[hpsdr] VHF-millimeter up/down converters?

Sun Apr 19 08:28:48 PDT 2015

Hi Glenn,
Just my 2 cents: 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 )

73, Helmut, DC6NY

-----Ursprüngliche Nachricht-----
Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Glenn
Elmore
Gesendet: Sonntag, 19. April 2015 16:16
An: Joe Martin
Cc: hpsdr at openhpsdr.org
Betreff: Re: [hpsdr] VHF-millimeter up/down converters?

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

Joe,
That trying to push direct ADC/DAC conversion higher is not the way to do
this is my opinion also. However, I'd rather not do it with they typical
banded approach. That is dedicated per-band filtering accompanied by a clean
LO and mixers to simply move the Angelia (or
whatever) spectrum to and from an amateur band.

Rather, I'd like to add an additional conversion with a similar LO to above
the highest range of a wide-range clean LO that can be locked in 50 MHz or
smaller steps down to some much lower frequency.  Looking at it in the
receive direction, set the variable LO below that higher IF to downconvert
the previously upconverted band or [50 MHz] range range/band of interest.
Reverse it on TX.

These are exemplary numbers only for receive, not actual choices:

[100 MHz through 3500 MHz] input goes through 5400 MHz multi-section LPF to
Mixer1.
LO1, steppable 5650 - 2150 MHz  goes to Mixer 1  to gives 25 MHz wide
IF1 = ~5700 MHz.
After BPF, IF1 goes to Mixer2.
LO2 fix tuned at [5425 MHz] goes to Mixer 2.
[275-300 MHz] output of Mixer2 filtered in 25 MHz BPF=IF2 goes to Mixer 3.
IF2 goes into Mixer3.
LO3 = fixed 250 MHz goes into Mixer 3.
Output of Mixer3 is 25-50 MHz goes to Angelia.

Turn it around, use mostly common LOs (probably duplicate LO1 for transmit
to maintain high tx/rx isolation)

This is the general approach used in RF-microwave spectrum analyzers, also
turned around for TX.
I need to draw this but can't do it without more than ASCII.

Glenn n6gn

Inputs from Mixer1 and LO2 to Mixer2 takes this IF2 and converts in down On
04/18/2015 10:53 PM, Joe Martin wrote:
> Hi Glenn,
>
> FYI, I am routinely using the ANAN-100D (it contains the Angelia
transceiver board) to do pulsar radio astronomy at 424-436 MHz and
hydrogen-line work at 1420.2 MHz by using the ANAN-100D as an IF stage in
the radio telescope.  To access the UHF/Microwave frequencies with the
ANAN-100D I use the appropriate LNAs for the band of interest (out on  the
dish) and a MiniCircuits mixer and 50 MHz low pass filter in the shack that
feeds the ANAN-100D, typically using a 28 MHz IF from the mixer but I also
use 40 MHz IF occasionally; the ANAN-100D receives those IF frequencies
fine.
>
> Using down converters appears to work much better in terms of weak signal
sensitivity than does striving to make the Angelia operate at frequencies
higher than 60 MHz directly.
>
> 73, Joe K5SO
>
>
> On Apr 18, 2015, at 3:50 PM, Glenn Elmore wrote:
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> I'm a total newbie on this list. I hope this is an appropriate posting.
>>
>> I'm wondering who might have worked on, or be working on, frequency
extensions for OpenHPSDR.  Specifically, it seems to me that an effort to
extend the range of OpenHPSDR to include 50 MHz - 6 GHz or higher must have
been considered if not attempted or accomplished by someone by this time.
Who has done this or might be interested in discussing it?
>>
>> I'm asking because, although new to OpenHPSDR with an Angelia just
freshly boxed up and working, I already see the desirability of having
coverage of 144,220,432,900,1296 and 2304. It seems to me that it would be a
shame to limit this to a conventional banded transverter approach and that
doing a conversion to a higher fixed IF followed by a down conversion to
cover,say 50 MHz to 6 GHz with a clean LO up/down converter is an obvious
choice.  Allow this is a "radio" project, continuous coverage would allow
extension of signal analyzer and vector network analysis throughout this
range and should be a pretty useful capability.
>>
>> Is this already being done by someone?
>>
>> Glenn Elmore
>> n6gn
>>
>>
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>

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