80M Full wave loop 450 ohm ladder line with 4:1 Balun

[k7iou]

 80M Full wave loop 450 ohm ladder line with 4:1 Balun on AM!
Guys I would like to hear for you if you are using the 80M loop with 450 ohm ladder line & 4:1 balun on AM.
I am considering a current balun and the information is overwhelming for current baluns but not much with loops. Another issue is using AM mode. Some mfg's won't recommend their baluns for AM use due to constant carrier. So if your an AM'er and use a loop with ladder line and balun I would like to hear about it! I even would consider building a balun if its a proven design that supports a loop and AM mode.
73
de k7iou

[KA0HCP]

No problem operating AM or TTY with any Balun, regardless of it's rating or recommendation.....

Just turn down the tx power to stay with the Balun rating!

[WD8KDG]

A full wave loop is very forgiving! Feed it anywhere with any transmission line; low to the ground, up high & it still works. I've got one in the back yard, wound around things, sections up high, other sections down low. Didn't bother with a feed line, just brought the ends back to the shack and connected to feed thru insulators on the wall of the shack. Tunna's on the other side.

Two large DPDT frankenstein knife switches do the connections between a 40 meter dipole and the loop. One knife selects the antenna, the other to one of two tuners.

Johnson KW flashbox takes care of the Desk KW, the other tuner is the universal Transmatch (Lou McCoy) and has a 4:1 balun.
This tuner is shown in the ARRL handbook of 1976, pg 584. Three Amidon T-200-2 cores are wrapped with 3M #27 glass tape and wound with 15 bifilar turns of #14 teflon insulated wire. Good for 2K PEP. Tunna number two goes to a Junkston 500.

Lots of good info here on link coupled tuners, use the search feature. By the way, the loop is a cloud burner, but fits on a small lot.

Craig,

[WU2D]

I am a believer in these loops and have played with then off and on. The noise reduction is significant and if fed as you describe with open wire and a good tuner, they really become versatile. I have a compromise loop up right now. It is a horizontal 80M full wave roughly pentagonal in shape, erected in an open swampy area about 150 ft from the house and 30 ft into the woods. It is low at only about 35 feet. I buried coax out and brought it right up to the feedpoint where I have several beads and a 1:4 Balun. That is it. It is resonated for 3.6 MHz. SWR goes way up 3885 and that hurts the efficiency. It is very nicely matched on 40, 20, 15 and reasonable on 10M. I know that it is not as efficient as a 75M dipole because I had one roughly in the same area and Al VTP runs a dipole and easily straps me on 75 M. This is the price of coax feed with no tuner. That said I got on 40M last evening at 8 PM with 3 Watts and got a 599 from NC. So when matched it is efficient.

[k7iou]

I did put up 280' wire, 53' at tower in corner with 3 other corners @ 17' feet high as this is as high as I get do since I am in the desert. 70' of 450 ohm ladder line & a High Q 4:1 balun with a Palstar AT 1500 tuner.
It seems to work well.
I would like a higher power rated balun. One mfg doesn't recommend his Remote 1.5k balun due to duty cycle of AM. I explained to him 350 watts of carrier X 4 is only 1400 pep but he still advised me not to use his balun.
So my research continues to find a sutable balun for AM with power......
73 de k7iou

[Steve - K4HX]

If that manufacturer was Radio Works, I can tell that their high power baluns will handle 300-400 watts of AM. They claim otherwise but I've used their 1:1 baluns for many years without a problem. IIRC, I'm using their 2K or 5K models.

Of course you can always make your own balun that will handle the power and it will cost less than most or all of the commercial units.

[WA2ROC]

I have been using a full wave 80 meter loop about 40 feet in the air fed with 450 ohm window like for more than 3 years, but I only feed in 100 watts from my Apache, or sometimes, heaven forbid, an SSB signal from my KWM2-A or Heath Marauder.

The balun is inside my tuner, a 1500 watt Tucker T-3000, and it works just fine.

You will find that the loop is very noise resistant, with a much lower noise level than a dipole or a vertical.

[k7iou]

If that manufacturer was Radio Works, I can tell that their high power baluns will handle 300-400 watts of AM. They claim otherwise but I've used their 1:1 baluns for many years without a problem. IIRC, I'm using their 2K or 5K models.

Of course you can always make your own balun that will handle the power and it will cost less than most or all of the commercial units.

The RemoteBalun's power rating is conservatively rated at 1500 watts. It is not possible to put a specific value on this specification because the power rating depends on many factors. Among those factors are the impedance and reactance presented to the RemoteBalun, the operating frequency, and duty cycle. They are interrelated and build upon themselves. The 1500 watt power rating assumes normal duty cycle modes (CW and SSB) with the balun operating into a moderate impedance electrical environment. If you operate AM, RTTY or other modes where the transmitter produces high power for long periods of time (a high duty-cycle), you will probably destroy this balun or any other balun for that matter. It is possible to use ferrite baluns like the Remote Balun but you should derate the maximum power delivered to your tuner. The same thing holds true for very high or very low impedances.

[wc4r]

I have used an 80m loop for many years. It is by far my best antenna. I do use a balun from Balun Designs. I run 375 watts AM carrier all the time for long periods. He will stand behind the product with that power too. Never an issue.
http://www.balundesigns.com/servlet/the-115/4-cln-1-balun%2C-balun%2C-4/Detail

[k7iou]

I have used an 80m loop for many years. It is by far my best antenna. I do use a balun from Balun Designs. I run 375 watts AM carrier all the time for long periods. He will stand behind the product with that power too. Never an issue.
http://www.balundesigns.com/servlet/the-115/4-cln-1-balun%2C-balun%2C-4/Detail

Waiting to hear back from Bob at Balun Designs.
Do you use your loop multiband or 80m only?

