Shortwave Shielded Loop Receiving Antenna - Build It
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- čas přidán 27. 08. 2024
- This is a repost of old antenna making video. The main advantage of this antenna is the null provided in direction perpendicular to the plane of the loop. You can use this to somewhat null out a local noise source or otherwise locally strong signal. Nothing is perfect.
The shield is the antenna; the potential produced at the gap. Maintain symmetry.
When building this antenna, it is critical that symmetry is maintained about a plane formed through the center of the shield gap and the feed-point, with the feed-point exactly opposite the shield gap. However, it is NOT critical the shield be shaped in a perfect circle; but as closely possible. Nor is it critical the flexible wire be centered inside the shield. Just make sure there are no kinks or curls in the wire when pulled through. And don’t let wires cross (the connector to spin) when tightening the SMA connector. Run the coax down and away in the plane of the loop to a preamp in a weatherproof box. Wrap all joints in weather proof.
This antenna will work fine from wavelengths 10 meters down to 160 meters, but the antenna size compared to the HF wavelengths is small so the signals (voltages) produced on the antenna will be small. It is necessary to use a low noise pre-amplifier to increase the signal before input to a receiver. Preferably this preamp is mounted at the antenna in a weatherproof box. The preamp can be powered from DC on the coax using bias tee’s. I am using a low noise preamp from SV1AFN, an ebay bias tee’s, and an LM317 voltage regulator board to adjust 20 Vdc down to 12 Vdc to power the preamp.
This antenna is made on the basis of PA0FRI/PA3GZK Wide Band Active Loop Receiving Antenna.
RBN
www.reversebeac...
Antenna Plans: pa0fri.home.xs4...
See also: pa0fri.home.xs...
Preamp: www.sv1afn.com/...
HF Bias Tee’s get from ebay.
LM317 Voltage Regulator Boards get from ebay
Importance of the loop shield balance: www.w8ji.com/m...
How the shielded loop works: owenduffy.net/...
Small receiving loop antenna, magnetic loop antenna, magloop antenna, ham radio antenna, small loop antenna.
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Nice work.
Congratulations, well thought out design. 73.
Hi GMT 400, can you tell me what is the diamter of the plywood fixture you made to bend the copper tubing ?
Sure, the diameter is 37 3/4 inches. No particular reason. I think it was the closest piece of plywood I had wide enough for a circle around 10 foot circumference. The copper pipe is about 10 feet long.
Awesome thanks
Tesla states your copper should be mirror finished, polyurethane, and then painted with black rubber. It took me a long time to understand why.
Because black tech looks Batman.
was it in total recall?
Hi GMT 400, I just purchaed the parts you listed here, Do you have a photo of the preamp, voltage regulator & Bias T connected to your Loop ?
I just put it in the community section for you. I am using the ebay bias T shown. Not the minicircuits one, as it got taken out by lightning strike. The bias T from ebay works just fine. Cable from the shack goes into the box then to the bias t RF+DC, then out of bias-t to the preamp RF Output, then from the Preamp RF input to out of the box to the loop.
Do I need to use an external DC power supply to feed the voltage regulator ?@@GMT_400
@@GMT_400How do I find the "community Section" ?
@@billblodgett8237 tap the green icon under the video, to go to the channel page. There should be a community tab there has the pic of the preamp.
Hi GMT, I bought a Mini Circuits Bias T ZFBT-4R2GW-FT+ , it takes 24 volts to power it, will this work with the same preamp you used for your antenna ?@@GMT_400
that all went a bit blue room
Is this antenna useful for receiving MW as well as SW wave
Hi, it will receive fine at MW. The loop itself is no different than a non-shielded type in terms of signal on it. It just uses the voltage produced at the gap and coupled to the inside wire. There are other preamps you can look at as well which may have better feed point impedance matching if you only work MW. Take a look at the links in the description.
Gooood 💐💐💐💐
HI GMT, do I need an external power supply to feed the voltage regulator ?
That preamp will require 12 volt DC power. If you are powering from a 12 volt DC supply, you will not need the voltage regulator. If you are powering from a higher DC supply, you can use the voltage regulator to adjust down voltage to 12 volts to power the preamp.
It's complicated
And stupid
1000ft ground wire antenna 📶 end to end 🔚
Does it put off spurious emissions?
Hi. This is a receive only antenna, no transmitting. It will not put off spurs or birdies. On receive, I do not get any spurs in the output spectrum of my SDR, Red Pitaya. I also use filtering to eliminate signals outside the HF bands 160 meters to 10 meters.
@GMT 400 okay cool. Thanks