I've been building antennas since 1979 on CB and from 1984 on ham radio. For anyone just getting started, this has to be the best, clearest description of the gamma match I have ever seen. Yes they do work and, if your making longer antennas, say for 10 Mtrs or 15 Mtrs...not having a plastic 'centre feed', these antennas are very strong and will face windy conditions much easier.
This is the standard gamma match that comes with many commercial yagi antennas. Thanks so much for the explanation of the way it works. They are an easy and great way of tuning
I am fairly new to antenna design and construction. This video was very well done and helped me immensely in understanding the principles behind a gamma match. Thank you!!
Of course the real explanation of a gamma match and how it works is an interesting discussion. First of all, the parallel conductive segment to the driven element steps up the impedance, much like a folded dipole. This in turn adds inductance. The variable capacitor component is then used to tune and cancel this additional inductance out.
This is great valuable information on the Antenna, driven element and gamma match. Any additional information on 27 mhz antenna building would be great. Whether, it be 4 element beams or multi-directional antennas. Thanks for the information tutorial, enjoyed it. Billy...Albq. N.M. 2 / 16 / 2023
Length of a half wave antenna in feet = 468 divided by frequency in MHz. This can be applied to any band. Thanks for watching and check out my other videos to see some of my other creations. 73
If they are setup correctly, the gamma works great. I had a 2 element V Quad several years ago, it was gamma matched and had an SWR of 1:1.3 or less from 25mhz through to 29mhz. I still have the QSL card from a guy in country that no longer exists in Europe. We chatted on 27.650 USB for almost 2 hours one night, at an S9 or above. Damn great antenna that one, I still miss it. Nothing came close for OOB usage and pirate CB radio. A fellow I used to compete with for contacts had a 5 element Yagi about 10 foot higher than my quad and he needed 100w more than I did to make the same contacts. Nothing beats a well tuned antenna, and the gamma match is a fast easy way to acheive that.
A great tutorial on Gamma Match's. I've been building yagis now since 1972, and have used many feed hookup designs. "T" matches. Delta feeds, Pigtails, and of course Gamma Roads. and I can tell you I've stayed with the Gamma on 99% of my builds . I make most of mine with RG8 coax center dialectrics for the center inside an alumimun tube from a HF mono bander thru 6m,2m 220 mhz 432 Mhz to even 900 mhz yagi's and with great success in feeding. adjusting and performance. thanks for reminding me that my choice was correct! and for sharing. de Ellis WA1RKS
Saw this thumbnail and thought it was another video of a silent key called Stan Gibilisco. He's got hundreds of videos on his channel but sadly passed away a number of years ago. The presentation and style of this video is uncanny in similarity to his ham and electronics tutorials.
The capacitance cap on a Hustler 4 BTV could be used as a Gama Match! You replace the ones you use with aluminum stripes. Or buy replacements from DX Engineering! They sell tubing and parts to build your own antenna,
Hands down the best description I've seen of the gamma match. I just got a yagi that uses one and it works, but I couldn't make heads or tails of it. Your explanation of the variable resistor was excellent. Question: How does the location of the strapping point come into play? It can't be arbitrary.
The shorting strap combined with the variable capacitor when properly adjusted form a resonant loop which tunes out reactance and induces a standing wave in the driven element. Hope this helps. Thanks for watching and share with your friends. 73 de VO1DV
@@toddhowell2299 experimentation with various settings until you achieve resonance. Forming a resonant loop sometimes takes a bit of trial and error but with patience you can tune the match 1:1
@@toddhowell2299Get a $60 nanoVNA and hook it to the antenna. You can see exactly how each of the adjustments affects the SWR curve as it moves around the band. It helps a lot.
interesting as always, great info for antenna builders. Here's one for ya, how could you incorporate that same idea into a vertical antenna? I know how i might do it, but just curious if my idea would suck.. LOL
Your explanation helped me. Yes the center is at zero voltage, its just hard to seperate grounding and the null point of a driven circuit. The far side of the half wave looks like it should be driven. Hard to remember the voltage on the right half will induce a voltage on the left side. I keep wanting to think the atenna works because the right hand, driven side, sucked the left side electrons past the ground, null point, to the right hand high side. Right???
When you look at this thing, think of a center tapped transformer, and the voltage wave across it. The null point of the "sine" wave is the ground point aka neutral, and each end the opposite of each other. Doesn't matter which end is energized the other is opposite. So you tune the injection point and the other follows suit. In my limited understanding...
