Crazy Weather and Antenna Installation

Discussion in 'Chat' started by W5HRO, Oct 10, 2015.

  1. W5HRO

    W5HRO Administrator

    This morning we got up and ate breakfast and took our Mercedes GLK-350 over to the dealer for it's B1 service. When we left it was in the high 70's and 100% sunny and it was suppose to get really hot today and be 97 tomorrow. By the time we left the dealer the temp had dropped 10 degrees and fog rolled in from I don't know where and it started to sprinkle. I looked at my iPhone's forecast and it had changed drastically. Now the sun is back out and it’s getting really hot like they had originally predicted and the forecast is back to what it was before.

    What the heck is going on, El Nino?

    Anyway, I’m getting ready to cut the wire and build up my new dipole today and put it up tomorrow if the weather doesn’t spaz out again ::)

  2. KC9UDX

    KC9UDX Member

    Alls I know is it's too dang hot. It must be 70.
  3. W5HRO

    W5HRO Administrator

    Got the antenna all cut and put together and went outside yesterday and took the old 20' pole down from the side of the house then realized I needed to modify the wooden bracket I put up years ago at the top of the eve where the old pole was clamped. The new 40' mast is thicker at that point so I had to run down to the hardware store and get some new bolts and a clamp for it plus the next size lag bolts that are also longer to screw back into the house to hold the heavier mast.

    Anyway, got the one hole repositioned and the rest drilled out bigger and I will repaint it either tonight or tomorrow then put everything up later this week after work. It’s not supposed to rain until Saturday.

    We occasionally get heat waves here for a week or two in October, but I think El Nino is making things a little strange this year.

  4. KE5YTV

    KE5YTV Guest

    I'm wondering when El Nino is going to get cranked up. Here in Dallas it's hot and dry. October is supposed to be our second wettest month. If you get some rain out there on the left coast send some our way. :neutral:
  5. KC9UDX

    KC9UDX Member

    We were supposed to have sunny skies, heat (75º) and very high wind today.

    We had cloudy skies, drizzle, and a little breeze.

    It always amazes me that "they" think they can reasonably predict the weather fifty years from now.
  6. W5HRO

    W5HRO Administrator

    Well, I finally got my new 75-meter dipole up today and my noise level has decreased about 75% :icon_thumbup: I can’t believe it because it's like night and day. I can tune up fine on 40-meters as well. Probably some overall gain loss on 40, but it still works good enough. I made the whole thing 130' from end and it came out resonant right at 3650kc. Close enough...

    Anyway, my old ladder line fed dipole must have been picking up most of the noise because its length was too short or something. Even with my Plasma TV turned on now the noise is almost completely gone. Now maybe I can hear something. It’s up a lot higher now too.

    It looks like rain outside now so we will see what happens. The forecast no longer calls for it though.
  7. KC9UDX

    KC9UDX Member

    What is the height?

    I'm guessing you have it up 50' or more.

    I have one 134' up twenty-five feet and it's resonant about 4.0.

    I just can't get it higher yet. I have very young trees. They were put in in the last 25 years. I'm thinking about putting masts in the trees, or putting a 60' mast in the centre for an inverted vee. Next year, like I said last year...
  8. W5HRO

    W5HRO Administrator

    The ends are up 40' now. Before they sloped down to only 10'

    I'm surprised yours came out resonate at 4Mc. I made sure each leg on mine was exactly 65'. I made marks out on the front sidewalk with my 100' tape measure and had the XYL hold the balun at the first mark while I went to the other mark and ran each wire thru the end insulators at the other mark. 65' is exactly a 1/4 wave at 3.600Mc so to have it come out to 3.650Mc was close enough, but I was still surprised it wasn't dead smack right at 3.600Mc on the money. I think the heavy Radio Works 1:1 current balun must be shifting it a hair bit for whatever reason. I picked 3.600Mc because that's the bottom end of the 75/80-meter phone band.

    What matters if having the length long enough for the lowest frequency you will be operating on. You can then tune it on almost any band (frequency) above that even if it’s fed with coax. The problem is when it’s shorter. Usually the height above ground will not effect where it is resonant, it will just raise the VSWR where it's resonant.

