[hpsdr] VHF-millimeter up/down converters?

Wed Apr 22 12:04:23 PDT 2015

If pursuing the traditional heterodyne mixer down converter approach, I would strongly suggest that they each be designed with different IF output frequency ranges. That way multiple bands can be fed into a single SDR IF radio that can then be watching and listening on multiple bands simultaneously. And therefore have multiple panadapter / waterfalls always running at all times. And at least 1 (preferably 2) RX per band for as many bands as the user can successfully listen to at one time.

The common DC - daylight radios that are out there all have MAJOR shortcomings when it comes to usability. These usability shortcomings are primarily in two key areas: 1) poor or non-existent scopes, 2) they can only be used on one band at a time.

Duane
N9DG

--------------------------------------------
On Mon, 4/20/15, Helmut <dc6ny at gmx.de> wrote:

 Subject: Re: [hpsdr] VHF-millimeter up/down converters?
 To: n6gn at sonic.net, "'Joe Martin'" <k5so at k5so.com>
 Cc: hpsdr at openhpsdr.org
 Date: Monday, April 20, 2015, 1:44 AM

 ***** High Performance Software
 Defined Radio Discussion List *****

 Glenn,

 Phase noise was a 'part of my life', hi and I know very well
 what is
 possible, determined by physics and currently offered on the
 market at
 reasonable prices. I wish you a successful design. Maybe you
 will give us
 more information after selecting and evaluating the
 components.
 Good luck.

 73, Helmut, DC6NY

 -----Ursprüngliche Nachricht-----
 Von: Glenn Elmore [mailto:n6gn at sonic.net] 
 Gesendet: Sonntag, 19. April 2015 22:17
 An: Helmut; 'Joe Martin'
 Cc: hpsdr at openhpsdr.org
 Betreff: Re: AW: AW: [hpsdr] VHF-millimeter up/down
 converters?

 Whether one does a traditional banded transverter (up/down
 converter) or one
 of the architecture I'm suggesting, everything still depends
 upon
 LO(s) spectral purity. The best one can do is to transfer
 the best aspects
 of the best references at various offsets to the output
 signal. 
 Long term stability from Rubidium, GPS, quartz, 
 mid-offset from quartz or
 SAW and wide offset from the fundamentals of the resonator,
 probably
 varactor or perhaps YIG. All of these are candidates but at
 different cost
 points.  The goal would be to come as close as possible
 to maintaining
 Angelia's spectral purity to as high as possible at
 microwave/millimeter at
 a reasonable cost.  I think that this is a reachable
 target. The
 specifications of a modern spectrum analyzer, which are
 considerably better
 than your(Helmut) example, are probably a good starting
 place. Even economy
 ones can do -125 dBc in 1 Hz bandwidth at 100 Hz offset at
 100 MHz, how they
 roll off beyond that, at other offsets, depends upon the
 design. Long term
 generally is not a problem. 
 At SSB sorts of offsets, 1 to 10 kHz, it depends on the
 references chosen,
 implementation and architectures.

 I have operated meteor scatter, weak signal and EME on
 bands  in the range
 of 2m through 10 GHz. I know about at least some of the
 issues. 
 My goal is to produce (first for myself!) an "all-band"
 companion for my
 Angelia to allow the benefits of SDR through at least our
 5.7 GHz band. 
 Having already done this in the more traditional banded way
 I would probably
 chose to do it in a wider-band continuous way which could
 also easily extend
 SA and VNA SDR applications to mid-microwave.  In a
 previous career, I
 designed references and converters for HP spectrum
 analyzers, some of which
 are still in production.

 This is fundamentally an analog rather than a purely digital
 architecture.
 Until we all have inexpensive 16 bit converters to 50 GHz I
 think we're
 stuck with this!  Even so, I think much of Angelia's
 performance can be
 translated to/from these higher bands. Some aspects will not
 likely be quite
 as good but probably in use, these shortcomings will not be
 obvious. In any
 case, I'd expect it to work as well as the best available
 conventional
 banded transverters.

