Re: [time-nuts] C-Max Receiver Experiment

[Justin Pinnix]

Update -

I attempted to look at the analog signal.  I looked at the output of the
crystal.  With the scope's low-pass filter turned on I was able to see a
very weak sine wave with a period of roughly 15us.  It was too weak for any
analysis.

http://www.fuzzythinking.com/wordpress/wp-content/uploads/2011/11/60khz.png

I also looked at the demodulator out.  This is a much larger amplitude
signal, though it has already been rectified.  However, I was able to see
good correlation between it (blue) and the TCON output (yellow)

http://www.fuzzythinking.com/wordpress/wp-content/uploads/2011/11/dem_out.png

Most importantly, I've been reading up on the subject and have adjusted my
expectations.  I didn't realize that frequency measurements (like those
done by the HP117 and Fluke 207) don't actually use the timecode part of
the signal.

Page 11 of http://tf.nist.gov/general/pdf/1383.pdf tells me that WWVB is
3-4 orders of magnitude better than WWV for frequency measurements, but
that the two services' time uncertainties overlap and WWVB is at best 1
order better.  As a matter of fact, my measurements of the C-MAX line up
with the top end of that estimate (and Tom's :-)).

I'm still planning on capturing a long set of timings, but I need to do
some hardware mods first.

Thanks,
-Justin

On Mon, Oct 31, 2011 at 1:04 PM, David J Taylor <
david-tay...@blueyonder.co.uk> wrote:

>  Hi David,
>> Thanks for pointing out the problem with the figures in my webpage.  I
>> have
>> fixed it.  I'm going to attempt to capture the analog signal by probing
>> the
>> QOut pin.
>>
>
> The updated images make the effects clearer.  It will be interesting to
> see the image capture.
>
>
>  Good point about "precision" - it's all relative.  This is an extension of
>> a previous project of mine - a clock I built around an LPro.  Setting it
>> to
>> the Thunderbolt is a bit of a pain and I was hoping to build in the C-Max
>> to make it more "fire and forget".  I was hoping for a time signal within
>> several microseconds of UTC without the need of an outdoor antenna. Like
>> most of my projects, the journey is more interesting than the destination,
>> so even if I don't accomplish that goal I'm still having fun.  Embedding a
>> consumer GPS is probably the more practical solution.
>>
>> Thanks,
>> -Justin
>>
>
> Microseconds, no.  Milliseconds perhaps.  But sometimes nothing at all
> depending on the time of day and season of the year etc. etc.  Let's hear
> more about the project as it progresses.
>
>
> Cheers,
> David
> --
> SatSignal software - quality software written to your requirements
> Web:  http://www.satsignal.eu
> Email:  david-tay...@blueyonder.co.uk
>
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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[Peter Bell]

> Next time I have the unit open I will take a look.  Are there obvious
> markings to distinguish the boards (it's a board and not a box), as I recall
> looking but no seeing any.

It's been a while, but from what I remember the boards look almost
identical - the standard configuration has a part of 9-pin D-Types, an
SMB connector for the antenna and a 3-pin header for the power.
Probably the best thing to do is to look for the P/N and google it.
Those older units seem to have fallen into the memory hole at Trimble,
though - they don't quite deny ever making them, but seem to have
almost no info on them now.

I have had a look on my external hard drive that's got all the old
crap backed up on it, but came up blank - that doesn't mean it's not
there, just that my "filing" system has failed :)

Regards,

Pete

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Re: [time-nuts] 10811 thermal fuses

[J. L. Trantham]

OK.  I am now in my shop and I have the items in my hand.

I got the replacements from Allied.  They are marked '141 degrees C
D139ZPXL'.  I think they were NTE.  They are 4 mm dia., 13 mm long, and the
leads are 1 mm dia.

The HP/Agilent parts are marked 'UMI 1A 250V 115 degrees C'.  They are 2 mm
dia., about 9.5 mm long, and the leads are 0.52 mm dia.

Therefore, the lead diameter would appear to be the rate limiting step in
this approach.

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dan Rae
Sent: Wednesday, November 02, 2011 6:40 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 10811 thermal fuses

Joe, I had forgotten that it is a tight squeeze in there, so yes, they 
may be too big to fit easily!

