SWR meter project

Overview

The goal is to produce a relatively cheap (<$200, maybe <$50) antenna analyzer design. The cheaper version should have at least 2 significant digits of accuracy.

This will be based on analog components with digital controls with the ability to store data that can be downloaded via computer for post processing as well as displayed live.

This project is in early planning stages. A prototype of the analog portion has been built and tested.

modules

• HF module
• VHF/UHF module
• digital control and display module
• battery module

Analog portion

The core of the analog system is a phase detection chip (part number?) with a 35mhz - 3ghz range and a SPI controllable oscillator. Two chips will be used so that sign of the phase can be detected.

For high frequencies (>100mhz?) the chips and oscillator will be tied to a strip line.

For low frequencies, the oscillator will be down converted using DDS methods and the detectors will use an SWR bridge.

Each chip will output 4 voltages (0-3v?) corresponding to magnitude and (unsigned) phase of two ports.

Each band will need filters.

Digital portion

• A cpu with at least 8 ADCs and enough rom space for display control code
• SPI to control LCD, oscillator, DDS; the LCD may need a dedicated bus for fast refresh
• suggest $7 touch screen LCD (ebay, adafruit)
• suggest two push buttons and a rotary encoder for control

Suggested functionality:

• data uplink and program control via usb
• data storage via microSD card
• frequency sweep and graph (sample rate / averaging?)
• continuous SWR display (at a fixed frequency?) for live tuning
• signal generator
• programmable band edge presets

Optional functionality (fodder for v2):

• Antenna switch to merge all bands to one port
• 2 port / 4 port mode (for antenna vs. filter testing)
• battery / voltage probe / built in charger

Live demo display

The plan is to have a display in the atrium that (among other things) displays life feeds from various SDRs.

It could show:

• spectrum analysis (with labels?) ; random spectrum, broadcast spectrum, etc
• live audio feed? (speakers? bluetooth?)
• sit on PSK31 frequencies and display
  • spectrum graph
  • multi-decode, show text
  • pick out call signs and guess location on map
• beacon / wsprnet map, show HF paths between ucf / beacon
• ADSB map
• SSTV pictures -- slideshow or live reception?

All RF displays should be labeled with frequencies and indicate if they are live or not.