# How Do I Delay and Phase Match a Cable with a VVM - RF Cafe Forums

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Buzzard
 Post subject: How do I delay and phase match a cable with a VVM Posted: Wed Jun 16, 2010 7:19 am
 Lieutenant

Joined: Wed Jun 16, 2010 7:04 am
Posts: 2
I need to delay and phase match a new cable to a reference cable at a frequency of approximately 900MHz. The reference cable is about 90 feet long and I need to ensure the VVM 'phase' measurement of the cable under test is for the same wave/cycle. Is it a matter of starting at a low frequency (say 4Mhz) and gradually trimming, measuring and increasing the frequency in small steps...this could take a while to get to 900Mhz, so i'm sure someone out there has a better method.

karthik
 Post subject: Re: How do I delay and phase match a cable with a VVM Posted: Sun Jun 20, 2010 12:29 am
 Colonel

Joined: Tue Apr 11, 2006 8:13 pm
Posts: 39
Hi Buzzard,

Do you need an equivalent time delay, or the same phase?

Karthik

Buzzard
 Post subject: Re: How do I delay and phase match a cable with a VVM Posted: Mon Jun 21, 2010 5:49 am
 Lieutenant

Joined: Wed Jun 16, 2010 7:04 am
Posts: 2
I need to match the delay of the reference cable, it has an 1-5/8" EIA flange on one end and a 1-5/8" to N-type connector on the other.

karthik
 Post subject: Re: How do I delay and phase match a cable with a VVM Posted: Sun Jul 11, 2010 8:49 pm
 Colonel

Joined: Tue Apr 11, 2006 8:13 pm
Posts: 39
 Hi Buzzard,In order to phase match the cables, you would need to know the characteristics of the two cables. If you know the dielectric being used in each cable, then you can compute the 'guide' wavelength in each cable, given by, lambda_g = 300/(f*sqrt(e_r) ), where, f is in MHz and lambda_g is in meters and e_r is the relative dielectric constant of the cable. Based on this, you can compute the total phase for a given length of cable (at that frequency) since 1 lambda_g = 360 degrees. Based on this, you can phase match the two cables.I hope I have understood your question right and that this helps...Karthik

Posted  11/12/2012

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