Dan

On 11/2/2011 2:59 PM, J. L. Trantham wrote:
> These look like the ones I got from Mouser or whom ever.  They look
> different from what I got from Agilent.  The ones from Agilent are
smaller,
> about the size of a 1/4 watt resistor, short leads, pre-bent, to allow
them
> to 'plug' into the PC board of the 10811.  Cutting the leads and
> 'pre-bending' probably explain the higher price from Agilent.  Or it could
> be the computerized tracking expense.
>
> Joe
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]On
> Behalf Of Dan Rae
> Sent: Wednesday, November 02, 2011 4:30 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: [time-nuts] 10811 thermal fuses
>
> While looking for something else I stumbled on an eBay seller in Hong
> Kong offering five 113°C thermal fuses for $6 including shipping, which
> seems like a reasonable deal...
>
> Item number:130579771801
>
> Usual disclaimers apply, and before anyone complains, yes, it's a
> generic photo.
>
> Dan
>
>
>



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Re: [time-nuts] 10811 thermal fuses

[Dan Rae]

Joe, I had forgotten that it is a tight squeeze in there, so yes, they 
may be too big to fit easily!


Dan

On 11/2/2011 2:59 PM, J. L. Trantham wrote:

These look like the ones I got from Mouser or whom ever.  They look
different from what I got from Agilent.  The ones from Agilent are smaller,
about the size of a 1/4 watt resistor, short leads, pre-bent, to allow them
to 'plug' into the PC board of the 10811.  Cutting the leads and
'pre-bending' probably explain the higher price from Agilent.  Or it could
be the computerized tracking expense.

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]On
Behalf Of Dan Rae
Sent: Wednesday, November 02, 2011 4:30 PM
To: 'Discussion of precise time and frequency measurement'
Subject: [time-nuts] 10811 thermal fuses

While looking for something else I stumbled on an eBay seller in Hong
Kong offering five 113°C thermal fuses for $6 including shipping, which
seems like a reasonable deal...

Item number:130579771801

Usual disclaimers apply, and before anyone complains, yes, it's a
generic photo.

Dan







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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changesaffect the unit

[Alan Melia]

re my last, suggesting it was an 8ch GPS.. I have just realised I was
looking at the Rb version manual not the OCXO version which does have a 6ch
receiver. (at least on the manual version I have )

apologies ...put brain in gear before etc.

Alan G3NYK

- Original Message - 
From: "Robin Kimberley" 
To: ; "'Discussion of precise time and frequency
measurement'" 
Sent: Wednesday, November 02, 2011 9:01 PM
Subject: Re: [time-nuts] Monitoring the Rapco 1804M - how antenna
changesaffect the unit


> The ET6000 used Trimble Bullet antennae when I was selling them in the UK.
I
> seem to remember about 35db of gain in that antenna.
>
> Rob Kimberley
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Joe Leikhim
> Sent: 02 November 2011 18:52
> To: time-nuts@febo.com
> Subject: [time-nuts] Monitoring the Rapco 1804M - how antenna changes
affect
> the unit
>
> I tried a similar Garmin antenna with my Datum ET6000 and the lock times
> were really long, even with the antenna on a 14 foot pole above the roof.
I
> attribute a lot of this to the long 8 ft RG174 style coax pigtail. I have
to
> wonder if the gain of the preamp as published actually includes the
inherent
> cable loss, and even if so the preamp must be screaming in gain to make up
> for the loss. I intend to get a proper antenna.
>
> Here is a comparison of specs of these type antennas:
>
> http://gpsinformation.net/main/gpsantrev1.htm
>
> --
> Joe Leikhim
>
> Leikhim and Associates
> Communications Consultants
> Oviedo, Florida
>
> www.Leikhim.com
>
> jleik...@leikhim.com
>
> 407-982-0446
> WWW.LEIKHIM.COM
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>
>
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Re: [time-nuts] 10811 thermal fuses

[J. L. Trantham]

These look like the ones I got from Mouser or whom ever.  They look
different from what I got from Agilent.  The ones from Agilent are smaller,
about the size of a 1/4 watt resistor, short leads, pre-bent, to allow them
to 'plug' into the PC board of the 10811.  Cutting the leads and
'pre-bending' probably explain the higher price from Agilent.  Or it could
be the computerized tracking expense.

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]On
Behalf Of Dan Rae
Sent: Wednesday, November 02, 2011 4:30 PM
To: 'Discussion of precise time and frequency measurement'
Subject: [time-nuts] 10811 thermal fuses

While looking for something else I stumbled on an eBay seller in Hong
Kong offering five 113°C thermal fuses for $6 including shipping, which
seems like a reasonable deal...

Item number:130579771801

Usual disclaimers apply, and before anyone complains, yes, it's a
generic photo.

Dan


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[time-nuts] 10811 thermal fuses

[Dan Rae]

While looking for something else I stumbled on an eBay seller in Hong 
Kong offering five 113°C thermal fuses for $6 including shipping, which 
seems like a reasonable deal...


Item number:130579771801

Usual disclaimers apply, and before anyone complains, yes, it's a 
generic photo.


Dan


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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changesaffect the unit

[Alan Melia]

Hi Rob I picked up a couple of "mushroom shaped" (white flat top rounded
edges prob 70mm diam.) antennas with a small right-angle bracket and a TNC
connector (5v supply) no nameplate but they seem to work fine on 20 feet of
RG-58.

The manual for the 1804M says its an 8-channel receiver and I recollect it
being a  Trimble.

Alan G3NYK

- Original Message - 
From: "Robin Kimberley" 
To: ; "'Discussion of precise time and frequency
measurement'" 
Sent: Wednesday, November 02, 2011 9:01 PM
Subject: Re: [time-nuts] Monitoring the Rapco 1804M - how antenna
changesaffect the unit


> The ET6000 used Trimble Bullet antennae when I was selling them in the UK.
I
> seem to remember about 35db of gain in that antenna.
>
> Rob Kimberley
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Joe Leikhim
> Sent: 02 November 2011 18:52
> To: time-nuts@febo.com
> Subject: [time-nuts] Monitoring the Rapco 1804M - how antenna changes
affect
> the unit
>
> I tried a similar Garmin antenna with my Datum ET6000 and the lock times
> were really long, even with the antenna on a 14 foot pole above the roof.
I
> attribute a lot of this to the long 8 ft RG174 style coax pigtail. I have
to
> wonder if the gain of the preamp as published actually includes the
inherent
> cable loss, and even if so the preamp must be screaming in gain to make up
> for the loss. I intend to get a proper antenna.
>
> Here is a comparison of specs of these type antennas:
>
> http://gpsinformation.net/main/gpsantrev1.htm
>
> --
> Joe Leikhim
>
> Leikhim and Associates
> Communications Consultants
> Oviedo, Florida
>
> www.Leikhim.com
>
> jleik...@leikhim.com
>
> 407-982-0446
> WWW.LEIKHIM.COM
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>
>
>
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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[Joe Leikhim]

So easily a 20 dB shortfall. I will look out for a similar antenna. Thanks

On 11/2/2011 5:01 PM, Robin Kimberley wrote:

The ET6000 used Trimble Bullet antennae when I was selling them in the UK. I
seem to remember about 35db of gain in that antenna.

Rob Kimberley

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Joe Leikhim
Sent: 02 November 2011 18:52
To: time-nuts@febo.com
Subject: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect
the unit

I tried a similar Garmin antenna with my Datum ET6000 and the lock times
were really long, even with the antenna on a 14 foot pole above the roof.  I
attribute a lot of this to the long 8 ft RG174 style coax pigtail. I have to
wonder if the gain of the preamp as published actually includes the inherent
cable loss, and even if so the preamp must be screaming in gain to make up
for the loss. I intend to get a proper antenna.

Here is a comparison of specs of these type antennas:

http://gpsinformation.net/main/gpsantrev1.htm

--
Joe Leikhim

Leikhim and Associates
Communications Consultants
Oviedo, Florida

www.Leikhim.com

jleik...@leikhim.com

407-982-0446
WWW.LEIKHIM.COM


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-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.1834 / Virus Database: 2092/4591 - Release Date: 11/02/11


--
Joe Leikhim

Leikhim and Associates
Communications Consultants
Oviedo, Florida

www.Leikhim.com

jleik...@leikhim.com

407-982-0446
WWW.LEIKHIM.COM


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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[Robin Kimberley]

The ET6000 used Trimble Bullet antennae when I was selling them in the UK. I
seem to remember about 35db of gain in that antenna.

Rob Kimberley

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Joe Leikhim
Sent: 02 November 2011 18:52
To: time-nuts@febo.com
Subject: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect
the unit

I tried a similar Garmin antenna with my Datum ET6000 and the lock times
were really long, even with the antenna on a 14 foot pole above the roof.  I
attribute a lot of this to the long 8 ft RG174 style coax pigtail. I have to
wonder if the gain of the preamp as published actually includes the inherent
cable loss, and even if so the preamp must be screaming in gain to make up
for the loss. I intend to get a proper antenna.

Here is a comparison of specs of these type antennas:

http://gpsinformation.net/main/gpsantrev1.htm

--
Joe Leikhim

Leikhim and Associates
Communications Consultants
Oviedo, Florida

www.Leikhim.com

jleik...@leikhim.com

407-982-0446
WWW.LEIKHIM.COM


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[time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[Joe Leikhim]

I tried a similar Garmin antenna with my Datum ET6000 and the lock times 
were really long, even with the antenna on a 14 foot pole above the 
roof.  I attribute a lot of this to the long 8 ft RG174 style coax 
pigtail. I have to wonder if the gain of the preamp as published 
actually includes the inherent cable loss, and even if so the preamp 
must be screaming in gain to make up for the loss. I intend to get a 
proper antenna.


Here is a comparison of specs of these type antennas:

http://gpsinformation.net/main/gpsantrev1.htm

--
Joe Leikhim

Leikhim and Associates
Communications Consultants
Oviedo, Florida

www.Leikhim.com

jleik...@leikhim.com

407-982-0446
WWW.LEIKHIM.COM


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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[Dave Martindale]

By the way, this doesn't mean that the GA-27 is a poor antenna design,
it's just not the best antenna choice for this situation.

The GA-27 is intended as an external antenna for Garmin's handheld
receivers, which normally operate with passive patch or helix
antennas.  So the receiver itself needs to be sensitive enough to work
well when an unamplified antenna is connected directly to the
receiver, and the GA-27 preamp only needs to provide enough gain to
overcome the losses in the cable plus a bit more.  Additional gain
could be detrimental in some circumstances (e.g. when placed near
transmitting antennas on a vehicle), so the GA-27 might well be the
best antenna for the Garmin handheld receivers.

But a GPS board module is intended to be built into some piece of
equipment, and probably expected to always be fed from a remote
amplified antenna, never a local passive antenna.  In those
circumstances, it makes sense to put all the necessary gain at the
antenna preamp and let the receiver be less sensitive.  The
manufacturer will recommend some antenna for use with the receiver,
and though you don't usually have to use that particular antenna, it's
probably a good idea for your antenna/cable/splitter setup to provide
roughly the same signal level at the receiver.

- Dave

On Wed, Nov 2, 2011 at 01:19, David J Taylor
 wrote:
>> I've made a small Web page describing what happened when I changed the
>> puck antenna on a Rapco 1804M for a more sensitive one.  The Rapco 1804M
>> expects a big outside antenna.
>>
>>  http://www.satsignal.eu/ntp/Rapco-1804M-notes.html
>
> This page has now been updated to provide a comparison between three puck
> antennas - the Garmin GA 27 (BNC), a 3rd-party low-cost puck, and a Gilsson
> puck antenna.  It seems that the even higher signal level from the Gilsson
> benefits the 1804M more than the other two.
>
> Cheers,
> David
> --

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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[David J Taylor]

Ah, I didn't realize this was based on the Trimble board - I was
having a mental seizure and thinking it was using a Motorola OnCore,
as so many of the others did.  Are you really sure it is an SV6?
Trimble also made an SV8 timing that was in the same form factor  and
if it was using that it would certainly explain why you sometimes see
more than 6 satellites - although I have a vague memory that if you
talk to it as if it was a 6-channel board it starts pretending to be
one for reasons of backwards compatibility, so even if you do have the
SV8 in there it likely won't do you much good.


Next time I have the unit open I will take a look.  Are there obvious 
markings to distinguish the boards (it's a board and not a box), as I 
recall looking but no seeing any.


As the unit is only required for frequency, I am not intending to 
modify it.
 It has OCXO with quite good specifications, so it will more than meet 
my
needs.  It would likely meet my needs five minutes after being switched 
on!


True, but this is time-nuts.  The pursuit of more accuracy than you
need is the whole purpose of the list :)

Regards,
Pete


Yes, I know!  Sad, but 10 Hz at 150 MHz and PCs to within a few 
microseconds will do me nicely!


Cheers,
David
--
SatSignal software - quality software written to your requirements
Web:  http://www.satsignal.eu
Email:  david-tay...@blueyonder.co.uk 



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Re: [time-nuts] VIGO time interval devices

[Mark Spencer]

If anyone was ever to "review" such a device the actual power consumption would 
be usefull to know.   The likely savings in electricty costs could provide some 
justification for replacing one of my HP5370B's (:

Devices that could also easily run from a DC power source could have merit as 
well.  

