[time-nuts] GPS antenna in silicon/RTV encapsulation

Fri Apr 18 17:27:37 UTC 2014

 For the group -

 Re: [time-nuts] GPS antenna in silicon/RTV encapsula

 I have been reading the comments on this for a few days. Here is the scoop - Almost every adhesive known to man is absolute bad news when applied to RF components.

Adhesives are sticky because they consist of "polar molecules" that tend t align with any RF field. Water is a polar molecule and that is why is get hot in a microwave field. So in general, adhesives are very lossy at even low RF frequencies. 

There is a subset of the Microwave industry that provides well characterized adhesives to that industry. Special foams have been developed for potting of microwave antennas and even those cause changes in impedance and pattern that the designer must account for.

The parameters you are interested in are the "dielectric constant" which will determine how much the velocity of propagation is reduced in the material, and the "loss tangent" which is the microwave version of the "dissipation factor' often specified for dielectric in capacitors. You want a low dielectric constant and a very low loss tangent -  approaching 0. These are not commonly in adhesives. That is
why "Potted" antennas are often potted in a foam consisting of not a lot of adhesive and a lot of low loss gas bubbles.

Google "loss tangent" for more information.

The short answer from this olde microwave engineer - do not try to pot your antenna, it will be rendered inoperative unless you use one of the microwave specified potting materials. Rather provide an air filled enclosure / radome of some very thin walled plastic.

-73 john k6iql

-----Original Message-----
From: time-nuts-request <time-nuts-request at febo.com>
To: time-nuts <time-nuts at febo.com>
Sent: Fri, Apr 18, 2014 10:00 am
Subject: time-nuts Digest, Vol 117, Issue 66

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Today's Topics:

   1. Re: time-nuts Digest, Vol 117, Issue 61 (HagaaarTheHorrible)
   2. Re: GPS antenna in silicon/RTV encapsulation (Jim Lux)
   3. quartz clock/watch question (Robert Roehrig)
   4. Re: time-nuts Digest, Vol 117, Issue 61 (Bob Camp)
   5. Re: Measuring the accurcy of a wrist watch (Chris Albertson)

----------------------------------------------------------------------

Message: 1
Date: Fri, 18 Apr 2014 15:17:58 +0200
From: HagaaarTheHorrible <hagaaar587plus7 at googlemail.com>
To: time-nuts at febo.com
Subject: Re: [time-nuts] time-nuts Digest, Vol 117, Issue 61
Message-ID: <A14E3790-E838-4043-8344-D371F9B81200 at googlemail.com>
Content-Type: text/plain;	charset=us-ascii

Hi Dave and thanks for the quick answer!
My thesis is about a phase noise measurement device I developed, which primary 
use is to measure phase noise/jitter of audioband DACs. I probably won't be 
focussing on jitter too much but would like to know if there even is one 
accepted standard definition. 
For example, in the different definitions I found so far, the seperation between 
jitter and wander sometimes is given to be at 1Hz, 10Hz and sometimes just mushy 
definitions like "very low frequencies"...
I doubt it is that important for my thesis anyway, but I'd really like to know 
for myself, so if anyone has a pointer for me it would be greatly appreciated!

> 
> 
> 
> Von: "Dave Brown" <tractorb at ihug.co.nz>
> Datum: 17. April 2014 11:21:25 MESZ
> An: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
> Betreff: Re: [time-nuts] Jitter Definition
> Antwort an: Discussion of precise time and frequency measurement 
<time-nuts at febo.com>
> 
> 
> It depends on what your thesis is all about- you could try some of the ITU 
documents for 'official' definitions but these may or may not be relevant to 
your thesis.
> DaveB, NZ
> 
> ----- Original Message ----- From: "HagaaarTheHorrible" <hagaaar587plus7 at googlemail.com>
> To: <time-nuts at febo.com>
> Sent: Thursday, April 17, 2014 2:54 PM
> Subject: [time-nuts] Jitter Definition
> 
> 
>> Hello there,
>> 
>> I tried searching the archives (and google, IEEE, NIST, ITU), but didn't 
really find a satisfying answer, so I thought I'd ask directly.
>> 
>> In short:
>> Is there any kind of standard definition for Jitter which is commonly 
accepted?
>> 
>> I (think I) understood Jitter and phase noise by now, yet I need to give some 
references in my bachelor's thesis, so I'm looking for a definition. So far I 
haven't found a real definition of the different "types" (RMS,p2p,c2c,...) and 
components(RJ,DJ) of Jitter, but I guess there must be some kind of accepted 
standard!?
>> If anyone could point me to some "official sources" which are "accepted in 
the industry", I'd be very grateful.
>> 
>> Thanks in advance and best regards
>> 
>> Hag
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there. 
> 
> 
> 

------------------------------

Message: 2
Date: Fri, 18 Apr 2014 06:09:14 -0700
From: Jim Lux <jimlux at earthlink.net>
To: time-nuts at febo.com
Subject: Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
Message-ID: <535123FA.1030704 at earthlink.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

On 4/17/14, 11:09 AM, Lester Veenstra wrote:
> The classic DIY test of material for RF use is give it 60 seconds in a
> microwave oven.
> If it gets warm, it?s not a good candidate.
>

that's fine if you're looking for a gross measure of suitability.

