Posted by: m1paf | March 1, 2009

Moxon Construction Paper Updated

I’ve updated the PDF (found here) showing how to build the 20m Vertical Moxon. It now includes some more images of various assembly steps.

73 Paul

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Responses

  1. Paul,

    Excellent document but I fear everyone will be building these now and we won’t get a look in.

    Should be good for the economy though as houseprices near the beach will soar.

    cheers Steve

  2. Hi Paul,

    I’m in the upper panhandle of Alaska, the capitol city of Juneau. I can’t run the design files because I only have a Mac to work with, yet very much want to build this 20 meter configuration of the Moxon as my first DX antenna, and get the same performance and one-pole portability you have with yours.

    I only received a license two years ago and haven’t been able to afford a radio yet, so have spent all my time studying antennas. I wanted a one-pole design if possible because of cost and time in setting up, and because I’ve learned over the decades that simplicity is usually the best way for reliability in design.

    Much reading led me to the Moxon, partly because Cebik liked it so well. I’ve read about four different configurations of vertical Moxons now, starting with Pete Millis’ Brighton design. When I read your first write-up and saw the antenna I knew it was what I had been looking for from the beginning.

    I’d ideally purchase the exact components you did to get the same performance you have, but the Moonraker mast would be expensive to ship from Britain to Alaska, and that and a very small budget aren’t compatible.

    In researching the Moonraker I noticed that the Spiderbeam 40’ glass fibre antenna is now being offered in the US. Do you think it would change the performance characteristics if that mast were used in place of the Moonraker were I to tailor the height above ground to match your design and everything else were the same? It appears to be made simply of fiberglass rather than a mixture of graphite and glass, which I understand can detune an antenna.

    I’d very much appreciate your help if you can give it. I have a lot to learn. At the same time, I’m very excited about the possibility of building this. Though inland from from the seacoast proper, Juneau sits on salt water inside passages, and there are several long open stretches of open water to work across. I’d like to get into both EU and deep into the Pacific from here for DX if possible. If I can figure out the pole, the rest of it I think I can bring together over the next six months, a bit at a time, and build it, hopefully before field day. Thanks for your time if you can give it.

    Sincerely,

    Eric Bailey
    WL7CMT

  3. Hi Eric,

    This is just a quick note to say I’ll post a response later this week. Just got back from a week long trip to the Outer Hebrides activating the island of Barra.

    In short you can do what you are asking.

    73 Paul.

  4. Thanks for your note, Paul. I’m very much looking forward to your response.

    I was able to see some of your trip via your blog and another photo of your antenna in action, and am very excited to talk with you about it. Must have been beautiful on Barra.

    See you this coming week, and thanks.

    73,

    Eric

  5. Hi Eric,

    Sorry for the delay replying but I’ve had to catch up with work. As I said in my earlier note any fibreglass pole will be OK providing it’s physically strong enough. I have one of the 40′ Spiderbeam poles and it will not be strong enough at the upper end if you use the same poles as I did for the booms. An alternative would be to use thinner poles for the booms and brace them with some kevlar guys back to the mast. Whilst this would work I suspect the main mast would be unstable and tend to bend over as tension goes onto the wire. I know they are more expensive (quite a bit) but if you get hold of the larger Spiderbeam mast (60′) that would work OK as it’s 1.5″ diameter at 33′ extension.

    Alternatively try sourcing a push up GRP mast that can be shipped from the USA or Canada – I’m sure you will find one somewhere.

    Another alternative is to use the crossed poles method – use two poles taped together at the centre and put them up in an X and fix the Moxon to that. This would be reasonably easy to put up as the wire would hold the poles in the X shape while you lifted them up. Guy them at the centre and away you go.

    The main thing to remember is that as long as the support is non-conductive (for RF and DC) it should have no effect on the performance of the antenna – you just need something to hold it in shape. If you can’t get the parts I used or they are too expensive – don’t worry – let necessity be the mother of invention.

