[Amps] Squirrely 30L-1

[RAY FRIESS]

I'm having a similar experience with one of my 30L-1 linears.   It will tune okay on all the bands,but is squirrely on 40.   I can't find a dial spot where it will tune.  Works just fine on other bands, butI spend most of the time on 20.
 > Date: Fri, 15 Jun 2012 11:33:30 -0700
> From: jerry at tr2.com
> To: amps at contesting.com
> Subject: Re: [Amps] Squirrely 30L-1
> 
> > The first sensible step would be to measure the parasitic resistor values.
> 
> *** That would be hard.  I would have to unsolder the coils around them. 
> And I'm not convinced that the squirrely-ness is an actual VHF parasitic.
> I do have a spectrum analyzer good to 450MHz - wouldn't be too hard to
> set up some sort of voltage probe thingie to sniff the output ( without
> actually connecting to it ).
> 
>    What I *might* do is verify the grid resistors and caps, make sure that
> the grids really are well grounded.  I can measure the reactance to
> ground with my MFJ259B.  And look for RF ground loops from aged
> metal-metal connections.
> 
> > The second thing would be to accept that Chinese 811A's will never be
> > completely stable on 10-15M
> 
> *** I wonder why?  Does that caveat extend to Chinese 572B's ( Taylor et
> al )?   I might stick some American tubes in it this afternoon and see
> what
> happens.  And if the Chinese 572B's are not good, I might need to cancel
> my order with RF Parts.
> 
> >
> > The third would be the ability to understand that 2dB additional NF on
> > 10-15M might only make a difference
> *** This is certainly true :).
> 
>                       - Jerry Kaidor
> 
> 
> 
> 
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps