Wednesday, November 1, 2017

Magnetic Loop Antenna For Transmitting

After the success of my receiving magnetic loop, i wanted to give a try on transmitting loop. It has both good and bad results.

One fine evening my friend OM Prem VU2RPC and myself started fabricating the magnetic loop to transmit on 40meter.

Used 3/4" copper tube used for air conditioner with a length of 9 feet.
Wide spaced variable capacitor 30-300pF salvaged from old valve transmitter
2.5SQm wire for inner loop.
Construction is as simple as possible. Just used 3/4" PVC pipes.
Just maintained the outer loop dia as 3feet, and inner loop 0.5feet.

We had about 10 contacts within 15 mins, it was sunday. The tough part is to keep the SWR.
The loop is very narrow bandwidth, even 10KHz change is frequency will affect the SWR to 3:1. Really bad, so maintain power level not more than 50 watts.
The RF from the antenna was also very severe, we can feel the radiation.

Result :
The overall result is,
It is definitely compromised antenna for receiving. There is no doubt, we had no noise pick up, and very good gain also.

For transmitting it not a good antenna. Unless we want to use just for only one frequency, like beacon. Because the bandwidth is too narrow. We have to adjust the variable capacitor for every change on frequency.

No comments:

Post a Comment