Great explanation. How does it work when there is no capacitor present and there is a direct connection via a aliding bar, as with a yagi i use and a halo i have just built?
Your “sliding bar” adjusts to find resonance. The “sweet spot” I am guessing as I haven’t seen your antenna. Glad your antenna is working for you. Keep up the good work.
On your 6m halo -- is the "halo" fully closed opposite the feed point / gamma match ? If so, is the overall tube length just 1/2 wavelength? I'm trying to find novel ways to build a more compact dipole for the high bands w/o inductive lengthening. great presentation of the gamma match! thank you so much!
@@madeinfoxtrap5539 Certainly, antennas are kind of mysterious and your explanation just made sense and made for comfortable understanding, thanks again.
Thanks for the axplantion about capacitance but what about the distance between center and shorting bar .the capacitor consist of shift and tube and the area can be changed according to their diameters so what about the distance between center and shorting bar please advice me.thank you very much.
Best I can tell you is experimenting until you achieve 1:1 Adjust until you reach resonance. A bit of trial and error involved but with some patience this design can be tuned flat.
@@bryanst.martin7134 mmmm not sure but I would go out on a limb and say no. If any decrease in sensitivity by any type of coating it would be negligible and probably so little that it ‘s unmeasurable
@@madeinfoxtrap5539 Thank you. Welding is one of my skills, and Al Oxide is tough thermally and electrically. Not sure how that may relate to low voltage, higher frequencies and such. Maybe the high level of signal amplification makes it negligible?
@@bryanst.martin7134 sorry I misunderstood. Anodizing is a coating applied to aluminum whereas oxidizing is generally caused by the oxygen in the air. This may be alleviated by coating with a thin film of grease or your favourite anti-oxidizing agent.
5:54 Isn't vacuum a worse insulator then air? I'm a pilot and I fly an airplane that can go up to 23,000 feet with a piston engine with magneto driven ignition system. We've had problems with arcing inside the magnetos at high altitude before because the less dense air is a poorer insulator. They sell pressurized magnetos to fix this problem. So I'm confused as to why a vacuum capacitor would handle a higher voltage. That seems at odds with my experience in another domain.
Look up “vacuum variable capacitor” They are used in high voltage applications Magnetic Loop Antennas use them They are normally expensive You are not flying in a vacuum While the oxygen may be thinner At higher altitudes there is still enough Oxygen for the engine to run. Magnetos behave differently than capacitors They have to produce a spark for ignition If a capacitor arcs a spark it may be catastrophic. Hope this helps and thanks for watching !
No it’s a monoband antenna but the 1/2 wave design characteristics may be applied to other bands. 1/2 wave driven element with 1/16 wavelength gamma rod may be applied to any band. According to antenna theory “Voltage at the center of a half wave antenna is zero” So this allows the driven element to be grounded at the center.
If you want perfection, hi efficency of you antenna system can't be broadband! Broadband is delusion of low cost propaganda! Professional systems make in 3 or 4 section selective super tuned systems from exciter lpf antenna system!
Great demonstration Thanks, One question, Is the distance between the gamma rod/capacitor to the radiating element non-critical, does it need designing in, or is it just a matter of practicalities? I really like the pf=7x wavelength rule of thumb. Thanks again
Usually 4 inches for 2M Hint : You are creating a resonant loop with the combination of capacitor , shorting bar , connector bracket and the radiating element.
