LF

All posts tagged LF

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

 

17-02-2013 pa0rdt-Mini-Whip

pa0rdt Mini Whip Amplifier

 

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