[TenTec] Argonaut 509

[geoffrey mendelson]

On Nov 14, 2009, at 4:22 AM, Gary Harmon wrote:

> I bought a pickup load of old HAM stuff this week and in the pile  
> was a sad
> looking 509.  Besides the cabinet and sides unfastened, there were two
> little switches added to the front panel and one to the back.  One  
> of the
> front switches was marked CW FILTER and the one on the back was  
> marked AGC.
>
> Were these common mods or just someone's attempt to improve the radio

There were lots of mods, the most common was add an audio filter, or  
the cw filter from a later rig. My GUESS is the CW mod is an audio  
filter. Ten Tec sold one as an add-on, and the circuit was publicly  
available and easy to copy.

I seem to recall an AGC mod existing, but no details about it. You may  
be able to find it with a web search.

Other common mods were changing 10m to 30m, improving the SSB  
performance, adding an internal crystal calibrator etc.

With out the mods, the rig worked pretty well, but it does use the  
same IF filter for SSB and CW, if that bothers you, an audio filter is  
an easy add-on.

Another mod is to replace the Dual Gate Mosfet with a 3n211 or it's  
RCA equivalent. Since both are only available as old stock, there may  
be better more modern equivalents. The mod was simply unsolder the old  
one, put in the new and re-align.

The manual with all schematics, alignment instructions, etc can be  
downloaded for free from Ten Tec.

http://radio.tentec.com/file_download/140/Model+509+Argonaut+Owner+Manual.pdf

> Are these little radios still in demand?


In that condition, as a user, yes. But no Japanese collector is going  
to swap it for an OII. :-)

If you search YouTube for TenTec (or Ten-Tec) 509, you will find some  
interesting videos, include an Argo 509 Digitial (ala the 544).

Geoff.


-- 
geoffrey mendelson N3OWJ/4X1GM
Jerusalem Israel geoffreymendelson at gmail.com