Cantanna NH-31 versus NH-31A (s/b HN-31)

[JF]

On 8/21/05 Robert Myers wrote:

>Can someone tell me what the difference is between the NH-31 and the
>NH-31A versions of the Cantenna?
>Also, I have an empty NH-31....should I disassemble it and clean those
>copper bands that contact the big carbon resistor, or does anyone ever
>bother with that?


Typo, I think - should be "HN-31" instead of "NH-31".

The -31 has a small box on the lid with an extra jack (RCA) for
outputting a DC voltage proportional to RF input power which could be
used for monitoring on a meter;  however, the voltage is not linear
and also varies with frequency, so it's only a rough indication and not
very useful.  Picture at:
http://www.radiomuseum.org/dsp_modell.cfm?model_id=73898

The -31A did not have that box, only a SO-239 jack on the lid for the
coax input. Picture at:
http://www.radiomuseum.org/dsp_modell.cfm?model_id=73924

DO NOT burnish the 3 contact bands on the ends of the power resistor:
the originals were silver-plated brass and should not have corroded if
they were submerged in oil - if you use anything abrasive it will take
off the thin silver plating.  If they are in fact plain copper bands,
then they are not original.

If there is some kind of deposit on the sides contacting the resistor
they may have been installed incorrectly, or the wrong kind of oil might
have been used, or they may have been overheated.  I don't know if
there's a silver polish that will remove tarnish without damaging the
silver plate - you might ask at shops that repair jewelry/tableware or
deal in antique coins.

If they are damaged you could make some new thin brass strips and ask
an electroplating shop to silver-plate them.  Before installing, shape
them according to the directions in the assembly manual.

73

John    KE5ZB

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html