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Clothesline Reel AKA Yo-Yo Antenna of Inslulated Wire

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WI2D, Mar 21, 2010.

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  1. WI2D

    WI2D Ham Member

    Dear antenna theorists and practitioners,

    My question is probably like one from the joke below.
    ---
    A student asked a professor one day:
    - Sir, when you sleep, do you put your beard above or below blanket?
    The old man replies:
    - Uh... I do not know. Never thought about it.
    Some time later they meet again and all exhausted professor jumps on the young fellow with accusation:
    - Because of your damn question, now I can not sleep at all: either way feels uncomfortable.
    ---

    So, here it goes.
    I have built a dipole of adjustable length similar to one described by KC8VWM. However, an insulated wire was used instead. Understanding that this approach creates coils at the end of each dipole leg, I am now debating whether I should strip the insulation. This way different turns of the wire on the reel will be in contact with each other eliminating the coil.
    Commercial 'Yo-Yo' variant of this antenna with insulated wire marketed by hamradiofun.com.

    Should I worry about described coils and strip the insulation?

    Thanks & 73,
    WI2D - Andrey
     
  2. KC8VWM

    KC8VWM Ham Member

    Hi Andrey,

    Since it's my portable antenna design you are constructing, I suppose I might be able to answer your question how it works. :)

    When you unroll the wire from the reel, it changes resonance in terms of it's operating frequency.

    [​IMG]

    This is the tuning aspect of this design. You will not require an antenna tuner to work every band from 40 - 6m using this antenna.

    The wire left inside the reel is really just a "metal ball" which exists at the end of the wire. This "ball" is similar to the one installed on the end of your car antenna.

    Bare wire works best for this project because the wire ball inside the camping reels becomes a resonant part of the actual antenna design. It is because of that fact insulated wire will not work for this design.

    You need to include the "metal ball" inside as it extends to the rear of the reel as it's a functional part of the actual antenna length.

    Design Instructions:

    First, start out by designing the entire wire antenna to function on 40m as an ordinary dipole. (around 32' 11' when fully extended from the reels) 14 gauge flexweave is used in this design however "thinner" wire may be used. Stranded is typically better than solid wire because it's usually mechanically stronger and resists kinking etc.

    Once we design a 40 m dipole, next, we want to reel in just the right amount of wire for it to reach and function on the 30m band.

    For example, since we know a 40m dipole is 32' 11" and if a 30m dipole is 23' 2" long, then we simply subtract the difference and that's where the 30m band will be located on the wire. (subtract around 8' 9" +/- )

    Next, check and tweak for best VSWR on the 30m band by adjusting the wire a few inches +/- in or out of the reels on both sides of the dipole until the best VSWR has been achieved at the desired operating frequency.

    Next use a paint marker, to mark that spot on each side of the dipole at the point it folds over the tab on the end of the reel for future reference. (see photo below)

    [​IMG]

    Now "tune" the antenna again but do this calculation for the next band when going from 30m to 20m.

    For exmple, to adjust the antenna from 20m to 17m all you need to do is calculate the differences in terms of wire length required between the next two bands in order to find how much wire needs to be reeled up inside. (subtracted.)

    For example.

    If one leg of a dipole cut for 20m CW portion of the band is:

    16' 7" long and if

    One leg of a dipole for 17m CW portion of the band is

    12' 11" long

    And if the antenna has a good VSWR reading on the previous band, then collapse the wire inside the reel exactly 4' 2" and that will be the difference between operating on 20m to 17 meters.

    Once you have done that, check the VSWR again, (tweak the wire length and inch in or out of the reel if necessary) and now mark that spot on the antenna wire using the paint marker.

    Lather, rinse, repeat. :)

    Do the same thing above but for changing bands from 17 to 15 meters.

    Next you adjust and mark the wire going from 15 to 12m

    12 to 10m and so on...

    Complete the calculations and wire marking procedure on every band until you have markings on your roll up antenna wire for every band from 40m though 6 meters.

    You can also include and mark it for 2 meters if you like!

    Now to operate on a regular basis using ONE high performance and lightweight portable antenna for every amateur radio band from 40 - 2m AND without requiring any tuner, all you need to do is count how many wire marks it takes to operate on a particular band.

    For 40 meter operation, you simply unroll all the wire from the entire reel. (no paint marks required)

    30 meters = 1 paint mark on each side of the dipole
    20 m = #2 paint mark
    17m = #3 paint mark
    15m = #4 paint mark

    etc etc..

