Elecraft receiver experience

[wb7ond]

After this weekend's hamfest I was reading my new ARRL 2007 handbook to see
what might be NEW in ARRL testing of receivers, I came across this sentence
that I thought pretty well summed up my experience with my K2 receiver.

On page 10.7 3rd column  "When using a good receiver with a linear front end
and a clean LO, amateurs accustomed to receivers with poor phase-noise
performance report the impression of a seemingly emptier band with gaps
between signals -- and then they begin to find readable signals in some of
the gaps.

This whole section in the handbook reveals the "science" behind the efforts
engineers put into receiver design and why phase noise is so important for
both the receive and transmit performance.

Dick
WB7OND
"hanging around for shipment 2"
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[Brett gazdzinski-2]

 
Being a mostly tube guy, I have not read much about
phase noise.

Do tube circuits have phase noise?
Do discrete components (solid state, transistors) in
coil and cap VFO circuits have phase noise?

What is the worst source of phase noise?
What circuits have little or no phase noise?

My ears are shot, but I always thought some
of the old analog stuff sounded much cleaner
than digital stuff.

I was listening to a stronger SSB signal on the K2
not that long ago, and it had strong artifacts
up and down the band that caused hard copy on some
CW signals.
Was that phase noise?



Thanks for any info,

Brett
N2DTS

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of DickandSandy
> Sent: Monday, September 03, 2007 9:20 AM
> To: [hidden email]
> Subject: [Elecraft] Elecraft receiver experience
>
> After this weekend's hamfest I was reading my new ARRL 2007
> handbook to see
> what might be NEW in ARRL testing of receivers, I came across
> this sentence
> that I thought pretty well summed up my experience with my K2
> receiver.
>
> On page 10.7 3rd column  "When using a good receiver with a
> linear front end
> and a clean LO, amateurs accustomed to receivers with poor phase-noise
> performance report the impression of a seemingly emptier band
> with gaps
> between signals -- and then they begin to find readable
> signals in some of
> the gaps.
>
> This whole section in the handbook reveals the "science"
> behind the efforts
> engineers put into receiver design and why phase noise is so
> important for
> both the receive and transmit performance.
>
> Dick
> WB7OND
> "hanging around for shipment 2"
> _______________________________________________
> Elecraft mailing list
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> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

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[KK7P]

> Do tube circuits have phase noise?
> Do discrete components (solid state, transistors) in
> coil and cap VFO circuits have phase noise?

Oscillators have phase noise.  Properly designed -- with attention to
this -- the phase noise can be managed and made small.  Crystal
oscillators are usually the cleanest, but they also have it to varying
degrees.

The worst are oscillators with improper gain using low Q components in
the frequency determining section.  This is also a description of many
voltage controlled oscillators (VCOs) used in frequency synthesizers.
Early synthesizers used in Amateur radio products were often truly awful
in this regard.

The higher in frequency one goes, the harder it is to have low phase
noise close to the carrier being generated.  Thus, it is generally
easier to have a certain amount of phase noise 500 Hz from the carrier
at 1 MHz than it is at 1 GHz.

This is part of the reason that many radios that feature up conversion
(for general coverage) have poorer phase noise than most radios that do not.

73,

Lyle KK7P

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[Brett gazdzinski-2]

Lyle,
Thanks for the info.

Would I be right in assuming the more conversions, the
higher the phase noise, even if crystal oscillators are used?
 
In the homebrew receivers, I used B+W coil stock, which
I think has very high Q...

Brett
N2DTS

>
> Oscillators have phase noise.  Properly designed -- with attention to
> this -- the phase noise can be managed and made small.  Crystal
> oscillators are usually the cleanest, but they also have it
> to varying
> degrees.
>
> The worst are oscillators with improper gain using low Q
> components in
> the frequency determining section.  This is also a
> description of many
> voltage controlled oscillators (VCOs) used in frequency synthesizers.
> Early synthesizers used in Amateur radio products were often
> truly awful
> in this regard.
>
> The higher in frequency one goes, the harder it is to have low phase
> noise close to the carrier being generated.  Thus, it is generally
> easier to have a certain amount of phase noise 500 Hz from
> the carrier
> at 1 MHz than it is at 1 GHz.
>
> This is part of the reason that many radios that feature up
> conversion
> (for general coverage) have poorer phase noise than most
> radios that do not.
>
> 73,
>
> Lyle KK7P
>

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[N2EY]

In a message dated 9/3/07 9:34:19 PM Eastern Daylight Time,
[hidden email] writes:


> Would I be right in assuming the more conversions, the
> higher the phase noise, even if crystal oscillators are used?

It's not that simple.

A multiconversion rx with quiet oscillators can have less phase noise than a
single-conversion rx with a noisy oscillator.

>
> In the homebrew receivers, I used B+W coil stock, which
> I think has very high Q...
>

That's only one component. Good but not perfect. The key is for the entire
oscillator *circuit* to be high Q, not just one or two components.

73 de Jim, N2EY


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