[TenTec] Argosy 525

[Dr. Gerald N. Johnson]

I think the tentec of that era that preceded the Corsair and Corsair II
that used a double gate mosfet mixer rather than a diode ring and super 
sturdy RF and IF amp stages didn't do as well in strong signals. Though 
if the diodes for the switching diodes were poorly chosen their loss 
could cause the band pass filters to be narrowed and those very diodes 
to not handle strong signals. They shouldn't have affected drift, 
possible that's the PTO in need of lubrication or rebuild.

You don't need all the available RF gain on 80 and 40 and you make it a 
lot easier on the receiver by backing off on the RF gain control so it 
can handle the static crashes much better.

The wrong diodes will not improve the diode switches. True PIN diodes 
work measureably better than 1N4007 and 1N4007 work better than 1N914. 
There was an article about that in VHF Communications years ago that I 
found on an New Zealand ham's web page (I do have the original magazine 
too). http://homepages.ihug.co.nz/~jaking/TS-940_02.htm#_Toc155846465

Googling intermod in switching diodes turned up many ham and deep 
technical references.

73, Jerry, K0CQ

On 8/1/2010 1:52 PM, Shawn Upton wrote:
> Speaking of the Argosy 525 analog version, I have a question.  I
> bought one a decade ago, and made a few contacts on it, but made the
> mistake of doing the upgrades (mixer diodes I think, certainly the
> diode switches, and some filtering in the audio section).  Afterwards
> it seemed drifty, power would drop off at band edges, and worse, the
> front end seemed to not handle signals like my Yaesu FT-840.  Most
> likely all my fault and not necessarily due to the mods (but it gives
> you the background).
>
> So, my question is, can the 525 handle the big(ger) signals too, or
> does it need extensive rework to do so?  I'm not a contester, but
> static crashes and nearby signals are commonplace on 80/40.  I'm just
> wondering what can be expected if I go through the rig and restore to
> stock or redo the mods a second time (maybe I got the wrong diodes).
>
> Shawn Upton, KB1CKT
>
>
>
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