    It's just that easy... :)

    [​IMG]

    Please let me know if you or anyone else has any questions or needs additional assistance with this portable multiband antenna design.

    My Best.
     
    Last edited: Mar 22, 2010
  3. WI2D

    WI2D Ham Member

    Charles,

    Thank you for posting the detailed description of the antenna construction.

    Using bare wire was exactly my intent. But because I could not find thin stranded buss wire I went with the insulated one.
    The sleek Teflon insulation makes the wire convenient to work with and protects its strands from being separated and broken.
    Looking at it now I am wondering is it really worth it to strip the insulation?

    Unless there is a good advice against stripping, I will do it just to remove the doubt. At the end, worn out wire is easy to replace.

    73,
    WI2D - Andrey
     
  4. KC8VWM

    KC8VWM Ham Member

    Yes, any wire you have available will do the job just as long as it's bare.

    Insulation means the wire is thicker in terms of limiting how much wire can be stuffed into the reels. So basically, more bare wire will go inside the reels without any difficulty.

    To make the "knot" on the inside of the reel to keep the wire from slipping off the end of the reel when fully extended, simply twist the end of the wire on the inside of the reel around a #6 nut and solder.

    Another tip, place a smudge of white lithium grease along the "friction points" on the inside of the camping reels. This is located between the outer "track" edge of the inner spinning yellow reel and the outer shell it rides along. This helps ensure the reels will always function with ease.

    My Best,
     
  5. LA3AKA

    LA3AKA Ham Member

    It shouldn't make any big difference between using insulated or stripped wire for this kind of antenna. since the inductor is at the end of the antenna it has very little effect on the resonance frequency of the antenna. The length of the antenna might be a little bit shorter with isolated wire due to the velocity factor for isolated wire (3-4% depending of thickness of wire and isolation and type of isolation), but this should not cause any problem as you can adjust the length very easy. If you can fit enough wire inside the reel without stripping off the insulation, I would not bother doing it.

    73 de LA3AKA
     
  6. G0GQK

    G0GQK Ham Member

    I thought Aka Yo-yo was a Japanese pop star.

    G0GQK
     
  7. WI2D

    WI2D Ham Member

    Johnny,
    Thank you for your comment.

    So, the dipole length can not be used as an exact reference of proper antenna configuration and SVR should be measured for final tuning.
    It appears that presence of relatively small artifacts at the leg ends will just slightly affect the resonating length of the antenna.

    Could anybody point to a theoretical basis for this?

    Cheers,
    WI2D - Andrey
     
  8. KJ6FOB

    KJ6FOB Ham Member

    Sorry for the simplistic question, but how do you power this antenna? Thanks...
     
  9. KC8VWM

    KC8VWM Ham Member

    I think what you are asking is how the antenna is fed (powered) at it's feedpoint.

    [​IMG]

    This is a typical hardware store schedule 40 - 2” PVC cap with stainless steel eye screws attached on each side. The S0-239 connector is installed as illustrated.

    [​IMG]

    Installed on a 20 foot aluminum telescopic "painters" extension pole. Note the loop installed on top of the PVC cap enables you to suspend the feedpoint up in a tree.


    [​IMG]

    Portable lightweight multiband antenna system.

    Everything fits inside this nylon zip up bag. Including the LMR-200 feedline!

    This is not yet another "compromise" portable antenna design. It's a maximized performance portable antenna system. I doubt many other shorter and commercially made portable antenna designs can compare in terms of thier performance and yet somehow pack up into a small package of similar size.
     
  10. LA3AKA

    LA3AKA Ham Member

    As you move out from the center of the dipole the current decreases and the voltage increases this means that the impedance also increases. In order to compensate for the increased reactance you will have to increase the impedance to null out the capacitive reactance. At the end of the antenna the current will be 0 (ideally) or close to zero. this will give a very high impedance/reactance and thus a very high inductance is needed to null out the reactance. For a shortened dipole, the further from the load point you place the inductor, the bigger it will have to be because of the increased reactance. If you put the loading coil at the end of the antenna legs it needs to be very high. Because of this a coil at the end of an antenna leg have little influence on the resonant length of the antenna.


    73 de LA3AKA
     
  11. KJ6FOB

    KJ6FOB Ham Member

    Thanks for the info and the pictures helped a lot. I'm new to all this, but am interested in antenna design.

    After looking at your photos, I have a couple of other questions.

