New Shack/Antenna Analysis Paralysis

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W0KDT, Sep 14, 2018.

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  1. W0KDT

    W0KDT Ham Member QRZ Page

    OK, kinda dumb newbie question on antenna tradeoffs:

    I’m a repeat offender, having been a ham in high school and now 50 years later having re-upped my General. I am setting up a station based on a Yaesu shack-in-a-box FT-991a.

    I have a discone on the roof for 2m and 440 and it lets me hit essentially all the repeaters in town. So the HF is the next step:

    I have no space nor interest in a beam, so my choices are a wire antenna or a vertical.

    A ground-mounted vertical would have to be next to the house and its metal gutters. I am not keen on burying a bunch of radials either. So I have tentatively rejected that idea.

    A roof-mounted vertical would work, but I am too old to be crawling around on the roof but my young neighbor will help. I don’t want to ask him to run and anchor a jillion ground plane wires though. A Gap Challenger with its 3 counterpoise wires is about the max feasible on the roof plus a few guy wires if necessary.

    I could also put a tripod and mast on the roof to support the center of a wire antenna like the Buckmaster 4-band OCF. This gets me 40M to 6m, but not 80m. A local Elmer will sell me one of these for $100. I cannot deal with a wire antenna that is much longer due to trees and lot size. I am limited to about 60 feet on each side of the center. From high school days, I have an affinity for 80 meter phone but I am not hampered by any knowledge of what goes on there these days. So an antenna that won’t do 80 meters is a slight negative for me unless someone tells me that’s silly.

    Bottom line is I am in analysis paralysis. Suggestions, discussion would be welcome. Money is not a huge issue but installation difficulty is.
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I suspect you may be younger than I am (67) and I'm up on the roof all the time, and still climb towers.:) But people are all different.

    The 60' either side of center is definitely enough room for a dipole that covers 80 meters! A full-sized (1/2-wavelength) 80m dipole is 133' long but a dipole for 75 meters (the "phone" end of the 80m band) is only 123 feet long (for 3.8 MHz). Assuming you use 5' of rope at each end, you could install a 110' long doublet and let 12' of "extra wire" just hang down from each end insulator, and the dipole would be resonant about 3.8 MHz. And that works fine.

    The key issue is "height above ground." If all you want is local ragchewing on 75m (within a few hundred miles), even a low dipole will work quite well. But if you want to stretch your wings a bit and make pretty easy contacts out to 3000 miles (a lot more stations to work that way!) on 75 meters, you'd want the dipole to be as high as possible, preferably at least 60' above ground. A strong tripod with a tall, rope-guyed mast at the peak of the roof could potentially get you there, even if each end is lower.

    There are also parallel dipoles (commercially preassembled) like the Alpha-Delta model DX-CC which is only 82' long end-to-end and covers 80-40-20-15-10 meters. It's shortened by loading coils on 80/75 meters but acts like a full-sized dipoles on the higher bands; on 80 or 75 meters it loads up well for about 50 kHz of the band, which may be all you need, or if not a tuner in the shack can be used to extend its useful frequency coverage on that band: https://www.alphadeltaradio.com/pdf/DX-CC, DD, EE, LB, LB Plus Instructions-10.pdf

    Height is key.
     
  3. NH7RO

    NH7RO Ham Member QRZ Page

    I'll suggest something that I use (albeit only on 40m since I have other antennas for other bands):

    https://www.scorpionantennas.com/home-antenna_c_19.html

    I added a 5-foot copper mast (in place of the stock whip) and a 60" circular cap hat and mounted it atop a 6' T-post in the back yard. This thing rocks for a shortened vertical!

    Just think; 10-80M easily tuned to resonance and one feedline.

    If you mounted it atop your roof you could get away with using the heavy duty version hamsticks Ron lists as an accessory if you didn't want to run elevated radials the usual way, too.

    73,

    Jeff
     
  4. WE6C

    WE6C Ham Member QRZ Page

    I say run wire as long as possible, feed it in the center, install loading coils to resonate it at the lowest freq you want to use, feed it with ladderline, and you're good for that freq and up.

    You can google "short dipole loading coil calculator" and get coil dimensions that are very close.

    No radials needed with that setup.
     
