Question about dipoles ?

[Beetle]

Forget the "G5RV". Put up a center-fed dipole (or doublet), as long overall, and as high and as safe from power lines as possible. Feed it with 450 ohm parallel feeders and a matching network that's rated for at least twice the power you're putting out - maybe 3x or 4x.

Experiment - just do it safely.

 

[Captain Kilowatt]

Forget the "G5RV". Put up a center-fed dipole (or doublet), as long overall, and as high and as safe from power lines as possible. Feed it with 450 ohm parallel feeders and a matching network that's rated for at least twice the power you're putting out - maybe 3x or 4x.

Experiment - just do it safely.

Was going to say the same thing but I got paged and had had to do some work.

That is exactly what I have been using albeit with a remote auto tuner outside the house at the transition between coax and ladder line. Works far better than a G5RV.

 

[Oatmeal]

I thought the bare wire would cause alot of noise on the radio, where insulated wire would quite the noise down....

 

[Captain Kilowatt]

I have seen where insulated wire will reduce precipitation static cause by electrically charged snowflakes hitting the the bare wire and discharging but that is rare and the wire needs to have a DC path to ground and not all of them do.

 

[Beetle]

I thought the bare wire would cause alot of noise on the radio, where insulated wire would quite the noise down....

Experiment and see if it does. Experiment with horizontal polarization and with vertical. See what difference it makes in YOUR specific situation.

 

[Heavy Metal]

http://www.packetradio.com/catalog/...ucts_id=2425&zenid=6kmvhrbn2bg4tma0n4g25mif04




What about a folded dipole

 

[Oatmeal]

Update, I didn't buy a dipole, instead built a coax fed 40m dipole, out of wire I had left over from a project here....used 12ga solid copper wire, and went with 33ft each leg...hung it up 20ft off the ground to the center bone, and one of the legs is 16ft off the ground and the other one is about the same....took a little bit to get it tuned due to all the metal I have close to me but I got it.....swr on 7.1 and 7.2 is a 1.2 and on 7.3 it's a 1.5 using a rat shack meter to tune it.....no fancy mfj antenna analizier stuff here....ended up folding 11.5" of wire back on it's self, and one end is tied off to a tree and the other to a pole...it seems to talk ok, have talked to a few guys from another forum who says it's working fine...don't have much radio time here these days..

By the way, I did use insulated wire, thats what I had, and the noise isn't as bad as I thought it would be...

 

[DainBramage]

....used 12ga solid copper wire, and went with 33ft each leg...nded up folding 11.5" of wire back on it's self......

are you sayin that the antenna is now 21 1/2 feet per side,.... 43 feet total?

 

[Oatmeal]

No, I have total of 64.08ft

 

[Oatmeal]

Just going to ask, what you guys think about the Jr dipole that W8AMZ builds ?.....

Any you guys running one of these?..

 

[Beetle]

It's a half-size G5RV, which means it isn't a G5RV at all. A G5RV is 102 feet long, with a matching section of parallel line and then fed with coax. It's a 20 meter antenna (as Varney designed it), with passable operation on a few other bands. It will probably still need a tuner; you'll still have relatively high losses in the coax where the SWR is high, and you'd likely do better feeding it with parallel line the whole way.

 

[543_Dallas]

Twin feedline all the way to a balanced tuner is the way to go. The problem is most tuners on the market that fit the bill are overpriced crap with a cheesy internal balun. There are plans out there to build your own.

I started with a 40 meter coax fed dipole but wanted more bands. If you decide to go with a g5rv look into buikding the ZS6BKW version. This is what I am using until I build a tuner. The idea is to have the swr as low as possible where the coax meets the open feedline on as many bands as possible because high swr on a coaxial feedline = loss.

I built the zs6bkw with everything a couple of feet longer. Soldered some alligator clips to a pl259 and started trimming. I felt this way was better than taking a premade dipole out of the bag and just hanging it up. Swr is 1.5:1 ish on 20 and 40. Flat on 12 and around 5:1 on 75. I don't remember what the other bands were.

I've worked 15,20,40,80 with it. With my murch t-match I can tune up anywhere 10-80 but it just sucks on some bands. It's not an ideal antenna but it's more fun than a mono band dipole.

Use the best coax you can and keep length as short as possible. Use a 1:1 current balun or some form of CMC choke at the coax/ladder line junction.

 

[Oatmeal]

Beetle, even if I use LMR 400UF coax it still has a lot of loss ?...

 

[543_Dallas]

Even high quality coax is very lossy when the load presents a high swr. This loss will also make you see a lower swr with a longer run of coax. More loss = less reflected power. This is why you see a lot of people selling a g5rv recommend a lengthy 70+ feet of cheap coax.

The attenuation specs for 50 ohm coax are only accurate when it's feeding a 50 ohm load. Rg11 is cheap low loss 75 ohm cable BTW.

 

[Beetle]

Beetle, even if I use LMR 400UF coax it still has a lot of loss ?...

To echo what 543 said, yes. Coax is NOT a perfect feedline, especially when there's a significant amount of reflected power. Of course, if you mount a remote ATU within a foot or two of the feedpoint, you can really minimize the loss.