Hello- I am trying to build a yagi antenna with gamma match tuned for 166.38mhz from the information in this video. I used a piece of lmr400 with a drilled aluminum tube, but ive clearly done something badly wrong as i have an SWR over 80 according to my nano vna. This is my first antenna build so im not sure what went so wrong- i suspect that I didnt ground it properly. Does the coax need to be soldered onto something as i have seen with split dipoles? I also thought maybe the sheath on lmr 400 disrupts capacitance. Your help would be much appreciated
Lot to unravel without a video but the driven element should be 1/2 wave center grounded Yes the shield of your coax Feedline should be bonded to the antenna. The center of your coax should be bonded to the gamma rod. If you are using a piece of coax for the gamma rod only use the centre conductor and insulation inside the gamma tube. Marine grade heat shrink tubing is great for insulating the gamma rod if it is not fitting perfectly. Using both conductors of a piece of Feedline as a gamma rod would certainly cause trouble as coax itself has its own capacitance between the two conductors separated by a dielectric ! Make a video so I can see what you are doing. 73
@@madeinfoxtrap5539 Many, many thanks. I made a split dipole antenna before you replied and got an swr of 1.6 using the same measurements/calculator as my previous failed antenna. After reading your reply I simply connected the coax sheath to the center of the driven element taking extra care to make sure the sheath and any stray braids didn't touch the center of the coax which was connected to the insulated wire (not coax this time) inside the gamma tube. Despite extremely poor unsoldered connections I managed an swr of 1.4 after fiddling a bit with the location of the gamma tube. My goal right now is to make a much more refined version that can take being mounted permanently outside, and then post a video guide for building antennas for MOTUS bird telemetry applications. I am sure I will have many more problems to work through but am relieved to no longer have an swr over 100 haha. Thanks again
Is there any difference if the center of the element is separated and ground going to one side and driven going to the other side while using a gamma match on the driven side? I am using a 3 element yagi I made with wire and the driven is divided in the middle, braid to one side and center to the other side and no gamma match. What is the effective difference?
It's the difference between having an adjustable match, and relying on the native impedance of the design of the antenna with no adjustment other than physically changing the antenna.
I have a sdr to spot the airplane's in my town, and build my own antenne and it works fine, but now i want to hear the airport tower and planes, can i do that with this antenna you show?
Not sure how far away from the airport you are but for any antenna to operate at utmost efficiency it should be a multiple of the wavelength You are using. Any antenna will work to receive but a resonant antenna will be the most efficient. If you are some distance from the Airport maybe an array like a yagi or cubicle quad could afford some gain. There are also RX preamplifiers to boost incoming signals from farther away. Yagi and quad are directional and offer a little gain depending on the number of elements. Other antennas used for RX in VHF bands are the DISCONE. Others have told me that they work fine. Hope this helps. Thanks for watching and share with your friends.
IIRC, matching method would not have an effect. It's the antenna design, feed point placement, and related factors that dictates gain and pattern. Also, height as well as surroundings will be in play.
@@tahoma6889 yes indeed there are many factors at play. I’ve heard from others that the hairpin match can be tricky to tune. I haven’t had a reason to try that matching system so I am not able to say anything about it. After getting great results with the gamma match on a half wave antenna I did make a 5/8 wave antenna for 2M and used a “shorted” or inductive matching system through a two turn coil. That’s about as close to the hairpin match as I have ventured.
@@madeinfoxtrap5539 hairpin just takes some getting used to. With todays tools we can zero them right in. It was a hassle back in the day when we were limited to an swr meter or dip. 😁
If performance-wise its the same, sounds like an easier match to build. Heard somewhere that a hairpin match is balanced, so it may need a 1:1 balun to match an unbalanced coax
Sir, what is the best dimensions of gamma match lets say for a 7 element 2 meter yagi? The reason I ask is because I've seen different lengths use, some 5, 7, even 11 inches gamma tube.
The best length is the one that works. The length may vary depending on the overall dimensions of the gamma match. The best I can tell you is to experiment until you find the best length for you.
I've known people to run into trouble with building random gammas. There is a segment in the ARRL, at least in my 70s edition. It discusses this and shows plans for a VHF version which can be scaled for any frequency.
Thanks. I have a 2meter version Yagi with a gamma match. Can't get it matched to where I will like it. Breaking down the adjustments, should I fix the strap position and only adjust the capacitor to best match SWR then tune the strap position second, or the other way around? Thanks again! KE6KBM
Keep adjusting both points (one at a time) and you will eventually find the sweet spot. At first it seems a bit difficult but with patience and experience you will develop a familiarity with it and it will get easier. Thanks for watching.
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I've been building antennas since 1979 on CB and from 1984 on ham radio. For anyone just getting started, this has to be the best, clearest description of the gamma match I have ever seen. Yes they do work and, if your making longer antennas, say for 10 Mtrs or 15 Mtrs...not having a plastic 'centre feed', these antennas are very strong and will face windy conditions much easier.
Thanks ! I’ve had good results as well.
This is the standard gamma match that comes with many commercial yagi antennas. Thanks so much for the explanation of the way it works. They are an easy and great way of tuning
@@henrythinks thanks and thanks for watching. Share with your friends
Excelente proyecto.. mil gracias por la cortesía de compartirlo.
best explanation I've seen on this!
Thanks for watching and share with your friends.
Such a good explanation and fairly easy to build, setup up, and use.
