Which balun do I use?

[KX5JT]

So I currently use a 102' g5rv.  It's okay when I shove 130 to 200 watts of carrier into it but... it's time to improve so I will do the balanced line 135 foot doublet.  I picked up 450 ohm ladderline (but it's the heavier stuff made with #14 Gauge wire).  My station is up against the wall and I will run coax (maybe 10 foot) to a balun mounted outside on a wooden post (it'll be enclosed and weatherproof) then the windowline up and out to the feedpoint about 35 feet high.... best I can do for now with the ends about 15 feet for an inverted vee, it'll take about 60 feet of window line to get to it from the balun outside the radio room.

So I know I will get the 5kw rated current balun  http://www.balundesigns.com/servlet/StoreFront 
but... should I get 4:1 or 6:1?  300 to 50 ohms is 4:1 but 450:1... closer to 6:1 right?

Any help on this will be appreciated!

KX5JT

[Ed-VA3ES]

It's an interesting question.  While the feeders are indeed 450 ohm, the actual antenna will be approximately 50 ohms.   Are you feeding the short coax section with a tuner? 

I think the balun I use is 4:1, in the tuner, which directly feeds my 450 ohm line. 

[w4bfs]

a 135 ft doublet will be resonant at the low end of 80 m band so the feed Z at 3880 kHz will be higher and complex  ..... my experience with baluns of any sort tend to be unsatisfactory in this scenario .... if you are going to try to feed this as a short 160 m ant the feed Z will be very low and complex ... other bands a mix of high and low Z and complex .... this is why most folks who are serious about antenna efficiency will go to the trouble to bring the ornery twin conductors inside .... make the wall penetration with two SHORT coax lines ...73 ...John

[KF1Z]

I agree with John,

Use 2 coax cables, with the shields tied together... use the two centers for the feed.
That is a balanced line.

Yes, slight difference in impedance, but it shouldn't hurt.
(I used 100' of "double-coax" then 65 feet of window line... it worked fine)

I would try to make the entire balance line at least 60 feet long (64'+)

Then feed the whole thing with a balanced tuner.

[K3ZS]

Are those baluns peak rated or continous.    Read this web site, on choosing baluns, it will answer a lot of questions:

http://www.dxengineering.com/techarticlepopup.asp?ID={3E5220F7-2D0F-45B5-85F7-3B654F804C4F}

[K3ZS]

I looked at the balun designs web site.    It looks to me that the dual core 5Kw rated one with the teflon tubes is about the same as the dx engineering baluns rated for tuners, at about the same price.    The 4:1 would be OK if you are mainly dealing with higher impedances.  DX Engineering sez you would be better off with a 1:1 current balun, because you could just as well have a low impedance, depending on your feedline length.    The DX Engineering baluns are potted after construction.    I don't know if the Balun Designs are or not.    They must be a new company, I will add them to my list.

[W2VW]

Are you using an antenna coupler?

[Ed-VA3ES]

I bring my 450 ohm line right into the house via a pair of ceramic feed-thru insulators.  I mounted the feed-thrus  on the outside wall and used  two lengths of threaded rod to go through the wall, cut to the appropriate length.  Another pair of feed-thrus on the inside wall of the basememt.    The feed line is kept away from metalic structures and is simply stapled to the basement rafters  right to my tuner.  The current tuner is a Dentron Super Tuner with internal balun.   When I intend to run QRO, I will be using a balanced tuner.   I experience no RF in the shack.

My dipole is 133', centerfed at 54 feet.  The line  goes down the tower  separated from the structure with home-made stand-offs, and transposed all the way down (light twist in the line).  It crosses over to the house 10 feet off the ground, thence to the  feed-thrus.  Right now, it's  a semi-inverted-vee, but eventually it'll be horizontal, once I hang one end on the street light, and the other end in the neighbor's fir tree. 

[KX5JT]

Are you using an antenna coupler?

At the moment, I have only a t-match.  It started out life as an MFJ-962D, which is a T-match rated at 1.5KW PEP with a two unbalanced outputs and a "balanced" output via a built in 4:1 torroidal balun all routed through a ceramic wafer.  Running medium power AM zorched the wafer.  I gutted the thing out and have only an input so-239, the two aircaps and one roller inductor (in T-match configuration) and an output so-239.  No more selector or balun hardware in it at all.  That's what I have to use for now so thus the balun necessity. 

Some day in the not-so-distant future I will build a proper over-ratted balanced line L-match, but until that day, this is what I have available.  I will be running my dx-60 (or my ricebox) into an sb-200 amp for 100 to 200 watts of carrier, and in the case of the dx-60, upward carrier to 400 upon modulating.  Eventually, the Johnson Viking I will be on the air as well... and of course I'm dreaming of one day homebrewing a plate-modulated high power (legal limit with extra room to breath) txmittter.  (By then I will have an L-match on a plywood or something very robust.)

