[time-nuts] Antenna problems

Sun Aug 22 17:29:31 UTC 2010

Thanks Mark & David for the tips

Peter, DG4EK


----- Original Message ----- 
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To: <time-nuts at febo.com>
Sent: Sunday, August 22, 2010 2:00 PM
Subject: time-nuts Digest, Vol 73, Issue 95


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> Today's Topics:
>
>   1. Antenna problems (Peter Krengel)
>   2. Re: Antenna problems (Mark J. Blair)
>   3. Re: Antenna problems (David Bobbett)
>   4. Re: Phase noise measurement (was -  no subject) (dk4xp at arcor.de)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 22 Aug 2010 04:15:26 +0200
> From: "Peter Krengel" <krengeldatec at gmx.de>
> Subject: [time-nuts] Antenna problems
> To: <time-nuts at febo.com>
> Message-ID: <8A8FA241387E4BDBA95D68DA228A4597 at xpserver>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi group,
>
> Warren found out that the signals  TB gets out of my small ceramic typ
> antenna are too weak. They are too noisy.
>
> So I had a look for a good antenna and found some commercial typs called
> choke-ring antenna. As they are really expensive is there any DIY solution
> avaliable?
>
> I have a lathe so its possibly to machine rings if I get the dimensions...
>
> Thanks a lot making me a "nut" ;)
>
> regards
> Peter, DG4EK
>
> ------------------------------
>
> Message: 2
> Date: Sat, 21 Aug 2010 19:35:37 -0700
> From: "Mark J. Blair" <nf6x at nf6x.net>
> Subject: Re: [time-nuts] Antenna problems
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <9334AF5C-B13E-4916-AD59-30FB646FB1D8 at nf6x.net>
> Content-Type: text/plain; charset=us-ascii
>
>
> On Aug 21, 2010, at 7:15 PM, Peter Krengel wrote:
>> Warren found out that the signals  TB gets out of my small ceramic typ
>> antenna are too weak. They are too noisy.
>>
>> So I had a look for a good antenna and found some commercial typs called
>> choke-ring antenna. As they are really expensive is there any DIY 
>> solution
>> avaliable?
>
> I think that the TBolt wants a fair amount of gain up at the antenna, 
> based on the signal levels it reported from the roof antenna feed at work 
> (we're in the GPS industry) compared to what I normally see from our 
> "normal" GPS receivers. Mine is installed at home with a Lucent/Alcatel 
> +26dB antenna which I believe was primarily intended for use at cellular 
> base stations, and my TBolt sees nice, strong signals from it with about 
> 9m of feedline. These antennas are all over eBay, both used and unused, 
> and with or without the pole mount. The TBolt will power them with its +5V 
> bias. An eBay search for "lucent gps antenna" should turn up a few 
> antennas and several mounts at the moment.
>
> There are probably many other antennas that will work fine. I'd suggest 
> looking around for active GPS antennas meant for outdoor fixed 
> installations (they'll generally have a somewhat pointy radome to keep 
> snow, birds, etc. from accumulating on them), powered by +5VDC, and with 
> at least 20dB of gain. Used ones can be cheap.
>
>
> -- 
> Mark J. Blair, NF6X <nf6x at nf6x.net>
> Web page: http://www.nf6x.net/
> GnuPG public key available from my web page.
>
>
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sun, 22 Aug 2010 09:58:59 +0100
> From: David Bobbett <d.bobbett at tiscali.co.uk>
> Subject: Re: [time-nuts] Antenna problems
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <4C70E6D3.7040503 at tiscali.co.uk>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>  Mark is absolutely right about this Peter, the Tbolt receiver is
> 'deaf' by modern standards. In fact I seem to remember the Tbolt
> documentation specifically mentions the use of a +26dB aerial. I use a
> +16dB Lucent unit on top of the TV pole here in Central England and
> although there is enough signal, the mapping feature of Lady Heather
> shows that I am operating about 10dB below the expected signal level.
> I'll be buying a +26dB aerial very shortly so that I can upgrade the
> installation when it next gets serviced.
>
> You can get them from eBay for less than 30 Euros, they are purpose
> designed for use outside and I have never had any problem buying from
> China. I bought all my Tbolt gear from 'fluke.l' without a hitch and
> would recommend him.
>
> David
>
>
>
>
> On 22/08/2010 03:35, Mark J. Blair wrote:
>> On Aug 21, 2010, at 7:15 PM, Peter Krengel wrote:
>>> Warren found out that the signals  TB gets out of my small ceramic typ
>>> antenna are too weak. They are too noisy.
>>>
>>> So I had a look for a good antenna and found some commercial typs called
>>> choke-ring antenna. As they are really expensive is there any DIY 
>>> solution
>>> avaliable?
>> I think that the TBolt wants a fair amount of gain up at the antenna, 
>> based on the signal levels it reported from the roof antenna feed at work 
>> (we're in the GPS industry) compared to what I normally see from our 
>> "normal" GPS receivers. Mine is installed at home with a Lucent/Alcatel 
>> +26dB antenna which I believe was primarily intended for use at cellular 
>> base stations, and my TBolt sees nice, strong signals from it with about 
>> 9m of feedline. These antennas are all over eBay, both used and unused, 
>> and with or without the pole mount. The TBolt will power them with its 
>> +5V bias. An eBay search for "lucent gps antenna" should turn up a few 
>> antennas and several mounts at the moment.
>>
>> There are probably many other antennas that will work fine. I'd suggest 
>> looking around for active GPS antennas meant for outdoor fixed 
>> installations (they'll generally have a somewhat pointy radome to keep 
>> snow, birds, etc. from accumulating on them), powered by +5VDC, and with 
>> at least 20dB of gain. Used ones can be cheap.
>>
>>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Sun, 22 Aug 2010 13:23:10 +0200 (CEST)
> From: dk4xp at arcor.de
> Subject: Re: [time-nuts] Phase noise measurement (was -  no subject)
> To: time-nuts at febo.com
> Message-ID:
> <19147149.1282476190211.JavaMail.ngmail at webmail18.arcor-online.net>
> Content-Type: text/plain; charset=ISO-8859-1
>
>
>
>
>> > NXP   BF862, available from  digi-key.
>> >
>> Don't these devices have relatively high flicker noise?
>
> 1/f corner is well below 100 Hz. Look at the noise voltage plots of
> that audio guy I cited.
>
> My results for the BF862 were the same shape, absolutely somewhat worse
> in amplitude because I wanted a differential input and less FETs in 
> parallel.
>
> Most of my BF862 had abt. 12 mA IDss, btw.
>
>> The input capacitance is relatively noncritical in this application
>> (phase noise measurement) since it is shunted by the much larger output
>> capacitance of the low pass filter at the mixer IF port.
>
> The 300 pF Cin of a single  IF3602 could seriously detune the input low 
> pass
> and the 200 pF feedback capacitance in a stage with substantial voltage
> gain would destroy the bandwidth unless cascoding is provided.
>
> I think, I'll test some Analog Devices ADA9848-2 in parallel. It's hard to 
> beat
> that combination of noise, 1/f, bandwidth, offset stability and price.
>
> Such a preamp can be used as an add-on to a scope or FFT-Analyzer, too,
> to characterize power supplies, references or oscillator bias circuits.
> It's fun to enter 60 dB probe gain into a scope channel menu
> and still see usable traces  with uV/div scale factors.
> ( with a low pass, of course)
>
> There are noise nuts, too!  ;-)
>
> Gerhard
>
>> > One heroic effort for  audio is here:
>> > http://www.diy-audio-engineering.org/index.php?board=2.0   HPS5.1
>
>
>
>
>
>
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