The open wire feeders are getting rather slack. This causes the wires to twist together during high winds. I had noticed a slightly higher SWR and some scratching noises while receiving on the USA Rhombic.
I had to examine the entire run of the antenna feeder and the antenna itself. Looking up into the bright sky is rather difficult for me due to the condition of my left eye after the accident, but with a good pair of binoculars it only took me about one hour to find and correct the problem.
I guess some maintenance is called for before winter…
hello Serge,
I have sent you by email a scanned copy of a chapter called ‘Travelling-Wave Antennas above Lossy Ground’ from the book ‘Theory and application of antenna arrays’ by M.T. Ma Senior Member of the Technical Staff, Institute of Telecommunication Sciences, Office of Telecommunications, U.S. Department of Commerce and Professor – Adjoint of Electrical Engineering, University of Colorado, published in 1974.
The book is probably still under Copyright and I don´t want to break those rules.
This chapter will answer all of your questions, I especially draw your attention to the conclusion in table 6.28 on page 384.
note that the Yopt angle is the half-angle of th Vee Antenna.
http://tf4m.com/download/table6.28.gif
The software I referred to is VOACAP – you can download this from
http://www.greg-hand.com/hfwin32.html
This software includes models for a lot of professional antennas in HF ANT.
The wire I use for my antennas is either CopperWeld or AlumoWeld around 3-4 mm in diameter. The breaking strength is around 900kg and I have not yet had a wire break under tension.
If you browse my website you will find a lot of information about rhombics and their construction.
73
Thor
Hello Thor!
Nice talking to you on the band at last!
What kind of wire are you using for your antennas? I’ll have a look further on your WEB and might bump into the information but still interesting to hear your comment.
I told you about my Vee beam that I was using for quite some time. The wire is from the ordinary open telephone line. It is very cheap and rugged. One of the leg is still up since 1992! It is starched 150 meters! I moved away and left it hanging. Go there now and again to see how long it will survive there for.
Now, Thor I am not qualified much about this type of antennas and there is not much info about them on the WEB. Rhombic is not easy in town so I look forward to Vee beams more. So
I got number of questions about them.
Say if I have an opportunity to set a Vee beam the way it is represented on the picture.
http://www.ljplus.ru/img4/u/a/ua3xds/land.jpg 100.69 Kb
What is the critical height for it? What would be estimated impedance? What kind of gain on different bands do we expect? How is it possible to terminate it? What termination will do to the properties of the antenna? What would be the optimal frequency for that angle between the legs? What else you can say about the set up?
I risk asking those questions because you said you had the software that can pretty much answer to all of them! Have a look at my WEB sight: http://r3x.sitecity.ru/
Hope to speak to you soon Thor! 73! Good luck!
Serge RX3XX.