    73 Paul M1PAF

  6. Thanks for taking the time to write, Paul. I wholly understand about work.

    I’ll figure out a way. Snow plows up here have solid fiberglass 6’x1/4″ fiberglass wands on the ends of the plow that might work. They’re used to show the operator where the blade limits are when s/he’s working high volumes of snow that billows up to cover the entire blade when the plow’s moving fifty miles per hour clearing highways. Flexible, light, and tough, they’d work to keep tension on the antenna wire, have very little wind resistance, be light for portability, and they’re relatively inexpensive at something like $6.00 US each. They’re something to start with. Instead of ring bolts I might be able to just cinch-tie some light pigtails to snap the antenna to on each end of the top spar, and then flex the top wands as I pull the antenna down to the lower set. Uppers and lower spars flexed, the antenna would nicely hold shape. It might wobble a small amount in the wind, but not much probably. It’s a place to start playing around with, anyway.

    I emailed Moonraker with the TMF-15 nomenclature, and they told me the stick would cost something like L250 just to ship because the mast was so long. Being that yours is collapsable, I couldn’t understand that. I sent them a jpg of your mast and even your area and name to see if they could match an invoice to it to get a positive ID on the model, but they didn’t recognize the mast, the TMF-15 designation, and couldn’t find an invoice. I can’t believe the mast can be that much to ship. Something crossed up somewhere, especially if customer service doesn’t recognize the mast in the .jpg.

    I haven’t found a replacement mast here yet but I can see the concept and will figure something out if the Moonraker idea falls completely through. Your design is gracefully simple, and easy on the eyes, as well as being a great performer and portable. I’m looking forward to getting it up and running. Even with the salt water fjord system up here and being far from blue water I’ve found an almost clear sight line to Antarctica, more than 9,300 miles over salt water. I’d like to try that to start with.

    How did it perform on Barra?

    Thanks again,
    Eric

  7. Eric,

    There is a typo in the parts list. After checking the mast part number is TMF-1.5 NOT TMF-15 as stated in the document. Apologies for that and I’ll correct it.

    73 Paul M1PAF

  8. Eric,

    You asked about the Moxon and how it performed on Barra. In short it was as we expected – excellent. At the end of a weeks operating we made just under 6.3k QSO’s of which about half were on 20m. Furthest contact was South Island – New Zealand and we worked a lot of Australian and Japanese stations plus many in the nearby countries such as Indonesia and Malaysia. The Moxon was a little further from the sea than would have been ideal (5 – 6m) but it didn’t seem to make too much difference. It was interesting to talk to DX stations to see what they could hear coming out of Europe and on many occasions were were one of only 2 or 3 stations that could be heard. We were working people with very simple antennas (dipoles) at DX distances without too much trouble which for me is an indication of how well the Moxon receives. We also had little difficulty hearing the stronger DX stations over the top of the European stations – as noticed in previous years.

    We ran linears this year and the antenna handled our 400 watts without any problems whatsoever and the SWR was unchanged throughout the week hovering around 1.1 – 1.2 : 1.0 for the upper part of 20m.

    We had force 10 gales and nothing fell down or broke which surprised us as we expected some damage but none whatsoever.

    Regards,
    Paul

  9. I think I found the problem on the mast company communications, Paul. The dash between TMF and 15 won’t translate in the search engine. Here’s the page, and what I think is your mast. Dose it look right? Note the nomenclature is sans dash above the image. When I stuck in the nomenclature without the dash the mast popped right up.

    http://www.moonrakerukltd.com/Poles-and-Masts/Telescopic-Masts/TMF-15

    I found this offering in the US that looks as thought its good enough to consider going with. The clamps are made of Lexan plastic. Eham reviews are all 5.0. Wall size is 1/8th inch. No reference to wall thickness on the Moonraker offering, but it sounds like the 1/8th might be strong enough. What do you think?

    I offer the links in case anyone else in the US asks about your mast they can be forwarded for consideration. There might be a better one, but I haven’t found it yet. These people supply wholesale to a lot of retailers for use as their house brands, apparently, and also extrude a square stock that looks interesting. Clamps and poles can be had individually.

    http://www.mgs4u.com/fiberglass-push-up-mast.htm

    http://www.eham.net/reviews/detail/7041

    Is the wall thickness on your mast more than 1/8th thick?

