[TowerTalk] Measuring electrical length of coax...

[Bob Nielsen]

On Thu, Jul 14, 2005 at 07:45:53PM -0500, W0UN -- John Brosnahan wrote:
> At 10:10 AM 7/14/2005, Dino Darling wrote:
> >Hello John, how do you test your lines and what equipment do you use?
> >
> >I've experimented with the MFJ 259B for stubs and phasing lines, but if it
> >is critical, I'll order lines from M2.  I'd sure like a good method that I
> >could employ myself.  Also, do you short the end of the coax or leave it
> >open.  The MFJ book lists both methods.
> 
> I am spoiled ROTTEN!  In the old days I used an HP-8405A Vector Voltmeter.
> But now I use an HP-4195 Spectrum/Network Analyzer.  I can cut a tenth inch
> off and watch the null shift by a few KHz.  It makes it TOO easy.
> 
> There are lots of ways with Antenna Analyzers and Grid Dip Oscillators, but
> once you have the expensive gear you won't go back.    ;-)

Ah memories!  I used an 8405 to phase match the T/R modules and 
transmission lines for the NASA ATS-1 satellite's VHF repeater about 40 
years ago, after all other methods I had tried gave conflicting results.  
We had ordered one for this purpose at Hughes Aircraft, but quick 
delivery was impossible unless you had a military priority (the 8405 had 
just been introduced), so the HP salesman let me borrow a demo model 
over the weekend, which was all I needed to complete the job.

73, Bob N7XY