    Anyway, now I can start working on my projects again like adding the bias shift relay setup in my 4-400CG RF deck for the SB-10 SSB adapter and the new T-368 exciter deck.
  9. KC9UDX

    KC9UDX Member

    I have 1:1 VSWR awfully close to 4.0Mc.

    I currently have 67' of wire on each side, measured by attaching end insulators, and staking them to the ground along with the end of a measuring tape. I cut the wires exactly 6" too long per the tape. That 6" is removed when attaching the centre insulator.

    I had 67'6" per side when I put it up, but my centre insulator shattered in a recent wind storm. So when installing a new one, I lost a foot total length.

    The antenna is fed with 50' of 450ohm window line, and 50' of RG213. There is no balun.

    I put this antenna up this year to replace an identically constructed one that was only 130' in length. It resonated somewhere above 4.0Mc (I'd have to consult my notes to remember how much). I wasn't sure if I did something wrong with that one, so I made this new one and ended up with the same result.

    The window line runs parallel to the one side of the antenna, about 35' away from it. Due to the low height of the antenna, there's not much I can do about that. That's the next likely suspect for why the antenna resonates so high.
  10. W5HRO

    W5HRO Administrator

    That's what is causing it.

    First, if each or your legs are 67' then 234 / 67 = 3.5Mc. The ladder line needs to also be a 1/4 wavelenght long, the 67'. Plus if you are going to couple ladder-line and coax together then you should really use a balun at that point, but that's not what's causing it.

    The main problem is your ladder-line length needs to be the same length as one of the legs. With only 50' then 234 / 50 = 4.68Mc. That combined with the 67' or < legs is exactly what's doing it. 67' + 50' = 117'. So... 468 / 177 = 4.000Mc.

    One of the biggest mistakes people make is thinking the length or their ladder-line or open-wire line in general doesn't matter and that it can be any old length. Unfortunately that is completely wrong. The length does matter because it will determine where the resonate point is. Each side of the ladder-line length and the leg of the actual antenna combined should equal a 1/2 wavelength unless you are using an 1/8 wavelength ladder-line feeder like mine was.

    Live and learn...
  11. W5HRO

    W5HRO Administrator


    I drew up the dipole (Zepp) below and it may explain things a little better. I think what happens is many people are so use to using unbalanced coax for feed-line that they don't understand ladder-line (open-wire-line) works completely different. Then length of the ladder-line adds to the length of each leg of the actual antenna. In your case the ladder-line length section should have been 67' instead of 50'. So what you need to do is change the length of the 50' section to 67' or the few feet shorter to compensate for the loss after replacing the center insulator. Maybe just splice in the extra feet for now. You may still be able to get away with not using a balun to couple the ladder-line to the coax, but adding the extra missing feet to your ladder-line length will bring the resonate point down to where it needs to be.

    Basically during operation everything folds back and the ladder-line will not radiate when that happens. That’s why the ladder-line length and each leg of your antenna should be 1/2 wave total on each side.

    Hope that makes sense.

  12. W5HRO

    W5HRO Administrator

    Went up on the roof this last weekend and did one final mod to the new dipole and just finished it last night.

    The weight of the heavy Radio Works 1:1 balun and coax were making the center feed point of the antenna hang way down. Luckily during our trip to Tulsa last August I brought back a big box and a can of some old antenna hardware I used and didn't use back in the 1970's. One of which was an old Radio Shack hinged roof mount they had not made in a few decades that I never used.

    Anyway, ran down to the local hardware store and got a piece of PVC pipe and used that from the roof mount to the balun to get the thing up around 6 to 7 feet higher at that point. Worked great :icon_thumbup:


    Looks like rain tonight too...
  13. K4TQF

    K4TQF Member

    70 degrees here tomorrow... unfortunately, torrential rain also.
    Seeing your roof mount gave me an idea. I was going to cantilever a piece of pipe from this pine tree with a pulley on the end in order to pull up an inverted V. While looking around the yard this AM, I found a 20 ft section of what appears to be a top rail for a chain link fence. ( no chain link here ) I think I'll just haul it up in the top of the tree and lash it to the trunk vertically, leaving about 10 feet sticking out the top and 10 feet for lashing.
    That should put the apex around 40' and the wires in the clear.