Home Brew 4:1 Air Core Balun...

Discussion in 'Ham Radio Discussions' started by W4INF, Apr 22, 2008.


Do you think you will build one from the plans?

Poll closed May 22, 2008.
  1. Yes, sounds interesting and I need one

    11 vote(s)
  2. No, but I thank you for the work

    2 vote(s)
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  1. W4INF

    W4INF Ham Member QRZ Page


    Coming soon, digital article on my site on step-by-step build of a home brew 4:1 air core BALUN.

    Just got a check out of AL, +20 report, so it must be working. Also, with my HB doublet and Z-100, I am able to tune ALL bands 1.5 or less. With the Spiro 4:1 BALUN, I could not get below 2.5 on 80m and 20m.

    You can see the first one I made, the "prototype" which also works 100% FB, however it was made with Romex and I used split bolts. The new one uses 14ga stranded and is all soldered. It should handle 1kw, at least 600w no problems. The Romex version should be able to do 1.5kw easily. Same plans, different materials. You can even step down to smaller wire for QRP!

    In the next week, I will have a new post with the link to the article.

    Thx 4 looking-
    Last edited: Apr 22, 2008
  2. N8GAV

    N8GAV Ham Member QRZ Page

    I made one just like that one Andrew with #18 mag-enamel wire and incased it in a plastic Coke bottle. It worked better then I expected 1.2:1 or better 80-10 and 2.5:1 on 160 with my tuner. It handles 1 kw or so and was a lot of fun to built.
  3. W6GQ

    W6GQ Swap Meet Moderator Volunteer Moderator QRZ Page

    Is this your site?


  4. W4INF

    W4INF Ham Member QRZ Page

    Yes sir, it is a continued work in progress... I still have a lot of coding to do to the web app to really finish it up. Written in VB/ASP.NET with a Access database back end and all done in Notepad. :p

    Am I doing okay with it? Just curious...

    I just looked at the bottom of the page, I got my call and name on it. Doah!

  5. W8UNX

    W8UNX Ham Member QRZ Page

    Works fine in Firefox. Looking at your source, I'd suggest moving your CSS to an external file as it makes site-wide layout changes easier. There isn't anything wrong with in-lining your CSS, but if your site grows and changes, you will likely find it a pain to manage. Just my $0.02.

    The balun is interesting. What are the specs on your homebrew doublet?
  6. W4INF

    W4INF Ham Member QRZ Page

    Doublet is 90ft long fed with 75ft of RatShack 300ohm twinlead (foam core) at 25ft AG. BALUN is the 4:1 HB, and tuner is LDG Z-100, this setup is SMOKIN'!!

    I have the 66ft doublet on my website, just sub 45ft legs for the plans and your working the same as me!

    I have 2 of these, 1 is fixed and the other is in the back of the Jeep for portable ops. Now I need to build another BALUN for portable and put the LDG BALUN in the closet! HA HA!

    What little bit of CSS I have, I am lucky TO have.... I know little about it, mostly an HTML guy and do a lot of ASP.NET programming. But thx for the tip, I will look into that!!! I know what your saying and I likely should do that.

    Take care,
  7. KC7YPJ

    KC7YPJ Ham Member QRZ Page

    got another project for ya andrew, take your 4:1 voltage balun wind a new one with 12-20 turns (20 is working for me), straight thru rather than the foldover wireing involved with the 4:1 voltage balun pictured, solder your so-239 on, center to white grnd to black (or whatever 2 colors you have chosen) other end of the windings slap couple of bananna jacks on and you've got an efective 1:1 current balun.
  8. W4INF

    W4INF Ham Member QRZ Page

    Ryan, thx for the info! I was wondering what difference there was between a 4:1 and 1:1!
  9. EI8DRB

    EI8DRB Ham Member QRZ Page

    Hi Andrew... nice site. Did you write the do the RSS puller yourself? Nice work if you did. The little tooltip popups are nice too... inobtrusive, but when you need them, there they are!
    I'm more a LAMP developer than an ASP/.NET, but have great respect for anyone that can make Access do anything worthwhile :)

    Looking forward to the balun plans.
  10. W4INF

    W4INF Ham Member QRZ Page

    Thx for the kind words... But what do you mean the RSS puller? I have not done anything with RSS at this stage.

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