  5. AE1N

    AE1N Ham Member QRZ Page

    I have had great success with verticals. You do NOT need extensive verticals. If you raise the bottom a few feet above ground you will do well with just 4 radials, a good ground system and heavy buss to the cold water pipes in your house. An artificial ground can be helpful also. And a tuner to ensure every bit of RF is going down the feedline. --- Layne AE1N
     
    NH7RO likes this.
  6. W9KEY

    W9KEY Ham Member QRZ Page

    WB2WIK mentioned Alpha-Delta, which also has a 40 meter multiband dipole that is 40 ft. Check their various offerings at:
    https://www.alphadeltaradio.com/pg1.html

    Including the: DX-EE - “No-Trap” 40-20-15-10 meter dipole or inverted V. Also covers 30-17 & 12 meters with an antenna tuner. Overall length is 40 ft.

    I have one of the 80 meter models and am quite pleased with it (however, I'm a new ham with nothing else to compare it to). Picked up one of their SWL versions at a swapfest for about the cost of the wire, not realizing it was not specifically tuned for the ham bands. Sent Alpha-Delta an email inquiry (on a Sunday) which was immediately answered by their president (I believe), along with a spec sheet and modification suggestions. VERY impressive service - which I certainly didn't deserve!! How can you not like a company that treats you like that? I intend to purchase other items from them in the future.

    Their antennas use heavy 12 ga wire, which is gray in color for some bit of "stealth". Rugged construction. Mine doesn't have a 1:1 balun - which I might add sometime in the future. Only issue -- without an antenna tuner, my ICOM radio tuner (3:1) only provides acceptable SWR on about 1/3 of the 80 meter band. But the other bands all tune fine.

    73 ..... Fred, W9KEY
     
  7. W4PG

    W4PG Super Moderator Volunteer Moderator Platinum Subscriber QRZ Page

    Over the years I've had very good success with the Cushcraft R-series verticals. HyGain makes similar verticals. They easily mount to a brick chimney on the roof using old style TV mast aluminum bands around the chimney or mounted on the side of the house using a long 1 1/2 inch pipe stuck in the ground then braced to the house. You don't need to run long radials as these antennas are designed with fairly short counterpoise "radials" at the bottom of the antenna that serve the purpose. You can also mount them in the middle of the yard of you like. There are "tilt over" mounts you can get to help with raising and lowering them at the mounting site for adjustments in SWR, etc. They take full power and work well.

    ...............Bob
     
  8. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Two important data are missing:

    (1) Do you want to work DX on 80m/40m, and

    (2) How high could you get the center of a hypothetical multi-band dipole?

    If you can only get the dipole 30 or 40 feet high, the radiation pattern would not be conducive to DX on 40 or 80. You will still be able to work DX occasionally on those bands when conditions are just right, but many evenings you will just hear others working DX you can't hear.

    On the other hand, if you don't care about DX, height becomes less crucial.

    BTW, at the current point of the solar cycle, one have lots of fun with antennas for 40 and 20m alone. On these two bands it is often simple to put up effective antennas. It is nice to have 80 and 160, but those bands require large/high antennas, which usually require more planning than 40 and 20m ones. 15M is rarely open; 12 and especially 10m are more frequently open, due to E-skip, but there isn't much activity right now even when the band is open, since so many assume it is always closed.

    So, consider throwing up a 20/40 fan dipole now and continuing to examine your options on other bands. (And, if you serious about working DX, and you stick with the hobby, you will almost certainly end up with verticals of some kind on 80 and 40m. Just warning you.)
     
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  9. NH7RO

    NH7RO Ham Member QRZ Page

    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Great point that bears repeating, IMO. Easy to implement and lots of bang for the buck in many cases. (Disclosure: I am biased towards chasing dx).:)
     
  10. W0KDT

    W0KDT Ham Member QRZ Page

    Wow. Thanks for all the input. This feels a little like going to one of those engineering meetings where you start with five alternatives and boil them down to ten!

    I really don't know whether I will want to work DX on 80 and 40. I feel like Rip Van Winkle waking up to a new ham world. No code requirement, a bunch of new ham bands, SSB CW, FM on 2 meters, ... I have no idea what I will end up wanting to do, so I am trying to balance money and hassle with not precluding too many options.

    Re the center of a dipole, we have a single-level house where I could put like a 5' tripod and a couple of mast sections on the roof. So maybe 30 feet total? 40 feet? XYL is already not too keen on the discone up there but I can probably get away with a second tripod. I looked briefly at the MFJ cobweb antenna but I think a 24' span is more than I dare.
     

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