Remote antenna switching #antenna
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A recent QCX mini purchase means I will soon need a 20m dipole to accompany my 40m when operating from my home shack.
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Alan G4ZFQ
Just wondered if any of you had built a remote QRP antenna switch?Ted, Ordinary relays are fine for HF, just keep connections short. Don't forget the diode across the coil:-) 73 Alan G4ZFQ |
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Thanks Alan
Just found these on ebay for £3, I think at that price it is worth a go. They are not latching so one configuration will need to be constantly powered. I also need to make sure that the control wiring (which will be in the same 32mm conduit as my coax feed) does not introduce RF into the shack. They also do multiples, hopefully all with diodes as standard :) 73s Ted  |
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Steve in Okinawa
I've used quite a few of these modules for antenna switching up to 50 MHz. They save a lot of room and control wiring, and will handle quite a bit of power too. Each relay has an LED on the board to show when it's activated. High marks. JS6TMW
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Curt wb8yyy
Ted
If you have a 40m dipole installed, just add the 20m dipole wires to the same coax. This is called a fan dipole. The wires can be tied closely together with insulators, or merely tied off to different places at the end. No relay or added coax necessary. Another nice multiband antenna is end fed halfwave efhw. Instructions to build qrp versions on the web, need 1 toroid and 1 fixed capacitor. These radiate on even harmonics also, unlike center fed, Enjoy your radiations. Curt wb8yyy |
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Steve - thanks, these do look great for all sorts of apps and super cheap, I have ordered one to have a play.
Curt - thanks also. That one is new to me so I had better read it up. High wire antennae are no go here so the current 40m dipole lies atop a 1m high beech hedge oriented N/S. Works surprisingly well and has also WSPRed as far as Tasmania and the South Pole. 73s Ted |
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geoff M0ORE
You can do the same with trap dipoles for different bands on each
section of fan. Adding traps to a dipole will reduce the bandwidth
of the aerial, if you have, say, a trap dipole for 6 bands, then
the lowest frequency band will have a very sharp cutoff frequency.
By using a limited number of traps in each dipole, say two or
three, and then combining into a fan arrangement, you get a much
wider bandwidth at the lowest frequency. Try to arrange the traps
in alternate bands.i.e. 40m, 17m and 12m in one leg of the fan and
20m, 15 and 10m in the other leg. Extend the wires on the 20/15/10
section to cover 80m. No trap is needed for 80m. If possible, have
one section of the fan ends going up in height and the other
section going down so it looks like a bow tie. It is often stated
that a 40m dipole will match on 15m. This is true for dedicated
dipoles but not if traps are involved. On 08/12/2020 13:58, wb8yyy via
groups.io wrote:
Ted |
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Ed Kwik
A good tuner will let you use the 40 meter dipole on 20 meters. The 40 meter dipole may even give you some gain on 20
Ed AB8DF |
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I've got a homebuilt Z-match employed already (although not really necessary as the 40m is cut/tuned pretty well) - maybe I'll try that first. |
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Steve in Okinawa
I'm sure you'll find a use for them HIHI
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Dave N3AC
nothing significant On Tue, Dec 8, 2020, 11:07 Ted 2E0THH <qrp@...> wrote:
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Steve - that looks like a really fun box of tricks, I love stuff like this! Dave, many thanks - I need to do some homework so I properly understand how these antennae work together. Everyday with this hobby, you learn something new. |
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