    It looks like you are using 4 reels. I'm not sure how the wire contuinues through all the reels? Also, where the wires connect to the SO-239, do both of them connect to the center pole of the connector? is there a ground somewhere?

    This looks like a cool design that would work great for camping ultra portable use.
     
  12. KC8VWM

    KC8VWM Ham Member

    Correct 4 reels are used.

    2 of the reels are intended for the wire

    The "outer" reels contain dacron rope are they are intended to anchor the antenna and keeps the ends of the antenna elevated off the ground.

    Photo:

    Note the flexweave wire (antenna) is on one side and Dacron rope (anchor) is on the other side. This rope leads to the second reel installed at the ground.

    [​IMG]

    The second reel attached from the antenna photo above (reel containing rope only side) is anchored into the ground as shown below:

    [​IMG]

    Another installation perspective showing the antenna wire reel connected to the feedpoint.

    [​IMG]


    [​IMG]

    Note the two reels on one side of this dipole illustrated and how the rope serves to suspend the end of the dipole antenna in the air. Keeping the ends of the dipole elevated in the air helps to maximize antenna perfomance.
     
  13. KC8VWM

    KC8VWM Ham Member

    [​IMG]

    Feedpoint (SO-239) connection details:

    Making the Feedpoint (PVC Cap) :

    Study the photo above. The SO 239 connector is fed with short wires to both sides of the dipole. Eyescrews are used with nuts and washers on the inside and washers and wingnuts are installed on the eyescrew on the outside of the the 2" PVC cap.

    ** USE ALL STAINLESS HARDWARE ** to construct the design. This prevents corrosion ("rust" :) ) from occurring on any metal connections if the antenna is left outside in the rain etc.

    1. Drill a hole and install SO 239 connector.

    2. Drill two holes on each opposite side of the PVC cap and install eyescrew with one nut - 2 washers - and one wingnut on the "outside" of the PVC cap side.

    3. On the inside of the PVC cap, install two washers and one nut.

    4. Connect two short wires of equal length from the SO-239 connector between the two washers on the inside of the PVC and secure BOTH nuts together. (The nut on the "inside" of the cap is tightened and pressing against the nut installed on the "outside" of the cap.)

    5. Loop the antenna wire around the eyescrew before connecting between the washers and tightening the two washers together using the wingnuts. This ensures added mechanical strength and prevents the wire from becoming frayed otherwise from tension occurring directly at the "wingnut" location. No tension is placed at the wingnut / washer point because the eyescrew is now taking all the stress when the wire is wrapped on the eyescrew in this manner.

    The SO 239 connector is screwed into the PVC. All connections inside the PVC cap are weatherproofed to maintain the connections.

    Setting up and deploying the antenna:

    #1 Place antenna on an aluminum painters pole and install the (LMR 200) feedline into the S0 239 connector shown in the example below:

    #2 Unreel some antenna wire from the antenna before fully deploying the pole.

    [​IMG]

    #3 After the pole is pushed up into the air, find the paint mark on the wire corresponding to the desired band you wish to operate:

    [​IMG]

    #4 "Lock" the wire around the tab at the end of the reel at the paint mark position. This ensures no more wire will come out of the reel. The wire when "locked" on the tab should look like this:
    [​IMG]

    #5 Unreel the rope side and secure in the ground.

    [​IMG]

    #6 Your "no compromise", no tune - ultra portable KC8VWM multiband dipole antenna is now setup and you are ready to operate:

    [​IMG]
     
    Last edited: Mar 24, 2010
  14. KJ6FOB

    KJ6FOB Ham Member

    Excelent writeup Charles. This may be my first home brew antenna to try. I do not have any HF gear yet, but that won't stop me.

    Only one thing I'm still unclear on. On the inside of the PVC, where the wires come down to the SO-239,, where on the SO-239 connector do they connect to? the photo of it doesn't show it. Thanks again for taking the time to Elmer a new ham.
     
  15. KC8VWM

    KC8VWM Ham Member


    You bet Frank. :)

    These photo's should better detail how the SO 239 connections are made to the outer eyescrews.

    SO-239 connector on the inside:

    [​IMG]

    SO-239 connection to the outer eyescrews:

    [​IMG]

    Eyescrew to antenna detail. (Wrapped around eyescrew to reduce stress on the connection details.)

    [​IMG]

    Incidentally, this also works as an excellent antenna to use after you upgrade to HF. I have installed and used this antenna design on small antenna restricted lots in the city. Performance was exceptional. Also it can be installed and taken down very quickly. (Actually timed it - This design can be installed and taken down in less than 5 minutes.)

