23cm (1.2GHZ)

23CM is operated with an Icom IC-9700.

The Amplifier

Is from VHF Design. capable of over 300w. The controller can be seen in the bottom left of the above picture.


The Antennas

I use 4 x 44element antennas stacked and bayed. The array can be elevated also.

The Mast Head Preamp is a Sam Jewell VLNA23. This has a 3 pole bandpass filter installed before it to keep interference out.

Band pass Specification:-

Through loss at 1296MHz: 0.3dB

Bandwidth at -3dB: 110MHz

Attenuation at 950MHz (mobile phone): >45dB

Attenuation at 450 to 850MHz (television): >55dB

Input return loss, both ports: >20dB

Interface box to control PTT, Voice messages & IF out to large monitor pan-adapter

One of the disappointments of the Icom IC-9700 was it only has one PTT port to key amplifiers. Rob M0DTS came up with a solution to provide separate PTT for each of the three bands. Using an Arduino Nano /code and the CI-V data from the radio. Ive added band Led indicators to his circuit connected to the Arduino pins and brought the 12khz IF signal from the accessory socket to give a full screen pan-adapter display via a SDR-IQ as seen in the above picture. The 4 buttons are for stored messages. The green one is for contest and auto CQ calls.

Visit www.m0dts.co.uk for more info on the switch and a whole lot more. Use at own risk no responsibility for damage to equipment accepted.

Arduino INO file is here

Pin 5 on the acc socket has the 12khz out signal this must be enabled in the menus, pin2 is ground.

The four message buttons connect to the mice socket pin 3 and 6. The resistance across the switches sets the message to send. The messages are stored in the IC9700 from the menu system.

Had to sneak this picture in of the last flight of the Vulcan bomber ” Personal flypast of my antennas” 🙂

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