carpool?

I'm from Kitchener, and I'd be willing to make the trip as my mom's about 1/2 way in picton. Anyone interested in carpooling?

Thanks, Ivan
 

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Is this an open invitation to contributers of this forum? I haven't been actively contributing to this forum, but I have been rounding up materials to build some Yagi's this winter. If the invitation is open, I'll bring some food!

I suppose i should have asked this before I started looking for carpoolers...

Thanks, Ivan
 

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Discussion Starter #9
This thread is intended to stir the imagination, and to gauge the interest level for such a gathering. Details and date have yet to be decided..

I suspect we'll begin preparations a few weeks in advance, so that any computer modeling / calculations can be done beforehand, and measurements and materials will be ready for construction on the actual day.

The idea is, you may have the need and the knowledge, but lack the facilities to build. I have the facilities, and together we can produce some good antennas.

So, if you're thinking that this might be for you.. then start considering exactly which yagi you might need/want to build. Then play around with the K7MEM yagi calculator for starters. The only downside with his calculator, is that it gives the wrong impedance (200 ohms, rather than 300 ohms, as Autofils determined for us all last year).

Still, at this point we do have October, November, December, Christmas, and New Years to pass, before preparations begin in earnest!

Cheers
 

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Is this an open invitation to contributers of this forum?
Yes, but as noted earlier: "Posting your interest here now won't reserve a spot for you [it's too early for that], but it will help motivate me to actually make this happen in a few months time."

Cheers
 

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mlord,you may want to check out VK5DJ yagi calculator, its has more desing flexibility.

balm, if you want to carpool just let me know.
 

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mlord,you may want to check out VK5DJ yagi calculator, its has more desing flexibility.
Err.. thanks for the suggestion, really!

But no, it is far less flexible than the K7MEM calculator. The former runs only on a specific vendor's operating system, whereas the latter runs universally on any platform.

That's important to me, since I don't pay good money for commonplace software like operating systems. Just like I don't pay good money to watch free television, either. ;)

And oddly, neither of those two programs seems to produce antennas with the 300-ohm impedance we need here. But they can be a good starting point.

Cheers
 

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mlord, I will check out the K7MEM calculator. In general if you are designing 1/2 wavelenght open dipole the impedance will be near 75 ohms requiring a 1:1 balun at the feed point if you are using 75 ohm coax, a folded dipole will have an impedance near 300 ohm requiring a 4:1 balun for 75 ohm coax. There are many other factors that will vary impedance including distance in between the terminations at the feed point. Baluns are what I am trying to understand at this point.
 

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I think the K7MEM calculator has to be considered the standard here at this site for VHF yagis due to all the use and references to it.

For folks wishing to attend who want to get into the RF design side of things, I'd recommend visiting the K7MEM site for familiarization before the Build Party.
 

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Thanks mlord and Stampeder, K7MEM's website is a valuable resource for the electronic hobbyist and hams. I will keep his site as a bookmark along with this one;)
 

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Discussion Starter #16
mlord, I will check out the K7MEM calculator. In general if you are designing 1/2 wavelenght open dipole the impedance will be near 75 ohms requiring a 1:1 balun at the feed point if you are using 75 ohm coax, a folded dipole will have an impedance near 300 ohm requiring a 4:1 balun for 75 ohm coax.
Yeah, that much we already know about.

The K7MEM site's descriptions might lead one to believe that the yagi designer there yields about 300 ohms (with folded dipoles). But when other folks in this forum enter the results into 4nec, it spits out "200 ohms" (or 50, for non-folded).

Which makes sense for just about any application other than television.

Cheers
 

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Discussion Starter #17
At some point this winter, say January/February timeframe, I'm thinking of building some yagis.

Here, I want one for UHF 60,65,66, and so do a couple of my mates.
Heh.. it was a nice early afternoon here, so I just couldn't wait.. there's now a shiny new UHF-65 yagi up on the tower!

That's one less for me to build this winter. Now I just need the rain to stop long enough for a photo or two!

Edit: Photos posted in the original UHF/VHF yagis thread.

Cheers
 

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I'm interested

Hi mlord,

I would really like to come. I live in Barrhaven and have made a few antennas that are in my attic.

Thanks,

Glen
 

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mlord,you may want to check out VK5DJ yagi calculator, its has more desing flexibility.
Here is a NEC file for VK5DJ folded diplole model for those folk who would like to play around to see what the intended antenna will do.

This one was calculated by balm for Channel 22 and approx 16 dBi. I added some comments to show where the calculated outputs should be entered.

The model can probably be used as a template for other calculator outputs too
Code:
CM NEC file for VK5DJ's YAGI CALCULATOR results
CM Folded version
CM All dimensions in meters
CM 
CE

SY R1_P=0.030    ' Position of the reflector on the boom
SY R1_L=0.281    ' Length of the reflector  

SY DP_POS=0.145  ' Position of the Folded Dipole
SY DP_LEN=0.277  ' Tip to Tip length of the dipole 
SY DP_DIA=0.050  ' Diameter of rounded ends of Dipole

SY D1_P=0.188    ' Position of the first director
SY D1_L=0.253    ' Length of the first director 
  
