[Premium-Rx] Receivers for MW and 160 meters.

[w3sz]

If you are going to do it, I'd suggest that you use Linrad for the signal  
processing.  It is much more powerful at this time than the SDR-1000  
software;  I have used both for several years and the difference is not  
subtle.  With Linrad I used a homebrew front end for several years that  
worked extremely well for me, and I am sure you guys could do better in  
that regard and get even better performance.

http://www.antennspecialisten.com/~sm5bsz/linuxdsp/linrad.htm

For LO's you can actually get very good performance with PTS synthesizers,  
which are available on eBay frequently and at reasonable prices.  I first  
used them for NMR research 20+ years ago, and use them as LO for  
everything from VLF thru Microwaves.  You will find their phase noise,  
while not equal to that of a state of the art crystal oscillator designed  
for low phase noise, is surprisingly good for a frequency agile LO.  They  
are easily computer controlled via parallel port or GPIB.  The PTS40 page  
link below gives a graph of phase noise performance.

http://www.programmedtest.com/

http://www.programmedtest.com/pts040.html

Listening to signals on 160 with Linrad and a home-brew front end is an  
INCREDIBLE experience.  I have never had it equaled with a conventional  
receiver.  Have fun and keep us all posted.

73,

Roger Rehr
W3SZ
http://www.qsl.net/w3sz/start.htm

On Thu, 10 Feb 2005 23:33:27 -0800, Chuck Hutton <charlesh3 at msn.com> wrote:

> That's my dream receiver, and it is do-able. What's your LO design: a  
> DDS,
> or a DDS followed by a PLL to clean up the DDS spurs?
>
> When do we start working on it?
>
>
> Chuck
>
> -----Original Message-----
> From: premium-rx-bounces at ml.skirrow.org
> [mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Karl-Arne  
> Markström
> Sent: Thursday, February 10, 2005 10:55 PM
> To: premium-rx at ml.skirrow.org
> Subject: Re: [Premium-Rx] Receivers for MW and 160 meters.
>
> I certainly agree with prevoius posters that nothing can be substituted  
> for
> front-end selectivity.
> Off-channel signals that have been eliminated through preselection simply
> cannot cause problems downstream.
>
> Proper choice of mixers (the SS-1R has been mentioned) helps a lot, and  
> if
> paired with preselection
> and a low-noise oscillator as in the G3PDM receiver design the results  
> can
> be spectacular.
>
> To take up previous discussions about diplexers, it is my firm belief  
> that
> lumped-constant
> diplexers intended to smooth out impedance variations near the passband  
> from
> crystal or mechanical
> filters would be impractical.
>
> The exception may be the route taken in the E1700/E1800 where a 90 degree
> hybrid absorbs the
> impedance mismatch from crystal filtering behind the mixer.
>
> A proposed design for a very high-performance MW and 160 m receiver  
> would in
> my opinion look
> like this:
>
> 4 dB Cohn-filter preselector with a - 3dB passband of 0.5 to 1 % of the
> centre frequency;
>
> Push-pull MOSFET feedback low-noise amplifier, Gain 10 - 12 dB, NF < 2 dB
> and IP3 > 50 dBm;
>
> A passive power divider to the I and Q signal paths, each with a  
> high-level
> "Tayloe-mixer" driven from a
> low-noise frequency synthesizer via high-speed logic I and Q LO drivers;
>
> Passive low-pass filtering in each signal path in the mixer;
>
> Low-noise I and Q baseband preamplification before 24-bit A/D conversion;
>
> "Software Defined Radio" signal processing a'la the SDR-1000 software
> downstream
>
> Such a receiver, as modeled in HP/Agilent "AppCad", shows an NF of  6 - 8
> dB, an IP3 with 10 kHz spacing of around
> 40- 45 dBm (30 kHz spacing IP would probably be impractically high to
> measure with "normal" lab gear).
>
> Should the ultimate in sensitivity be needed (for example when using
> Beverage antennas in extremely quiet locations), the preselector and the
> low-noise amplifier (preferably preceded with some filtering) could trade
> places.
> This would yield a receiver with a noise figure of around 4 dB and a  
> dynamic
> range of >110 dB in SSB bandwidths.
>
> 73/
>
> Karl-Arne
> SM0AOM
-- 
Roger Rehr
W3SZ
http://www.qsl.net/w3sz