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Finally got it all figured out.? It's a bit of a complicated mess.? There is a total of 5 different? 'Q's'? involved on the GM3SEK? PI-L spreadsheet.?

? The short of it is.... I had to maladjust the 'total network Q' (line 39) to '7.74' ......so that the 'PI network Q'? (line 82, called? 'Q0PI' ) = 6.0? ? The 'PI network Q'? ? is what Peters is using to enter his Q of 6.? This is the PI-net portion of the PI-L.?

On the GM3SEK sheet, only line 38 can be changed.? It spits out everything else.?

INPUT Q? ? =? 4.4? ( Line 83)? ( called Q1)
OUTPUT Q = 1.6? ( line 89) ( Called Q2)

Input Q + Output Q =? PI network Q.? (4.4 + 1.6 = 6.0)? ?( PI network Q on Line 82)

The L NETWORK? Q? = 1.7? ?(line 75) ( called QL)

OVERALL NETWORK Q? ( called? Q0) =? ?PI network Q + L network Q ( 6.0 + 1.7 = 7.7)?

I also used Peters 200 ohm image Z, and 1100 ohm plate load Z.? ?Then the main coil? comes out to peter's 29.0 uh.? ? I did have to maladjust the plate choke to 141.5 uh? to get the main C1 tune cap = to peter's? 350 pf.? ( the plate choke value has a big impact on the C1 cap...as the 2 are in parallel electrically.?

Software spits out 1487.2 pf for the C2 cap.? ( close to peters 1500 pf)

Software spits out 7.66 uh? ( close to peters 7.65 uh)?

?

Short of it is I'm entering...? 'overall network Q'... ..while peter is entering .... ' the PI net Q'?

?

BTW, coil current in the main coil is? INPUT Q x dc plate current.... and not PI net Q? x DC plate current.? ? (I verified this via actual measurement).? 4.4 x 2.75 dc amps? = 12.1 RF amps in the main coil.? ? ?Same deal with the simple PI network ( INPUT Q x DC plate current = coil current.)

So it's semantic at best.?
BUT, you still can't use a low Q 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

?

The lower Q concept works on 160+80m...... but not 40-10m.? The Tube C is just too great.?

?

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If it's shipped freight, it likely is dropshipped directly from the factory (Hammond). Mine was.

Steve, K0XP

On Mon, Mar 4, 2024 at 08:23 AM, NI5L wrote:

Mine went from Hammond to DigiKey and then was shipped to me.

?Hmmm, interesting...

The two I ordered (although back in 2020/2021) both drop-shipped direct to me in Texas, from Hammond in Canada)

--
73,

~Alan

Mine went from Hammond to DigiKey and then was shipped to me.

Hi Jim,

I use the formulas by Eimac and also the PIEL software depending on
what computer I use.

My values for the anode capacitors are the total values.

Any strays and tube capacitance etc. as well as inductor lead length
are not taken into account.

I guess you deducted capacitances like that of the tube from your
figures.

The current through the coil of the pi part is indeed Q*Ia where you
used 3.2 and not 6.

With a Q of 6 the current is 6*.2.75A= 16.5A.

You also used different frequencies, I used 1.8 and 7MHz but that will
not change much.

I am operator at the M/M contest station DR1A so familiar with
fighting harmonics.

But how many stubs will you connect to a multiband amplifier?

A single stub will kill some harmonics but not sufficient enough, we
use cacaded stubs made from LDF cable behind the mono band amplifiers.


I measured a YC-179 bolted to the chassis.

73

Peter

And this is copper after >40 years:

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] High Temperature in Toroid of the PI-L
network (Alpha 78)

Datum: 2024-03-10T16:29:32+0100

Von: "Jim VE7RF" <jim.thom@...>

An: "[email protected]" <[email protected]>

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. ?


Links:
------
[1] /g/ham-amplifiers/message/40324
[2] /mt/104698543/8135091
[3] /g/ham-amplifiers/post
[4] /g/ham-amplifiers/editsub/8135091
[5]
/g/ham-amplifiers/leave/12941173/8135091/773995006/xyzzy

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Hi Jim,

?

