Roast my Yagi

[Borage257]

Better a bad start than none at all. Roast my "junkyard" yagi, not a soldered joint in it. No idea what SWR is. It was cut with a center frequency of 465MHz. Hasn't been tuned yet. The NanoVnA is in the mail.

 

[axorlov]

Looks good! You will likely need a common mode choke on your coax, but maybe you could get away without it. And clean the mess on your workbench! It affects the SWR.

And the special praise for this tool (I do not know the english word for it, the push driver maybe?) with the purple handle, in the middle of the picture, that looks like a long screwdriver. I haven't used it myself in 30 or so years, and this is the first time I see it in the last 20 years in the the time-relevant picture. What other ancient wood working tools do you have? Judging by the looks of your workbench you may have some!

[Lscott]

1 hour ago, Borage257 said:

Better a bad start than none at all. Roast my "junkyard" yagi, not a soldered joint in it. No idea what SWR is. It was cut with a center frequency of 465MHz. Hasn't been tuned yet. The NanoVnA is in the mail.

 

Hum, the black wire between the two half of the driven element looks like you're trying to use a "hair-pin" matching section. Any changes in dimensions will impact the match.

Hairpin Article Match.pdf Baluns.pdf

[Borage257]

1 hour ago, axorlov said:

Looks good! You will likely need a common mode choke on your coax, but maybe you could get away without it. And clean the mess on your workbench! It affects the SWR.

And the special praise for this tool (I do not know the english word for it, the push driver maybe?) with the purple handle, in the middle of the picture, that looks like a long screwdriver. I haven't used it myself in 30 or so years, and this is the first time I see it in the last 20 years in the the time-relevant picture. What other ancient wood working tools do you have? Judging by the looks of your workbench you may have some!

That tool is called a Yankee Screwdriver or a push screw driver. I have a few stanley/bailey pattern planes, a European style scrub plane and few other ( brace and bit etc). Use em too when I have a mind to.

[Borage257]

44 minutes ago, Lscott said:

Hum, the black wire between the two half of the driven element looks like you're trying to use a "hair-pin" matching section. Any changes in dimensions will impact the match.

Hairpin Article Match.pdf 133.61 kB · 1 download Baluns.pdf 924.06 kB · 0 downloads

I've been looking for information on hair pin match considerations. Post the wrong answer on the internet to find the right one!

[Borage257]

The antenna kinda works. I tested it briefly pointing away from my local repeater I still got a squelch tail, but i was able to faintly pick up a repeater about 40 miles away. I have a broken tape measure I will likely turn into a better yagi.

Would ferrite chokes work better than my attempted balun?

[Lscott]

6 minutes ago, Borage257 said:

The antenna kinda works. I tested it briefly pointing away from my local repeater I still got a squelch tail, but i was able to faintly pick up a repeater about 40 miles away. I have a broken tape measure I will likely turn into a better yagi.

Would ferrite chokes work better than my attempted balun?

Likely may work good enough. You can tell by moving the coax around. If the SWR changes very noticeably it isn't working. 

[axorlov]

19 hours ago, Borage257 said:

Would ferrite chokes work better than my attempted balun?

Quick and dirty test for common mode is to measure SWR when not touching the outside of connector with your finger, and then measure SWR again when touching connector with your finger. No change in SWR indicates that there is no or negligible common mode current, while huge swings (4:1 or so) indicate there is a very considerate common mode current.

[Lscott]

On 8/21/2022 at 12:27 AM, Borage257 said:

I've been looking for information on hair pin match considerations. Post the wrong answer on the internet to find the right one!

Oh, if you want to try your hand at modeling the antenna try this software. It's free now.

https://www.eznec.com/

[Borage257]

Glamour shots and meter readings. 40 miles from my roof top. SWR at 468MHz is 1.024

 

[Lscott]

The match is better than I expected.

Looking at the photo the BNC to Banana Jack adapter is a terrible idea. You would have been better off looking for a short coax with a BNC connector on the ends, then cut one off and attach the free end to your Yagi.

[Borage257]

2 hours ago, Lscott said:

The match is better than I expected.

Looking at the photo the BNC to Banana Jack adapter is a terrible idea. You would have been better off looking for a short coax with a BNC connector on the ends, then cut one off and attach the free end to your Yagi.

I know it is, but you gotta smoke with the pack you got. I'll be getting some better terminations soon(tm). The cable was found in a pile of junk out in the truck yard where I work.

[Lscott]

4 hours ago, Borage257 said:

I know it is, but you gotta smoke with the pack you got. I'll be getting some better terminations soon(tm). The cable was found in a pile of junk out in the truck yard where I work.

I guess you can't beat free.

[Hairbear]

I’ve never had roast Yagi but I’ve heard it tastes like chicken.

[Ian]

On 8/25/2022 at 9:37 AM, Lscott said:

The match is better than I expected.

Looking at the photo the BNC to Banana Jack adapter is a terrible idea. You would have been better off looking for a short coax with a BNC connector on the ends, then cut one off and attach the free end to your Yagi.

It's already reading 1.04, I wouldn't change a single thing!  … But yeah, that would have been more elegant looking.

 

Still, it's hard to beat free. 

[Q12]

Had good Conversation with owner of this Yagi!
 

Comes in real good and quiet.
 

Can't really Roast Something if It can do the Job!

[Borage257]

On 8/22/2022 at 8:01 AM, Lscott said:

Oh, if you want to try your hand at modeling the antenna try this software. It's free now.

https://www.eznec.com/

Here is the model put together in EZNEC. I found a yagi template an put in my dimensions. Not sure how to put hair pin matches in.

Here are the measurements from https://sites.google.com/view/kn9b/yagi:

YAGI Antenna Solution

Reflector Element; Length = 12.84 In, Position on Boom = 0.00 In
DP/Driven Element; Length = 12.40 In, Position on Boom = 4.02 In
Director Number 1; Length = 11.00 In, Position on Boom = 9.21 In
Director Number 2; Length = 10.92 In, Position on Boom = 14.40 In
Director Number 3; Length = 10.88 In, Position on Boom = 19.58 In

Key Parameters
Gain = 8.0 dB
3 dB Beamwidth = 72 °
One Wavelength = 25.94 In
Freq = 465.000 MHz
# Elements = 5
Length Units = In