[k7iou]

Bob at Balun Designs recommended the #4114 4:1 balun, so I just ordered it.
73 de k7iou

[N2DTS]

What about using one as a recieve only antenna?
Would you have to tune it?

I dislike having to tune antenna's or wasting power in tuners.

I like low noise though...

I always wanted to try one of these:

http://www.pixelsatradio.com/product/shortwave-magnetic-loop-antenna/

Big loop, very low noise wide dynamic range preamp.

[k7iou]

What about using one as a recieve only antenna?
Would you have to tune it?

I dislike having to tune antenna's or wasting power in tuners.

I like low noise though...

I always wanted to try one of these:

http://www.pixelsatradio.com/product/shortwave-magnetic-loop-antenna/

Big loop, very low noise wide dynamic range preamp.

I tried a similar antenna and wasn't impressed and got rid of it.
My experience a tuner doesn't waste power, it matches the impedance. Unless you are using a full wave 80M on 10M Hi hi  

[WZ5Q]

Howdy Y'all,

Years back, when I owned the 10acres on the ridge up from the River House, I ran a 1058' Loop up at 120'. At that time I used 450Ω Window line all the way to the shack, a Radio Works 1.5KW 4:1 Current balun, 6' of co-ass to a Drake MN2700 Tuner. I was operating legal limit AM on 20M when I thought someone shot at me from the treeline with a shotgun. I heard a loud explosion and stuff bouncing off the window glass. Upon inspection PVC was everywhere, I had indeed blew up the Radio Works Balun. I admit, this was totally my fault as I was using this device outside of its ratings. I installed a DX Engineering 10KW 4:1 Current balun rated for Tuner use and never had another problem with that antenna system.

As others have stated, most of the power ratings for baluns are given when working under a specific SWR with low duty cycle modes. If you deviate far from the SWR rating as seen when multibanding an antenna system or using a high duty cycle mode, then you must de-rate the power capability of the balun, which I failed to do. 

I now use OWL exclusively with my homebrew LCT. I no longer have that evil ferrite in my transmission line. 

[WU2D]

Hey I am pretty convinced that the 80M full wave antenna if resonated in the center of the band, will give an excellent match on 40 and 20 Meters too; and with no tuner. The key is to use the 1:4 Balun at the feedpoint. Now this guarantees a mismatch, because the antennas impedance not a perfect 200 Ohms plus J0 (or 50 Ohms for that matter) but it will not be significant because at multiples of even frequencies it is likely to be between 50 and 400 Ohms. When you operate it with no regard to SWR like I do at 100 Watts, you obviously get loss. However my serious three core homebrew Balun has not failed at that power even at 5:1 SWR. Again, I also use several large clamp on Beads with Ties on them below the Balun.

The ideal would be to locate a remote tuner below the loop and run ladder line straight up to the feed.

[Steve - K4HX]

NEC 2 modeling seems to show the same. The SWR (200) numbers are what the SWR would be on a 50 Ohm coax after the 4:1 balun.

Horizontal Loop
l = 68.7' per side
h = 60'
fo = 3750 kHz
height  = 60 feet
ground = "average"
Rel. dielectric constant 13.000, conductivity: 0.00500 mhos/meter


   f          R      X        SWR (50)   SWR (200)

3750      128     0          2.6            1.6
7150      239  -115         5.9            1.7
14175    215  -335          15            4.4
21225    438  -335          14            3.7
28850    257  -24           5.2            1.3

[WU2D]

Very nice Steve. This shows the effect of using the balun to allow the antenna to work multiband efficiently. It is real folks. A practical low noise alternative to the trap dipole, fan dipole, off center fed Windom or G5RV in the "no tuner" coax fed family.

Might be worth running a 2:1 balun model and seeing how that works. I think that most folks assume that these loops are somewhere around 100 Ohms in the full wave band and when low enough, the impedance comes down to an acceptable level for 50 Ohm coax feed for single band.

[Steve - K4HX]

I've noticed a similar situation with my 40 meter 2-element delta loop array. It shows very close to 50 Ohms on 20, 15 and 10 meters.

[Steve - K4HX]

Looks like other than on 80 meters, the 4:1 balun is the better choice.

2:1 balun SWR results below.

 f          SWR (100)
3750           1.3
7150           3.0
14175          7.7
21225          7.0
28850          2.6

[WU2D]

Yup I believe that about the two element array. It likely brings the impedance down beautifully to 50 Ohms. But for single band operation of a horizontal loop, it looks like a 2:1 Balun would give the flattest performance across the band.

Here is one idea fora 2:1. A 2:1 impedance ratio would have a winding ratio of 1.4 : 1 which is easy to do with a conventional transformer approach. Wind 14 turns on two or three stacked T-200 cores and this is the loop secondary side. Now wind 10 turns for the Coax side.

[k7iou]

My new balun arrived today from Balun Designs.
Sure is a piece of art.
Bobs reply to my question with my antenna.

The model 4114 should easily handle your AM power and also provide your tuner with some margin when tuning.  This balun has excellent transformation and RF choking as well.

73,

Bob, KZ5R      Balun Designs