Matchbox feeding coax?

[W7SOE]

I have a 40m dipole fed with coax.  There is a 1:1 current balun at the feedpoint.  I have a Johnson Matchbox with balanced output.  Can this feed a coax feedline, perhaps through a balun?

I WOULD like to replace the coax with ladder line but the idea conflicts with the xyl's sense of aesthetics...

BTW, how far would ladder line have to be from a rain gutter, in case I want to sneak it up. 

Rich

[KF1Z]

I don't know anything about the match-box.... if it is easily made to have an un-balanced output or not.... if so.... go that way....

If not.... well you COULD  use a true bal-un. ( losses be what they may)

Of course, if you can talk your YL into it....
The balanced line would probably be a better choice all around....

I would say an absolute minimum of a foot  away (more is better) from the gutter. ( at right angle to it, try not to run it along with the gutter)


I am supposing you want to use the 40 meter ant on other bands?

[w3jn]

Replacing that coax with W7FG ladder line will be the best and cheapest investment you'll ever make to your station.

[W7SOE]

The ladder line is becoming more and more appealing....  I think I will sneak it up...

I suppose I should get rid of the 1:1 current balun at the feedpoint. 

The mast is metal, I will have to keep the feeder away from it, I could just slope it away but that is more noticeable than having it come down parallel to the mast.

The feedline will also have to run down the side of the house, I'll have to verify where the pipes in the walls are.

I believe the modern rig will require a balun at the transceiver now.

Rich

[Rick K5IAR]

Rich,

I have a buddy who uses PVC pipe and hose clamps to make standoffs for his window line.  I'm sure it would work just as well with ladder line.

Rick/K5IAR

[Pete, WA2CWA]

I have a 40m dipole fed with coax.  There is a 1:1 current balun at the feedpoint.  I have a Johnson Matchbox with balanced output.  Can this feed a coax feedline, perhaps through a balun?

I WOULD like to replace the coax with ladder line but the idea conflicts with the xyl's sense of aesthetics...

BTW, how far would ladder line have to be from a rain gutter, in case I want to sneak it up. 
Rich

See Figure 1B below. It shows how to connect a coax line to either 275 W or KW matchbox. I bought a 275 watt matchbox years ago that had a plexiglas plate with a SO-239 mounted on it and wired per the diagram. The plexiglas plate was held in place by one of the balanced line screws. Worked very well. Coax is neat; balanced line is ugly, so says my interior/exterior decorator.

[k7yoo]

The matchbox will feed coax using EFJ instructions but the matching range is limited as compared with the balanced mode. You could do the "ugly" and hang a balun on the balanced output to feed coax. I did this once for an experiment using an RF works "5KW" balun (who dey kidding). It worked OK as long as the impedance excursions and power weren't excessive (whatever that is), but the best idea is balanced feedline.
Skip

[wa2zdy]

I believe the modern rig will require a balun at the transceiver now.

No it won't.  Coax from the rig to the SWR bridge.  Then to the Matchbox, then balanced feeder of your choice directly to the flattop with nothing at the feedpoint but an insulator.  No baluns anywhere.

This will make a great multiband antenna on every band where the antenna is at least a half wavelength long.

Good luck.

[W7SOE]

Well that all makes sense.  I will start planning the great coax abatement mission...

Any idea how well I will get out on 80m using a dipole cut for 7.290?  The 40m length is all I have room for, same old story.

I have not heard any AM activity on 40m here in the NW but plenty at 3870, sigh.

Thanks

Rich

[WA1GFZ]

open wire line is beautiful and if you have Johnson spreaders you are a real ham. Coax is for beams.

[W7SOE]

I am missing the decades of experience to be a real ham.   

I have been licensed for only a year, I was bit hard by the boatanchor bug, I was infected by an ex-coworker, an RF engineer.

