Love them... Yogi Beara. I thought the same thing when I first hear of a Yaggi, ha

42 dude, 42.

Don't. TEMPT. me!! 73,

I did not need to learn that...

Enjoy - it's a great hobby! 73!

Absolutely! Although I can hear the safety sallys getting triggered at that from here...

Big, very big. The driven elements would be approx 33 ft each, spanning 66 ft wide. The reflector would be 5% larger 69'4". The director would be 5% smaller than the driven element at 31'4". However, 40m yagis are typically loaded so you can make it about half this size and the coils make up the difference.

Great question - it's because IMPEDANCE acts a little different than RESISTANCE. If the two elements were literally touching, both impedance and resistance between them would be zero. If I add a wire (hairpin) between the elements, resistance will be zero; however, impedance will vary depending on frequency. By choosing a correct length of wire for the frequency of interest (146ish MHz in this case), I could create a situation where the antenna's impedance (roughly 73 ohms) is placed in parallel with the impedance of the hairpin, and works out to a total impedance of 50 ohms. One of the concepts that has been hardest for me to grasp since I got into ham radio has been the difference between resistance and impedance, so no foul struggling with it!! Kinda help? 73,

Robert, great question - the coax that runs to the yagi has a nominal 50 ohm impedance. Therefore, any antenna attached to it would work best if its nominal impedance were also 50 ohms. Unfortunately, many antenna designs have different impedances. If you ignore this and just plug the antenna into the coax anyway, your antenna will likely have a high SWR (VSWR if you're a cool kid). This can easily be fixed with any number of different impedance matching transformer designs. Some look like what 'normal' folks would call a transformer - windings on either side of a metal, ferrite or air core - but some don't. Hairpin (aka Beta or shunt) matches are one of those. Other common impedance matching transformers include the gamma and T matches. Hope that helps!

@@hamradioexperience okay... but if you put it on either side of the driven element what is the purpose for the gap? Aren't you effectively closing the circut?

@@rsedaker so that's the weird thing about impedance matching transformers. At low frequencies, you're absolutely right, i.e., if you took an ohmmeter to the driven element, you'd read basically zero ohms, but ohmmeters only measure low-frequency impedance effectively. It turns out that, because the hairpin length is a significant (albeit small) percentage of the 2m wavelength, instead of acting as a short, it acts like a small inductor to cancel the capacitance inherent to the yagi's design! Digging further into this would be a great topic for a video. It's kind of mind blowing how a wire is a resistor and an inductor at different frequencies. It's not something we normally deal with in everyday life outside of the radio hobby.

Someday I'll do something cool with it....!!

All great thoughts. I ended up buying an offset attenuator to go with my antenna. I did discover that cheap HTs are NOT good for fox hunting, but word on the street is Christmas might take care of that problem for me. Regarding the work mat, that may have been done, and there may be permanent damage on the table to show for it.......... 73,

The awkward thing is, at high frequency (like 144MHz), the antenna presents like a ~72 ohm load. It'd be better for the radio if it saw 50 ohms. If I shorted the elements with a ~1/2" or less wire, it would be a short, like you'd expect. Because I used about 5in of wire, It acts like a bit of a load (again, only at high frequencies), bringing the antenna's total impedance to 50ish ohms. Hard concept to grasp! And good thinking on the 1/4-20...shoulda done that. 73,