Thursday, 27 December 2018

First FT8 QSO!!!

I finally moved my operating position from the hall downstairs where I didn't receive any FT8 signals better than -15 or so. Now I am upstairs and signals are coming in 0 to -10. So I clicked on the huge signal coming in at 0 to -8, and low and behold he received me and I got my first FT8 QSO!

Here it is

Screenshot 2018 12 27 at 16 26 21

I am using the fixed frequency QRPver transceiver with their 6W PA amplifier into a WonderWand loop on the window sill, I have it in line with my home designed and made VSWR meter (see previous postings) and I get an SWR of 1:1.50. Anyway this is very encouraging.

Note

When I received my transceiver from QRPver it was tuned to JT65 7076kHz, I delved inside and tuned it down to 7074kHz and it has settled about +50Hz high right now but quite functional. Nice little unit. Audio I/O is via a very cheap Amazon USB sound dongle to my MacBook.

The other thing I have done is to use a 40dB attenuator in the audio output line as otherwise it overloads the USB Dongle microphone input. The QRPver audio works at line levels, which is OK for the headphone output to the TX input, but too much for RX output to the microphone input.

Screenshot 2018 12 27 at 13 47 41

Screenshot 2018 12 27 at 16 28 03

Very pleased with myself.

Sunday, 16 December 2018

Aerial plans

For years I have been stuck with without aerial, I have a small loop and a pull up whip both tuned, but they are very inefficient... What's worse is that my house is old, and insulated on the outside - layer of aluminium and then polystyrene blocks! So I am living in a Faraday Cage. Seems stupid. but he facts are that where I living no outside aerials are permitted, and I do not have a way to run a cable from my loft to my operating position in the downstairs hall.

But now, we are going to re-arrange the house, which will mean an upstairs bedroom will be my new location, a simple drop down from the loft above. So a loft antenna it is.

First I need a balun as it will be a sort of tuned dipole as much as I can get into the space. The target frequency is the 40m band. So here it is

IMG 0813

A conventional design built in a small plastic box. Looks good. Two terminals and a PL259 connector.

Tuesday, 27 November 2018

BARSSBy - The new project (an SSB Exciter)

We have just finished our BARSicle program "LEARN - CODE - BUILD" during which we learned about Digital Synthesisers, RF Power meters and a Direct Conversion RX, we coded using Arduino and built kits of each.

So what's next? Well after the first part of the program which covered topics that could be enjoyed by Foundation Level Amateurs, we planed to move on to those that are permitted to design and build transmitters (and in the mean time get those M6's up to M0's). The overall objective being to build an SSB exciter and a Power Amplifier, with Audio and RF Vox switching, letting us enjoy FT8 digital QSOs.

BARSSBy

First the SSB exciter. For this we need a few building blocks:

MIXERS - for generating DSB signals to pass to a Xtal filter to get SSB, and then again to mix to the output frequency.

MIXER This will use a Mini Circuits SBL-1 mixer, rather than the tedious process of winding our own balun toroids.

XTAL FILTER - a ladder filter, component values yet to be chocen

XTALFILTER SSB generation frequency, for a TX on 40m (7MHz) will be in the range 9-11MHz, depending on Xtal availablility

GENERAL PURPOSE VARIABLE GAIN AMPLIFIER - based on the MC1350 IC

AMP This will serve as a gain block where needed, the AGC input is used to set the gain.

BAND PASS FILTER - again a common general purpose design we have used before in our DCRX.

BPF The frequencies needed for the SSB carrier and the VFO output mixer will be provided by a Si5351 synthesiser - the one from the BARSicle project we previously built. This will allow us to accurately position the carrier for USB or LSB output, and generate a very accurate transmit frequency.

The AF input will come directly from the headphone output of your PC.

Tuesday, 13 November 2018