Use wide strap from bandswitch COM contact.....over to the load cap. If
wire is used instead, it will add a ton more L.
Think of it this way, the entire 10m portion of the coil PLUS the 10m tap
to bandswith, then through the bandswitch...and back to the load cap is ur
total 10m inductance.
Wide strap has miniscule inductance vs wire. What you need to do is to
dump as much stray C as possible...and ditto with the bandswitch to load
cap L.
The PI network can be viewed as 2 x L networks back to back. The 1st L
network will step the plate load Z down to aprx 20 ohms. The 2nd L network
will step the 20 ohms UP to 50 ohms. The shunt cap in any L network is
always at the higher Z end. The 20 ohm point is just before the load
cap. That last tiny bit of coil + the larger value load cap is the step
up, 2nd L network. The load cap of course, is at a 50 ohm point.
The plate block cap assy will have more current through it, vs lower freqs.
Typ, the tube C will make up 90% of the total, required C1 tune C on 10m.
Think of it as the C1 tune cap being a tiny variable padder, in parallel
with the tube C.
The tube C (anode to chassis) is electrically in parallel with the C1 tune
cap. Problem is, the plate block cap is between em. All that normal anode
to chassis RF current now also has to flow through the plate block assy.
This effect is only on upper HF / 6M.
Jim VE7RF
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|