Dec 2, 2009

Upgrade current VHF station II; the plan

What is my goal?
Pure and simple: have more fun in hearing (seeing?) weak signals, participate in a few contests and/or work new dx, on 144MHz.

Throw in some new hardware !!??
Now there's a lot you can do to upgrade your VHF station boosting the performance in theory, like:

- adding a pre-amp
- additional (band-)filtering
- mount the transverter near the antenna
- install extreme low-loss coax
- raising the antenna height
- buy new high performance equipment with DSP, add SDR receiver etc.
- low noise power supply

However, none of these will offer gain by principle.
All the above need to be seriously evaluated before implementation.

Hardware performance simulation
I do like VK3UM's EME system performance calculator a lot.
This great application allows you to evaluate your set-up and simulate any future upgrades.
See free software at:

A typical view shot looks like this:

Mind you: there is RX Noise Figure which is determined by hardware only. And there is System Noise Temp and Noise Figure, which show the real life situation when terrestrial or sky noise is added to the equasion.

The hardware setup is clearly cut into pieces:
Coax to the 1st RF stage (LNA)
Coax the the second RF stage (receiver)
Settings for coax type, connector and relay contact losses.

The program calculates both a total receiver noise figure based on pure hardware only, and a total system noise figure/noise temp, based on the environmental terrestrial sky noise (not EME).
Toggling the LNA on/off switch the total system noise figure gains 3dB at receiver performance.

The plan
Let's start evaluating the current total receiving performance.
There's only 2 building blocks in VK3UM's performance calculator. So I need to cut my 144MHz receiver chain in separate parts and evaluate the individual blocks first, before starting to calculate the total system performance.

my current blocks:

1. Antenna (Tonna 17el @12m AGL)
2. Coax into shack (2 pieces of EcoFlex-10 and -15 +5 connectors)
3. 144/28MHz transverter (Elecraft XV144)
4. 28MHz IF transceiver (Elecraft K2, modified for bettter 28MHz performance)

First step: evaluate transverter +IF receiver performance

I will need to do a MDS test on the K2 IF receiver

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