Remote tuner ideas

[Steve W8TOW]

For my new 160m/40 ant location, I am planning on building a remote ATU.
It will be of the Johnson KW MB design, (kinda).
The antenna (currently in use) will be located about 250' from the shack in its new location at
65'. It is a coax fed dual band dipole using coils.
Here is the plan:
Change from coax to ladder line into ATU. Aproximately 70'.
Then about 250' of coax into shack.
The question is:
I have a nice wx proof fiberglass enclosure for the ATU ...Since it will be 250 ft from the shack, should I
worry about rf radiation from it???
I also have a metal wx proof enclosure, but would rather use the fiberglass one...what advantages??
disadvantages???
73 steve
w8tow

[K1JJ]

Hi Steve,

At 250' away, the tuner field is very weak. Even mounted on the wall in the shack w/o shielding, many of us ran 1KW with no RF in the audio, etc.

You can use a metal enclosure as long as the coils are spaced X2 diameters away from the walls. 1X diameter is the rule, but X2 is better.   Fiberglass is FB - either way, does not really matter if you keep the coils away.

BTW, in keeping with your low loss system, I wud look for some surplus hardline for the 250' run. Most hams are afraid of the big 1 1/4" or 1 5/8" stuff and it can be had for a song these days.  Make your own connectors for cheap using Home Depot copper plumbing dept sleeves/adapters.  Might as well have the coax as low loss as the openwire for a total system, OM.  Esp on the higher bands.

Good luck.

T

[W2VW]

Consider losing the antenna coils. They are unnecessary when using ladderline feed. You can do anything that those coils would do with the right tuner and feedline.
If you can come up with enough good high current/Voltage switching, 2 tuners sharing one variable cap driven by a small DC motor will work real well.
You might want to examine some alternative tuner designs to minimize switching requirements.
I found 2 neat ways to cheat with the "Balanced Balanced" tuner design to dual band it with very minimal switching.
No need for any enclosure at all with balanced designs. Go for weather resistance and ease of service as top priority.
What antenna length?

[Steve W8TOW]

OK on the suggestions! Good ideas...
For coil material, I have a edge wound coil out of a Gates BC tx, the caps are from a BC610...
I can ditch the "loading" coils no propblem...
THis antenna is gonna be at 65'...

BTW, as I worked in the CATV biz back in the 80's (after leaving ajob at a 5kw AM station)
I was actually planning on using a run of 3/4" hardline...something I used many a times in the past with
great success.
I had made my coax connectors from copper plumbing hardware and SO-239's...they worked great!
73 steve

[W2VW]

How long are you planning on making the dipole?

[Steve W8TOW]

Well, unfortunately, the antenna is gonna be short, no more than 200" tip to tip,
Currently with the loading coils ...it is the same size as a 75m dipole...which works on
40m/160m...
73 steve

[WA1GFZ]

Make the feed line heavy to handle the current.