REFLECTOR: Radio weak and scratchy

[Dave Philipsen]

Brian Michalk wrote:
> I found a good primer on SWR, and it shows how to build one for what 
> looks like less than $5.
> http://ludens.cl/Electron/swr/swr.html
>
> However, If it indicates bad SWR, so what?  How would the problem get 
> fixed?  If the problem is in the antenna, it seems to me like he needs 
> a way to check for problems external to the radio.  Something like a 
> fox and hound to see what's happening to the radiated signal along the 
> path of the cable.
>
> A TDR (time domain reflectometer) would locate where a cable break or 
> mismatched impedance is, but is out of my league in terms of equipment.
> http://en.wikipedia.org/wiki/Time-domain_reflectometer
>
As I mentioned previously, I have an MFJ-259B antenna analyzer.  While 
it is certainly not a high-end unit, it does a pretty good job for the 
price (under $300).  Here's an excerpt from a catalog description:

/MFJ-259B gives you a complete pictures of your antennas performance. 
You can read antenna SWR and Complex Impedance 1.8 to 170MHz
Read Complex Impedance as series resistance and reactance (R+jX) or as 
magnitude (Z) and phase (degrees). You can determine velocity factor, 
coax cable loss in dB, length of coax and distance to a short or open in 
feet. You can read SWR, return loss and reflection coefficient at any 
frequency simultaneously at a single glance. Also read inductance in UH 
and capacitance in pF at RF frequencies. Large easy-to-read two line LCD 
screen and side-by-side meters clearly display your information. 
Built-in frequency counter, Ni-Cad charger circuit, battery saver, low 
battery warning and smooth reduction drive tuning and much more.
Super easy to use! Just set the band switch and tune the dial -- just 
like you transceiver. SWR and Complex Impedance are displayed instantly!

Heres what you can do
Find your antennas true resonant frequency. Trim dipoles and verticals.
Adjust your Yagi, quad, loop and other antennas, change antenna spacing 
and height and watch SWR, resistance and reactance change instantly. 
You'll know exactly what to do by simply watching the display. Perfectly 
tune critical HF mobile antennas in seconds for super DX -- without 
subjecting your transceiver to high SWR. Measure your antennas 2:1 SWR 
bandwidth on one band, or analyze multiband performance from 1.8 to 
170Mhz! Check SWR outside the ham bands without violating FCC rules. 
Take the guesswork out of building and adjusting matching networks and 
baluns. Measure distance in feet to a short or open in faulty coax. 
Measure length of a roll of coax, coax loss, velocity factor, impedance. 
Measure inductance and capacitance. measure resonant frequency and 
approximate Q of traps, stubs, transmission lines, RF chokes, tuned 
circuits and baluns. Adjust your antenna tuner for a perfect 1:1 match 
without creating QRM. And this is only the beginning! the MFJ-259B is a 
complete ham radio test station including -- frequency counter, RF 
signal generator, SWR Analyzer, RF resistance and Reactance Analyzer, 
Coax Analyzer, Capacitance and Inductance Meter and more!/

I don't work for MFJ or sell for them.  Just relaying information that 
might prove helpful.  This unit costs less than one-third of the price 
that Garmin charged to "realign something".

-- 
Dave Philipsen
Velocity STD FG
N83DP