Hello Tasa
I am not a professional like You and build my homebrewing receivers
out of a big junkbox just for fun but I also don't finish the job
because if I build a receiver over two or more years in the same time
I design and begin to work on many others.
Bias design: In the FST3253 data sheet from Fairchild I found no rDSon
versus Vin curve. Only a typical Ron of 4 Ohm at Vin = 0 V and a Ron =
8 Ohm at Vin = 2,4 V is shown. A rating for the best analog Vin
operation is not provided in the data sheet. So I made the bias for
experiments variable with an old 741 OpAmp. The RFinput is fixed for
tests with 50 Ohm and a transformer ratio of 1:4 to 200 Ohm as the
best value for the INA163. At 10 MHz RFinput I found a bias of 2,35 V
gives the minimum noise in the FST3253 plus INA163 system ("measured"
with soundcard and spectran). You see I am a real amateur without
professional measuring tools.
I am very interesting for Your VHF S/H RX design with 50 MHz because
in time I design a receiver with a H-mode-mixer as first mixer (with a
IF = 45 MHz and 45 MHz quartz crystal roofing filter) and a second
mixer with a QSD (I/Q-S/H)-"mixer". My own experimental QSDs works
only very well between 1-30 Mhz. Above the insertion loss are to big.
I hope You found leisure for a QEX articel or better You published
Your design for a selected crowd of homebrewing folks ;-)
73
Chris
--- In [email protected], "Tasic Sinisa" <[EMAIL PROTECTED]> wrote:
>
>
> Hello Chris,
>
> I saw your design some times ago and congratulation for you design
and big
> job to finish equipment. I am R&D engineer and for me it is very
hard that
> is something finished HI!!!
>
> I made a lot of experiments and design in CAD to see influence of this
> VCC/2 voltage. My conclusions are that S/H will work even that is
not biased
> (I tested this practically). Problem is if you use as classic
demodulator
> IMD higher order 5,7... will be very high for high input level. I
have some
> design classic DC receiver better dynamic than famous R2 and RX super
> heterodyne type with 74HC4066 If I find time I shall publish it
because it
> can be interested for some designers. Insertion loss in that design
is not
> too sensitive to exactly VCC/2 but you will have a loss in dynamic
range if
> output signal are not around half VCC. 4053 .4066 are CMOS IC but
problem is
> that in this use with big R in divider Vcc/2 10K or even 2k2 we haven't
> VCC/2. I am using in all new design 1K.
>
> I designed and tested as dead bug construction also real new type
of VHF
> (50 ,144 432,1280 MHz) S/H RX with outstanding performances extra
simple
> and without 2 (twice)or 4 times higher LO. I hope that I shall
find some
> free time to write article for QEX. This RX is much,much simpler
than DSP10,
> or RX from SM5BSZ or S53MV but performances is hard to believe that
coming
> from few extra cheap components. there is no classic 1 dB compression .
> Demodulators are working even with input signal higher than LO linear .
>
> What is your experience with VCC/2? I wish you successfully SDR
design and
> I hope that we shall stay in touch.
>
> VY 73/72 Tasa YU1LM/QRP
>
>
>
> Original Message -----
> From: "Chris Hirt" <[EMAIL PROTECTED]>
> To: <[email protected]>
> Sent: Thursday, July 27, 2006 1:06 PM
> Subject: [soft_radio] Re: 4 new HF SDR designs from YU1LM/QRP
>
>
> > Dear Mr. Tasic-Tasa
> >
> > I look at http://www.qsl.net/yu1lm/homebrew.htm. Great!!
> > Thanks for puplishing Your fantastic job of Your SDR experiments with
> > 4066 and 4053 switches (my own QSD experiments are at
> > http://home.pages.at/chirt/HDR2005.htm.)
> >
> > Mostly of the homebrew SDR receivers have a bias voltage 1/2 of the
> > Vcc. In Your ADTRX1 You also divide +5V / 2 = 2,5 V. Do You test other
> > bias voltages or is this bias the best for the 74HC4053 ? My own
> > experiments shows a great performance sensitivity dependent of this
> > voltage.
> >
> > 73
> > Chris
> >
> >
> >
> > --- In [email protected], "Tasic Sinisa" <tasa@> wrote:
> >>
> >> Hello SDR OMs,
> >>
> >> I uploaded 4 new SDR designs. All 4 new designs are based on use
> > 74HC4053 IC
> >> as S/H (sample and hold ) element in demodulators , modulator and
> >> transceiver.
> >>
> >> 1. SDR HF I/Q S/H (Sample and Hold) Receiver-DR3X from 30 kHz-35 MHz
> > for 3
> >> bands harmonically related with 1(one) oscillator or 1 XTAL
> >>
> >> 2.SDR HF I/Q S/H (Sample and Hold) Receiver - DR2B from 30 kHz- 35
> > MHz
> >> with external LO (local oscillator)
> >>
> >> 3.SDR HF I/Q S/H (Sample and Hold) Mono band Receiver - DR2C from 30
> > kHz- 50
> >> MHz with LO (local oscillator) at receiving frequency
> >>
> >> 4. Low power SDR HF I/Q S/H (Sample and Hold) transceiver- ADTRX1
> > from 30
> >> kHz-35 MHz with external LO- part1
> >>
> >> VY 73/72 and GL in SDR homebrew Tasa YU1LM/QRP
> >>
> >> www.qsl.net/yu1lm
> >>
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>
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