full wave loop balun needed?

[ghutch]

guys building a full wave loop to play with at the beach....reading some web pages i see the loop has a feed impedance of 102ohms? i will feed with 213 coax...i think i need a 2-1 balun? but dont know for sure? i see plansd on the web to wind a 4-1 balun it might work as well? any help would be great.
coax has a 5 coil loop right at the feed point coax connector. loop will be vertical fed 1/4 wave up from the bottom corner... bottom corner will be 4 feet off the ground..

 

[RADIOOMAN]

Assuming the antenna is to be used on 10/11 meter.
Use 1/4 wavelength of 75 ohm coax.(velocity factor corrected length )
Simple, cheap and effective if the choke is wound properly.

 

[HomerBB]

For 11 meters loop to 50 Ohm coax I simply use a 6' length of RG59 audio/video cable.

108 x .66 = 71.28

Close enough to 72" for me to simply buy a couple of these -

a 6' long 75 Ohm cable with one of these -

make the loop wire long, put it together and trim the loop wire back to a good SWR, and it's done.

 

[RADIOOMAN]

For 11 meters loop to 50 Ohm coax I simply use a 6' length of RG59 audio/video cable.

108 x .66 = 71.28

Close enough to 72" for me to simply buy a couple of these -

a 6' long 75 Ohm cable with one of these -

and it's done.

It don't get any easier than that.

 

[W5LZ]

I'm assuming those connectors are a 'double-female' and a screw-on PL-259??
- 'Doc

 

[IMD262]

I'm assuming those connectors are a 'double-female' and a screw-on PL-259??
- 'Doc

the top one looks like a F to PL-259.

 

[HomerBB]

I failed to mention I used a SO239 at the loop wire ends.

One of the two F to PL259

on each end of the 6' RG59 transformer and one barrel connector

to the 50 Ohm coax.

 

[ghutch]

The 75 ohm coax I have is tv coax this will work?
Workin on the spreader now....using PVC pipe but looks like a wood dowel is needed. ... Sags some but this may get better as I put some tension on the wire. Using 12 ga stranded with insulation intact.

 

[Captain Kilowatt]

The 75 ohm coax I have is tv coax this will work?
.

Sure it will. Just don't run a crap load of power through it and you will be OK.You do need the 75 ohm characteristic of it to transform the impedance down to 50ohms. the only problem with TV type cable is that the shield is often aluminum and not able to be soldered hence homerBB's idea to use the F/PL-259 adapters.

 

[HomerBB]

. . . the only problem with TV type cable is that the shield is often aluminum and not able to be soldered hence homerBB's idea to use the F/PL-259 adapters.

Yep, you got it.

 

[wavrider]

Solder It Alp 21 Aluminum Solder Paste 7 1 Gram Syringe No Mess No Waste | eBay

I have never used it but have read reviews and it is supposed to work.

 

[Captain Kilowatt]

Solder It Alp 21 Aluminum Solder Paste 7 1 Gram Syringe No Mess No Waste | eBay

I have never used it but have read reviews and it is supposed to work.

I haven't used that product but I have used some special solder containing a special flux for soldering aluminum with so-so results. I would rather use the adapters. The problem with soldering aluminum is that you need 100% clean aluminum and aluminum will begin to oxidize milliseconds after being exposed to air and this creates problems in soldering. Welding aluminum uses a blocking gas to prevent oxidizing while welding it. Even mirrors that are made by depositing aluminum vapor on glass is created in a partial vacuum to eliminate oxidizing.

 

[vkrules]

cable

I use quad shield cable that they use over here for pay tv. plenty of braid to solder to.

 

[ghutch]

Well the update....thanks guys for the guidance ....this was a snap to build. Took all of 1 hour to build after i found the connectors...RS had all of these. Works well...swr at 1.5 or less....very quiet. Took it to the beach Sunday and worked a few stations in Europe and South America. Bad install on my part as I was only able to get it 15 feet at the apex....corners were at 6 feet off the sand. Used a metal paint pole and the bottom was inches above the bed of my truck
Used an A or inverted V pattern with one support in the center and corners out at the bottom....feed point was center bottom...Horizontal polarity I think driven at the bottom. Worked well but seems the Wilson 1000 does drag in more noise and signals?. Plan to test with the feed point 1/4 wave down from the apex...this is to change polarity to vertical...see how that works vs the Wilson next weekend. And get a non metallic support/s
But...for a roll and go antenna this thing is great! If it was in the clear without my auto being the bulk of its support it would be a wonder! If I guy had a couple trees in the clear this would be a great base antenna and cost 20.00 or less