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Просмотр полной версии : Direct Conversion HF Transceiver - VK3AJG



K2PAL
28.07.2006, 07:01
По теме,ТПП!
New mixer design

EU1ME
28.07.2006, 07:57
По теме,ТПП!
New mixer design (http://members.ozemail.com. au/~jgprice/images/QSDMixer.png)
А чего в нем для нас new?

TASA
28.07.2006, 11:29
Hello SDR OMs,

I tested exactly the same schematics last year with minor differences . This is substitute for original schematics in SDR1000 with FST3253 IC. I was disappointed with results upper limit was only 10-11 MHz at 14 MHz this schematics was working very bad. My design with 74HC4066 and 74HC4053 are working much better and upper limit is over 35 MHz!!!

www.qsl.net/yu1lm
www.yu1lm.qrpradio.c om

VY 73/72 GL in SDR home brew Tasa YU1LM/QRP Hello SDR OMs,

EU1ME
28.07.2006, 12:16
I was disappointed with results upper limit was only 10-11 MHz at 14 MHz this schematics was working very bad. My design with 74HC4066 and 74HC4053 are working much better and upper limit is over 35 MHz!!!
Странно, у меня на 25 МГц все нормально было. Чем вызвано ограничение? Потерей чувствительности или подавления БП?

TASA
28.07.2006, 13:31
Hello Alex,

1. First at 14 MHz sensitivity was 2 dB worse than on 10 MHz or 3 dB worse than on 7 Mhz. At 21 MHz I lost more than 10 dB in sensitivity (I used 330 Ohm resistor instead 220 after detector) .
2. In TX part balancing was about 45-50 DB at 7 MHz than 25 DB at 14 MHz . At 21 MHz balancing was going down to only 15 dB( Output swing for OP AMP TL084...for 100 load at output is big problem high distortions. Min R load for good compromise is about 270-330 Ohms output swing 9 Vp-p )
3. When I made my SDR RX DR1 with 74HC4052 it was really disaster (DC coupled connection) AT 14 MHz sensitivity was down 10 DB at 21 MHZ 30 db!!!! Some switheches was ON when time was OFF and vice versa and that was the reason for bad performances.

VY 73/72 GL in SDR home brew Tasa YU1LM/QRP Hello SDR OMs,

EU1ME
28.07.2006, 14:07
Извиняюсь, я решил, что Вы на FST3253 получили такое безобразие. А речь все же о 4052 как в оригинале.
У меня 3253, с ней все ОК
73!

AlexanderT
28.07.2006, 15:28
Неужели такая разница из-за микросхемы??

K2PAL
28.07.2006, 17:24
Hi;

I put some links yesterday on this site and my links came up repeated. I requested the site's admin to correct the issue by removing the duplicates, however he removed all my links.

Additionaly,my booss ......I will try later :)