SY D2_P=0.292
SY D2_L=0.251
  
SY D3_P=0.416
SY D3_L=0.248

SY D4_P=0.559
SY D4_L=0.246
  
SY D5_P=0.720
SY D5_L=0.244
  
SY D6_P=0.893
SY D6_L=0.242

SY D7_P=1.074
SY D7_L=0.240

SY D8_P=1.264
SY D8_L=0.238
  
SY D9_P=1.463
SY D9_L=0.237

SY D10_P=1.670
SY D10_L=0.235

SY D11_P=1.886
SY D11_L=0.234
 
SY D12_P=2.107
SY D12_L=0.233

SY D13_P=2.332
SY D13_L=0.232

SY D14_P=2.559  ' Position of the 14th director
SY D14_L=0.231  ' Length of the 14th director 


' Add more or delete directors if required

  
SY Wire_Radius=0.00127
SY Refl_Radius=0.00127

SY s00_x00=R1_P
SY s00_y00=R1_L*0.5

SY s12_x00=DP_POS

SY s14_z00=0.0
SY s15_z00=DP_DIA*0.5*SIN(22.5)
SY s16_z00=DP_DIA*0.5*SIN(45)
SY s17_z00=DP_DIA*0.5*SIN(67.5)
SY s18_z00=DP_DIA*0.5

SY s14_y00=DP_LEN*0.5
SY s15_y00=(DP_LEN-DP_DIA*(1-COS(22.5)))*0.5
SY s16_y00=(DP_LEN-DP_DIA*(1-COS(45)))*0.5
SY s17_y00=(DP_LEN-DP_DIA*(1-COS(67.5)))*0.5
SY s18_y00=(DP_LEN-DP_DIA)*0.5

SY s21_x00=D1_P
SY s21_y00=D1_L*0.5

SY s22_x00=D2_P
SY s22_y00=D2_L*0.5

SY s23_x00=D3_P
SY s23_y00=D3_L*0.5

SY s24_x00=D4_P
SY s24_y00=D4_L*0.5

SY s25_x00=D5_P
SY s25_y00=D5_L*0.5

SY s26_x00=D6_P
SY s26_y00=D6_L*0.5

SY s27_x00=D7_P
SY s27_y00=D7_L*0.5

SY s28_x00=D8_P
SY s28_y00=D8_L*0.5

SY s29_x00=D9_P
SY s29_y00=D9_L*0.5

SY s30_x00=D10_P
SY s30_y00=D10_L*0.5

SY s31_x00=D11_P
SY s31_y00=D11_L*0.5

SY s32_x00=D12_P
SY s32_y00=D12_L*0.5

SY s33_x00=D13_P
SY s33_y00=D13_L*0.5

SY s34_x00=D14_P
SY s34_y00=D14_L*0.5

' Add the coordinate calculations of additional directors here


GW	2	3	s12_x00	s14_y00	s14_z00	s12_x00	s15_y00	s15_z00	Wire_Radius
GW	2	3	s12_x00	s15_y00	s15_z00	s12_x00	s16_y00	s16_z00	Wire_Radius
GW	3	3	s12_x00	s16_y00	s16_z00	s12_x00	s17_y00	s17_z00	Wire_Radius
GW	4	3	s12_x00	s17_y00	s17_z00	s12_x00	s18_y00	s18_z00	Wire_Radius
GX	4	001

GW	9	13	s12_x00	s18_y00	-s18_z00	s12_x00	0	-s18_z00	Wire_Radius
GW	10	15	s00_x00	s00_y00	0	s00_x00	0	0	Refl_Radius
GW	11	15	s21_x00	s21_y00	0	s21_x00	0	0	Wire_Radius
GW	12	15	s22_x00	s22_y00	0	s22_x00	0	0	Wire_Radius
GW	13	15	s23_x00	s23_y00	0	s23_x00	0	0	Wire_Radius
GW	14	15	s24_x00	s24_y00	0	s24_x00	0	0	Wire_Radius
GW	15	15	s25_x00	s25_y00	0	s25_x00	0	0	Wire_Radius
GW	16	15	s26_x00	s26_y00	0	s26_x00	0	0	Wire_Radius
GW	17	15	s27_x00	s27_y00	0	s27_x00	0	0	Wire_Radius
GW	18	15	s28_x00	s28_y00	0	s28_x00	0	0	Wire_Radius
GW	19	15	s29_x00	s29_y00	0	s29_x00	0	0	Wire_Radius
GW	20	15	s30_x00	s30_y00	0	s30_x00	0	0	Wire_Radius
GW	21	15	s31_x00	s31_y00	0	s31_x00	0	0	Wire_Radius
GW	22	15	s32_x00	s32_y00	0	s32_x00	0	0	Wire_Radius
GW	23	15	s33_x00	s33_y00	0	s33_x00	0	0	Wire_Radius
GW	24	15	s34_x00	s34_y00	0	s34_x00	0	0	Wire_Radius

' Add more director wires here

GX	17	010

GW	100	31	s12_x00	s18_y00	s18_z00	s12_x00	-s18_y00	s18_z00	Wire_Radius

GE	0
LD	5	0	0	0	58000000
GN	-1
EK
EX	0	100	16	0	1.0			
FR	0	31	0	0	480	6
RP	0	1	61	1000	90	0	3	6		
EN

The NEC results for 518MHz are

Raw Gain 16.21 dBi
SWR 1.278 (for 300 Ohms) 1.1997 (for 200 Ohms)
Impedance R 236 X 15.77

So it looks like this one is also optimized for 200 Ohms.
 
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