[time-nuts] Cutler NAA on 24.0kHz....
johncroos at aol.com
johncroos at aol.com
Sun Aug 17 14:48:12 UTC 2014
A good approach to carrier recovery would be the following chain -
1 AGC or limiter amplifier - I would use AGC followed by a limiter to keep the input to the doubler constant.
2 Analog Frequency Doubler with a bit of Q in the tank tuned to 2X carrier frequency Digital when it screws up does so with bad manners. The tank provides some frequency memory - not obtainable with
a digital doubler.
3. A slow PLL that locks onto and tracks the 2X carrier frequency. I would use a counted down VCXO for this to ensure a long coast time.
Loop bandwidth should be of the order of seconds or more and have a damping factor of 1 or more. the classic 0.707 damping tracks fast but overshoots and hunts before settling down. Fast tracking is not
the requirement here. Stable control of the PLL is.
4. A 2x divider stage to output the original carrier frequency. This could be a flip flop as the amplitude output of the PLL would be constant.
I have made a few PSK and BPSk carrier recover circuits of this type for both micrwave spread spectrum links (20 GHz and UP and also for
use with FSK at VHF). If the carrier is stable and there is no Doppler a very slow Pll does a world of good. See Gardner "Phase Lock Loop Techniques".
the whole thing could be built on little more than 8
square inches of PWB and I am being generous.
MSK is alive and well in a couple of FAA procurements, both past and present. The appeal
is the constant envelope and reduction of adjacent sidebands.
John Roos K6IQL
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Today's Topics:
1. Re: Cutler NAA on 24.0kHz.... (Kenneth G. Gordon)
2. Re: Cutler NAA on 24.0kHz.... (Kenneth G. Gordon)
3. Re: Cutler NAA on 24.0kHz.... (Kenneth G. Gordon)
4. Re: Cutler NAA on 24.0kHz.... (Kenneth G. Gordon)
5. Re: Cutler NAA on 24.0kHz.... (paul swed)
6. Re: Cutler NAA on 24.0kHz.... (Kenneth G. Gordon)
7. MIT Flea (bownes)
8. Proper way to manually connect Vfc (Ole Petter Ronningen)
----------------------------------------------------------------------
Message: 1
Date: Sat, 16 Aug 2014 09:20:34 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: Re: [time-nuts] Cutler NAA on 24.0kHz....
Message-ID: <53EF84D2.25672.CD9FACD at kgordon2006.frontier.com>
Content-Type: text/plain; charset=ISO-8859-1
On 16 Aug 2014 at 11:33, Bob Camp wrote:
> Hi
>
> I would be *very* surprised if the NAA antenna was 50% efficient (transmitter
RF
> to radiated power).....
According to this:
http://www.scribd.com/doc/145116437/THE-BIGGEST-LITTLE-ANTENNA-IN
-THE-WORLD-US-Navy-s-VLF-antenna-at-Cutler-Maine
The company which designed and built the dual trideco antenna system at
Cutler had to guarantee >50% radiation efficiency, and they achieved an
antenna radiation efficiency of 74.9% when using the 6 panel trideco.
When I read this, I was truly amazed.
Although, this site:
http://www.navy-radio.com/commsta/cutler.htm
does say that with 2 MW input, the ERP is 1 MW, which would indicate at
least 50% radiation efficiency.
I am still amazed.
> Given that it?s already up and running with good signal levels, that?s not a
big
> deal.
Very true indeed.
Ken W7EKB
------------------------------
Message: 2
Date: Sat, 16 Aug 2014 09:26:40 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: paul swed <paulswedb at gmail.com>
Cc: time-nuts at febo.com
Subject: Re: [time-nuts] Cutler NAA on 24.0kHz....
Message-ID: <53EF8640.15583.CDF9281 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII
On 16 Aug 2014 at 10:24, paul swed wrote:
> Ken
> At least last night NAA was running just fine using a fluke 207 and 4 ft of
> wire. The antenna is behind a metal rack that shields it in NAAs direction.
Ha! At VLF you could probably bury your antenna in a grounded, steel pipe 4
feet into the ground and still hear NAA.
