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.
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