If you're concerned about things like dielectric constant or tenths of a 
dB, that's probably not as good a test.

That is, getting warm in a microwave is a sign of "certainly not 
suitable", but not getting warm is not a sign of suitable.

------------------------------

Message: 3
Date: Fri, 18 Apr 2014 08:00:01 -0700 (PDT)
From: Robert Roehrig <k9eui at yahoo.com>
To: timenuts <time-nuts at febo.com>
Subject: [time-nuts] quartz clock/watch question
Message-ID:
	<1397833201.64991.YahooMailNeo at web181002.mail.ne1.yahoo.com>
Content-Type: text/plain; charset=us-ascii

When a quartz watch or clock is assembled, what method is used to get it as 
accurate as possible?

------------------------------

Message: 4
Date: Fri, 18 Apr 2014 10:12:46 -0400
From: Bob Camp <lists at rtty.us>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] time-nuts Digest, Vol 117, Issue 61
Message-ID: <E7C598ED-8903-4C55-AB96-ED5875523ECD at rtty.us>
Content-Type: text/plain; charset=windows-1252

Hi

The dividing line between wander and jitter is a ?legal" one rather than a 
physics one. It?s a breakpoint in a spec where the treatment of the noise 
changes from ?do this? to ?do that?. In most cases you pass wander and you 
attenuate jitter. Different specs put the line at different points based on 
hoped for system performance. 

Bob

On Apr 18, 2014, at 9:17 AM, HagaaarTheHorrible <hagaaar587plus7 at googlemail.com> 
wrote:

> Hi Dave and thanks for the quick answer!
> My thesis is about a phase noise measurement device I developed, which primary 
use is to measure phase noise/jitter of audioband DACs. I probably won't be 
focussing on jitter too much but would like to know if there even is one 
accepted standard definition. 
> For example, in the different definitions I found so far, the seperation 
between jitter and wander sometimes is given to be at 1Hz, 10Hz and sometimes 
just mushy definitions like "very low frequencies"...
> I doubt it is that important for my thesis anyway, but I'd really like to know 
for myself, so if anyone has a pointer for me it would be greatly appreciated!
> 
> 
> 
> 
> 
> 
>> 
>> 
>> 
>> Von: "Dave Brown" <tractorb at ihug.co.nz>
>> Datum: 17. April 2014 11:21:25 MESZ
>> An: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
>> Betreff: Re: [time-nuts] Jitter Definition
>> Antwort an: Discussion of precise time and frequency measurement 
<time-nuts at febo.com>
>> 
>> 
>> It depends on what your thesis is all about- you could try some of the ITU 
documents for 'official' definitions but these may or may not be relevant to 
your thesis.
>> DaveB, NZ
>> 
>> ----- Original Message ----- From: "HagaaarTheHorrible" <hagaaar587plus7 at googlemail.com>
>> To: <time-nuts at febo.com>
>> Sent: Thursday, April 17, 2014 2:54 PM
>> Subject: [time-nuts] Jitter Definition
>> 
>> 
>>> Hello there,
>>> 
>>> I tried searching the archives (and google, IEEE, NIST, ITU), but didn't 
really find a satisfying answer, so I thought I'd ask directly.
>>> 
>>> In short:
>>> Is there any kind of standard definition for Jitter which is commonly 
accepted?
>>> 
>>> I (think I) understood Jitter and phase noise by now, yet I need to give 
some references in my bachelor's thesis, so I'm looking for a definition. So far 
I haven't found a real definition of the different "types" (RMS,p2p,c2c,...) and 
components(RJ,DJ) of Jitter, but I guess there must be some kind of accepted 
standard!?
>>> If anyone could point me to some "official sources" which are "accepted in 
the industry", I'd be very grateful.
>>> 
>>> Thanks in advance and best regards
>>> 
>>> Hag
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there. 
>> 
>> 
>> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

------------------------------

Message: 5
Date: Fri, 18 Apr 2014 08:43:53 -0700
From: Chris Albertson <albertson.chris at gmail.com>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] Measuring the accurcy of a wrist watch
Message-ID:
	<CABbxVHuGHW=goO5rxbJhOsJLspYfRXpt+shPC2AzrWwFX_0jiw at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

On Thu, Apr 17, 2014 at 11:12 PM, Hal Murray <hmurray at megapathdsl.net>wrote:

>
>
> Steel makes very good springs.  Are there any non-magnetic materials that
> are
> close?
>

I think they can use some kind of non-magnetic stainless steel

Also this might be a moot point because I got a good strong signal by
placing the watch on top of the guitar strings.  I did not have to restring
the guitar.   The wall clock works even some inches away.  You don't have
to get really close to the magnets.   If you were building a sensor, just
use a plain iron core and 1/4 pound of #40 wire

>
>
-- 

Chris Albertson
Redondo Beach, California

------------------------------

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