I don't have a schematic anymore...so I'm winging it! Keep in mind that the 509
is a fairly quite receiver. The signals tend to stand out with good
sensitivity. I was dumb to sell it.
Let me ramble.
1. We need to assertain if you have a sensitivity problem or a problem that is
just affecting the S-meter. (I think you have already narrowed it down to the
frontend with your probe testing.)
2. How does the 509 compare with the 817 on the other bands? Are they all poor?
3. If the other bands are good, I would look for a bandswitch problem or a
connector issue. It seems to me the boards do plug in.
--
Joe Hutchens ( AJ8MH )
http://webpages.charter.net/aj8mh-radio/
---- Roscoe Primrose <roscoe@aiko.com> wrote:
> On 1/28/09 10:45 PM, Joe Hutchens wrote:
> > I've had the antenna selection switch on the back get dirty. Cleaning it
> > solved my problem...back when I had a 509.
> >
>
> Thanks for the idea. Bypassed the switch, no big deal since I'm not
> using a separate receive antenna, no change in sensitivity...
>
> OK, who's next ;-)
>
> 73s, AJ4LL
>
> > --
> > Joe Hutchens ( AJ8MH )
> > http://webpages.charter.net/aj8mh-radio/
> >
> > ---- Roscoe Primrose<roscoe@aiko.com> wrote:
> >
> >> My Argonaut 509 seems to have a serious receiver sensitivity problem.
> >> The other night when 80M was fairly noisy, I was getting noise at S6-S8
> >> on an FT817, hooked the same antenna to the 509, an even with the RF
> >> gain all the way up, the S-meter baorly moved, if at all. RF noise is
> >> generally not enough to move the S-meter, and I've made several easily
> >> understandable QSOs with no motion of the S-meter. The S-meter is
> >> working, with very strong signals it does occasionally get up to S-9. I
> >> originally thought the problem was the first stage dual-gate MOSFET, but
> >> I'm pretty sure that's not the problem at this point. When
> >> troubleshooting the first stage MOSFET, when I hooked a DMM lead to gate
> >> 1 I get a stronger signal (not just noise, but signal as well) from the
> >> test lead than I do from the antenna connected to the unit. On the RF
> >> front-end board, the antenna signal goes through an input cap, a
> >> transformer/cap combination that's a 9MHz trap (VFO), through a tuned
> >> transformer which is part of the pre-selector, through a coupling cap,
> >> and to gate1 on the MOSFET. Connecting the DMM lead directly to gate1
> >> causes an increase in signal& noise, connecting it anywhere before the
> >> coupling cap results in no change in signal level. I changed the
> >> coupling cap, but there was no change in performance.
> >>
> >> Anyone familiar enough with the front-end on these rigs to have an idea
> >> as to what I can check next?
> >>
> >> Thanks, AJ4LL
> >>
> >> --
> >> "The tree of liberty must be refreshed from time to time with the blood of
> >> patriots and tyrants. It is it's natural manure."
> >> Thomas Jefferson, 1787.
> >>
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>
>
> --
> "The tree of liberty must be refreshed from time to time with the blood of
> patriots and tyrants. It is it's natural manure."
> Thomas Jefferson, 1787.
>
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