44 ft Doublet Opinions?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by 2I0TWF, Apr 15, 2011.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-rl
ad: L-Geochron
ad: Left-3
ad: HRDLLC-2
ad: abrind-2
ad: MessiPaoloni-1
ad: Left-2
ad: L-MFJ
  1. 2I0TWF

    2I0TWF Ham Member QRZ Page

    Hi all, this is probably more directed to the model experts. I have looked at various opinions on this antenna most good, some bad.

    I have just completed a home brew fed with 300 Ohm windowline to a MFJ tuner and tested the tuning. I can tune all bands from 40m up.

    My original dipole was cut for 20m so I assume this will be some sort of improvement due to its reported pattern. Also is it reasonable on 40m? Miracles are not expected!

    I know the bigger the better however this is the max size I can build and hang.

    As always your input is appreciated.

    Carl
     
  2. W5DXP

    W5DXP Ham Member QRZ Page

    Walter Maxwell, in Reflections, gave us a rule of thumb for the length of a dipole. He said it should be at least 3/8WL long. Your 44' dipole is 3/8WL long on 8 MHz. To meet the rule of thumb for 7 MHz, it should be 49' long. But if 44' is the best you can do, in the immortal words of my friend Don, KE6AJH/SK, "Halitosis is better than no breath at all."
     
  3. N5YPJ

    N5YPJ QRZ Moderator QRZ Page

    I had one before flat top at 30 - 35 ft. It was a bear to match on 40, sometimes I couldn't and when I could, don't even breath on the tuner. 20 & 17 were good, 15 a little fussy to tune, 12/10 weren't open enough to try. If you are willing to tinker with your feed line length on the different bands you may have better results.
     
  4. WA4FNG

    WA4FNG Ham Member QRZ Page

  5. N0GMT

    N0GMT Ham Member QRZ Page

    Howdy!

    If 44 feet is as far as you can stretch out, have you thought about a Slinky Dipole?

    I had one for a while, about that long, it worked well on 40 and up as a dipole. And i could tie both legs together and feed it as a vertical on 80.

    You need capacitance hats on the ends. I used two 3 foot brass brazing rods stuck through holes drilled in the plastic insulators.

    Some folks might poo-poo this idea, but if you can't get a full-sized dipole up, this might be your next best solution.

    (Don't buy any of the ready-made ones, go to the toy store, buy a couple of Slinkys, and make it yourself!)

    Rob
    N0GMT
     
  6. AK5B

    AK5B Ham Member QRZ Page

    44ft should work well on 10m; that's an extended double zepp for that band, if I'm not mistaken.
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Not a bad idea, but slinky dipoles are really monoband antennas. The good thing is, you can "change bands" fairly easily if you can reach the antenna.

    End-loading with "capacitance hats" is also a pretty good way to reduce the resonant frequency of an antenna without impacting performance too much.
     
  8. AJ8MH

    AJ8MH Ham Member QRZ Page

    I've been using a 44 foot doublet for years, and don't have a single complaint. During the past 2 years, I've only used my current one on 30 through 10 meters. It's up 32 feet and I've worked a lot of DX running 100 watts, but it will soon come down and a 4 element beam will take it's place.

    I also have a home-brew linear loaded vertical doublet that I use on 40 meters, and it outperforms the 44 foot horizontal doublet on that band.

    Put up what you have room for, keep it simple, and see what happens, but keep in mind what your radiation pattern looks like. A longer antenna isn't necessarily a good thing unless one of your gain lobes just happens to be pointed in the needed direction. (I also use MFJ tuners, but the 4:1 baluns have been changed to 1:1 current baluns.)

    Have fun experimenting with your antenna.

    Joe
     
  9. 2I0TWF

    2I0TWF Ham Member QRZ Page

    Thanks for the replies folks very helpful.
     
  10. K4SAV

    K4SAV Ham Member QRZ Page

    44 ft is a pretty good length for 20 meters thru 10 meters, if you need a single wire for multiple bands. You didn't say how high the antenna is, and that will be a factor in how well it performs. You didn't say how long the ladder line is. That won't be a big factor unless you try to use it on 40 meters. The ladderline loss will be high on that band. "TLDetails" program shows 4.6 dB of loss for 100 ft of Wireman 551 ladderline on 40 meters.

    The direction you place the antenna will also be important in determining whether you like the antenna or not. It fires perpendicular to the wire on all bands. On the high bands like 10 meters, the beamwidth is very narrow, about 33 degrees. It will do well for stations within that beamwidth but poorly for stations outside that beamwidth. The beamwidth is wider on the lower frequencies, 82 degrees on 20 meters.

    Jerry, K4SAV


    Note: Some programs give very optimistic attenuation factors for ladderline. TLW assumes 0.082 dB per 100 ft matched line loss on 10 MHz. While it may be possible to fabricate a ladderline with that attenuation, that's not a close number for Wireman 551. Published data by Wireman is 0.2 dB per 100 ft at 10 MHz, and I think that may be close for that frequency, but for low frequencies they do a straight line projection, and apparently do not include low frequency resistive losses and I think the error at 160 meters is large. TLDetails program seems to be more accurate for this ladderline (0.264 dB per 100 ft at 10 MHz and 0.252 dB per 100 ft at 1.8 MHz for matched line loss). It is possible to fabricate your own ladder line that can have a much lower loss.

    TLDetails is a free program,
    http://www.ac6la.com/tldetails.html
     
Thread Status:
Not open for further replies.

Share This Page

ad: elecraft