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Re: RE: S band for 6 bucks

Mike, N1Jez wrote:


> One of the things that has always bothered me about these converters 
> is
> their instability. I understand why it happens. The crystal doesn't 
> even
> have the most basic of heaters that we typically use in Uwave.
> Here's a project I was going to try someday when we got a good Mode S 
> bird back in the air...
> Disconnect the LO on one of these units and feed it from a GPS locked
> source. This sounds hard, but there are fairly easy ways to do it...
> I've been developing a simple GPS Stabilized 10 MHz source based on 
> the
> original design by James, G3RUH. We have a bunch of them working in 
> New
> England. See: http://mysite.verizon.net/n1jez/index.html near the 
> bottom of
> the page
> With these simple units, we're seeing accuracies on the order of  < 2 
> Hz per
> GHz "woggle". So if this was used as a reference, you could expect to 
> see <
> 5 Hz woggle at 2.4 GHz.
> Now, how to use this to generate 2256 MHz for the LO? As part of the 
> 10 MHz
> project we're using "Qualcomm" boards to generate very accurate signal
> markers for Microwave use. I used the system this past weekend during 
> the
> VHF Contest for a long distance contact on 24 GHz. Both stations lined 
> up
> their IF's with our GPS based markers and when we transmitted, we 
> instantly
> heard each other with no retuning! That's at 24 GHz. Should be a piece 
> of
> cake at 2.4 GHz.. (it's DC <grin>)
> The Qualcomm boards can be seen at the SBMS website. See:
> http://www.ham-radio.com/sbms/sd/projindx.htm
> Scroll down to the "3036/3216 Rectangular" and "Texas" boards. These 
> are
> programmable PLL VCXO's that use a 10 MHz reference. This sounds 
> scary, but
> if you look at the conversion info, it's pretty straight forward. I 
> have
> several in use here as signal markers for all bands 2304 MHz through 
> 47 GHz.
> There is a spreadsheet that allows you to set the programming for 2256 
> MHz.
> The key to the board is that it uses a 10 MHz reference. That's where 
> the
> simple GPS 10 MHz oscillator comes in. You simply inject the reference 
> and
> you have an LO that is easily within 5 Hz on Mode S. If you're looking 
> at
> doing computer controlled doppler correction, imagine a Mode S 
> downconverter
> that was rock stable....
>> Now, all that is left to do is to retune the combline input filter.
>> Looking at Roger's photos at:
>> http://www.themidwives.org/CalAmp/ (thanks kc8zfn).
>> I retuned the filter by observing the IF output of the downconverter 
>> on
>> a spectrum analyzer.  However, if you have a good clean and stable, 
>> but
>> low level 2.4 GHz. test signal AND you keep the downconverter's input 
>> to
>> your receiver from overloading it, you can retune the combline filter
>> without a spectrum analyzer.
> Here again the "Qualcomm" board and 10 MHz ref can help. The board can 
> be
> programmed for 2400 MHz. It will generate a _very_ strong accurate 
> marker
> there. But there's even an easier way. We've found that the 10 MHz 
> that we use in the GPS Osc will actually generate harmonics every 10 
> MHz
> through 2.5 GHz.....
> Also for a simple receive indicator, if you have an FT-817, the S 
> meters in
> these things are non-linear on the low end, but in a good way for our 
> use.
> The typical FT-817 has been found to exhibit about 1 dB per S unit on 
> the
> low end of the meter.... So it gives a decent indication of small 
> changes.
> I'm told the sensitivity can be adjusted in the hidden "alignment 
> menu" on
> the unit, but I haven't played with it.
> Those of you thinking about trying 10, 24 and even 47 GHz on P3E will 
> really
> appreciate having accurate signal markers on these bands. Right now 
> we're
> seeing accuracy of about 15 Hz at 10 GHz, 35 Hz at 24 GHz and 75 Hz at 
> 47
> GHz. These are measured with complete systems that take into account 
> all the
> variables in a Uwave system. Certainly good enough for our purposes as 
> a
> marker.
> One final thing for those thinking about P3E 10/24/47 GHz, check out
> VE1ALQ's new updated Reflock 1 board. See:
> http://www.ve1alq.com/clpd_pll/clpd_pll.htm  Darrell has solved the 
> problems
> that plagued the original CT1DMK design. I have built up 2 and they 
> work
> superbly! One is being used at 47 GHz. Interestingly one problem we're
> running into is something call "Mode Hoping" or "Mode Jumping" of the
> crystal. You can hear examples of this at:
> http://www.ve1alq.com/clpd_pll/47_ghz_warble.htm There are several 
> files
> from VE4MA and myself of a couple of our crystals....
> Just some quick thoughts....
> 73,
> Mike, N1JEZ
> AMSAT #29649

