Medium Wave LPAM transmitter

I did some experiments with the receiver IC KT0936M lately. I built a simple SW and MW receiver with this chip. To be able to do some experiments with the MW radio I thought it would be a good idea to make a small MW LP (Low Power) AM transmitter. 

                            Medium Wave receiver with KT0936M

For reasons of stability I started with a 1015 kHz crystal oscillator. The modulation of the transmitter is done by a 5W LF amplifier TDA2030A. The output of the LF amplifier goes into the input of the small transformer in the DC supply line.

I used a 2N2219A  as PA stage. I think it delivers about 500 mW. A pi-filter provides the proper interface to the antenna.

MW LPAM Transmitter schematic

With this low power AM modulated medium wave transmitter I have a good radio signal in the house. Of course our radio liscence does not permit the use of this transmitter for broadcast purposes. 

MW LPAM transmitter 

The LF amplifier;

70 MHz Sporadic E contacts

This week now and then the 4 m band opened because of Es.

I made FT8 QSO's with Spain (EA6SX) and Greece (SV2DCD, SV2JAO..) on 70.154 MHz

One QSO has already been confirmed by eQSL:

Path to OH is also open once in a while;

Radio Caroline

Lately I have been experimenting with a KT0936M module on the medium wave. I discovered that Radio Caroline puts a firm signal strength at 648 kHz at my QTH. The music they play is from the 60’s-90’s. Like to hear their music through my 5 Watt tube amplifier 😊

Here   https://www.radiocaroline.co.uk/#648_am.html   you can read that Radio Caroline returned to the medium waveband on 648 kHz AM as a legal broadcaster at the end of 2017, after applying for, and being granted, the Ofcom licence for the Essex and Suffolk areas of South Eastern England. Radio Caroline is using an RF power of one kilowatt from a Nautel ND2.5 transmitter.

More:  https://en.wikipedia.org/wiki/Radio_Caroline

 

 

First steps in satellite communications

The Satrover QO100 transverter enables you to use the geostationary OQ100 (Es’Hail-2) satellite. I was able to explore this equipment with Gerard PA2G. With the use of an IC-705 and the satellite dish aimed at the OQ100 satellite (elevation 27 degrees, azimuth 153 degrees in the Rotterdam area) we were able to receive satellite SSB/CW/FT8 signals at appr. 10 GHz (converted to 144 MHz by the transverter).

Making an uplink at 2.4 GHz will be the next step.

SATROVER transverter and LNA/Helix antenna
 

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.

Solar flare hitting Earth

A powerful M9.8-class solar flare erupted from the sun (AR3500) on Wednesday (Nov. 29) at 2:50 p.m. EST (1950 GMT), hurling a super-hot plasma eruption known as a coronal mass ejection (CME) toward Earth. The flare is expected to hit Earth today (Dec. 1, 2023).

Hopefully our internet and radio communication systems can withstand the amount of electromagnetic energy that is brought in by this -almost X-class- solar flare

Note: I have not heard of any damage to communication systems whatsoever.