[time-nuts] mixers for frequency measurement

Don Latham djl at montana.com
Thu Jan 19 15:31:57 EST 2012


Oh dear I had the wrong idea. Thought PIN's were designed for switching.
There is a breed of "ultra-fast" diode for protection in MOSFET
switching circuits like h-bridges. Any better?
Don

Bob Camp
> Hi
>
> PIN = designed to be slow (not so good an idea)
> Avalanche = reverse breakdown (not a good conduction mode, noisy)
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Don Latham
> Sent: Thursday, January 19, 2012 2:22 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] mixers for frequency measurement
>
> Soooo, PIN diodes? avalanche?
> Don
>
> Bob Camp
>> Hi
>>
>> Complicating the matter - the time it takes for the junction to go
>> from
>> full
>> on to full off also contributes to the noise. An ideal mixer would
>> switch
>> instantaneously.... It's always a tradeoff between various noise
>> sources.
>>
>> Bob
>>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]
>> On
>> Behalf Of ed breya
>> Sent: Thursday, January 19, 2012 12:36 PM
>> To: time-nuts at febo.com
>> Subject: [time-nuts] mixers for frequency measurement
>>
>> Yes, they are Schottkys, just like the ones used in most mixers - but
>> much bigger and slower. They would have to be properly impedance
>> matched, and could be driven to higher power levels, with higher
>> diode conductance, so (I think) much lower noise. Of course,
>> amplifying up to higher power will add noise, so it's not "free" in
>> that respect.
>>
>> Ed
>>
>> Stefan wrote:
>> 1N5817 are schottky diodes. Wouldn't they saturate much earlier than
>> a 2N2222A? If saturation is the right word with a schottky diode...
>>
>> I wrote:
>>  > 5 or 10 MHz could be made even better. I wonder how a ring of
>> matched
>>  > 1N5817s would work at saturated power levels - maybe +20 dBm or so.
>>
>>
>>
>>
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>
>
> --
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> R. Bacon
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
>
>
>
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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com






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