I use the formulas by Eimac and also the PIEL software depending on what computer I use.

My values for the anode capacitors are the total values.

Any strays and tube capacitance etc. as well as inductor lead length are not taken into account.

I guess you deducted capacitances like that of the tube from your figures.

?

The current through the coil of the pi part is indeed Q*Ia where you used 3.2 and not 6.

With a Q of 6 the current is 6*.2.75A= 16.5A.

?

You also used different frequencies, I used 1.8 and 7MHz but that will not change much.

?

I am operator at the M/M contest station DR1A so familiar with fighting harmonics.

But how many stubs will you connect to a multiband amplifier?

?

A single stub will kill some harmonics but not sufficient enough, we use cacaded stubs made from LDF cable behind the mono band amplifiers.

?

I measured a YC-179 bolted to the chassis.

?

73

Peter

?

?

?And this is copper after >40 years:

?

?

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] High Temperature in Toroid of the PI-L network (Alpha 78)

Datum: 2024-03-10T16:29:32+0100

Von: "Jim VE7RF" <jim.thom@...>

An: "[email protected]" <[email protected]>

?

?

?

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.?

开云体育

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 supressor.

?

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

?

?

?

?

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] High Temperature in Toroid of the PI-L network (Alpha 78)

Datum: 2024-03-09T21:33:32+0100

Von: "Jim VE7RF" <jim.thom@...>

An: "[email protected]" <[email protected]>

?

?

?

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

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As already mentioned, the physical size of L and C is meant with smaller of course.

And a Q of 5-6 with Pi-L is sufficient where 9 with a simple Pi might not be sufficient for harmonic supression.

?

With Pi-L you don?t need 1/2" coil tubing and multiple band switch sections in parallel with a 3CX6K

?

73

Peter

?

?

?

?

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] High Temperature in Toroid of the PI-L network (Alpha 78)

Datum: 2024-03-08T18:56:21+0100

Von: "Jim VE7RF" <jim.thom@...>

An: "[email protected]" <[email protected]>

?

?

?

<Pi-L is great.

<Not only the capacitors become smaller in size also the coils and band switch can be made much smaller with that far lower current through them.

?

<73

<Peter

## Not quite.? In software, or in Orr's books, on any PI-L,? BOTH the C1 and C2 caps are a lot lower value, BUT the main Coil ('L1')? is one helluva lot bigger in value. Coil has to be a lot bigger in value, since the C1 tune cap is a LOT smaller in value.? ? ?In the GM3SEK? PI / PI-L software, he uses a specific common? formulae to?arrive at the ...'image Z'.... that the PI-L initially transforms the plate load Z? down to....and is typ in the 200-400 ohm range.? Then the 200-400 ohms is transformed down to 50 ohms.? On the software? spreadsheet, the actual image Z can be manually changed to anything you want... like 100-1000 ohms.?

?

###? In both the ORR book? and GM3SEK software, the Q remains the same for both the PI and also PI-L.? Done that way, the harmonic suppression is substantially increased by using the PI-L config.? BUT the C1 + C2 values are much reduced? vs the PI ( using the same loaded tank Q)..and the main Coil (L1) is increased substantially.?

## here's the rub.? Use the PI-L config, then reduce the Q by a bunch, the C1 + C2 values? become even smaller still, BUT the main coil..L1, become even bigger in value...too big.? So you end up with a huge main coil value, but less current through it, and degraded harmonic suppression ( but still adequate), and you still have the 2nd coil (L2) to install, and tap the 2nd coil...pita.?

?

##? after running all of this several times through software, and actually testing it on the bench, I came to the conclusion, the PI-L was a wasted effort.? It's easy to test on the bench. PI or PI-L built on a spare sheet of aluminum, with a resistor on input side ( to simulate the tube's plate load Z)...and an analyzer plugged into output side.? Both caps are individually mapped out beforehand? for fractional turns on turns counter vs pf.? Calculated coil values are done via lcr meter, and taps done in the correct spots.? ?If a roller used, the fractional turns are 1st mapped out? vs turns counter.?

