[hpsdr] [Fwd: Re: Proposal for a 'low-end' RX/TX board for HPSDR]

[Richard Hosking]

Damn I keep hitting reply to sender instead of reply to all!

R

-------- Original Message --------
Subject: 	Re: [hpsdr] Proposal for a 'low-end' RX/TX board for HPSDR
Date: 	Sun, 30 Jul 2006 20:26:08 +0800
From: 	Richard Hosking <richardh at iinet.net.au>
To: 	Phil Harman <pvharman at arach.net.au>
References: 
<BD06837F0655E84288539771399A41FF01534503 at XSJ-EXCHVS1.xlnx.xilinx.com> 
<d20013450607261514u79f52a0ds3d171a0278d3b6ff at mail.gmail.com><32aa05ee0607261557x5d985f5fo3a5a8e91e587cb86 at mail.gmail.com> 
<44CB6071.9010501 at iinet.net.au> <006e01c6b3cb$e0b88580$0201a8c0 at phil>



Thanks Phil

I would have thought the maths is not a major issue as the PLL will 
presumably not have to shift too often - and there will be plenty of 
time for the controller and loop settling etc. I would have thought it 
would be better to confine the VCO to as narrow a range as possible.
FWIW there are good measurements of phase noise of the synth I was 
involved in with John Miles at http://www.thegleam.com/ke5fx/synth.html
I would expect this current design to be much better due to the narrower 
tuning but a bit worse due to higher freq. (and presumably better with a 
high quality VCO)
We used a Minicircuits ROS ultrawide range series

As I understand it dividers are relatively quiet wrt phase noise so you 
should get most of the theoretical phase noise improvement due to division.
On this issue, what is the effect of "Gray code" dividers vs say a 2 bit 
counter in the divide by 4 I/Q section?
A binary counter such as a 74AC163 would have a sequence 00 01 10 11. 
The two bits changing simultaneously causes higher noise due to jitter 
between them. The Gray code divider will have a sequence 00 01 11 10 
(forgive me if this is not news to everyone)

We didnt attempt to shield anything on this board and it was just a 
double sided board.
I dont know what effect this would have.
One interesting effect was that PLL spurs occurred near harmonics of the 
clock and within PLL loop bandwidth - might be worth a BPF at 800KHz. No 
doubt there are expert RF designers on the list..

Richard

Phil Harman wrote:

> Hi Richard,
>
> Please find  attached a paper which discusses the LO. There is also an 
> alternative proposal that has 10kHZ output steps  that will make the 
> maths much easier but  complicates the LO PLL.
>
> A lot of this has not been made public as yet since we are not yet 
> ready to 'go public' with some of the design options since we are 
> trying to complete a deal with a VCO manufacturer that will provide a 
> very high performance 2.4GHz VCO at a very low price.
>
>
> 73's  Phil...VK6APH
>
>
> ----- Original Message ----- From: "Richard Hosking" 
> <richardh at iinet.net.au>
> Cc: <hpsdr at hpsdr.org>
> Sent: Saturday, July 29, 2006 9:19 PM
> Subject: Re: [hpsdr] Proposal for a 'low-end' RX/TX board for HPSDR
>
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> There seems to be broad consensus about the mixer.
> What about the LO for an HF board?
> I presume it would have steps of about 50KHz, given the bandwidth of the
> audio board.
> We could use a microwave PLL divided down
>
> Richard
>
> Philip Covington wrote:
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>>
>>
>>> Hi Ray, Phil_C, Phil_H, Bob, et al,
>>>
>>> Bob's idea of a potential QSD (July 07, 2006) with fast analog
>>> switches is very interesting. There might be a small error, though.
>>> Pin 2 of U5 obviously should go to Pin 1 of U2?
>>> <svn://206.216.146.154/svn/repos_sdr_hpsdr/trunk/N4HY/Horton/QSD.pdf>.
>>>
>>> Using those components I figured out another configuration. Instead of
>>> using 90° narrow sampling pulses, I plan to use 180° wide pulses in
>>> quadrature. Transformer coupled dual line receivers split the I and Q
>>> signals from the DDS to pair of opposite pulses with minimal skew and
>>> timing errors.
>>>
>>> See this and tell me what I possibly missed:
>>> <http://kotisivu.dnainternet.net/ahti/sdr-1000/newmix2.pdf>
>>>
>>> Ahti OH2RZ
>>>
>>>
>>
>> Hi Ahti,
>>
>> Here is another one to look at:
>>
>> <http://www.philcovington.com/HPSDR/TEMP_STUFF/isd_07262006-1.pdf>
>>
>> I went slightly different and used a SN74AUC2G53.
>>
>> 73 de Phil N8VB
>> _______________________________________________
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>>
>>
>>
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