Hi Mike:

Thanks for the very well written description of your GPS Stabilized 10 
MHz source for stabilizing microwave LO's.  I agree completely.  Knowing 
EXACTLY what freq. you are on when trying to make microwave contacts 
greatly simplifies working other stations.

I have built a few homebrew 10 GHz. transverters.  My portable 
transverter uses a precision 10 MHz. OCXO reference for the LO.  It is 
very accurate, but I wanted something even more accurate for use at 

I have a mast-mounted 10 GHz. transverter.  Since it is mast-mounted, I 
wanted a LO that was stable and accurate in frequency and immune from 
temperature stability problems.  I had planned on running a 10 MHz. 
reference to the tower-mounted LO from a precision TCXO, located inside 
the house.  I had also planned to connect this TCXO to a distribution 
amp and provide a common 10 MHz. external reference to several pieces of 
test equipment on my bench.

I found a great deal on a couple of Rubidium standards and I installed 
one of them inside the mast-mounted transverter.  At 10 GHz., it is 
accurate to within less than 100 Hz.

I have an HP-58540A GPS Time and Freq. Reference Receiver that I am 
playing with for use with one of my portable 10 GHz. transverters.  It 
works well, but after reading about  CT1DMK, Luis Cupido's  "Reflock" 
(Phase lock a VCXO to a standard 10MHz or to a GPS(1pps)) I decided that 
I wanted to discipline a Rubidium standard with a GPS signal.

Now there is a "New & Improved" Reflock II board.  It looks like the 
redesigned boards will be offered by TAPR.  Kits are also available from 
VE1ALQ at:

I plan on using the Reflock II boards for all future microwave LO's, 
except mode U, L & S hand-held, portable satellite operation.

I would like to build a small, battery powered unit capable of duplex 
operation with L-band TX conversion and S-band RX conversion.  Something 
that can be hung on your belt or a shoulder strap and used with an 
dual-band VHF/UHF HT.

Using the Qualcomm boards for a precise microwave marker signal 
generator is something that I have wanted to do for some time now, but 
projects like this $6 S-band downconverter keep getting in the way. :-)

The largest stumbling block for most Hams wanting to build or modify 
microwave transverters and downconverters is a good microwave signal 
source with KNOWN freq. output.  Trying to tune a downconverter and not 
knowing that you are receiving a 2.5 GHz. marker instead of 2.4 GHz. 
marker is a waste of time and very frustrating.

Your reference to the Qualcom boards and the SBMS website 
(http://www.ham-radio.com/sbms/sd/projindx.htm) is good advice.

Your ideas on using precision reference oscillators for microwave LO's 
are even more important for future C-band & X-band and above satellite 

I really miss AO-40.  I prefer CW & SSB satellite operation, but AO-51 
doing great on mode V/S now and there are more S-band satellites on the
way.  AO-51 mode V/S is generating a lot of interest in S-band operation 
and it provides a good opportunity to get equipment working and checked 
out while we look forward to SSETI Express, AMSAT Phase 3 (P3E), and 
hopefully someday, Eagle.


AMSAT # 5562
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