 If I do continue on this, I will likely not be interested in
 spending a lot
 of effort on the HPSDR interface. It will likely be
 satisfactory to stop at
 I2C or similar control/monitor of the system. I can do this
 myself with
 Arduino/PIC sort of control. But it would probably be more
 useful to
 OpenHPSDR if someone else wanted to contribute to this by
 working on
 integrating and interfacing to the rest of the system. This
 would make, for
 example, extension of the VNA application to 6 GHz a lot
 cleaner and
 possibly faster.

 If anyone else is interested in helping, contact me off
 list.

 Best,
 Glenn n6gn

 On 04/19/2015 09:40 AM, Helmut wrote:
 > Glenn,
 >
 > unfortunately things are not so easy to handle at these
 frequencies:  
 > Assume a typical phase noise of the LO1 say -90 dBc/Hz
 @ 10 kHz offset.
 Relative to
 > our bandwidth B we will get:    -90dBc +
 10logB = -56 dBc . That means
 that
 > a strong neigbouring signal – say -53 dBm- at a
 distance of 10kHz 
 > produces a noise of -109 dBm. This will flood all weak
 signals within this
 distance.
 >   
 > 73, Helmut, DC6NY
 >
 > -----Ursprüngliche Nachricht-----
 > Von: Glenn Elmore [mailto:n6gn at sonic.net]
 > Gesendet: Sonntag, 19. April 2015 17:52
 > An: Helmut; 'Joe Martin'
 > Cc: hpsdr at openhpsdr.org
 > Betreff: Re: AW: [hpsdr] VHF-millimeter up/down
 converters?
 >
 > Helmut,
 > I think this need not be the case. By using
 same-architecture LO1/LO2 
 > along with wide PLL bandwidth, phase noise can
 correlate out far 
 > enough to cancel and not be an issue. You'll notice
 that with the 
 > mix-up mid-down approach, correlated noise cancels.
 This is the done 
 > in high performance spectrum analyzers and gives
 performance as good 
 > as the references can provide, even out to millimeter
 wavelengths some
 times.
 > I only suggested 6 GHz as a target because filtering
 can be done 
 > within common PCB materials (stripline filters etc) and
 SMD parts and 
 > connectors can work just fine to there without heroic
 efforts. Parts 
 > are pretty cheap too.
 >
 > There will certainly need to be pre/post amplification
 provided, just 
 > as there is presently in Angelia. That can be done as
 it conventionally
 is.
 > For EME and weak signal this may mean both are antenna
 mounted even.
 > The goal is to get clean Angelina performance, say 25
 MHz of 
 > bandwidth, translated to/from VHF-6GHz and let the
 banded details be 
 > done separately - akin to putting LPFs and HPFs on
 Angelia's in/out for
 the QRO arrangements.
 >
 > I believe it is possible and practical to do all this
 at reasonable 
 > cost
 > - though I'm unsure of exactly what price/performance
 target OpenHPSDR 
 > targets.  Has a charter or statement for OpenHPSDR
 been written that 
 > talks about this?
 >
 > Glenn n6gn
 >
 >
 >
 >
 > On 04/19/2015 08:39 AM, Helmut wrote:
 >> Hi Glenn,
 >>
 >> Just my 2 cents: I think this three-mixer-design
 will not provide 
 >> adequate performance for severe weak signal and/or
 contest 
 >> application on the VHF, UHF and SHF bands. The
 phase noise of LOs at 
 >> that these frequencies is on principal too bad and
 dominates the 
 >> dynamic of the whole system. A lot of
 pre-amplification is necessary 
 >> to meet the noise figure requirements. This
 degrades the dynamic
 performance further.
 >> At the present time conventional transverters are
 the better choice.
 >> As some guys know I run on VHF  a 
 modified Mercury  and Penelope in 
 >> undersampling mode with similar performance to the
 HF bands (details 
 >> http://www.hamsdr.com/data/GlobalFileUploads/9636__VHF%20DDC+DUC.pdf
 ).
 >> That's a nice option for the 2m band.
 >>
 >> 73, Helmut, DC6NY
 >>

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