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Copyright: 1996 - 2024

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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2010, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts.

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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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