I am fairly new to antenna design and construction. This video was very well done and helped me immensely in understanding the principles behind a gamma match. Thank you!!
Thank you for your comment and thanks for watching. Share with those of your friends who may be interested.
Of course the real explanation of a gamma match and how it works is an interesting discussion. First of all, the parallel conductive segment to the driven element steps up the impedance, much like a folded dipole. This in turn adds inductance. The variable capacitor component is then used to tune and cancel this additional inductance out.
Thanks for explaining this so well, I've often seen it. Now I know how it works!
@@acestudioscouk-Ace-G0ACE Thanks !
And thanks for watching
Check out my other videos on my
RUclips channel and share with your friends
great presentation
@@grumpy_ken thanks !
And thanks for watching.
Nicely done. Love the KISS method. Keep it simple and sturdy.
This is great valuable information on the Antenna, driven element and gamma match. Any additional information on 27 mhz antenna building would be great. Whether, it be 4 element beams or multi-directional antennas. Thanks for the information tutorial, enjoyed it. Billy...Albq. N.M. 2 / 16 / 2023
Length of a half wave antenna in feet = 468 divided by frequency in MHz. This can be applied to any band. Thanks for watching and check out my other videos to see some of my other creations. 73
I’m just starting with ham. This is so well done, thank you sir.
Thanks for watching ! Check out my other videos on this channel and share with your friends who may be interested.
If they are setup correctly, the gamma works great. I had a 2 element V Quad several years ago, it was gamma matched and had an SWR of 1:1.3 or less from 25mhz through to 29mhz. I still have the QSL card from a guy in country that no longer exists in Europe. We chatted on 27.650 USB for almost 2 hours one night, at an S9 or above. Damn great antenna that one, I still miss it. Nothing came close for OOB usage and pirate CB radio. A fellow I used to compete with for contacts had a 5 element Yagi about 10 foot higher than my quad and he needed 100w more than I did to make the same contacts. Nothing beats a well tuned antenna, and the gamma match is a fast easy way to acheive that.
A great tutorial on Gamma Match's. I've been building yagis now since 1972, and have used many feed hookup designs. "T" matches. Delta feeds, Pigtails, and of course Gamma Roads. and I can tell you I've stayed with the Gamma on 99% of my builds . I make most of mine with RG8 coax center dialectrics for the center inside an alumimun tube from a HF mono bander thru 6m,2m 220 mhz 432 Mhz to even 900 mhz yagi's and with great success in feeding. adjusting and performance. thanks for reminding me that my choice was correct! and for sharing. de Ellis WA1RKS
Thanks !
73 de VO1DV
How do you know where to clamp the shorting bar to the driven element?
Fantastic explanation, thank you for sharing you experience and knowledge 👏
Thanks !
And thanks for watching.
Check out my other videos on my
RUclips channel and share with
Your friends
Wow! I get it now. Thank you so much for the simple explanation! Ugh... amazing.
Thanks for watching !!
Check out my other videos on my
RUclips channel and share with your friends
Saw this thumbnail and thought it was another video of a silent key called Stan Gibilisco. He's got hundreds of videos on his channel but sadly passed away a number of years ago.
The presentation and style of this video is uncanny in similarity to his ham and electronics tutorials.
Thanks ! I’ll take that as a compliment !!
@madeinfoxtrap5539 it absolutely is. I adored his videos and your vid is just as worthy of praise.
Very nicely done?👍☘️
The capacitance cap on a Hustler 4 BTV could be used as a Gama Match! You replace the ones you use with aluminum stripes. Or buy replacements from DX Engineering! They sell tubing and parts to build your own antenna,
Excellent video! This answered many questions and solved many problems! Thanks!
Thanks for watching and share with your friends who may be interested. 73
Well done. Nice and clear description.
Thanks and thanks for watching. Check out my other videos and share with your friends who may be interested.
Excellent tutorial. Thank you for sharing this. 🤠👍⚡️🎙
Thanks and thank you for watching. Share with your friends who may be interested and check out my other videos on this channel.
Hands down the best description I've seen of the gamma match. I just got a yagi that uses one and it works, but I couldn't make heads or tails of it. Your explanation of the variable resistor was excellent.
Question: How does the location of the strapping point come into play? It can't be arbitrary.
The shorting strap combined with the variable capacitor when properly adjusted form a resonant loop which tunes out reactance and induces a standing wave in the driven element.
Hope this helps.
