On Fri, Mar 8, 2024 at 07:47 PM, Peter Voelpel wrote:
And a Q of 5-6 with Pi-L is sufficient where 9 with a simple Pi might not be sufficient for harmonic suppression.
With Pi-L you don?t need 1/2" coil tubing and multiple band switch sections in parallel with a 3CX6K
?
73
Peter
##? Nice try....still does not work on 40-10m.?
On 40m, min overall network Q that can be used with a PI-L? is? 8? ? (This is all based on having the MIN C1 being at least 14 pf).?
On 30m, min Q is? 10
On 20m, min Q is? 12
On 17m, min Q is? 12
On 15m, min Q is? 12
On 12m, min Q is? 9
On 10m, min Q is? 16
?
Your concept will work on 160m, with the lowest Q being? 5.... albeit? 56.65 uh required....which is looney tunes.? That would require a? huge chunk of? 8/10 ga? airdux.?
Your concept will work on 80m, with the lowest Q being? 5....albeit? 27.35 uh required.?
Then u still have that stupid L coil that has to be bandswitched...which requires one extra wafer....and it needs to be 1/4"? tubing.?
The bigger tubing would still be required on 40 -10m.?
?
I can understand the concept, and tested it on the bench.? But the bench tests jive 100% with the software.? ?The problem is, the 3x6 tube has? 42 pf? (between anode to grid)...and the above calcs are also? using the extra .6 uh pre-coil installed too.? With that removed, it all gets much worse.?
I checked my old notes.... and years ago thought.....'why not use a PI-L, but with a lot lower Q'.? Nice try on my part, but it does not work with the 3x3 /10/15/20.? ?All those tubes have too much anode to grid C when installed in the socket.?
It works on the alpha table top amps.... (on 80-15m only) with the small tubes they used, which have very low anode to grid C.?
And that pre-coil trick only works? on tubes that do NOT require a parasitic suppressor.?
?
The best I can come up with? is the simple PI network, with the Q of 9 on all bands.? ?The tube already has 6 db of 2nd harmonic attenuation ..then toss in the? slightly higher tuned input Q, and? the output tank Q of 9,? trust me, harmonic suppression is more than adequate.? ?Then toss in the ants provide an additional 9-13 db of harmonic attenuation.?
On? SSB, the 2nd harmonic will be double the BW. ( 6 khz).? ?3rd is? 9 khz .? 4th is 12 khz.? ?Nobody can copy harmonics of ssb signals.? On 40m ssb, all the harmonics are not only? stretched, they are also on the wrong sideband.? If on any freq > 7175 khz, the 2nd harmonic is above 20m band.?
?Side note, copper tubing in? 1/4" - 3/8" - 1/2"? is cheap? in the plumbing section of Home depot? ( aisle 16).? Cheap to silver plate too...with the cool-amp goop.?
End of rant.?
?
Jim? VE7RF