So this is going to be until then... my thought process is that even this design should beat out my 102' G5RV right?

[WA1HZK]

I never met a balun that could not be totally destroyed by a AM transmitter running any snot. Put up a resonant dipole and use a 1:1 COAX balun. on 75 I think thats about 18 turns around a piece of thin wall sewer pipe. If you want multi-band put up a 160 meter 1/2 wave and feed it with ladder line tuned with a LINK COUPLED antenna tuner. There are plenty of designs on this site. Nothing is simpler than the 1/2 wave resonant antenna up about 80 feet in the trees. It's the most bang for the buck. Get it up as high as possible. I have tried the other stuff = assorted fires.
Keith
WA1HZK

[W2VW]

Your original antenna system may have presented a medium to low radiation resistance to the MFJ tooner. The 4:1 divides that number by 4. On top of that is the reactance to deal with. Not a happy situation. A 1:1 probably would have made things a bit happier. That depends on feedline length.

Try a 1:1 and whatever tooner parts you have not cooked yet. The worst thing that can happen is it won't load up on some bands.

[W2VW]

I never met a balun that could not be totally destroyed by a AM transmitter running any snot.
Keith
WA1HZK

As far as those 4:1 "voltage" BalUns go you are 100%. A properly implemented BalUn will however do just fine with plenty of R.F.

Link coupled tuners are not the only way to skin a cat. The popular flashbox will leave one stranded in a lot of situations including 160.

Resonant antennas are for newbies and weenies unless they are  multielement arrays. '  '     '        '             '                 '                          '

[KX5JT]

This is certainly a "hot topic".  Everyone has an opinion and many of the opinions are not lining up.   

Here are my issues:  I don't have 100 foot trees to hang anything from.  I have two 10 -foot and one 5-foot section forming 25 feet of Cellphone Shack (aka RadioShack) with a 10-foot section of PVC on the top (the G5RV does use some 450 ohm windowline for the last 36 foot section and it must steer clear of metal... so the top part is pvc to allow the feedline to approach the feedpoint without metal near).  That's the only useful high point on my property.  I have to work with that until the day I can afford to grow more articifial solutions.  Presently the G5RV is stretched out to tie points ON THE GROUND but about 160 feet apart.  (That's a guess at this point).  This creates a Vee with an angle of about 120 degrees (another guess) with the ends of the G5RV up at about 9 feet, then the dacron rope the rest of the way to the stakes on the ground.  It makes for having to be careful when walking or mowing through the yard. 

I plan on putting some poles a bit farther out than those staked down tie points to give me tie points that are about 7 feet up.  (10 feet with three feet in the ground and supported with concrete).  I have the makings for this without having to spend more.  *Note it will not be pratical to add more sections at this point to my 35 foot mast without guying... I dont really want to start guying stuff before I get the end supports off the ground.  Yes I thought about this already* 

The "barebones" T-match tuner has no zorched components in it. The components in it are fine... the zorched antenna selector wafer is gone... the 4:1 balun is gone.  It was never zorched but I simply took it out knowing if I needed to use one, I didn't want to use that cheap thing... I want something that can take a beating.

I have concluded at this point, until major changes are made to my "shack" enviroment or I can afford to build a proper balanced match,  I will need a balun with the T-match.  It's not a balanced tuner.  Now I'm rethinking the outside, slightly remote mounting of it.  Maybe I CAN put it right behind the t-match with a simple three foot rg-213 jumper.  I would have to then exit my metallic enclosed shack with the dual-coax/shield tied together and to ground balanced feedline section out to the 450ohm #14 gauge based window line outside of the harmful metals way, then up to the doublet. 

So this is my best thinking within my pathetic budget for this spring antenna project.  Again I ask... which current balun is best?  4:1 ?? 6:1?? or now given DX-Engineerings take on things.... 1:1?? 

I mostly operate AM 80/40 but I want to be able to do anything from 80 to 10... (okay 160 would be very cool, but i have no strap for 160 on my sb-200 and certainly would be really stretched out to find the room for 260 feet of dipole.)

What say you?

[N2DTS]

I have been going through the same situation.
The G5RV would not work on 160, but on 80 it did ok I guess.
The antenna tuner (big heathkit) used to get quite warm, and has arc'd and cought fire in the past.
I then tried an alpha delta 160 to 10 meter antenna (100 feet long) and it worked fine but not at any power level, over about 150 watts carrier it melted the coils.

