I was just guessing, sometimes I guess wrong. Mismatched diodes in the
mixer can hurt. I really prefer in that case to break down and spend $5
on a MiniCircuits SBL-1 or SBL-1H if there's enough drive and it comes
with a matched set of diodes in the package. If there's not room
MiniCircuits makes HF mixers that are much smaller.
Not enough drive current in the PIN diodes could be a problem too.
On 8/1/2010 7:07 PM, Shawn Upton wrote:
> 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?
Usually. The PTO drive is a ball vernier that wears. Its function
depends on the preloading from the back end of the shaft and when the
balls wear a groove in the outer race the drive slips. The dial is on
the slow side of that vernier drive. Some swear there never is wear, but
the only benefit is cleaning and relubrication. TenTec won't admit what
the special grease is though. And on my Corsair II, there was a
significant groove worn in the outer race and in the inner shaft (knob
is on that one) that weren't present in the new parts.
>
> No RF gain on the Argosy. RF gain would probably be a great thing on
> 80/40 as you mentioned.
Sure would. It has helped every receiver I've ever used. Switching in an
attenuator on receive would be nearly as handy a technique, but might
take a bit of cobbling to make it work.
>
> Shawn Upton, KB1CKT
>
>
73, Jerry, K0CQ
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|