[K3PZN-List] Antennas

Curt Milton wb8yyy at yahoo.com
Mon Oct 9 12:30:47 EDT 2017 

Kyle
okay your reputation assembling coax is in question -- I rest my case that your dipole may be broken.  

cheapest way to build a dipole is to use a short piece of PVC pipe.  take the coax through a hole you drill in the PVC - for mechanical support.  do the same with the antenna wires.  provide sound mechanical construction, so that you can solder the coax to the antenna wires.  with patience and reasonable tools, anyone can assemble a dipole.  

no need to spend $40 for a balun for your application.  if you scrounge the hamfest maybe you can buy a center insulator with SO239 and screw lugs for the wires -- then it means putting a PL259 at each end of the coax.  either PVC pipe or a manufactured gizmo works as well.  

in the fewer words -- a balun intends to keep RF from leaking back onto the coax - particularly the outside of the coax.  it most of the RF radiates from the wires, a little radiating from the coax won't even be noticed.  many so-called baluns may not work well anyway -- there are special antennas (like many beams) that need them - but usually not a dipole unless it is very well elevated.  

Curt
 

    On Monday, October 9, 2017 8:56 AM, Kyle Thornton <kyle.3599 at outlook.com> wrote:
 

 Curt,
I will open that up after class today and take a look inside. I’ve found 1:1 baluns on eBay for $40 or so wasn’t sure if those would help. When the hurricane passes I will finish taking the dipole down and open it up (hopefully). The one leg is still up on the tower when I was trying it out as a sloper. I don’t have the coax actually cut. There’s an SO239 inside the PVC casing I made (and cemented together) and one leg goes from the center pin and the other goes from one of the screws on the SO239 it’s self. Last time I tried to strip coax I went through a whole 25ft section (radio shack coax so it’s fine) when I string the legs out I try and get them as tout as possible. Is that necessary or just pull them out and just lay them on the ground. I’ve been staking them down.
Kyle

On Oct 9, 2017, at 8:38 AM, Curt Milton via K3PZN-List <k3pzn-list at mailman.qth.net<mailto:k3pzn-list at mailman.qth.net>> wrote:

Kyle
I am suspicious there may be a connection problem with your dipole -- no way does a center fed with each leg at 33 feet not have a good SWR somewhere near 7 MHz.  when you cited 2.6 minimum SWR, I have seen this kind of number when one side is not connected to the coax.

Balun.  maybe lots of opinions here -- but practically for a dipole close to the earth - its pattern will not greatly change when using a balun.  I confess I have never used a balun on an HF dipole.  (I would on something like a 20m dipole up at 40 feet).

let me know what you think is broken on the R5.  if you look inside the box at the base you will see there are too large toroid coils in there.  hopefully those are not cracked -- but even if they are -- they could be glued back together with epoxy.  of course the wires connected these to the coax connector need to be intact -- honestly nothing else in there.  everything else is just a metal-to-metal connection.

I am remembering the wire rods at the base are rather flimsey - and should have survived.  any bent metal on the rods at the top could likely be straightened in a vise - or if not too badly bent - you may not notice any change in performance.  these rods add capacitance near the top of the antenna - maybe doing a little more than merely making the antenna look more cool (as the antenna is a bit short on 20m -- these rods likely do bring the resonance down lower in frequency).

hang in there -- antenna damage does happen --see if you can find why the dipole may not be connected to coax on both sides.  while this can be done visually, perhaps, if you have a DVM measure continuity from each wire to the feed end of the coax, to see if indeed you have an open.  Alert us if you are short anything material wise.

Curt


  On Sunday, October 8, 2017 9:04 PM, Kyle Thornton <kyle.3599 at outlook.com<mailto:kyle.3599 at outlook.com>> wrote:


Thanks Dave ill look into that!

Curt,
I never liked how it was set up either but its the only thing im able to do because of the HOA we have. I wish I had the space and height for a wire because I think thats part of the problem. The dipole has been cut EXACTLY for 40m but its resonate (1:1swr) at right around 60m which I havent used and really dont plan to use it. I like the verticals because I can leave it up and I can get 4 or 5 bands out of them. The dipole doesn’t have a ballon on it so maybe thats the problem? I need to get some fiberglass poles that just slide into each other that I could put up 40ft and string the 40m wire off that as an inverted V. Would a balon solve that issue with the dipole and make it resonate on 40m? Right now its got about a 3:1 SWR across the whole band.
Kyle

On Oct 8, 2017, at 7:45 PM, Curt Milton via K3PZN-List <k3pzn-list at mailman.qth.net<mailto:k3pzn-list at mailman.qth.net>> wrote:

Kyle
glad the R5 has done you some good -- and let's not assume it's dead.

bent metal damage -- this can be fixed with a vise - -and those radial things do not have to be perfectly straight.  I don't have a picture of your feedpoint damage -- I need a little more data or a picture.

i wasn't thrilled with your R5 installation anyway -- and I am more glad there seems to be no damage to the house!

let's re-group -- and get your dipole fixed.  I suggest ZERO spending on an antenna.  please let us know what you need to fix your dipole.

catch your breath and let's work this.

BTW - the ONLY magic of the R5 is its ability to match all those bands - as a radiator it is NO better than any other piece of metal - except for its ability to accept the RF on all those bands.  a pair of dipoles (even as inverted V) can beat it on 20 and 40 meters - the best bands right now.

Curt


    On Sunday, October 8, 2017 7:07 PM, Kyle Thornton <kyle.3599 at outlook.com<mailto:kyle.3599 at outlook.com>> wrote:


All,
So last Thursday was a pretty good day until I came down the hill behind my house going into my neighborhood. I usually always look over at my antennas just because why not. Well when I looked over this time I noticed the R5 Vertical had fallen and was hanging partly on the gutter and partly on the VHF tower right next to it.

The minute I got home I didn’t bother to do my homework because I was more concerned about what kind of damage I was looking at. I decided I was going to try and pull the R5 back up so I could safely take it down. But If anyone knows what kind of luck I have knows that didn’t happen as it was supposed to. The minute I put my hand on it, it came off the gutter and the tower and hit the rot iron railing and then onto the ground. One of the top radials is bent to about a 90 degree angle and since it was a permanent installation the coax was tight and it bent the SO-239 on the feed point.

I am not strong enough to unbend the radial. I took everything apart to see what other damage done that there was. Took the feed point off and the screws preceded to fall out and theres no real way with out undoing the rivets to get them back in. I have a feeling the feed point is no longer good as it hit the railing pretty hard.

So needless to say it wasn’t a very good day after that. My 40m wire is also not working the way it should but thats going to be worked out soon.

I was looking into replacing the R5 but after I looked at the bank account I figured I should make a budget first because that was another scary scene. I financially can not afford to replace the antenna no matter how bad I want to. It just wont happen. I was going to wait and get a QSO King but I have a very strong feeling thats not going to be feasible either. So now I have a VERY nice 891 thats collecting dust.

What does everyone suggest the next step should be? Ill probably be out of the hobby until I can get this done and I really don’t do VHF that much except to talk to mike. Everything is just to expensive and with out a job theres really nothing I can do. Im really not happy about any of this because I liked that R5 A LOT! Made TONs of good QSOs with it.

Thanks
Kyle
KC3FMP
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