I have tried the open wire line into the heathkit tuner using its balun, more fires.

I just put up a resonant dipole for each band, 80 through 10, use no tuner, and life is good.
There is NO  power limit with a dipole really...

Even though they are for beginners, a resonant dipole is what I have mostly used for the last 30 or more years.

Brett
N2DTS

[KX5JT]

I'm starting to think maybe I should build a "fan dipole" with resonant 80 and 40 meter cuts and feed with one coax.  Then I can put up a 20 through 10 meter vertical ground plane for the low angle dx I enjoy on those bands.  To heck with the tuner unless I need to move around 80 meters a bit.

[N2DTS]

I put up an 80 meter dipole resonant at 3870, unless I want to do CW, the swr is fine.
Its made out of (free) #10 insulated wire and cost me nothing.

The rump of the alpha delta is a fan dipole for 40, 20, 15 and 10 (the 15 meter uses the 40 meter section).
The 40 meter part resonates at 7280 (where it wound up) but is very broad banded.

The fan dipole has a few drawbacks, it radiates your 2nd harmonic nicely, and it can be a pain to adjust all those antenna's for low swr.

I also have a butternut vert, the 80 and 40 meter one, but no room for radials.
Sometimes, signals are just as strong as the dipole, not often.
On TX its a dummy load.

Its liberating to be free of the tuner, jump from band to band without tuning anything.
The 3x4D32 rig is parked on 40, the 813 is on 80, nothing to tune!



Brett
N2DTS

 

[Fred k2dx]

I would suggest doing the 120' doublet with balanced feedline all the way inside. Either use two short pieces of coax (RG8U sized!) at the entrance or a pair of the old cone shaped Johnson feed thru insulators. They can be still be had cheaply. Forget about the balun, any ratio, it's just not the right way to feed a multiband doublet. Get an old Johnson matchbox tuner. They can be had reasonably in the smaller variety. BTW, the smaller one has a wider matching range than the big one. The smaller one will handle all the RF you can get from your SB200 on AM or SSB. The power was rated at 275 watts of AM carrier. Johnson rated them at TX output. I ran the small one for years with just that amplifier and doublet. All you need to watch is the 'magic' lengths of the feedline (see any old handbook for the table). I think your 60' will be fine. That setup won't work on 160 but neither does your amp so don't worry about it. 80 thru 10 will be just fine. You may be pleasantly surprised how well the thing does on 10 - 20 meters.

Avoid any any MFJ crappy tuners... the old Johnsons are WELL built. They just don't do 160. There's a reason they still work after 50 years!

[K1JJ]

I'm starting to think maybe I should build a "fan dipole" with resonant 80 and 40 meter cuts and feed with one coax.  Then I can put up a 20 through 10 meter vertical ground plane for the low angle dx I enjoy on those bands.  To heck with the tuner unless I need to move around 80 meters a bit.

There's so many ways to put up a great antenna and all the ones described so far will work FB.

But, I like your latest idea, John.

A fan dipole will maintain the BROAD figure eight pattern that is very desirable when using non-rotatable antennas. In contrast, using an open wire fed single dipole on higher freqs causes the pattern to get sharper, then finally break into multiple lobes and nulls.  You get a small amount of gain, but in many directions you will be pissweak, down 20db or more.

With the fan dipole, you can also change bands instantly and the antenna is environmentally stable for feedline ice, rain, etc.

Use a pulley system so you can raise and lower it quickly for intial tuning. Yes, there is some interaction when tuning one element affecting others at times. But once trimmed, it's all set for good.

Support the dipole in the middle and wind eight turns of the coax onto a 4" PVC drainage pipe piece as the RF choke. (coax balun) You can also use the PVC pipe as the center insulator for the wires too... just drill holes on the ends.  Use rope connected to each end of the pipe to support it squarely.


I switched over from all openwire to all hardline here about 20 years ago. I still use openwire for special multi-element wire arrays where it is mandatory to match a high impedance.

The disadvantage of the fan is it will accept harmonics from the transmitter -  no attenuation added. This is not a problem with most modern rigs (or older ones) using a pi-network output.  I've used a log periodic for 10-20M for years and never had harmonic problems, but be sure to have someone listen for you on X2 X3 X4 freqs anyway.

To cover all of 80M with a low swr, you could always use two sets of legs - one set for 3850 and the other for 3650 or whatever.

As far as a vertical, yes that would be OK, but if it were me, I'd set up a SECOND fan dipole for 10-20 meters. Horizontals ALWAYS work well on the higher bands.  Especially cuz 1/2 wavelength of height and higher is easy to obtain up there.  That's when horizontals really play well. Heck, you'd only be down about 5db from a full size 3el Yagi at the same height.