--- On Tue, 11/1/11, Jose Camara  wrote:

> From: Jose Camara 
> Subject: Re: [time-nuts] VIGO time interval devices
> To: "'Arthur Dent'" , "'Discussion of precise time 
> and frequency measurement'" 
> Received: Tuesday, November 1, 2011, 11:50 PM
> There seems to be a deluge of these
> OEM counters, mimicking the 53132
> operation, with a bit better "specs" and built-in 3rd
> channel.
> 
>     Berkeley Nucleonics has them, Keithley
> has them, they all must come
> from the same Chinese OEM. Maybe the quality is good, maybe
> the specs are
> honest and apples to apples. Or maybe not.
> 
>     The only experience I had was with
> another Agilent knock-off, the
> BNC-branded arb generator model 645, which was cheaper than
> the Agilent,
> with a higher frequency capability (50MHz compared to
> 20MHz) and SCPI
> compatible. Didn't check side by side on a spectrum
> analyzer, but for the
> application I had it worked fine.  As a plus, it had
> also digital output on
> the back (16 bits) so it doubled as a cheap word
> generator.
> 
>     It would be nice for a real time nutter
> to get one (BNC often
> offered 1 month loaners) and measure the actual
> performance.  One thing we
> will only know 10 years from now is if they last as long as
> the HPs - or if
> the manufacturer will still exist.
> 
>     BNC has a comparison to Agilent and
> Pendulum on their site. Caveat
> Emptor. http://www.berkeleynucleonics.com/Comp/1105/1105_comp_chart.htm
> 
> Jose
> 
>  
> -Original Message-
> From: time-nuts-boun...@febo.com
> [mailto:time-nuts-boun...@febo.com]
> On
> Behalf Of Arthur Dent
> Sent: Monday, October 31, 2011 2:25 PM
> To: time-nuts@febo.com
> Subject: [time-nuts] VIGO time interval devices
> 
> Has anyone looked into the Picotest (also sold as Array)
> U6200A TIC? 
> 
> Looks like DC-6Ghz with 12 digits/sec and 40ps resolution.
> Check 
> 
> the specs at:
> 
> http://www.picotest.com.tw/product02.html
> 
> One seller on the popular auction site has them for $1270
> (with shipping).
> 
> http://www.ebay.com/itm/New-Universal-Frequency-Counter-meter-ARRAY-U6200A-/
> 270788500453
> 
> 
>  -Arthur
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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[Peter Bell]

> Yes, that in consistent with what I'm seeing, Pete, thanks.  I am told that
> the actual receiver is a Trimble SVeeSix, so why I occasionally see eight
> reports from the Rapco firmware I don't understand.

Ah, I didn't realize this was based on the Trimble board - I was
having a mental seizure and thinking it was using a Motorola OnCore,
as so many of the others did.  Are you really sure it is an SV6?
Trimble also made an SV8 timing that was in the same form factor  and
if it was using that it would certainly explain why you sometimes see
more than 6 satellites - although I have a vague memory that if you
talk to it as if it was a 6-channel board it starts pretending to be
one for reasons of backwards compatibility, so even if you do have the
SV8 in there it likely won't do you much good.

> As the unit is only required for frequency, I am not intending to modify it.
>  It has OCXO with quite good specifications, so it will more than meet my
> needs.  It would likely meet my needs five minutes after being switched on!

True, but this is time-nuts.  The pursuit of more accuracy than you
need is the whole purpose of the list :)

 Regards,
Pete

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Re: [time-nuts] VIGO time interval devices

[Javier Herrero]

A couple more :)

http://www.acquitek.com/u6200a/counter-test-measurement.html
http://www.ptsyst.com/U6200A-B.pdf (even with 20GHz input option)

Similar thing I found some time ago when looking for an electronic load. 
Same thing with several different branding, price ranging for 1 to 2.