In that year I have:

Restored and SX-42 (it hurt) and R-42 reproducer
purchased and brought to life an R-388
restored a Johnson Viking II
purchased a R-390A
5-10 other odds and ends
Had only about 4 QSOs, all on SSB 

I guess I am lopsided on the gearhead side vs actually operating.  I REALLY look forward to calling CQ on AM though.... 

73

Rich

[WU2D]

Coax is also great to bury - look Ma no wires! A lot of us bury coax or hardline until it is out of sight of the house and then feed in the woods.

Mike WU2D

[The Slab Bacon]

Any idea how well I will get out on 80m using a dipole cut for 7.290?  The 40m length is all I have room for, same old story.

You will be pleasently surprised how well it will work if you feed it with ladda line and have a tuna that will match it. I have been using a 60' flat top on 75m for many years now.

Real men use ladda line!!! Coass is for sissies!!

                                                     The Slab Bacon

[The Slab Bacon]

But seriously, balenced line is the best way to go if you want multi band operation with a single wire antenna. As long as you keep it balenced you wont have the high losses and radiation feedline problems that you get with coax cable under high swr conditions.
Just be sure that the conductors in the feedline are heavy enough to handle the feedlind current and minimize I-R losses. I like 14ga or heavier.

I have run my 60' flat top everywhere from 160-10m

                                                      The Slab Bacon

[Todd, KA1KAQ]

I've always liked balanced feeders for the look, especially chasing along the ceiling and down the wall. But in my current situation, it's not physically practical to use since the antenna runs parallel to the radio room, but the center is back around the corner. This requires two 90 degree bends to get back around with trees and a metal roof nearby. Plus I've always been a fan of separate ants for different bands.

But someday I'll have the open wire line in my dream shack. I've been accumulating those bumblebee stand offs for years and have a Flashbox standing by..... 

[wb1aij]

If you just attenuate the QRM from the XYL you can remove the BALUN and install the ladder line. Then your L,T, or PI tuner will be able to get the SWR down to 1:1 resulting is S9 signals on all bands. 10-4?

[Mike/W8BAC]

I remember seeing some pictures of K8VWX, Roy's shack. I have searched the web on and off since this thread started looking for them with no luck. They show wide spaced ladder line hanging on the wall rising from tuners I think and attached to balun's. Attached to the balun's Roy has coax leading away to his antennas. It is an unusual setup but judging by Roy's signal the system works just fine. If you know where to find the photos you might link them here.

I use an 80 meter W7FG doublet here and a Johnson KW match Box. The ladder line runs up the basement wall, through bee hives at the house foundation and up the outside wall. The outside feed line is only 3-4 inches from the aluminum siding and roof flashing with no noticeable effect.

Mike

[Todd, KA1KAQ]

I'd sure like to see Roy's pictures, Mike. Sounds like just the ticket. He puts  a strong signal into the northeast in the mornings, too. Used to listen to him and 'VH while getting ready for work.

If I could just run straight out to the backyard, I doubt I'd have an issue with the metal roof. But as things sit (and with house on market) I'd have to come out of the end where my radio room is (due south), then make a 90 degree turn west, and another 90 degree north just to get back to where the ant is. The wind whipping in the trees along with the height of the center would lay open wires across the roof at some point. But running it to coax is another matter.

[Mike/W8BAC]

I doubt I'd have an issue with the metal roof

I don't know about that Todd. Most metal roofs I've seen are steel. Unlike aluminum siding, the steel roofing might tend to interact with the RF. Depends on how close. I have seen corrugated aluminum for barns and sheds but not often or lately.

From what your describing that run to the antenna doesn't sound like fun using any type of feed line. I guess it's best to start planing the antenna farm at the new place.

Hopefully somebody will see this and know where to find Roy's pictures.

Mike

[WA1GFZ]

Back in my batch days the shack was in my son's room. I just blew a couple holes through the wall and fed the #10 feed lines through the holes. I was showing off the rig once and set the wall on fire so be careful routing open wire line......if you strap