Thanks for watching and share with your friends.
73 de VO1DV
@@madeinfoxtrap5539 Sort of. How does one know where on the driven element to attach the shorting strap?
@@toddhowell2299 experimentation with various settings until you achieve resonance. Forming a resonant loop sometimes takes a bit of trial and error but with patience you can tune the match 1:1
@@toddhowell2299Get a $60 nanoVNA and hook it to the antenna. You can see exactly how each of the adjustments affects the SWR curve as it moves around the band. It helps a lot.
Thank you for sharing very interesting.
Thanks for watching and share with your friends who may be interested
Thank you for your time, great explanation!
interesting as always, great info for antenna builders. Here's one for ya, how could you incorporate that same idea into a vertical antenna? I know how i might do it, but just curious if my idea would suck.. LOL
like a j-pole with a gamma match. There was a nice CB vertical antenna that used a gamma match. Avanti Sigma IV.
Your explanation helped me.
Yes the center is at zero voltage, its just hard to seperate grounding and the null point of a driven circuit.
The far side of the half wave looks like it should be driven. Hard to remember the voltage on the right half
will induce a voltage on the left side.
I keep wanting to think the atenna works because the right hand, driven side, sucked the left side electrons past the ground, null point, to the right hand high side. Right???
The gamma rod and shorting bar when tuned correctly makes a resonant loop which induces a standing wave in the driven element.
When you look at this thing, think of a center tapped transformer, and the voltage wave across it. The null point of the "sine" wave is the ground point aka neutral, and each end the opposite of each other. Doesn't matter which end is energized the other is opposite. So you tune the injection point and the other follows suit. In my limited understanding...
Very good explanation! You did a great job of taking theory into practicality. I finally understand the gamma match, lol!
You don't really.
Excellent information, thank you.
Thanks for watching and share with your friends who may be interested
Thank you so much for the excellent explanation.
Thanks !
Thank you for watching and share with your friends
Check out my other videos to see some of my other projects
Take care
73
Thank you for excellent explanation of aimetric to asymmetric transition adjustment. Is possible add static protection on antenna L grounding ?
If you mean an inverted “L” ?
I’ve never made an inverted L So I am not able to comment.
This design is center grounded.
Thank you, for the great contribution.
Great explanation,thanks
Thanks ! And thank you for watching
Check out my other videos on my
RUclips channel and share with your friends.
Great explanation. How does it work when there is no capacitor present and there is a direct connection via a aliding bar, as with a yagi i use and a halo i have just built?
Your “sliding bar” adjusts to find resonance.
The “sweet spot” I am guessing as I haven’t seen your antenna.
Glad your antenna is working for you. Keep up the good work.
Thank you so much!!!!!
Thanks for watching ! Share with your friends.
@madeinfoxtrap5539 thanks for your nice answer 👍
Weldone great video 73 py1ax
Good stuff!
On your 6m halo -- is the "halo" fully closed opposite the feed point / gamma match ? If so, is the overall tube length just 1/2 wavelength?
I'm trying to find novel ways to build a more compact dipole for the high bands w/o inductive lengthening.
great presentation of the gamma match! thank you so much!
Yes it is a half wave loop fed at the centre except the elements are bent
Thanks for watching !
Thanks for that.
Thanks for watching ! Check out my other videos on this channel and share with your friends who may be interested.
@@madeinfoxtrap5539 Certainly, antennas are kind of mysterious and your explanation just made sense and made for comfortable understanding, thanks again.
Thanks for the axplantion about capacitance but what about the distance between center and shorting bar .the capacitor consist of shift and tube and the area can be changed according to their diameters so what about the distance between center and shorting bar please advice me.thank you very much.
Best I can tell you is experimenting until you achieve 1:1
Adjust until you reach resonance. A bit of trial and error involved but with some patience this design can be tuned flat.
@@madeinfoxtrap5539 A little math can steer you closer, quicker. Does anodizing effect the sensitivity?
@@bryanst.martin7134 mmmm not sure but I would go out on a limb and say no. If any decrease in sensitivity by any type of coating it would be negligible and probably so little that it ‘s unmeasurable
@@madeinfoxtrap5539 Thank you. Welding is one of my skills, and Al Oxide is tough thermally and electrically. Not sure how that may relate to low voltage, higher frequencies and such. Maybe the high level of signal amplification makes it negligible?
