[NLRS] ALO-32 and 5.7GHz questions

[Dr. Gerald N. Johnson]

At MUD, Paul Wade did not compliment the A32. He measured significant 
phase noise and in the past has found that phase noise raised the 
threshold for detecting weak signals at 10 GHz by a couple dB. One happy 
user informed him after his talk (not heard by the whole audience) that 
IF the A32 was programmed for an integral frequency, not a fractional 
frequency AND the 10 MHz input was filtered to be a sine wave that the 
phase noise was cleaner. I don't know what the effect of a none sine 
wave is on the input for sure, but there always has been more phase 
noise from the PLL for a fractional division than an integer division. 
The makers of fractional division chips do try to minimize that or 
noticing it. When multiplying a VCO to 5 or 10 GHZ and the VCO has wide 
band coverage with only a few volts it only takes microvolts on the VCO 
control line to add phase noise and its easy to generate microvolts of 
noise from resistors, series or shunt or from ground noise when the VCO 
is inside the digital chip. Paul proposed using a VCXO in a separate box 
from the digital circuits with its own regulator to cut down on phase 
noise but admitted near the end of his talk that the common regulator 
was most of that problem.

As for the 10 MHz input its probably a case of distortion of the 
waveform by harmonics makes the zero crossing vary more than the basic 
frequency from that reference and that propagates through the reference 
dividers and the PLL to modulate the output since the sinewave has to be 
squared up to drive the digital logic. If the time of the selected slope 
crossing the trigger threshold varies the phase of the resulting digital 
signal varies.

There are distinctly separate schools of thought on the A32. Those who 
love it because it keeps them on frequency and those like me and Paul 
who believe its increased phase noise makes it damaging to the basic 
weak signal operation of the station.

There is merit in keeping the station simple for roving to the vicinity 
of clusters of activity.

With a change of feed the 18" dss dish isn't bad at 5760 and there have 
been dual band feeds for 5760 and 10 GHz designed for it by W5LUA and 
others around for maybe a decade.

There is much 6 GHZ commercial microwave link stuff floating around in 
surplus. I think Doug Reed has had some, probably still does.

I know a Harris LNA for that band tested quite good at CSVHF last summer 
and it also did at 10 GHz but for some reason I can't hear 10 GHz 
signals through it though my noise source shows a better NF with it in 
place. I suspect that it and my noise source both have more output and 
gain at 6 than at 10.368 GHz and that the lightly filtered 10G 
transverter has some spurious inputs lower than 10368. I'm setting up to 
measure the image rejection one of these days using a broad band mixer, 
a brick on 10.500 Ghz and my VHF signal generator. I'll probably add 
some attenuation after the mixer too so I can drive it with more than 
its threshold signal at the IF so the MDS I see is that of the 
transverter and preamp, not the mixer on the signal generator.

That Harris 6 GHz LNA is practically perpetual at a decent price on epay.

5 to 6 GHz bricks are relatively common too. As are circulators, 
filters, and "power amplifiers."

There is probably a software update for the A32 at least giving more 
frequencies if not better phase noise. Get with N5AC about that.

73, Jerry, K0CQ

On 10/25/2013 3:05 PM, Bill Davis wrote:
>
>
>    I MAY HAVE fallen and hit my head, but I am considering 5.7GHz for an addition to the station here.
>
>    At first, I considered the same approach as I used on 10GHz with transverter in the shack and PA/Preamp top side .... but looking at the economics .... maybe everything on the tower, using a ALO32.
>
>    I bought a ALO-32 at MUD when it was in Minneapolis, thinking I would use it for the 10GHz portable, but decided KISS was the best approach given my 10GHz rove style and distance from any way to trouble shoot anything in the field.
>
>    Given the lack of regular tropo activity and limited contest stations available, it will be a pretty high $/QSO band. So I am looking to try to keep the cost down. Contests and RS will be the payoff.
>
>
>    QUESTIONS::
>
> (1) My ApolLO-32 is (c)2008, any issues that should be a concern? Not sure of the different versions.
>
>
> (2) Before I consider ordering anything ... anyone have any excess 5.7GHz gear out there? I will be looking for a transverter and "BBQ" dish with feed. I would like Watts not mWs and wish a good noise figure without the need of a preamp. Purchase or trades possible.
>
>
> Thanks  73 Bill  K0AWU
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