Reception of the 70cm band.

Reception of the 70cm Amateur Band using a home made co-linear antenna.


Reception of VK3 repeaters

Successfully used a celeron Intel NUC to receive VK3 70cm repeaters. The SDR has sufficient cpu clock speed and the audio output is good.

Using the WIA Repeater List have bookmarked my local repeaters. This enables point and click on the frequencies.

70cm VK3RSE

Reception of VK3RSE 70cm band

70cm VK3RTU

Reception of VK3RTU 70cm band

70cm VK3RHF

Reception of VK3RHF 70cm band


Reception of 70cm simplex

Have been successful in receiving simplex FM transmissions on the 70cm band.

70cm Simplex

Reception of 70cm simplex


Dual Reception of 70cm

Have been successful installing dual sdr inputs from the home made 70cm antenna.

Plugged in dual RTL-SDR dongles to the antenna.

70cm Dual Inputs

70cm Dual Inputs

The NUC was successful in running two copies of Gqrx.

70cm Dual SDRs

70cm Dual SDRs


Hardware

Photos of the hardware used to receive the 70cm band.

7 feet of PVC pipe purchased from Bunnings.

7 feet of PVC Pipe

7 feet of PVC Pipe

PVC tee joint with cap purchased from Bunnings.

PVC Tee with cap

PVC Tee with cap

Pieces of co-axial cable were cut in to lengths of 284 millimeters. This being the length to match the 70cm amateur repeater outputs on 438 MHz.

The coaxial cable was purchased from Radio Parts.

This was calculated using the formula.
438MHz at Half a wavelength.
(300 / 438) * 0.5 or 0.342 meters.

Then needing to adjust for the velocity factor of my co-axial cable.
I found out that my Belden cable is 83%.
So 0.342 * 0.83 = 0.284 meters.

Pieces of Co-axial Cable

Pieces of Co-axial Cable

A 400MHz - 470MHz low noise amplifier was used with a 5 volt power supply. The power jack adapter was soldered to the pcb.

70cm 5volts powered Low Noise Amplifier

70cm 5volts powered Low Noise Amplifier

The power cable was wrapped around the pcb then yellow electrical tape was used to fix the power cable in place and also acts to insulate the pcb.

Taped LNA

Taped LNA

A 70cm Low Pass filter is inserted between the LNA and the antenna.

70cm Low Pass Filter

70cm Low Pass Filter

The LNA, low pass filter, 5 volts mains transformer, power jack adapter and RF adapters where purchased on ebay.

USB Cable Issue

Since building the antenna in 2016. Determined that the usb cable I was using to connect the computer to the RTL-SDR dongle was incompatible. I needed to swap out the usb 2.0 cable I was using for a better quality usb 3.0 cable. Once I did this my copy of Gqrx stopped crashing periodically.

Purchased a Celeron NUC and installed Ubuntu LTS with Gqrx.

Intel NUC PC

Intel NUC PC