@@bryanst.martin7134 sorry I misunderstood. Anodizing is a coating applied to aluminum whereas oxidizing is generally caused by the oxygen in the air. This may be alleviated by coating with a thin film of grease or your favourite anti-oxidizing agent.
Very well stated. thanks.
Very nice thanks for the explanation sir 😊, but may i have more explanation about the formula 7/m/w sir ? Thanks before from de YB1BBW
7 picofarad per meter of wavelength is the recommended amount of capacitance for a gamma match so 14 pF for 2 meters
Ok thanks sir 👍😊
5:54 Isn't vacuum a worse insulator then air? I'm a pilot and I fly an airplane that can go up to 23,000 feet with a piston engine with magneto driven ignition system. We've had problems with arcing inside the magnetos at high altitude before because the less dense air is a poorer insulator. They sell pressurized magnetos to fix this problem.
So I'm confused as to why a vacuum capacitor would handle a higher voltage. That seems at odds with my experience in another domain.
Look up “vacuum variable capacitor”
They are used in high voltage applications
Magnetic Loop Antennas use them
They are normally expensive
You are not flying in a vacuum
While the oxygen may be thinner
At higher altitudes there is still enough
Oxygen for the engine to run.
Magnetos behave differently than capacitors
They have to produce a spark for ignition
If a capacitor arcs a spark it may be catastrophic.
Hope this helps and thanks for watching !
Excellent tutorial
Thanks!
Hi, Were did you buy those SO-239 with the hole for screws and nuts,Thanks
I salvage those from old junk radios but you may find them online
where can 1 find a calculator to help build gama matches to length and diameter of tubing and rods
What about multiband? If the Gamma match is set for the lower band, do multiples also match?
No it’s a monoband antenna but the 1/2 wave design characteristics may be applied to other bands.
1/2 wave driven element with
1/16 wavelength gamma rod may be applied to any band.
According to antenna theory
“Voltage at the center of a half wave antenna is zero”
So this allows the driven element to be grounded at the center.
If you want perfection, hi efficency of you antenna system can't be broadband! Broadband is delusion of low cost propaganda! Professional systems make in 3 or 4 section selective super tuned systems from exciter lpf antenna system!
Sorry about your friend, sounds like an interesting guy.
He was a great guy. You can see pictures of his tower and antennas on the internet.
Look up VO1KBN. Thanks
Great demonstration Thanks, One question, Is the distance between the gamma rod/capacitor to the radiating element non-critical, does it need designing in, or is it just a matter of practicalities? I really like the pf=7x wavelength rule of thumb. Thanks again
Usually 4 inches for 2M
Hint :
You are creating a resonant loop with the combination of capacitor , shorting bar , connector bracket and the radiating element.
@@madeinfoxtrap5539 Right, gotcha thanks. Looks scalable. I'll be having some fun experimenting with that soon. 73 de GØUSL
@@G0USL 73 de VO1DV
Hello- I am trying to build a yagi antenna with gamma match tuned for 166.38mhz from the information in this video. I used a piece of lmr400 with a drilled aluminum tube, but ive clearly done something badly wrong as i have an SWR over 80 according to my nano vna. This is my first antenna build so im not sure what went so wrong- i suspect that I didnt ground it properly. Does the coax need to be soldered onto something as i have seen with split dipoles? I also thought maybe the sheath on lmr 400 disrupts capacitance. Your help would be much appreciated
Lot to unravel without a video but the driven element should be 1/2 wave center grounded Yes the shield of your coax Feedline should be bonded to the antenna. The center of your coax should be bonded to the gamma rod.
If you are using a piece of coax for the gamma rod only use the centre conductor and insulation inside the gamma tube. Marine grade heat shrink tubing is great for insulating the gamma rod if it is not fitting perfectly. Using both conductors of a piece of Feedline as a gamma rod would certainly cause trouble as coax itself has its own capacitance between the two conductors separated by a dielectric ! Make a video so I can see what you are doing.
73
@@madeinfoxtrap5539 Many, many thanks. I made a split dipole antenna before you replied and got an swr of 1.6 using the same measurements/calculator as my previous failed antenna. After reading your reply I simply connected the coax sheath to the center of the driven element taking extra care to make sure the sheath and any stray braids didn't touch the center of the coax which was connected to the insulated wire (not coax this time) inside the gamma tube. Despite extremely poor unsoldered connections I managed an swr of 1.4 after fiddling a bit with the location of the gamma tube. My goal right now is to make a much more refined version that can take being mounted permanently outside, and then post a video guide for building antennas for MOTUS bird telemetry applications. I am sure I will have many more problems to work through but am relieved to no longer have an swr over 100 haha. Thanks again
Is there any difference if the center of the element is separated and ground going to one side and driven going to the other side while using a gamma match on the driven side? I am using a 3 element yagi I made with wire and the driven is divided in the middle, braid to one side and center to the other side and no gamma match. What is the effective difference?
