10 GHz beacon project

[Rod Johnson]

I have been playing with this 10 GHz beacon project for quite a while ( many years in one manner or another).

  I am moving this discussion to the broader PNWVHFS group.  There has been some discussion on the PNW-microwave builder sub-group, but I am looking for more ideas, input and discussion.

 

  The basic beacon assembly, originally came to me from from NU7Z.  It is built around a 'brick' oscillator using a 96 MHz crystal.

  It now has an Arduino keyer module and a Qualcomm amplifier, and is supposed to be a nominal one watt output ( have not attempted to check that, because it is what it is, and I am not at all concerned about the actual output level.

The original beacon assembly has been in the hands of W7FU and KD7UO for modification and updating, and it is now back to me.

  The beacon has been running for over a year at my home QTH ( CN97al10), but has always been pretty unpredictable as to the operating frequency.  I have determined that the ambient air temperature changes are a huge part of the problem, so the entire beacon, except the antenna, is now in a foam  shipping box. The internal box temperature is stable at about 150 degrees F.;  +/- a couple.

 

 With the receiving transverter being a older DEM, and a modified  Icom IC-290A as an IF radio, the indicated IF frequency is about 144.065 too 144.075MHz.  If I open the beacon enclosure for a couple of minutes, the IF frequency drops to the range of  144.040 to  144 050, and it takes as much as an hour to climb back close to the normal +/- 144.070 range.  If left open overnight, the IF radio hears the beacon at about 143.985 to  143.989  That should correspond to a beacon frequency of something around 10367.940 MHz.

 Feel free to correct my math. I seem to be having trouble lately with decimal points)

  I now know the DEM transverter also has a temperature co-efficient as part of this frequency migration.  By wrapping the DEM transverter in padding, the indicated frequency also changes, but by a much smaller amount.

  As a  frequency reference, I am using a moRFeus synthesized signal generator set on 1296.000MHz ( to see where the 10.368 GHz signal will be found on the IF radio)  and listening for the 8th harmonic, which comes through on the transverter just fine at +/- 144.051 MHz.

 Calculating the difference, places the beacon on about 10368.024 GHz. (+/-).

  That is a fair amount higher than the label indicated ( marked as10367.904), but we do not know how accurate the old label was.

  Being in a controlled heated environment, I would expect the frequency would change. 

  The question now; is a variation of a few KHz. ( maybe as much as +/- 3KHz.)  going to make this beacon useless?

  Is it even worth setting up for continuous use part way up the SW slope of Tiger Mountain?

   I still have to figure out a way to protect it from the weather and get the slot antenna in the open, and outside the metal electrical box.

  Rod Johnson

 

 

 

 

[Edward R Cole]

Ron,

Let me preface this by stating I am not an expert (just comments based on "some" experience).

I am using a DEMI 10,368/144 MHz transverter (10mw output) with a DEMI 144/28 MHz transverter and K3 (on 28-MHz).

The 10-GHz transverter has the A32 PLL LO locked to a 10-MHz OCXO with 5xE-11 short term stability.  That means it  keeps the  1,136 MHz A32  within 1136,000,000/50,000,000,000 =  0.068 Hz and the 10,368 MHz signal to 0.616 Hz.

In practise I can adjust the transverter to within about 5-Hz measured by my EIP538 counter which has about 1-Hz frequency accuracy at 10-GHz (using a E-10 Rubidium 10-MHz reference).

The K3 uses an external 10-MHz reference for about 2.8 Hz accuracy. (E-7)

So  overall the system is about 5+1+2.8 Hz accurate (just round it off to 10-Hz).

With the original 1,136 MHz heated xtal LO, I had as much as 45-KHz error.  Maybe half that as that its based on working another DEMI transverter with xtal LO.  Certainly enough to challenge making a contact if you have to tune +/- 45-KHz.  Signals were too drifty for SSB.

Using the system with 10-Hz accuracy/stability, the OCXO turn-on drift is the problem until stabilized (20-30 minutes at minimum).  I run my station OCXO 24/7 to avoid that.

I am building a 10-GHz beacon based on the A32 PLL running 1,152.20 MHz that is multiplied to 9th harmonic of 10,368.180 Hz.  That drives a Qualcomm PA to 900mw (conservative as I have measured 960mw with -6 dBm drive).  The multiplier board is made by W1GHz and capable of +10 dBm output (I am deleting one amp stage to run -6 dBm).
KL7UW 10 GHz Beacon page

I haven't built the multiplier, as yet.  But measured the Qualcom with 20-dB directional coupler with some attenuators into a HP432A power meter.

I would guess the 96-MHz brick is not stable enough in your set up.  Measuring is complicated by the accuracy of both the DEMI transverter and the IC-290.

Note: the A32 is NLA so suggest looking at the DEMI digiLO which replaces it (for $99).  OCXO's can be found on e-bay fro $25-$50.
KL7UW FREQ REF Page

GL

73, Ed - KL7UW

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[James Morris]

Do you have a view of Mt Rainier from the proposed beacon location? If so, consider using a directional antenna pointed at the mountain so the signal bounces around.

I have a beacon (not running), which may give you some ideas on getting the slot antenna out of the enclosure.

See the photo at http://w7txt.net/10ghz-beacon-status/

[Pete Mahowald]

Regarding this question

The question now; is a variation of a few KHz. ( maybe as much as +/- 3KHz.)  going to make this beacon useless?

  Is it even worth setting up for continuous use part way up the SW slope of Tiger Mountain?

I think a variation of +/- 3 kHz is still very find-able.  And, more and more, people have an SDR or radio with a waterfall and can find signals visually.

Reliability may be a concern if it is at 150F for a long time.  Just the crystal needs to be temperature controlled, which is often easier to control with a heater.

Here's some info on the local-to-me beacon/linear translator, which functions as a repeater with a S meter, for TX and RX testing.  http://50mhzandup.org/Mt%20Allison%20Beacon%20upgrades.pdf  It was built by Gary K6MG.

--Pete K6TJ

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