Tuesday, May 13, 2014

New transceiver - Trevo

No, it's not the latest from the "East", it's not the latest from the brand that makes cooking ware.... it's simple the "Trevo", a new transceiver I'm building.

It's made in Ireland, were the water is free, (not anymore), by a Portuguese using mostly schematics from the rest of the world.... it can't go wrong....

The idea will be to have a medium performance transceiver for the everyday use, using some classic blocks without big fancy stuff. I'm building in blocks that at anytime can be changesd or replaced, also trying to use common components without compromising too much the performance. Most of the signal switching is done using relays (I might regret this in the future).

So far I made the following parts/modules:

*The BFO oscillator on the left, on the midle the mixer (ADE-1) and on the right the audio pre-amp chain. Isolated below, and still in the making is the AM detector

 *The IF amplifier chain on top, below on the left, the IF filters, one AM one SSB one LSB and one USB at 9.00 Mhz. On the right the first RF pre-amp and the attenuator.

*Bellow the audio amp on the left and on the righ just a makshift power supply, on top left an experimental mixer.
* The bandpass filtering section

* The mic amplifier on the right (741), SSB and AM modulator (by unbalancing) midle and left (MC1496).


Regarding the schematics, when I'm happy with the performance I will post them...just wait.


Since all transceivers have names/model, decided to cal this one "Trevo"; it could be the acronimouns for "Transmiter Receiver Evolution".... no, it's the Portuguese word for Shamrock which is one of the symbols of Ireland. I hope it makes sense....




Have a nice week and good luck!



2 comments:

YO9IRF said...

Interesting, do you have more details about the circuit (front end preamp, AGC system etc)? What LO do you plan to use ? Try replacing the diode mixer with a H-mode mixer, it's simple, cheap and provides much better IMD figures.

Razvan YO9IRF

Ricardo - CT2GQV said...

Hello Razvan,

Thanks for the comment.

The frontend is a mix of the "Speaky" bandpass with some adaptations. The rf preamp is similar to the K2, the att is 2 pi circuits in series(12 &| 6db). The AGC/IF amp is the "hycas", the s-meter is an inverter buffer amplifier. The LO is from the arrl 14Mhz transceiver so is the ssb generator and the audio pre-amp. Audio amplifier is an TDA1013B with electronic volume control. AM demodulator is a simple ge diode and buffer transistor. AM modulation is done by unbalancing the MC1496.
Regarding the H-mode, never tested one so for now I'm using only blocks I tested before. Might give it a go but for an IF buffered output. There will be an AM filter, one SSB, one LSB and another USB so I can switch between 2 SSB bandwiths and 1 AM. No provision for now on FM. I chose 9Mhz IF since I already have a good filter for 9Mhz. In the future if all goes well might try double IF so I can shift and change the with. Still trying to decide on the VFO, if "digital" or "analog" with PLL.

Regards,
Ricardo, CT2GQV