Re: Topband: Cutting Delay Lines
Thanks Wes and thanks all who replied directly . I've received some very good information. I should be good to go Ed N5DG On 7/13/2016 9:45 AM, Wes Stewart wrote: I have no idea how critical the phase shift is for your design, but I'll offer a couple of caveats. Unless you have characterized your cable, you don't know Vf or Zo. Furthermore, both of these vary with frequency. These effects are probably in the noise and with your instrumentation you will never know the difference. That said, finding a phase length at a multiple frequency doesn't necessarily predict the phase length at the design frequency. On 7/12/2016 8:04 PM, Ed Stallman wrote: I'm cutting a 40 degree and a 20 Degree Delay line using RG6 at 1.83MHz for a receive 8 circle array ! I know the velocity factor of the RG6 and have all the math worked out . After doing the calculations and trimming the RG6 back , I'm looking for X=0 at 4.118 MHZ ( or as close to X=0 as possible ) Now to my question: I'm finding the X=0 to be a broad range , looks to be + - 50 KHz on my MFJ 259b .. I know , I need a better analyzer ... Can I double of quadruple the frequency to narrow the span where X=0? Thanks Ed N5DG --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Cutting Delay Lines
In principle, any *odd* multiple of 4.118 MHz (the frequency where the cable is 1/4 wavelengths long) will work when the far end of the cable is open-circuited. If you short-circuit the far end of the cable, then look for X=0 at *even* multiples of 4.118 MHz. 73, John W1FV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Ed Stallman Sent: Tuesday, July 12, 2016 11:05 PM To: Topband Subject: Topband: Cutting Delay Lines I'm cutting a 40 degree and a 20 Degree Delay line using RG6 at 1.83MHz for a receive 8 circle array ! I know the velocity factor of the RG6 and have all the math worked out . After doing the calculations and trimming the RG6 back , I'm looking for X=0 at 4.118 MHZ ( or as close to X=0 as possible ) Now to my question: I'm finding the X=0 to be a broad range , looks to be + - 50 KHz on my MFJ 259b .. I know , I need a better analyzer ... Can I double of quadruple the frequency to narrow the span where X=0? Thanks Ed N5DG --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Cutting Delay Lines
I'm cutting a 40 degree and a 20 Degree Delay line using RG6 at 1.83MHz for a receive 8 circle array ! I know the velocity factor of the RG6 and have all the math worked out . After doing the calculations and trimming the RG6 back , I'm looking for X=0 at 4.118 MHZ ( or as close to X=0 as possible ) Now to my question: I'm finding the X=0 to be a broad range , looks to be + - 50 KHz on my MFJ 259b .. I know , I need a better analyzer ... Can I double of quadruple the frequency to narrow the span where X=0? Thanks Ed N5DG --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _ Topband Reflector Archives - http://www.contesting.com/_topband