> I
> did that test out of curiosity.
I LOVE curious... :-)
> Granted its 2 MW but then again the antenna is at best 50% efficient.
See previous post.
> Who knows maybe they have sections of the antenna down for maintenance.
The reason NAA has a double trideco is so they can continue to transmit
with one section down for maintenance.
It turns out that Cutler has a much-bigger-than-usual problem with lightning...
Ken W7EKB
------------------------------
Message: 3
Date: Sat, 16 Aug 2014 09:44:49 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: paul swed <paulswedb at gmail.com>
Cc: time-nuts at febo.com
Subject: Re: [time-nuts] Cutler NAA on 24.0kHz....
Message-ID: <53EF8A81.13919.CF02FFB at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII
On 16 Aug 2014 at 12:31, paul swed wrote:
> I wonder why? And I complain about my antennas.
> It turns out that Cutler has a much-bigger-than-usual problem with
> lightning...
Well, apparently, first of all, Cutler is situated in what turns out to be an
especially lightning-prone area of the country. Secondly, apparently the very
high RF field "encourages" ligntning strikes to the antenna system.
I read about this in a paper concerning the insulators used on that, and
other, Navy antennas.
The MTBF of failure for those insulators is phenomenal: something like 1700
years at worst-case.
I'll try to find that paper again and post the link for those interested.
Kenneth G. Gordon W7EKB
"Courage is being scared to death but saddling up anyway."--- John Wayne
------------------------------
Message: 4
Date: Sat, 16 Aug 2014 09:58:34 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: paul swed <paulswedb at gmail.com>
Cc: time-nuts at febo.com
Subject: Re: [time-nuts] Cutler NAA on 24.0kHz....
Message-ID: <53EF8DBA.5661.CFCC720 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII
On 16 Aug 2014 at 12:48, paul swed wrote:
>
> As a test this morning I connected the fluke 207 vlf radio that has a 1.1KHz
IF
> out to a XY scope using a very stable 1.1 Khz synth function gen. Indeed the
msk
> is a classic 4 corner eye pattern.
Kewel.
> Also I looked at the tracor 900 de-MSK-r
> option and they split the path and create a new signal that according to
> calculations would be 180 degrees and then sum it with the original.
But from my VERY preliminary glance at that schematic, it looks as though
the signal passes through two op amps. Doesn't the phase through any amp
change by 180 degrees? Therefore, through two op amps, it would swap a
full 360, which would equal zero at the output?.
> That is
> perplexing as that would be 0. They do pass it through a 100 Hz BPF. I wonder
if
> in reality the phase shift is 90 degrees and then summed. Its not really
making
> sense as to how that gets rid of the MSK. No description either. But it does
> some how because that signal is simply re-inserted into the 100Hz IF that
feeds
> the phase detectors and correction/locking circuits. Lets see if the diagram
of
> the tracor d-msk-r will come through
It did. Thanks.
Ken W7EKB
------------------------------
Message: 5
Date: Sat, 16 Aug 2014 13:35:52 -0400
From: paul swed <paulswedb at gmail.com>
To: Kenneth G Gordon <kgordon2006 at frontier.com>, Discussion of
precise time and frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] Cutler NAA on 24.0kHz....
Message-ID:
<CAD2JfAj8y4JxrZEDpi5CfN0cJ3--n8Ohy-OmBxBrXUfFJoMzmw at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Kenneth on the opamps that is correct.
But I put little U's to indicate phase. They actually represent the top
half of the input cycle.
In the top path it inverts once
The bottom path twice.
So that makes the top 180 out and the bottom in phase with the original.
However the 2 X RC sets the bottom path at I believe 180 degrees from the
input.
The final RC in the top and bottom path account for opamp filter delay and
note they are equal.
So thats has me scratching my head as to how this removes the MSK and
leaves a carrier that can lock.
One of the classic approaches to recover carrier or get rid of BPSK
modulation is to simply double the incoming carrier. Works great if you
don't loose the signal.
But I do not see this circuit doing that.
