Jon,
I agree 100%!
FWIW...
I used the same method last year on a 8877 amp with the same
results....the same... 10 meters was the only band that did not come out
exact. I held off promoting this method because of the 10 meter anomaly.
Terry
Jon Ogden wrote:
>
> OK, I had promised to report back on this subject, so here goes:
>
> Back a month or two ago, I said that I was going to simulate the
> impedance of my 4-1K's cathode by using two 220 Ohm resistors from each
> cathode pin to ground and by leaving the tube in socket (driving
> impedance is 110 Ohms). I could then use my MFJ-259 to tune my input
> pi-networks.
>
> Several people here said they didn't think that would work and that you
> couldn't simulate the complex impedance of a tube with a couple of
> resistors.
>
> Well, I have to tell these experts and the rest of us that they were not
> correct. The simulation worked VERY well. After designing the input
> circuits this way, and after using the amp for a while, I am pleased to
> report that simulating the input impedance of a tube using a couple of
> resistors DOES INDEED WORK!
>
> My SWR on all bands with the exception of 10M is nearly 1:1 in at least
> some portion of the band. On 10M, the SWR is about 1.3 or 1.4:1, which
> is still fine (it's probably off because the inductance in the leads of
> the resistors is probably significant at 28 MHz). 20M might be 1.2:1 or
> so. On 40M and 15M, the SWR is absolutely flat and on 80M it is very
> good as well (perfect in some spots, but the tuning bandwidth is
> considerably less than the higher bands).
>
> So folks, it does work. Don't let the so called experts fool you. Logic
> and common sense told me it would and it does.
>
> And by the way: all my caps are fixed. The only thing I can tune are my
> inductors.
>
> 73,
>
> Jon
> KE9NA
>
> --------------------------------------------------------------------------
> Jon Ogden
>
> jono@enteract.com
> www.qsl.net/ke9na
>
> "A life lived in fear is a life half lived."
>
> --
> FAQ on WWW: http://www.contesting.com/ampfaq.html
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
> Search: http://www.contesting.com/km9p/search.htm
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|