2 Meter Yagi Antenna w/ Gamma Match (Part 2/2)

[@DaveTadlock]

Normally all the elements are grounded to the boom when using a gamma match. An antenna with a dipole driven element uses an insulator to separate the two halves of the driven element and can be used to insulate it from a metal boom. Dipole fed antenna elements can be mounted on either a non-conductive boom or a metal boom using insulators. Hope this helps and thank you for watching! :)

[@DaveTadlock]

It was fortunate that the holes that I reused were spaced 12-3/8" which is an optimal length on two meters. The TV elements have also been trimmed to the correct lengths and were calculated using yagi antenna modeling software. This old TV antenna has been completely turned into a terrific little 2 meter amateur radio antenna. ;)

[@1942Grampz]

Dave, excellent videos on all your projects, very instructive and educational. Well done young man you are an inspiration to young amateur enthusiasts. All the best 73 ...Owen G0RCL

[@DaveTadlock]

@virtualbush Yes, the adjustment may be a bit tight. To increase frequency I could have made the gamma tube a few millimeters longer. Sliding only the grounding strap inwards seems to lower the frequency. SWR will of course also change with height and vary depending on the coax cable length. Thanks and 73! :)

[@virtualbush]

Perhaps some demonstration/information (A short Part 3?) regarding how to tune using the gamma in case the SWR is a bit higher than we might like. Enjoy! I will indicate that we would slide the tubing either in or out over the dielectric. Hopefully not inward in this case because your assembly is tight!

[@DaveTadlock]

@M0csi Glad you can use the info. Good luck with your antenna projects and have fun! :)

[@DaveTadlock]

@JuggledaJungle The original antenna worked great receiving the FM broadcast band (105 MHz) when the TV antenna was new and fresh out of the box from Radio Shack. But the antenna, old and broken now, has found a new useful purpose by being converted to transmit and receive on Amateur Radio (ham radio) frequencies. ;)

[@1migmaster1]

Sir Dave just wondering if i could have the radials pointing vertically instead of in a horizontal position.. and thanks for all the great instruction very detailed.....

[@DaveTadlock]

@zx636racer Element spacing is mentioned in part one. I simply removed the plastic TV antenna insulators and used the same holes to mount the elements. The spacing is 12-3/8" between all elements.

[@teddean7763]

Dave what the gentleman is referring to ? what did you use to isolate that driven Element from the main Boom did you use the old TV plastic mount to isolate the element from touching the main boom and the #10 screw as well or is it isolate at the gamma mach tube by using the11" RG-8 coax by leaving the isolate sheld around the center wire isolating it from the driven Element so there's know need to isolate the Element from the boom... I see when you were testing it the SWR didn't look to bad for not having the driven Element isolate from the main boom funny how the Gamma mach works with the driven Element with out being isolated from the main boom sharing the other elements I can see how it works hum , I have a 10 meter three Element Beam watch has a gamma mach tube and the driven Element is not isolate from the main boom as well and I had some what of a high SWR Inlass the gamma tube was not isolate very well I need to look in side the gamma tube and see if there is a short ? Well Dave love the videos keep up the good work and God bless.... Ted Dean KD2ARD ..... I love making my own Antennas system to work the bands 73s I do believe that you need to isolate the Element so the the Gamma tube will tune well for best SWR with in those frequencies you are opening on wather it be ssb or fm. I am going to build one out of and old tv antenna and will isolate the driven Element with Gemma

[@DaveTadlock]

@bognapalm If I remember right it has something to do with the formula for calculating a series LC circuit. The formula is in my old advance class study guide but I'll have to search for the book. Some yagi antenna modeling software, many available for free download on the internet, will calculate the length of the gamma rod for you. As for this style of gamma match you could scale it down for the 70 cm band but it might be a bit long and unsightly if used on a lower band such as 10 meters.