My second choice would be a simple flat top (as flat, long and high as possible) fed with good quality openwire to a good tuner. (But no longer than 1/2 wavelength for the lowest freq)   No baluns.

When ya get it running, see ya on 40M for some tests.

Good luck with it, OM.

T

[Fred k2dx]

The resonant 80/40 dipoles and a vertical would be a good solution. The vertical should be up in the clear for the higher bands - the base should be at roof level unless it's well out in an open field. two radials per band (elevated) will be ok. 40 m radials will work for 15 (if the vertical has 40). If you score just half of one element from an old tribander you have the makings of a 10/15/20 vertical on the cheap... usually opening the traps and cleaning things up is what is typically needed. If it's a director or reflector you may need to slightly play with adjusting the lengths but it should be no big deal. Maybe you could find one that has suffered a mishap for salvage.

Another thought John. If you score enough of a damaged tribander you could use one whole element as a pair of radials, that would make for a complete tri band groundplane made from 1 1/2 elements.

[K1JJ]

The vertical should be up in the clear for the higher bands - the base should be at roof level unless it's well out in an open field.

Yep, good advice, Fred.  So many verticals are erected down between buildings and guys wonder why they don't work.

I have first-hand experience - my first Novice antenna was a Gotham vertical with no radials, mounted ONE FOOT from the house. (short coax through the window)  I called CQ for 3 days on 3716 with no answers...

T

[Fred k2dx]

hehehe. Tom, my first vertical was out in the middle of our large yard. My novice buddies all concurred it should work, after all it was grounded to a 6' pipe driven into the ground and the SWR was about perfect. Radials? If the SWR was good they shouldn't be needed, right? We were so innocent back then... I don't think I ever worked anyone except the other guys in town!

Then I put up a resonant 80 meter inverted V fed with RG58, the apex up on the chimney at about 50' and the ends down to about 6'. Now that one played! Once I worked 2 land to 6 land with a homebrew 6v6 keyed oscillator at 2 watts out on 80m. Just couldn't understand why the vertical was such a dummy load...

[KX5JT]

Still toying with ideas....

.... so I can get the 275 Watt Johnson Matchbox for a few more bucks than a balun.  I can afford it.  Will it play with my 100- 200 watts of carrier?  Is that 275 watts rated for carrier, not pep?  I would think it is. 

So if i use the JMB with the dual-coax-grounded shields to the outside and hit the 450ohm window line to the 135 foot inverted vee..... will that be a nice low loss system and will it play okay on 40?

[N2DTS]

I once had a 275 watt matchbox, but it would not match my 100 foot antenna fed with open wire line.

It would not on 80, it got close on 40...

Likely some odd combo of antenna and feedpoint lengths....

Brett
N2DTS

[K1JJ]

John,

Here's an easy tuner to build. Also, do a search on this BB for "K1JJ Tuner" to find more pictures and examples of some the guys have built.  It now has both series and parallel configurations so you can match low or high impedances.

http://amfone.net/Amforum/index.php?topic=18054.0
* Take a special look at the six pictures of Dave, KA2J's tuner version on page two. That is a nice layout and easily duplicated by you.

This tuner is so somple and will handle 5KW ++ with the right capacitor and 1/4 - 3/8" copper tubing for the coil.
Mark the taps and make band switching quick.

T

[Steve - WB3HUZ]

I have concluded at this point, until major changes are made to my "shack" enviroment or I can afford to build a proper balanced match,  I will need a balun with the T-match.  It's not a balanced tuner.  Now I'm rethinking the outside, slightly remote mounting of it.  Maybe I CAN put it right behind the t-match with a simple three foot rg-213 jumper.  I would have to then exit my metallic enclosed shack with the dual-coax/shield tied together and to ground balanced feedline section out to the 450ohm #14 gauge based window line outside of the harmful metals way, then up to the doublet. 

Why can't you just run the ladder line right to the tuner?

Your current tuner can be a balanced tuner. Just put a good current balun on the INPUT side of the tuner and off you go.

I'm starting to think maybe I should build a "fan dipole" with resonant 80 and 40 meter cuts and feed with one coax.  Then I can put up a 20 through 10 meter vertical ground plane for the low angle dx I enjoy on those bands.  To heck with the tuner unless I need to move around 80 meters a bit.

This is a much easier and a far better idea. My 80 meter dipole is resonant at about 3800. But I’ve used it without any problems from 3670 – 3900. A 40-meter dipole cut for around 7200 or so should cover the entire 40meter band, or a least the phone portion.