Topband: Checking the integrity of 75 ohm cable

[Don Moman VE6JY]

Try to find/borrow a older Tek 1502 TDR, they are inexpensive on ebay
(~$100)  and show way more detail than any of the analyzers I've tried.

73
Don VE6JY


On Fri, Oct 16, 2020 at 5:50 PM Michael Walker <va3mw at portcredit.net> wrote:

> RigExpert has a variety of Antenna Analyzers that have a built in TDRs.
>
> I highly recommend them.
>
> Mike va3mw
>
> On Fri, Oct 16, 2020 at 5:15 PM Jim Brown <jim at audiosystemsgroup.com>
> wrote:
>
> > On 10/16/2020 1:26 PM, Gary Smith wrote:
> > > What would be an easy way to tell if these
> > > coax have been damaged in some way?
> > >
> > > I do have an old MFJ-259B
> >
> > That might give you a clue if the cable is open or shorted, but it's
> > unlikely to show chewing that doesn't cause an open or short, but allows
> > water intrusion, etc.
> >
> > The best tool is a vector analyzer that includes software/firmware with
> > a very good TDR function. I use the VNWA3EC, built by hams in the UK
> > from a design by DG8SAQ, who also does both firmware and software.
> >
> > https://www.sdr-kits.net/DG8SAQ-VNWA-models
> >
> > The TDR function in this unit is really excellent, and can be used with
> > the antenna connected. The procedure is to do a very wide sweep (I
> > usually sweep 50 - 500 MHz) so that fine detail shows up clearly.
> > Software then does an inverse FFT on the sweep to get the TDR, and
> > allows the user to choose which of five different windowing functions
> > provide the clearest view of the measurement.
> >
> > There are ultra-cheap VNAs around, but I don't know the capabilities of
> > their operating software.
> >
> > One way I test my RX antennas is to use them to listen on the AM BC band
> > while I switch directions, using this FCC website to tell me who is
> > where on each frequency.
> > https://www.fcc.gov/media/radio/am-query
> >
> > 73, Jim K9YC
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