[TenTec] Argonaut 505 alignment, filter, mod?

[geoffrey mendelson]

On 1/20/2014 6:55 AM, Neil Martinsen-Burrell wrote:
> I am the proud new owner of a fine condition Argonaut 505.  I'm very happy
> to find a five band QRP rig that is happy running off a 12V battery, even
> if it is 40 years old.  I do have a few questions and this seems like the
> best place to ask.

I have a 509 which I use, so these answers should be taken with a "grain 
of salt".


> 1) The receiver seems a bit deaf on 80m ( by A/B comparing with a TS-520)
> and I wonder if the problem could be solved by following the alignment
> procedure in the manual.  I can get my hands on an oscilloscope, but I
> can't tell by looking inside what hand tools I need to do the actual
> adjustments.  What are the proper tools to perform an alignment for this
> radio? And where is a good place to get them?

Do you have the manual. It's a good place to start. You can download it 
from the TenTec website.

Many years ago there was a WorldRadio article on the mods for the 509. 
One of them was a mod to replace the dual gate mosfet in the front end. 
This improved sensitivity.  It was a simple mod, you replaced whatever 
was there with a 40673 or equivalent. The wiring was the same and then 
you realigned the radio.

Another was to add an input attenuator, because at that time, on 40m in 
the US it was too sensitive.

I have found that with the 509 on 20m and up, if I can't hear them 
booming in, I can't work them.


>
> 3) Some have suggested that an audio filter outside of the AGC loop is not
> very useful.  Comparing the schematic of the Argonaut 509 to that of the
> 505, it appears that the patch point for the audio filter on the 509 which
> is inside the AGC loop could be added to the 505 as well.  Does anyone know
> if this mod is possible or desirable?  I have seen people talk about these
> radios as collector's items and this one appears unmodified, so I would
> also welcome thoughts on when it is appropriate to make a modification like
> this.
>


Lots of hams use external audio filters. You may find one you like, you 
may not.

If it is an unmodified radio, you may have to restring the dial cord or 
replace the dial lamps.

If you plan to work 10m, make a chart of the combination of the 
frequency indicator position and the dial settings.  Preferably using a 
frequency counter. It's easier to look it up than try and figure it out.

Geoff.

-- 
Geoffrey S. Mendelson 4X1GM/N3OWJ
Jerusalem Israel.