?

##? with tune + load caps tweaked for 1:1 swr, then compared to the mapping cheat sheet...they always come out dead on, or within? a few pf.?

?

Below is what the software spits out for PI, and also a PI-L? using 2 x different loaded Q values.??

?

##? ?3x6 tube. 7 kv loaded @ 2.5 amps.? 1.8 mhz.? ?68% eff.? PO = 11.9 kw? ?Plate load Z = 1556 ohms.? ?400 uh plate choke used.

For the PI network only, the overall network Q = 12? ?( Input Q= 10.4 )? ( output Q = 1.6)? Note Overall network Q =? input Q + output Q.? In the older arrl books, and also EIMAC, they only used the INPUT Q...and a value of 10 was common.? These days, they use total network Q...and use a value of? 12.? ?In software, only the overall network Q can be changed (but the input + output Q values are also spat out lower down in the results.?

##? FOR the PI-L config only, the overall Input Q is?also 12. (? PI network portion input Q = 9.9).? Input Q1 = 7.0? Output Q2 = 2.8? L network QL = 2.1?

.............................................................................................................................................................................................................................................................................................................................................................................................

PI config.? Overall network Q of 12? 1.8 mhz.?
C1 = 563.4? pf
L1 = 15.1 uh?
C2 = 2815.7 pf?

?

PI-L config? Same overall network Q of 12? 1.8 mhz.?

C1 =? 370 pf
L1 = 26.78 uh
C2 = 1581.8 pf
L2 =? 9.44 uh?

.................................................................................................................................................................................................................................................................................................................................................................................................

OK, now let's reduce the overall network Q down to 9.?

PI config. Overall network Q of 9.

C1= 423.4 pf
L1 =? 19.12 uh
C2 = 1839.0 pf

?

PI-L config. Overall? network Q of 9

C1 =? 252.0? pf
L1 =? 36.6 uh?
C2 =? 1283.5 uh
L2 =? 9.44 uh?

?

Ok, notice a few things here.
On the PI-L config, the L2 value remains the SAME, at 9.44 uh, whether the higher OR lower overall network Q is used.?
On the PI-L config, with the higher Q, the L1 coil value is insanely high. (26.78 uh)
On the PI-L config, with the LOWER Q, the L1 coil is now into the stratosphere. (36.6 uh).
OK, now you know why (failure prone) TORRIDS are typ used on the main coil? ( and also on the L2 coil on an alpha 77)

You folks have any idea how big the 1/4" tubing coil for the 160m portion of the tank circuit has to be? when? sky high values of L1 are used ???? ?Hint, it's just not happening.?

?

On Scotts latest 160-15m amp, I used a simple PI, and used an overall network Q of just 9.....on all bands.? ( see the PI config with the lower Q).
PI config. Overall network Q of 9.

C1= 423.4 pf
L1 =? 19.12 uh
C2 = 1839.0 pf

Done that way, his ceramic? 12-500 pf (@ 15 kv rated) vac tune cap will easily suffice for the C1 tune cap. Actual vac cap measures 12-540 pf...and they are small things.? Calculated value required at 1.8 mhz = 423.4 pf. ( vs 563.4 pf if the higher Q is used).

L1 coil only has to be increased a bit.? ( from 15.1 uh to 19.2 uh)
His ceramic 50-3000 pf @ 5 kv vac load cap is ample? for the C2 cap with the lower Q config.? ( but marginal with the higher Q config....2815.7 pf required).?
Ok, then it's dead simple, and NO padders used for either the tune or load caps..... or? having to use even? bigger tune + load caps, like a 12- 750 pf tune...and a 50-4000 pf load.? ( note I have several 50-4000 pf vac caps, and they are small things.? But my 10-1000 pf @ 15 kv motorized vac caps are big....and ditto with my plane jane 17-1000 pf @ 15 kv Jennings ceramic vac cap).?

