antenna

All posts tagged antenna

Couple of months ago high wind gusts bent a support tube in my tower.
Well, yesterday was repair day. Here are some photos.

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Photo taken earlier showing a bent support tube.

 

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Winch in place, getting ready to lower.

 

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Antenna on its way down.

 

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Faulty support tube removed.

 

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Not straight.

 

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On its way up again.

 

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Done!

 

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improvements: Support tube is now made of steel, before it was of aluminum. Also, notice the second support bearing in the middle. Hopefully this improvements will make it hold.

Still fighting with the old Fritzel beam 🙂 It is around 30 Kg but when it’s in the air it feels like a ton. (no crane here, just a ladder and raw muscle force. hi hi )
My mast tube where to weak 50x2mm alu. Antenna is slightly off balance and this imbalance bent my mast without any wind force at all. It looked like a banana.

Anyway, my current rotator is to weak for this size of a antenna, but I have a stronger one lying in my garage. The trouble is that I do not have a controller for it, so I just ordered a new controller from MDS, a RC1-Y.

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I got this antenna for free from a friend. It is really a FB DX-706 but the 706 configuration is to large for my small city lot, so I had  to down size it to a FB DX-506 configuration.
When I got it, the antenna looked like it have been run-over by a freight train. Some tubes where missing, most of the tubes where bent, traps where full of sand, cobwebs, dead bees and wasps.

Luckily there was no aluminum corrosion. Dismantled the howl ting and cleaned it up.

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Today I decided to try out the pa0rdt Mini Whip design.

I have only have tested it for å few hours, but so far I find it performing a lot better on the LF and MF spectrum compared to my other Active Antenna discussed I an earlier post on this site.

On shortwave up to 20m it seems to perform about the same BUT there is a very important difference between the two; pa0rdt design dos not overload when I simultaneously transmit on other bands. My other active antenna makes all kinds of crazy bi-products while transmitting.

I think I was a bit too hasty with my first report regarding the difference in performance of the two active antennas. Now, after a little more use I think they perform almost equally. The pa0rdt whip has a bit more gain but the SNR seems to be about the same.

 

pa0rdt Mini Whip Amplifier without whip

pa0rdt Mini Whip Amplifier without whip

 

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pa0rdt Mini Whip Amplifier

 

Last night while operating WSPR @ 475KHz I suddenly hear a hard and broadband noise on one of my receivers. Then I look at the swr meter monitoring the wspr transmitter and discover that it was all over the place. Reason, insulation failure at the base of antenna resulting in arcing.

Here is an active antenna for higher LF and MF frequency range using an U310 N-Channel JFET as amplifier.
Antenna are based on a la8ak (sk) design. It has a decent performance given its small size.
However, on lower LF and VLF range it performs poorly.

A little tip for anyone interesting using this design or similar designs. Do not power it by a noisy switching power supply. Switching noise will go straight into the receiver.

 

Bias tee PCB

Bias tee PCB

 

Left: Remote amp. with telescopic car whip Right: Bias tee

Left: Remote amp. with telescopic car whip Right: Bias tee

 

Remote amp. and antenna

Remote amp. and antenna

 

 

Bias tee mounted in a nice box

Bias tee mounted in a nice box

 

Blue LED in remote amp. shows that power is present. Green LED on bias tee indicates normal current load.

Blue LED in remote amp. shows that power is present. Green LED on bias tee indicates normal current load.

 

Remote antenna amplifier schematic

Remote antenna amplifier schematic

 

Bias tee schematic

Bias tee schematic

 

Here’s some pictures of an antenna I build for a local repeater site a few years back. Its a relative wide band design where VSWR is under 1.5:1 over 30+ MHz and the gain is up to around 7dBi at max. Antenna has worked flawlessly for several years high up on a mountain top in icy and windy conditions.
Antenna are made of TIG welded pipes of square stainless steel.
I have not designed this antenna by my self, its a replica of a commercial product, but with a few modifications when it comes to material used and physical dimension of the antenna and phasing network to lower the frequency a bit.

I’m trowing in a couple of pictures of the FOX DELTA ST2 Antenna Tracking Interface that I have build.
Unit works great, but on the bench for the moment. Antennas ain’t finished yet. 🙁
I’m in the proccess of building a 144Mhz 4×7-Element-Yagi array for EME. ETA not known.