[@DaveTadlock]

@808514 Thanks! I'm glad you enjoyed it. :)

[@DaveTadlock]

No. The driven element is attached directly to the boom. More information about building this antenna is on my web site. The link to my web site is on my KZbin channel. Click my username, then click the Feed tab. The link is in the upper right corner of the page. 73 and thanks for watching! :)

[@joee2047]

when you wrapped the copper part of the gamma match on the pin of the coax connector and than soldered it,,,, it was only to the center pin and not touching the side at all,,, is that correct,,, just so I know,,,, thanks!!!!

[@buckeye43210]

Could you rotate the connector 90 degrees? That way you'd have a straight on connection to the connector's center pin.

[@RT038]

Hey mate I just want to know the coax gama match how is the end made.

[@M0csi]

Thanks for the information with regards to the Gamma Match ... pictures or in this case now video ... tell a thousand words ... I will use this feed system for 440mhz on the beams I make ... Thanks Mike ...

[@techiefan1986]

Technically a 4 element yagi will only have 6dbd forward gain. Maybe 7.5 dbi. The gamma match method will add some loss, so may actually be less than 6db over a dipole, that doesn't impose such a matching method. The SNR improvement makes it a worthwhile antenna nonetheless however

[@roblawrence8622]

hi Dave,, ive just built this 2m yagi plus gamma match,, my first build ;) i enjoyed the build, thanks for the great videos,, im fairy new to 2m radio,, you say this antenna is horizontal for SSB so do you mean if i turn it vertical,, i can use it for FM ? cheers Rob

[@heffptbo]

what is in the middle of your gamma (the white insulator....with copper). Can you not just use the element, or double aluminum elements up together? When do you have to use a type capacitor in line with the coax?

[@richardpullen293]

Please tell us what the spacing between the gamma tube and driven element is. Thank You

[@genebodenberger]

I have watched these 2 videos multiple times. I am still confused, even with your last comment. Can the boom of this antenna be attached to ground? I am not talking about the negative connection on the SO-239. Could the boom be electrically attached to a metal post pounded into the ground? No one does antenna videos as well as you do on the entirety of KZbin. 73's KA7QJU, Gene.

[@DaveTadlock]

Yes. The entire antenna is grounded except for the center pin of the SO-239 and the coax lead running through the gamma match tube. No problem in mounting it to a metal mast. Thanks for watching and 73! :)

[@genebodenberger]

Thank you so much for the prompt reply. Will the antenna function the same if the only ground is supplied from the negative connection from an HT? If I hoisted it up into the trees with rope, would there be any negative affects of not having the boom earthed?

[@DaveTadlock]

Gene B It should work but yagi antennas are normally mounted on a mast.

[@shuttereye4740]

how long is your gamma?

[@honeybees1]

Is the driven element isolated from the rest of the antenna?

[@thekilomike6012]

The adjustment of the gamma match was not addressed and it looks wierd all the way to the end. Flip it over if you want it vertical for FM. The mast does not need to be grounded, the elements work in relationship to each other. Want more elements ? Male them a little shorter or the same as the last director. Space about the same. Check online yagi calculators.

[@ericlessard6653]

dave can you tell me the formula for figuring out the length of a refelector and director? thanks

[@joe41018]

how would i build a 900mhz RF yagi antenna i love this stuff

[@martingibson8273]

A tub of flux is your best friend for connector soldering..

[@JuggledaJungle]

this can be used as an fm antenna??

[@tyrionstark5734]

You should show on air testing more often.

[@JuggledaJungle]

what bout the frequency? it will transmit in 144 mhz?? how can you fix that to for example 105 mhz?

[@MegaSkimy]

Can I use this type of antenna for WiFi signal

[@DaveTadlock]

@matthewz07 Have fun with your new antenna and good DX! :)

[@asepasep1772]

Semoga sukses selalu ( prom indonesia)

[@mrcranevo1um267]

dave i just follow instruction... the same thing if i want to do vertical..

[@808514]

Excellent vid! 73, WH7WX

[@davidjames1684]

9.5 dBi is not 6.5 dBd.