On Sat, Mar 9, 2024 at 10:46 PM, Peter Voelpel wrote:
Sorry Jim,
?
I can?t follow your calculations and for what reason a Q of <8 should not be possible on 40m.
?
Lets assume a YC179 with 6kV on the anode and 2.75A anode current.
Tube output impedance will be 1.1kOhm at 10kW.
Pi-L intermediate impedance 200 ohms.
Coil currents will be about 15A.
?
Example for 160 and 40m at a Q of 6.
?
160m:
?
Ca 350pf, La 29?H, Cb 1500pf, Lb 7.65?H
?
40m:
?
Ca 90pf, La 7.5?H, Cb 380pf, Lb 1.97?H
?
3CX6000A7 has 12pf less output capacitance, at 6kV output impedance will be lower then 1.1kOhm as current will be higher and therefore La smaller , I guess a Q of 6 will be possible even on 20m with a Pi-L.
?
The whole tube family does not need a harmonic suppressor.
?
Harmonics of SSB signals can be copied. Once I did the CQ 160m contest and were phoned by a ham 120km away, he found my signal in the 80m dx window.
?
Copper / copper tubing is very expensive nowadays here and silver plating does nothing on HF.
I get more then 7 Euros for 1kg scrap copper like LDF cable leftovers.?
?
73
Peter
##? I just? plugged ur? YC-179 numbers into the GM3SEK PI-L software.? ?The YC-179 has 35 pf anode to grid C... which rises to 52 pf with grid flange bolted to chassis. I also allowed for an extra 5 pf of stray C on top of the 52 pf..( so a total of 57 pf used).? ? ?I also used ur 6 kv loaded @ 2.75 amps...and also used? your? 200 ohm image Z....and also ur? 61% eff, and used 1840 khz for the design freq.? ?And also used a 400 uh plate choke.? And also used ur 1100 ohm plate load Z....and also ur 10 kw output.??
##? This is what it spits out...for a total network Q of 6.? ( Input Q = 3.2? Output? Q = 1.0? ?L network Q =? 1.7 )? ?Coil current in L1? should be input Q X plate current or 3.2 x 2.75 =? 8.8 amps.?
C1- 215.7 pf
L1 - 35.53 uh
C2 - 1198.2 pf
L2-? 7.49 uh?
?
The above is not even close to ur calcs.? (?Ca 350pf, La 29?H, Cb 1500pf, Lb 7.65?H )? ?What are u using for software ????
.............................................................................................................................................................................................................................................................................................................................................................................................
Ok, let's try 40m (7150 khz)? and again using your numbers.?
C1-? 9.6 pf
L1 -? 9.14 uh
C2 -? 308.3 pf
L2 -? 1.93 uh?
Again, not even close to your numbers.? ? ?(?Ca 90pf, La 7.5?H, Cb 380pf, Lb 1.97?H? )? What are u using for making ur calcs ???????
A 1/4 wave shorted stub will kill all the even harmonics.... by 15-23 db.? Try listening to urself on a 2nd RX on the 2nd, 3rd, 4th harmonics..... while Tx'ing on SSB.? Say TX on LSB / USB on 7100, then listen on 14.200 and 21.300 and 28.400 mhz.?
?
Flexible Copper tubing has risen a bit in price, but is still relatively cheap.? Typ comes in 10'- 15' - 25'- 50' rolls.? And in 1/8"? to? 1.125" OD sizes....and every size in between.??
I hate the look of bare copper,? which really looks bad after several years.? ?The silver plating is cheap, and is strictly an aesthetic? thing.?
