Roger's Scrapbook

Some of my projects on this blog are inspired by the radiowork of Roger, G3XBM. I like his transverter designs in particular.

I found that Roger collected a lot of his work in his Project Scrapbook (currently issue 5). It contains a lot of nice experimental data and good projects.

You can find the scrapbook here:

https://sites.google.com/view/g3xbm4/book

Hope you like the scrapbook as much as I do.

QRV from Attica

During a recent trip to Greece (Attica, Agia Marina) I was able to use one of the radio repeaters near the capital of Athens. The repeater has callsign SV1B and is located on Mt. Pentelikon. RX frequency is 145.775 MHz and shift is -600 kHz. CTCSS is 88.5 Hz. 

The Quan Sheng porto worked fine and with callsign  SV1/PA2RF  I could made some clear qso’s a.o. with SV1IUY.

Platform for KT0936M experiments

The little KT0936M receiver IC has surprised me. To find out and explore the possibilties of this chip I made a simple platform.

A multiturn potentiometer enables me to select any of the more then 20 FM and SW bands. This KT0936M is a DSP chip and therefore frequency selection is very accurate. I  listened to stable, small band, 14 MHz CW signals (in AM mode).

Today I connected an LF amplifier with a TDA2050 IC. I was surprised by the quality of the sound.

Anyway, I have to discover a lot.

How can I display the exact receive frequency. There is no Fout pin. Also how can I receive Single Side Band signals. This chip does not have an IF since it it is a DSP chip. So, how can a BFO be added. At which operating frequency ?

Anyway (2), I am enjoying the reception of the broadcast AM stations from all over the world in the evening hours. The fading, the different languages, the memories..

Little Medium Wave radio

From a popular supplier of electronic goodies, I purchased a tiny MW/FM radio (not a DIY kit). It does not have a loudspeaker but should be used with headphones. I was interested in the performance of the MW part of the radio. 

And that really surprised me. It is a very sensitive receiver for the MW/AM band (530-1600 kHz) using a ferrite rod antenna. I thought nowadays the MW band should be almost 'dead'. But that is not the case. On this small radio I received a lot of broadcast stations past days. 

I removed the battery case from the radio to find out what was the engine in this receiver. It turned out to be the IC  KT0936M. After some research I found that the KT0936M is KT Micro's 3rd generation of integrated mono full band FM/MW/SW receiver chip supporting mechanical tuning with embedded MCU. The chip works with a supply voltage of 2.1V till 3.6V, so 2 AAA batteries can do the job. 

To my surprise the IC covers a wide range from 500 kHz - 110 MHz! The chip has been designed to facilitate following bands: 

- Maximum two FM bands with configurable FM frequency range within 32MHz-110MHz

- Maximum two MW bands with configurable frequency range within 500KHz -1750KHz 

-Up to 14 SW bands with arbitrary frequency range within 1.75MHz – 32MHz

 

The KT0936M has a high sensitivity, high signal-to-noise ratio and low distortion. 

KT Micro provides following values for sensitivity:

1.6uV EMF for FM
16uV EMF for MW
13uV EMF for SW

 
IC KT0936M provides direct and simple interface to support mechanical tuning. A pre-programmed low cost EEPROM can also be used to configure the radio band settings. No external MCU is required. 

If you search on the internet for KT0936M designs, you can find out how the specific bands can be selected (use of resistor network). The IC should be useable for our radio amateur shortwave bands. At least a BFO has to be added to the design.  . 

Danish eQSL's

Radiofriend Gerard, PA2G, made 2 FT-8 Special Event QSO's with Denmark. The event concerned the inauguration of King Frederik X. I think the eQSL's are quite special.