[TenTec] Argosy 525

[Shawn Upton]

I don't have the schematic in front of me, but going by the previously given link I do recall now it being a discrete diode mixer.  Actually, I think there may be a pre-amp there too, been a while, that might be more of a buffer/matching section than a high gain block.  Will find manual when I dig up radio again.  I think I did use the prescribed PIN diodes but I'm guessing the unmatched diodes in the mixer is a problem.

I do recall the dial indicator getting sticky and not always moving.  Is that a sign of needing a PTO rebuild?

No RF gain on the Argosy.  RF gain would probably be a great thing on 80/40 as you mentioned.

Shawn Upton, KB1CKT


--- On Sun, 8/1/10, Dr. Gerald N. Johnson <geraldj at weather.net> wrote:

> From: Dr. Gerald N. Johnson <geraldj at weather.net>
> Subject: Re: [TenTec] Argosy 525
> To: tentec at contesting.com
> Date: Sunday, August 1, 2010, 7:07 PM
> 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
>