Im playing with some wire yagis, and Id like to put relays at the ends of the parasitic wires to switch the director to a reflector (and vice versa). If Im driving the antennas with a full 1.5 KW, wh
Rob, I would switch in an inductor for a reflector and a capacitor for a director at the CENTER of the element. Use a shorted stub for the reflector and an open wire stub for the director. The voltag
I have done a reversible 2 element 80m one. the elements were cut for the driven element length, then I ran a 1/4 wave coax from the feedpoint of each element to a switchbox in the middle. In the swi
On 10/16/16 8:09 PM, Rob Katz wrote: Im playing with some wire yagis, and Id like to put relays at the ends of the parasitic wires to switch the director to a reflector (and vice versa). If Im drivin
I've done element loading and reversing using center switched loads at the end of a coax line just as K1TTT mentions. Works FB. Plus you have to contain the voltage pickup in the control wires headin
And don't forget the option of feeding both elements. there are some good designs out there for phased arrays. David Robbins K1TTT e-mail: mailto:k1ttt@arrl.net web: http://wiki.k1ttt.net AR-Cluster
On 10/16/16 8:09 PM, Rob Katz wrote: Im playing with some wire yagis, and Id like to put relays at the ends of the parasitic wires to switch the director to a reflector (and vice versa). If Im drivin
The voltage will be "high".. Measuring or modeling the voltage is challenging, but it goes in proportion to the current in the element, which *is* modelable and measurable. Moral of the story: switch
That is a good question. Years ago I thought of building an 80m vertical with a relay on top to make it a 160m inverted L at my P40A home but I did not know if even a vacuum relay would hold up and I
A friend here had a fixed 2-el quad on 80 and used a relay to switch the parasitic element from reflector to director. He burned out some relays before he finally got some high power vacuum relays. T
Rob, As an upper limit, the voltage on the ends of the DE should be about 3700 volts RMS or 5200 volts peak. This is based upon a 40M wire Yagi EZNEC model with a source power of 1500 watts, feed poi
On 10/17/2016 9:44 AM, john@kk9a.com wrote: That is a good question. Years ago I thought of building an 80m vertical with a relay on top to make it a 160m inverted L at my P40A home but I did not kno
As an upper limit, the voltage on the ends of the DE should be about 3700 volts RMS or 5200 volts peak. This is based upon a 40M wire Yagi EZNEC model with a source power of 1500 watts, feed point vo
I agree with Hardy, Dave, and Jim. My second element is a dipole fed with RG11, and I switch in lengths of coax that are shorted or open in the shack to switch it from CW to SSB (the coax acts as a t
Jim, Since EZNEC modeled currents are based upon all induced currents from other elements, the estimate should be at least as useful as previous replies of high or so high you dont want to know. The
Thank you Hardy and everybody for your responses. Ive built many wire yagis that are loaded in the middle. Im looking to put up a new 3-el on 40m with a rope catenary as the boom, so I want to elimin
Johns old idea seems like the perfect application of something in QST a while back: a pneumatic relay. A puff of air up a non-conducting piece of tubing would trigger the switch: I cant recall if it
I should add that it doesnt change needing a robust switching mechanism to handle the voltage, but at least resolves the issue of conductors to switch a relay being in the vicinity of the antenna. 73
There is literally no benefit to do the switching at the ends. But there are a lot of reliability issues so why take the hard road when there is no performance increment - and at the same time the he
For many years, I have had an insulator with a relay across it at the 60 foot point of my 90 foot vertical. At first I tried vacuum relays, with ratings up to 8000V. All worked for 6 months or so and