You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

BTW the driver element must be shortened from the "standard" formula for a half wave element if you are using a Beta match. As mentioned the feedpoint impedance must be lower than the coax impedance which is standard at 50 ohms. The Beta match is useable to about 35 ohms and preferably 25 ohms or less. I don't think you will achieve those parameters with a simple two element unless you use VERY close spacing but that adds other problems with gain and F/B ratio. My 6m yagi is six elements and OWL design.......Optimised Wideband Array and I use a 4:1 coaxial balun. Driver impedance is close to 12 ohms and I get a perfect match using it. Here is a link to some good info. http://on5au.be/content/a10/trans/beta.html

As an example of what I did check out these dimensions but keep in mind this is for 6m aka 50 MHz but notice the close spacing of the driver and the first director. This, along with the additional elements, lowers the feedpoint impedance considerably making the Beta match ideal for use with it. Dimensions on the left are in inches and are element spacing while dimensions on the right are for element lengths.

[ATTACH=full]58214[/ATTACH]

<blockquote data-quote="Captain Kilowatt" data-source="post: 787674" data-attributes="member: 39">BTW the driver element must be shortened from the &quot;standard&quot; formula for a half wave element if you are using a Beta match. As mentioned the feedpoint impedance must be lower than the coax impedance which is standard at 50 ohms. The Beta match is useable to about 35 ohms and preferably 25 ohms or less. I don&#039;t think you will achieve those parameters with a simple two element unless you use VERY close spacing but that adds other problems with gain and F/B ratio. My 6m yagi is six elements and OWL design.......Optimised Wideband Array and I use a 4:1 coaxial balun. Driver impedance is close to 12 ohms and I get a perfect match using it. Here is a link to some good info.&nbsp; &nbsp;&nbsp; <a href="http://on5au.be/content/a10/trans/beta.html" target="_blank">http://on5au.be/content/a10/trans/beta.html</a>As an example of what I did check out these dimensions but keep in mind this is for 6m aka 50 MHz but notice the close spacing of the driver and the first director. This, along with the additional elements, lowers the feedpoint impedance considerably making the Beta match ideal for use with it. Dimensions on the left are in inches and are element spacing while dimensions on the right are for element lengths.[ATTACH=full]58214[/ATTACH]</blockquote>

[QUOTE="Captain Kilowatt, post: 787674, member: 39"] BTW the driver element must be shortened from the "standard" formula for a half wave element if you are using a Beta match. As mentioned the feedpoint impedance must be lower than the coax impedance which is standard at 50 ohms. The Beta match is useable to about 35 ohms and preferably 25 ohms or less. I don't think you will achieve those parameters with a simple two element unless you use VERY close spacing but that adds other problems with gain and F/B ratio. My 6m yagi is six elements and OWL design.......Optimised Wideband Array and I use a 4:1 coaxial balun. Driver impedance is close to 12 ohms and I get a perfect match using it. Here is a link to some good info. [URL]http://on5au.be/content/a10/trans/beta.html[/URL] As an example of what I did check out these dimensions but keep in mind this is for 6m aka 50 MHz but notice the close spacing of the driver and the first director. This, along with the additional elements, lowers the feedpoint impedance considerably making the Beta match ideal for use with it. Dimensions on the left are in inches and are element spacing while dimensions on the right are for element lengths. [ATTACH type="full" alt="Homebrew six element 6m beam new tuning.jpg"]58214[/ATTACH] [/QUOTE]

Top Bottom