It's the difference between having an adjustable match, and relying on the native impedance of the design of the antenna with no adjustment other than physically changing the antenna.
Any tuning tips on a full-wave circular loop, 1/4" tubing for 10 meters
Look up “magnetic loops”. You may get some ideas.
I have a sdr to spot the airplane's in my town, and build my own antenne and it works fine, but now i want to hear the airport tower and planes, can i do that with this antenna you show?
Not sure how far away from the airport you are but for any antenna to operate at utmost efficiency it should be a multiple of the wavelength
You are using. Any antenna will work to receive but a resonant antenna will be the most efficient. If you are some distance from the
Airport maybe an array like a yagi or cubicle quad could afford some gain. There are also RX preamplifiers to boost incoming signals from farther away.
Yagi and quad are directional and offer a little gain depending on the number of elements. Other antennas used for RX in VHF bands are the DISCONE.
Others have told me that they work fine.
Hope this helps. Thanks for watching and share with your friends.
@@madeinfoxtrap5539 I'm 6,5 km from the airport.
@@andarthome142 you are very close !
Just about any antenna should work fine.
@@madeinfoxtrap5539 THX for your info.
@@andarthome142 thank you for watching !
Check out my other videos on my RUclips channel
Good luck !
wonder how is the performance compared to a hairpin matching, in terms of gain, bandwidth and directivity pattern
I haven’t tried that matching system so I am not sure.
IIRC, matching method would not have an effect. It's the antenna design, feed point placement, and related factors that dictates gain and pattern. Also, height as well as surroundings will be in play.
@@tahoma6889 yes indeed there are many factors at play. I’ve heard from others that the hairpin match can be tricky to tune. I haven’t had a reason to try that matching system so I am not able to say anything about it. After getting great results with the gamma match on a half wave antenna I did make a 5/8 wave antenna for 2M and used a “shorted” or inductive matching system through a two turn coil. That’s about as close to the hairpin match as I have ventured.
@@madeinfoxtrap5539 hairpin just takes some getting used to. With todays tools we can zero them right in. It was a hassle back in the day when we were limited to an swr meter or dip. 😁
If performance-wise its the same, sounds like an easier match to build.
Heard somewhere that a hairpin match is balanced, so it may need a 1:1 balun to match an unbalanced coax
Sir, what is the best dimensions of gamma match lets say for a 7 element 2 meter yagi? The reason I ask is because I've seen different lengths use, some 5, 7, even 11 inches gamma tube.
The best length is the one that works. The length may vary depending on the overall dimensions of the gamma match. The best I can tell you is to experiment until you find the best length for you.
@@madeinfoxtrap5539 Much appreciated it sir. All the best.
I've known people to run into trouble with building random gammas. There is a segment in the ARRL, at least in my 70s edition. It discusses this and shows plans for a VHF version which can be scaled for any frequency.
Thanks. I have a 2meter version Yagi with a gamma match. Can't get it matched to where I will like it. Breaking down the adjustments, should I fix the strap position and only adjust the capacitor to best match SWR then tune the strap position second, or the other way around? Thanks again! KE6KBM
Keep adjusting both points (one at a time) and you will eventually find the sweet spot. At first it seems a bit difficult but with patience and experience you will develop a familiarity with it and it will get easier.
Thanks for watching.
@@madeinfoxtrap5539 Thanks!!
@@markstocks9475A nanoVNA that allows you to see exactly what each of your adjustments actually do is a great help in tuning antennas.
Does the radiation pattern change with a gamma match half wave dipole vs. your standard non-matched dipole?
If the dipole is half-wave the radiation pattern will be the same. If the dipole is other than half-wave the radiation pattern will be different.
@@madeinfoxtrap5539 aah yes! Pattern is due to the radiating elements. Thanks!
Does the gamma match cut out the need for a Balun?
A BALUN is not necessary
Direct coax connection
Now do a video for the hairpin match. Por favor.
Sorry but I am not a fan of the hairpin match and I have no intention of experimenting with it.