Regards,

Javier


El 02/11/2011 12:19, Arthur Dent escribió:

Jose Camara-"Berkeley Nucleonics has them, Keithley has them, they all must
come from the same Chinese OEM. Maybe the quality is good, maybe the specs
are honest and apples to apples. Or maybe not."
---

Interesting to note that the Picotest/Array U6200A and the BNC 1105 use exactly
the same photos in their ads. The major difference seems to be the asking price.

http://www.picotest.com.tw/product02.html
http://www.array.sh/yq-u6200ae.htm
http://www.berkeleynucleonics.com/products/model_1105.html
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[time-nuts] VIGO time interval devices

[Arthur Dent]

Jose Camara-"Berkeley Nucleonics has them, Keithley has them, they all must 
come from the same Chinese OEM. Maybe the quality is good, maybe the specs 
are honest and apples to apples. Or maybe not."
---

Interesting to note that the Picotest/Array U6200A and the BNC 1105 use exactly 
the same photos in their ads. The major difference seems to be the asking price.

http://www.picotest.com.tw/product02.html
http://www.array.sh/yq-u6200ae.htm
http://www.berkeleynucleonics.com/products/model_1105.html
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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[David J Taylor]

Assuming it's using a timing-optimized receiver, the lack of a clear
view to the sky is probably the biggest problem.  Once they have a
valid almanac, they will normally select the satellites with the
highest elevation angles - and if you have an obstructed view that
might well include several that are not visible.  Obviously, the less
channels on the receiver, the bigger an issue this is - on top of
this, the timing receivers tend to be engineered to favor selectivity
over sensitivity (the idea being that the gain is in the antenna and
you can select it to match the cable losses).


Yes, that in consistent with what I'm seeing, Pete, thanks.  I am told 
that the actual receiver is a Trimble SVeeSix, so why I occasionally see 
eight reports from the Rapco firmware I don't understand.



I have no idea if the firmware in the Rapco will support the 8-channel
UT+ - but the fact that the monitoring software seems to have spaces
for up to 8 SVs gives me some hope it might (or possibly there is some
later FW that does).  This could be worth trying.

Regards,

Pete Bell


As the unit is only required for frequency, I am not intending to modify 
it.  It has OCXO with quite good specifications, so it will more than meet 
my needs.  It would likely meet my needs five minutes after being switched 
on!


Thanks for your comments.  I've updated the Web page about the 6/8 
channels, and added a couple of pointers for those who might want to try 
the antennas.  An outside one with a clear sky view would like be better 
than any of these puck antennas.


Cheers,
David
--
SatSignal software - quality software written to your requirements
Web:  http://www.satsignal.eu
Email:  david-tay...@blueyonder.co.uk 



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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[Peter Bell]

Assuming it's using a timing-optimized receiver, the lack of a clear
view to the sky is probably the biggest problem.  Once they have a
valid almanac, they will normally select the satellites with the
highest elevation angles - and if you have an obstructed view that
might well include several that are not visible.  Obviously, the less
channels on the receiver, the bigger an issue this is - on top of
this, the timing receivers tend to be engineered to favor selectivity
over sensitivity (the idea being that the gain is in the antenna and
you can select it to match the cable losses).

I have no idea if the firmware in the Rapco will support the 8-channel
UT+ - but the fact that the monitoring software seems to have spaces
for up to 8 SVs gives me some hope it might (or possibly there is some
later FW that does).  This could be worth trying.

Regards,

Pete Bell


On Wed, Nov 2, 2011 at 4:19 PM, David J Taylor
 wrote:
>> I've made a small Web page describing what happened when I changed the
>> puck antenna on a Rapco 1804M for a more sensitive one.  The Rapco 1804M
>> expects a big outside antenna.
>>
>>  http://www.satsignal.eu/ntp/Rapco-1804M-notes.html
>
> This page has now been updated to provide a comparison between three puck
> antennas - the Garmin GA 27 (BNC), a 3rd-party low-cost puck, and a Gilsson
> puck antenna.  It seems that the even higher signal level from the Gilsson
> benefits the 1804M more than the other two.
>
> Cheers,
> David
> --
> SatSignal software - quality software written to your requirements
> Web:  http://www.satsignal.eu
> Email:  david-tay...@blueyonder.co.uk
>
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Re: [time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

[David J Taylor]

I've made a small Web page describing what happened when I changed the 
puck antenna on a Rapco 1804M for a more sensitive one.  The Rapco 1804M 
expects a big outside antenna.


 http://www.satsignal.eu/ntp/Rapco-1804M-notes.html


This page has now been updated to provide a comparison between three puck 
antennas - the Garmin GA 27 (BNC), a 3rd-party low-cost puck, and a 
Gilsson puck antenna.  It seems that the even higher signal level from the 
Gilsson benefits the 1804M more than the other two.


Cheers,
David
--
SatSignal software - quality software written to your requirements
Web:  http://www.satsignal.eu
Email:  david-tay...@blueyonder.co.uk 



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