[time-nuts] Effect of the Antenna Delay in setting in Z380!A

[Tom Holmes]

Hi Dave...

Group delay really applies to any device, and mathematically is the rate of change of phase vs. frequency. It is usually of interest for bandpass devices, but no reason it can't be used for a piece of coax. The word 'group' comes from the idea of being interested in the delay over a range, or group, of frequencies, with no large gaps being implied.

For a bandpass device, the requirement is often that the delay be constant over the bandpass range, especially for digital signals. 

If you have an instrument that can measure time intervals, such as the HP 5335 counter, you can measure your cable delay to close enough accuracy, per Bob Camp's explanation of close enough.

Tom Holmes, N8ZM

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Artek Manuals
Sent: Tuesday, March 01, 2016 4:50 AM
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] Effect of the Antenna Delay in setting in Z380!A

On 2/29/2016 11:36 PM, Andy wrote:
> Dave wrote:
>
> For those of who might care I would assume that actually taking the coax
>> and measuring the delay at 1.5GHZ would be better than relying on the
>> manufactures published specs for velocity factor.  I was going to set up
>> and measure the delay with a signal generator and  good oscilloscope (I
>> have a 7104 1GHZ scope which still shows decent signal at 1.5 GHZ)
>>
>
> Technically I think what you would want to measure is the group delay, not
> the phase delay.
>
> Andy
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If by group delay you mean the additional delays inside the Z3801A I 
would think HP/Semetricom would have taken that into account in the 
firmware and that only delay external to the Z3801A is "compensated" for ...

Dave
NR1DX

-- 
Dave
Manuals at ArtekManuals.com
www.ArtekManuals.com

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