    There are not many portable antenna's designed on the commercial market which offer this much "no compromise" and maximized performance ability, no antenna tuner capability, maximized band coverage capabilities and "instant" portability in such a lightweight package.

    It's probobly the best design as it can get as far as portable station antenna designs go...

    Such a design is actually nothing new in terms of actual technology, it's just a good portable antenna design choice based on the basic fundamentals of solid antenna theory.
     
    Last edited: Mar 24, 2010
  16. KJ6FOB

    KJ6FOB Ham Member

    Again, thanks for your time. I can see exactly how it's connected, and will be saving the thread for future reference. Looks like a fun project.

    I live outside of town, and have 3.5 acres. Pretty much any antenna I put up will come with little resistance from anyone in my area. But having something like this is always a good deal for traveling and such.
     
  17. KC8VWM

    KC8VWM Ham Member

    The "limitation" most people experience in portable radio operations is without a doubt , is in their particular antenna system they are using.

    This KC8VWM no compromise portable antenna design offers the very best in terms of maximized performance in a small lightweight package.

    I think in terms of portability, band capabilities, actual on air performance, weight considerations, ease of construction, ease of instant "on air" installation, actual construction cost considerations and in terms of any maximized multi band portable antenna by design in comparison to commercial antenna designs, this KC8VWM portable antenna design construction is simply particularly hard to beat.

    Dare to compare. :)

    My Best,
     
    Last edited: Mar 24, 2010
  18. KJ6FOB

    KJ6FOB Ham Member

    Thanks again, Charles!
     
  19. N5YOZ

    N5YOZ Guest

    Can anybody comment on how well the flexweave holds up to being tied down to the plastic friction tab on the winder in the same place over and over again? I'm wondering if copperweld would hold up better or if it is even an issue.

    Does the size of the winder pretty much limit this to 40M and above?
     
    Last edited by a moderator: Apr 2, 2010
  20. KC8VWM

    KC8VWM Ham Member

    Flexweave is similar in construction and behaves similar to "rope."

    The tab it is wrapped around is more likely to break or become damaged long before the wire is "worn" out by such a tab. Plastic is relatively soft compared to the metal wire. I can tell you I have used this antenna in the photos since 2003. In that time I only had to replace one reel and never had a wire break issue as described caused by the tab. The reel broke when it was dropped on a hard asphalt surface from an installation height of 20 feet causing the reel to crack and break. The reason the reel broke was because it was windy and the telescopic pole and tripod support fell over because I did not anchor the tripod into the ground. The other reels and feedpoint PVC cap was fine. Other than that, the reel has hit ordinary "soil" on a few other occasions but never suffered any ill consequences. But if the reel should break for any reason, a replacement reel will usually run you a grand total of $2.99. I found out the antenna is field repairable and takes about 5 minutes to remove a broken reel and replace the wire inside a new one. As mentioned, only had to replace one so far and this antenna was deployed and abused on at least 75-100 occasions.

    I find most hardware store stranded wire stretches when tension is placed on it. This can cause the antenna to become detuned in the process. Copperweld is very strong, it doesn't stretch or detune like stranded does but it's very "stiff" and likes to kink. Additionally, Copperweld would probably "cut" itself into the plastic tab. I find it's difficult to reel up because it becomes an exercise similar in context to trying to wind the spring back inside a clock.

    18 ga. stranded wire would probably work OK but it's not as strong as "rope" (Flexweave) in terms of it's mechanical strength but on the plus side, you can stuff more 18 ga stranded wire inside the reel than you can 14 ga Flexweave wire. So, yes, more band possibilities may exist when using "thinner" wire inside the reel.

    Yes 40m is pretty much the limit when using 14 ga Flexweave inside the reel however, most of the time I would operate during the daytime hours in the daytime bands anyways. 40m is a usually good choice for the evening to late hours when sitting by the campfire.

    I suspect, even if you did operate a full sized 75/80m portable antenna, you may also need a lot of power behind your rig to overcome the higher noise levels encountered by the station you would be attempting to communicate with. Probably not something an FT817 QRP rig would easily achieve on it's own merits on that particular band choice unless you are using CW. However, I have no difficulty monitoring 75m/80m, 160m and even the standard AM broadcast band at night using the 40m dipole arrangement.

    My Best.
     
    Last edited: Apr 4, 2010
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