CT4ER Évora Portugal


Homebrew - QRP - Amateur Radio

The amateur radio station CT4ER, licensed since April 1976, is located in ÉVORA, the Museum City, which was considered a UNESCO World Heritage site.

In the HF bands I have been using homebrew equipment since I got a transmitting license in 1976. The transmitting power is about 50 Watts.

The antenna is multiband with traps made by CT1AYM.
The Windom FD3 is another antenna that I am using and that works very well. It is for 40, 20 and 10 meters but, with an antenna tuner it is working from 80 to 10 meters without any problems.
G5RV and WINDOM (FD4) were also tested here with the best results. For me the G5RV was the best but I have some space problems and the 300 Ohms TV tape breaks easily.

My location has a lot of QRM and QRN mainly in 80 and 40m bands.

My new QRP homebrew multiband transceiver already on the air but its output is only 250mW.
I have had some good QSO with 250mW both in the 80 and 20m bands. Reports of 57!!!!! or better are usual.
All QSO have been made in SSB for Portugal, Spain and other European countries.

For VHF I am using YAESU FT290R with 2.5 Watts. This equipment is generally used in PACKET and CW.
A lot of QSO have been made in SSB and FM both in Portugal and other European countries including England. I prefer the HF noise!!!!!!.
The VHF antenna is a vertical DIAMOND F - 22 2x7/8 6.7dB 3.2m.

KPC2 is my homebrew packet modem with a speed of 1200 Bauds. Usually it is working with a COMMODORE 64, Hi Hi Hi .

Yes, this was my first transceiver, TX / RX. It is a double conversion equipment.
The most part of the circuit is still working as original. In the other part, and through the years, some changes were done to update components and some working conditions.

The main IF filter is a 3180Khz from YAESU. These circuits are very similar to YAESU FT101.

The IC uA796 is used both in the product detector and in the balanced modulator. After several tests these circuits remain in their original and can be met in any radio amateur handbook.

The original MOSFETS were 40673, but, the ones that I had were a little noisy so they were changed to BFR84. It was easier for me to get these than the others. Thirty years have gone since this test was done.

The most part of FETs are MPF102. Others were tried but the results were alike. Today I am using others without any problems. In the CAG the 2N5486 was the one that worked with the best result. The bipolar transistors are 2N706, BC107 or others similar to these.

The IC CA3053 was changed to CA3028 for higher gain and a better signal/noise ratio.

The audio output can be as high as 5 Watts without any distortion, it is an IC uA706 from FAIRCHILD. Others have been tested and the results were alike.

A low or high impedance microphone can be used. The resistor connected at the micro amplifier input must be in accordance with the microphone, 560 Ohms is being used for a dynamic hand microphone. At first 250 Ohms resistor was used because the micro was 250 Ohms, too.

The DRIVE and FINAL AMPLIFIER diagrams are old enough to give a clear picture through my scanner. They are conventional and can be found in any radio amateur handbook.
The drive is 12BY7A and the final amplifier is 6146B polarized for 50 Watts. EF80 and 6GK6, between others, were used in place of 12BY7A without any result change.
My first tube for the final amplifier was a QE05/40, its plate dissipation was only 20 Watts. After being tuned it was in a very beautiful blue !!!!!!.
There is a switch to change from 50 to 10 Watts for QRP use. It switches the 6146 plate voltage from 600 to 250 Volts.
All coils were borrowed from old radio and TV apparatus. They were changed and tuned to the desired frequencies.
After the building and to test the transmitter a light lamp of 110 Volts, 40 Watts was used instead of a dummy load. Today, I have some dummy loads and one SWR meter which measures till 500 Mhz and one kilowatt.


mic.gif........Microphone amplifier used in my new transceiver

mic1.gif......Microphone amplifier used in my old transceiver

mic2.gif......Another microphone amplifier

cw.gif ........CW monitor and TX/rx control

cw1.gif.......CW monitor and TX/rx control

Soon other diagrams will be shown, so, from time to time, pay a visit to the CT4ER page. Thank you very much.

Do you know or remember THE AMATEUR'S CODE?????

Please send your suggestions to CT4ER in order that we can have a better page.

73 from Carlos/ct4er.