[time-nuts] Question on GPS and reference standards

Chris Albertson albertson.chris at gmail.com
Thu Dec 23 20:52:51 UTC 2010


I just looked up what it would take to build a 10:1 conjugate
regenerative divider.  This is not easy nor cheap.  The conjugate
number turn out to be f/10 and 9f/10.  9f/10 is close to f.

Question for the group?  What phase noise should be expected if a
conventional PPL was used?

I can't believe that a PLL derived 1Mhz reference is not good enough
for a 30Mhz HF transmitter.  Maybe different answer if the transmitter
were microwave

Not arguing, this is a real question.  I'm wondering how good a simple
and convention PLL is.      My problem is that I do the calculations
and it's not "real world" and I get perfect result.  Just wondering
how and what cause PPL to be not perfect and by how much.



On Thu, Dec 23, 2010 at 11:45 AM, paul swed <paulswedb at gmail.com> wrote:
> Oh I actually understand the radio.
> I was looking at the wenzel and will guess that would be quite expensive.
> This from a flea market junky.
> Regards
>
> On Thu, Dec 23, 2010 at 12:24 PM, <scmcgrath at gmail.com> wrote:
>
>> Because the Rockwell-Collins HF80 has sensitivity and selectivity which are
>>  avaialble only in Ham gear costing 7000+ definitely not in the
>> 'inexpensive' category,  it's transmit signal is also far cleaner than most
>> synthesized HF Rigs.
>>
>> So it makes sense to upgrade the reference oscillator to use this radio
>> with more modern modes such as PSK31 and coherent CW. (Occupied bandwith
>> less than 5 Hz)
>>
>> Scott
>> Sent from my Verizon Wireless BlackBerry
>>
>> -----Original Message-----
>> From: Joseph Gray <jgray at zianet.com>
>> Sender: time-nuts-bounces at febo.com
>> Date: Tue, 21 Dec 2010 22:39:38
>> To: Discussion of precise time and frequency measurement<
>> time-nuts at febo.com>
>> Reply-To: Discussion of precise time and frequency measurement
>>        <time-nuts at febo.com>
>> Subject: Re: [time-nuts] Question on GPS and reference standards
>>
>> Not knowing all the particulars and requirements, I may be off base,
>> but instead of spending money trying to frequency stabilize a 20+ year
>> old radio (HF-80), wouldn't it make more sense to spend it on a
>> modern, inexpensive HF rig? You can even get a TCXO option for some
>> rigs. This should be stable enough for most common HF data protocols.
>>
>> I assume that this is for Amateur use? If not, then my comments may not
>> apply.
>>
>> Joe Gray
>> W5JG
>>
>> On Tue, Dec 21, 2010 at 9:48 PM, Bruce Griffiths
>> <bruce.griffiths at xtra.co.nz> wrote:
>> > A conjugate regenerative divider will have  asinewave output.
>> > It only requires a mixer an amplifier or two and a couple of bandpass
>> > filters.
>> > It will have lower phase noise than all(?) alternative techniques.
>> >
>> > Bruce
>> >
>> > Tom Van Baak wrote:
>> >>
>> >> A good question for the group...
>> >> /tvb
>> >>
>> >>> Hi:
>> >>>
>> >>> I have both a GPS Frequency standard (Trimble Thunder Bolt) which
>> outputs
>> >>> the 10
>> >>> MHz reference and also the 1 PPS signal. In addition, I have a Collins
>> >>> AEU unit
>> >>> which has a 10 MHz Rubidium reference inside. Both units work well and
>> >>> produce a
>> >>> very accurate reference signal for the units that require a 10 MHz
>> >>> reference.
>> >>>
>> >>> The challenge is that I am looking for a source of a 10:1 frequency
>> >>> divider so I
>> >>> can create a 1 MHz reference for my Rockwell Collins HF-80 system. Can
>> >>> you
>> >>> suggest a source of a high quality frequency divider that outputs a
>> >>> (nearly)
>> >>> sine wave signal? We only need two units - one for production and one
>> for
>> >>> our
>> >>> development lab.
>> >>>
>> >>> The object is to provide a very accurate source of 1 MHz and 10 MHz to
>> >>> the
>> >>> various radio systems used in our disaster and humanitarian relief
>> radio
>> >>> network. When you send data, you need to be exactly on frequency.
>> >>>
>> >>> Any help would be great. Just need to be pointed in the right
>> direction.
>> >>> While
>> >>> we could try to design something to meet this objective, I am sure that
>> >>> someone
>> >>> has already done this.
>> >>>
>> >>> Thank you.
>> >>>
>> >>> Kevin
>> >>
>> >>
>> >>
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>> >
>> >
>> >
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-- 
=====
Chris Albertson
Redondo Beach, California



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