    What do you use for a base for it? I remember Scottish Isles as being mostly rock when I was on Skye in the 80’s, and from satellite images. Not much possibility of continually driving a stake in the ground and lashing a tube onto it to put the antenna in.

  10. Hi Eric,

    The Moonraker mast you found is the one I use. However, the masts you found seem much better value and look very similar. 1/8 wall thickness is identical so no problems there either. Choose a configuration that gives you a 33′ mast with a top section diameter of approx 9/8″ (30mm) to go ith the heavy duty Spiderbeam boom poles.

    As for the base I’ve never used one. Normally the mast sit’s on rock so it isn’t a problem – we locate the bottom of the mast with some rocks and the lowest set of guys hold the mast up while the antenna is being attached and the mast pushed up. If you really want to locate the base use the same technique we use with our verticals – get hold of some large steel angle, cut a length and weld a plate on the top and cut/grind a point on the bottom. The angle should be a snug fit inside 2 – 3″ diameter plastic drain pipe.

    Cut a 2′ length of drainpipe.

    Hammer the stake into the ground, slide the pipe over the stake and slot the mast into the socket made by the pipe. This won’t support the mast when fully erected but it will stop the bottom from kicking out and/or sinking into soft ground.

    Cheers,
    Paul M1PAF

  11. Paul,

    Would that I could get even half that kind of performance up here in this low sun spot period! It sounds like it worked wonderfully. Your words put a lot of pitch and coal in my fire to build one!

    I worked two of the three stations I’ve been able to talk to thus far on HF over the JOTA weekend, one in Oregon and the other way out on Kwajalain atoll in the Marshall Islands, both on 20 meters using a club station. It was exciting to think I’d just talked to somebody that far away! It took about an hour and a half of listening to find them, though. I wasn’t able to hear a great deal to try to work. Thanks as well for giving the side note about working dipoles at long distance, showing the antenna’s receive capability. It’s also nice to know the antenna will handle 400 watts without a problem.

    Out of curiosity, did you log what kind of antenna and wattage the NZ station was using? If both were pushing 400+ watts out of high performing antennas it would have made the connection a lot easier than a hundred or less watts.

    We also get hundred plus mph winds up here once in a while, and 50 mph is relatively common, but probably I won’t be working portable during those times because for the most part they’re in winter. With the temp below freezing, many times in the teens, the wind chill becomes so great that even in a car with a heater on full it is unbearably cold for any long length of time. It’s great to know it can handle wind, though.

    Thanks for describing how you anchor the bases. Both ways make complete sense.

    I’ve been thinking about how heavy 9913 Belden is for coax, and realized you must use something much lighter than that because it would pull hard on the antenna and possibly reshape it. I’d appreciate it if you’d recommend the coax size that you use for this. I think, with that, even as green as I am, I’ll be able to make if not an exact copy, something so close that it will perform as well as yours.

    You’ve put a lot of time into helping with this. I can’t thank you enough for taking the time to work with me. Hopefully others will see these entries on your blog, and our exchange will help them as well. I’m very excited to build your design!

    Again, thanks.

    73

    Eric
    WL7CMT

  12. Hi Paul,

    I am having some great fun building this. Sourcing some of the clamps for the spiderbeam to boom part of the project was tricky. I have however found two companies in the UK that supply these which may be of use to UK builders.

    1. http://www.parquip.co.uk/index2.html (Only seem to supply the 30mm unit.)

    2.http://www.kiowa.co.uk/products/cp4_heavy_series_polypropylene_pipe_clamp/FCP4A60 (Supply both the 30mm & 60mm clamps. Make sure you order the back plate as well.)

    For my boom plate I am making it in wood to start with and depending on the results I will make V2 out of tufnol. I only live about half a mile from the North Sea so I hope to have some reports for you soon.

    Thanks for putting together such an easy set of instructions to follow.

    Cheers,

    Bob – M6KLO


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