Regards
Paul
On Sat, Aug 16, 2014 at 12:20 PM, Kenneth G. Gordon <
kgordon2006 at frontier.com> wrote:
> On 16 Aug 2014 at 11:33, Bob Camp wrote:
>
> > Hi
> >
> > I would be *very* surprised if the NAA antenna was 50% efficient
> (transmitter RF
> > to radiated power).....
>
> According to this:
>
> http://www.scribd.com/doc/145116437/THE-BIGGEST-LITTLE-ANTENNA-IN
> -THE-WORLD-US-Navy-s-VLF-antenna-at-Cutler-Maine
>
> The company which designed and built the dual trideco antenna system at
> Cutler had to guarantee >50% radiation efficiency, and they achieved an
> antenna radiation efficiency of 74.9% when using the 6 panel trideco.
>
> When I read this, I was truly amazed.
>
> Although, this site:
>
> http://www.navy-radio.com/commsta/cutler.htm
>
> does say that with 2 MW input, the ERP is 1 MW, which would indicate at
> least 50% radiation efficiency.
>
> I am still amazed.
>
> > Given that it?s already up and running with good signal levels, that?s
> not a big
> > deal.
>
> Very true indeed.
>
> Ken W7EKB
> _______________________________________________
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------------------------------
Message: 6
Date: Sat, 16 Aug 2014 11:56:35 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: paul swed <paulswedb at gmail.com>
Cc: time-nuts at febo.com
Subject: Re: [time-nuts] Cutler NAA on 24.0kHz....
Message-ID: <53EFA963.29596.D68D0B8 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII
On 16 Aug 2014 at 13:35, paul swed wrote:
>
> Kenneth on the opamps that is correct.
> But I put little U's to indicate phase. They actually represent the top half
of
> the input cycle.
Yes, I saw those, but unless I am mistaken, you didn't add a "U" after the
second opamp, which would have returned the phase to the input's.
> In the top path it inverts once.
I see twice: once through the first op amp and again through the second one.
The second one then outputs to the IF.
Anyway, to me, it is a very interesting and simple circuit.
I LIKE "simple". I am a great believer in the KISS principle.
Ken W7EKB
------------------------------
Message: 7
Date: Sun, 17 Aug 2014 01:56:47 -0400
From: bownes <bownes at gmail.com>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: [time-nuts] MIT Flea
Message-ID: <F176734A-DE05-452C-A5CC-53A32ACA784A at googlemail.com>
Content-Type: text/plain; charset=us-ascii
Apologies for to those not in New England or not going to the Flea.
I'm heading out to the MIT Flea at oh-freaking-dark in the morning and I know
there are often several time nuts who go. If you happen to see a guy wander by
in a Horton Emergency Vehicles hat looking very tired, say Hi!
------------------------------
Message: 8
Date: Sun, 17 Aug 2014 14:15:19 +0200
From: Ole Petter Ronningen <olepr01 at gmail.com>
To: time-nuts at febo.com
Subject: [time-nuts] Proper way to manually connect Vfc
Message-ID:
<CAC+opHH1J8yHY4n9zN4SO+X_kePWqghdrZFUzWpg31PtiKvUrA at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Hello, all
I've started to build up a little collection of various OCXO's, and
measuring various deviations and variances and whatnot. I'm putting them
into proper enclosures, but up untill now I've adjusted them simply using
the Vref through a reasonably low tempco (20-100ppm/C) multiturn pot, with
just a .1uF cap on the Vfc pin to ground. Is this in fact the best way to
do it? Or is there another (reasonably simple) way to improve on that
setup?
I presume the reference-voltage present on most OCXO's are "clean enough"
to meet spec, but are there improvements to be had by using a separate low
noise regulator, for instance?
How about filtering, is there any reason to spend much effort on that, as
the OCXO's are in separate enclosures, with coax soldered directly onto the
10Mhz output? Not sure where the noise would come from, but I stand to be
corrected..
Sorry if this has been repeatedly answered (as I have a feeling it must
have been), but I failed to find it in the archives (perhaps poorly chosen
search-terms on my part)
Thank you
Ole P
------------------------------
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