What is considered "flat" for a balun?

[GerryR]

A quick update:

Well, to get any radiation from the vertical feed, I needed a Ruthroff 4:1 voltage balun and a choke between the vertical feed and the shack. So, I built one and bench tested it.

As with all projects, it is taking longer than anticipated, but I have put a lot of time into the chimney mount for the antenna. Here is a link to some pictures as to where I ended last evening:

Ham_Stuff pictures by GerryR_photos - Photobucket

Perhaps the antenna will be up this weekend.

Gerry

 

[hookedon6]

nice build on the mount,... looks like it will last forever.

is that your machine shop in the pix?

 

[GerryR]

nice build on the mount,... looks like it will last forever.

is that your machine shop in the pix?

Thank you, and yes, that is my shop. I retired recently (automation eng.) and now use the equipment mostly for gunsmith work and my "little" projects. Except for some of the hardware and the fiberglass telescopic mast, the unit is made from leftovers from past projects.

 

[KC9Q]

Gerry,

I'd like to see how your OCF is going. Did you do any VSWR measurements on it, how did it come out? Did you build a dual core design using the FT240-43 cores?

I built an 80 Meter OCF that functions from 80 to 6 meters resonably well. The VSWR on 30, and 15 Meters is sky high, but the antenna tuner (an AT-7000) takes care of it. The VSWR is also high on 80/75 Meters due to the antenna being just 20 ft above the ground, but again the antenna tuner takes care of it.

I think the type 43 core will give good low frequency response, but will become more lossy above 21 MHz because of the permeability value - i Think.

If I could figure out how to attach graphics I could show you the curves of my baulun and antenna.

73,
Mike
Near Chicago

 

[GerryR]

Mike,
I ended up building a Ruthroff voltage balun (single core, 4:1) using a FT240-61 toroid (Amidon) because I wanted the 10 ft. vertical feed to radiate. I put a choke at the bottom of the 10 ft. vertical radiator made up of ferrite beads (14 beads - #77 material) over about 18 in. of coax to keep RF out of the shack.

I measured SWR from the shack and it went from 8:1 on 80 M down to 1.6:1 on 10 M with a low on 12 M of 1.2. (The analyzer showed >25 on 160). Even though the tuner in my rig (FT-890) is supposed to only match a 3:1 (16 to 160 ohms), it has no trouble matching anything from 80 M thru 10 M. There is probably a reason for this, but I don't know the answer yet.

If you go to the link in one of my above posts, there is a picture of the balun and the installation. The antenna is just shy of 40 ft. above the ground, but it is only about 15 ft. above the roof.

What are you getting for readings from your antenna? I did build mine to a "recipe," but I'm not sure how close my build came to the theoretical. It seems to perform OK, but it could probably be optimized by someone who knows more about this than I do. Eventually I will figure this all out.

Gerry, KK4GER

 

[KC9Q]

Hello Gerry,

I made a 4:1 Current (Guanella) using two FT240-61 cores which produces a flat response from 1.5 to 60 MHz. I prefer the current balun over the voltage to get away from the transmission line radiation: Works very well if I must say so myself. I too have the high VSWR on 80 meters, but notice the VSWR is low below and above the 80 meter band for some reason – do you find that too? I will try to attach the curve so you can see what I’m experiencing from 1.5 to 30 MHz. The AT-7000 tuner can provide a match on 160, 80, 30, and 15 meters. No tuner is required for 40, 20, 17, 12, 10, or 50 to 51 MHz on 6 meters. Possibly we could get together on 14.222 MHz (Club Frequency) or some other frequency sometime. I had a 5/9 Q this evening with a station in New Mexico running just my 100 Watts and the OCF at 20 feet.

73,
Mike

 

[GerryR]

Mike,
I couldn't open the files. Could you email them to me at (totalautomation at kinex dot net) and I will try again. When are you usually on 14.222 ?