?

His tank circuit? consists of a total of 3 x tubing coils used.?
1/2" tubing used for the 20+15M coil (and also the small value uh used between the plate block cap assy and the C1 tune cap)
3/8" tubing used for the 80+40M coil.?
1/4"? tubing used for the 160M? coil.?

Of course, in normal operation the? required 19.12 uh for 160m consist of the total of all 3 x coils in series being used.? So the actual 1/4" tubing coil for 160m is a lot lower value than 19.12 uh? ( it's 10 uh)?
On 75m, the required 9.02 uh consist of the 1/2" tubing coil? plus the? 3/8" tubing coil in series.? ?Actual 3/8" tubing coil is just? 7.3 uh
On 20m, the required? coil is just 1.72 uh .? Since we incorporated the 'pre-coil' (.6 uh between block cap and C1 tune cap)? the actual value of the 1/2" tubing coil is now 1.72 + .6 = 2.32 uh. ( Scott just happened to have a mess of 2.32 uh 1/2" silver plated tubing coils in the junk box, used in henry RF generators, so we lucked out.? Only 2 x copper tubing coils had to be fabricated...( 10 uh, made from 1/4" tubing...and 7.3 uh, made from 3/8" tubing).??

?

NOTE, when a PI-L used, on the upper bands, like 20m-10m, you can't use the lower Q value,? even with the .6 uh pre-coil installed.? The C1 values end up negative pf.? The only fix is to increase the loaded Q a lot higher than 12.? This is the problem when using large metal tubes on upper HF..( with the 24.5 pf anode to grid C on a 3x6...which rises to 42 pf, when tube plugged into the grid ring. The extra 18 pf? comes from the proximity of the lower anode fins, to the chassis below em.? ? The PI-L values? ?don't work on upper HF...unless the Q is increased by a bunch.?

?

On the simple PI network? I designed in software, a loaded Q of 9 can be used...... including 15m. It's a 160-80-40-20-15m amp.? ?The .6uh pre-coil is used so the lower Q can be used on 15m.? ?The tube's 42 pf of anode to grid C plus the .6 uh coil, form a step down L network.? That steps down the 1556 ohms plate load Z....down to just 487 ohms on 21.225 mhz.? Ok, now a practical? PI network can be used, with reasonable values.?

Harmonic suppression is ample. On upper HF, with the extra pre-coil installed it's sometimes called a L-PI? (or a L-PI-L, if a PI-L used) .? Harmonic suppression on the lower bands is more than ample.
Per the VK expert, (Owen Duffy)? any tube already has 7 db of 2nd harmonic suppression in class A.... and close to that in class AB or B. (6db).? ?Then toss in the harmonic suppression of the PI network.? Then toss in the additional suppression from the PI tuned input circuit...and it's more than ample.??

W8JI sez he measured? 50 db of? 2nd harmonic suppression on an AL-1200? on 40m...(and even more on 3rd and 4th harmonics).? ?That amp uses a simple PI network on 40-10m.? JI sez the only reason they used a PI-L on 160+80m on that amp is so smaller tune and load caps could be used.? Trade off is, he still had to pad both the tune + load caps, and use a toroid on low bands.? Exact same, identical network used on the AL-1500 + AL-1200.?

A 26.78 uh / 36.6 uh total uh for 160m if either a higher Q / lower Q,? ?PI-L network on 160m, gimme a break, not happening.? Just look at how big that 10.0 uh (1/4")? tubing coil is in the u tube video (plus the other 2 x coils).? The RF deck would have to be double the size to even fit? the oversized coils in.?

?

?

?

?

?

?

??

?

?

开云体育

Pi-L is great.

Not only the capacitors become smaller in size also the coils and band switch can be made much smaller with that far lower current through them.

?

73

Peter

?

?

?

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] High Temperature in Toroid of the PI-L network (Alpha 78)

Datum: 2024-03-07T20:03:28+0100

Von: "W7WRX" <clark@...>

An: "[email protected]" <[email protected]>

?

?

?