Question regarding feeding with window line

I had given some thought to feeding a diapole with 450 ohm window line, the problem however arises with my tuner; it does not have connections for that type feed it only has coaxial connecters. Just wondering if there was some type of work around for this situation?

 

Use a 4 to 1 balun between the window line and the coax jumper to the rig.

 

I would use a short piece of RG8 coax to get from the tuner through the shack wall to the outside, and then put one of these on the outside wall: https://www.balundesigns.com/4/ The outside end of the coax shield should also be grounded to a ground-rod under where the coax comes through the wall.

I do not want un-shielded feed-line of any sort near my RFI generating computers, routers, switching wall-warts, monitors, ethernet cables, modems that also happen to live in my ham shack just a couple of feet from my radio/tuner. The main virtue of coax is that if properly applied, it prevents RFI originating in your own house from getting into your antenna(s) on receive.

Properly applying coax with respect to not transporting rfi from inside your own house to your antenna requires common-mode current blocking on the coax shield and grounding the coax shield outside the house.

 

Check out the MFJ-912 W9INN Balun. Mine worked great - takes full legal power. Follow it with a MFJ-915 isolator or similar.

 

Make an "ugly balun" (which isn't really a balun at all, but more appropriately is a choke).
It is as simple as rolling several yards of your coax feed in a nice neat single layer coil loop at the connection point of the balanced line to coax transition. Think of a 2lb coffee can form sized loop. Google ugly balun for hundreds of images for ideas on how to implement this type of choke.
If you plan to operate multiband, no need to go to any further expense with tailor made commercial balun. This will work fine and cost nothing but some extra length of the coax feed, and maybe a nice groundrod too.

 

Ugly coax chokes should be avoided. They can easily make common-mode currents worse. Here is the data why...

 

Get a BalUn (Balanced to Unbalanced) transformer. Most commonly available in 1:1 and 4:1 ratios.

Don't over think the ratio. All you need is for it to transform the impedance to a level your tuner can easily handle. Depending on your antenna, band you operate, installation either ratio may be suitable.

They are available from all the ham vendors in range of performance and costs. I suggest considering springing for a higher wattage unit that will be able to handle longer transmissions (like digital) and higher impedance matches without overheating.

I recently installed a 160m doublet with window line feed. Both a 4:1 and 1:1 worked satisfactorily, but the 1:1 gave an easier matching on 80m (second harmonic).

 

This right here.

And don't overpay, there is barely $10 worth of components in even a killowatt balun.

Rege

 

Very interesting read. Several of the findings may actually correlate to some of my shoot from the hip and see what we get results and just plain dumb luck.
Armed with the data it is possible to indeed make an airwound choke but my dumb luck performance obviously might not make for consitient results. You are better to be armed with the data and design using a ferrite resistive choke that exhibits better performance and less side effects per se' and may be a bit more forgiving and tolerant.
Funny thing is I am sure I have conditioned myself to doing certain things certain ways and if asked why I couldn't tell you the method to my madness other than it's what has worked for me. I always seemed to choose the airwound inductive type of choke simply because it never seemed to be as failure prone to ferrite core windings. It always seemed that when used broadband over bigger spans of freq. & outside of it's impeadance range, the ferrite core choke had been noticed to have a tendency to overheat and fail. Hence I chose airwound on multiband over the ferrite resistive choke. But this article seems to poopooh my logic and dumb luck..... Obviously if the ferrite core was saturating the core & overheating, it is simply because it is doing exactly as it should be doing in the first place! Just the wrong place (freq.) where you do not wish it to be doing it.
I guess there are alot of us who do things by the seat of their pants because that's the way we've always done it. That's Amateur Radio! I am glad we still have those smarty engineering types that do in fact contribute to the advancement and science of the radio and electronic arts and have a willingness to constructively share and explain it to us less advanced but always willing to learn common folk!

 

I set up an old Dentron Super Super tuner with a 4:1 (Voltage) & a 1:1 (Current) balun. 1:1 is always inline & I can switch in the 4:1 balun.
This uses twin RG6 or RG11 as a shielded feedline.
Having the 4:1 balun able to switch in gives more impedance choices to make it easier on the tuner.
You could do the same outside & just run the window line to it.

Ed