Re: Building my first amplifier. Where to start?
Its not hurting the tube.? You need to remember that this is Single side band with a duty cycle of 15 to 20 percent.? Even with heavy processor is not past 25%.??
What will the amp be used for???
This is a very common mistake made all over amplifier groups.?
Another one is Blower CFM and pressure.? All the time I see these guys saying you need X CFM or you need 300CFM!!!? That blower is to small....? I got advice from a guy that suggested I get a blower TWICE the size of the tube data sheet, Just for good measure.?
LOL
?But those ratings are for 24/7 full power at rated Plate dissipation for 8000 hours.? A ham using SSB will never need anywhere near those ratings.? Even if you ran A digital mode you still would never need broad cast ratings.
Another one is transformer current.? If the amp is for Ham use it will not need the full rating of the tube spec sheet in transformer.? Ever.?
?Its comical people buying 175lb transformers only to use the amp on side band and never even pull HALF the current its capable of.?
It should be built for its intended?purpose.. If it is meant to run Data modes at high power with long operation of a contest, I get it... over build the thing. But most of the time, the amp is just going to be used on SSB with Data or CW less frequently.
C
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Thanks for the link, im reading that as 3450v UNDER LOAD!? So unloaded he could be at near 4KV dc on a 3 KV rated tube.? Is "over volting" tubes this much typical?? Any rules of thumb to consider here i guess is my question,? Also 3KW PEP from a tube with
a 1Kw dissipation must be burning the candle at both ends.? Interesting data point!? thanks,
|
Re: Building my first amplifier. Where to start?
Yeah. His output power claims for all of his amps are out with
the birds. Pure BS.
73, Alek VK6APK
On 10/01/2024 6:03 am, desmond auld
GI0UTE wrote:
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Show quoted text
Thanks for the link, im reading that as 3450v UNDER LOAD!? So
unloaded he could be at near 4KV dc on a 3 KV rated tube.? Is
"over volting" tubes this much typical?? Any rules of thumb to
consider here i guess is my question,? Also 3KW PEP from a tube
with a 1Kw dissipation must be burning the candle at both ends.?
Interesting data point!? thanks,
|
Re: Building my first amplifier. Where to start?
Thanks for the link, im reading that as 3450v UNDER LOAD!? So unloaded he could be at near 4KV dc on a 3 KV rated tube.? Is "over volting" tubes this much typical?? Any rules of thumb to consider here i guess is my question,? Also 3KW PEP from a tube with a 1Kw dissipation must be burning the candle at both ends.? Interesting data point!? thanks,
|
The 12v rail is usually around 15 volts so the usually have dropping resistors just outside the meter where the bulb fits in. ?Measure the voltage before the dropping resistor and use a 12v bulb that fits and use whatever drop resistor you need.
On Tuesday, January 9, 2024, 10:52 AM, Bob <W4JFABob@...> wrote: Lou, 12 volts? Thanks Bob? W4JFA On Tue, Jan 9, 2024 at 10:42?AM Louis Parascondola via <Gudguyham= [email protected]> wrote:
Bob, the meter lamps are on the top of each meter.? It’s a plastic removable plate (small) that lifts out with the bulb.? The bulb runs off the control circuitry voltage.? Lou
On Tuesday, January 9, 2024, 10:11 AM, Bob <W4JFABob@...> wrote: Hi all, Just an update, we got the fan job done in my friends AL-80B amp. All is well.
I never noticed that the neither?of the meter lights work. The amp is already? put in it's place so it is a small "project" to get it out. Anyway, the schematic?that I found on line does not show the meter lights and unless I missed it, it doesn't list lights on the parts list either.
Does anyone know where the meter light voltage is picked up from and what is the bulb/lamp voltage?
If I can get this information ahead of time, I can get some LED's ready so we can pull out the amp, install the LED's and back together again.
Thanks and 73, Bob? W4JFA
|
Re: Building my first amplifier. Where to start?
This guy runs his at 3450volts with 3kw out with 60 in.
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?Hi guys.?I have pulled out my (big) plate transformer and made some measurements.? For voltage options I
have 2100 Vac, 2445Vac and 2550Vac measured with 240v ac supply (today over lunch..) as options to pick from.? The transformer is rated at 3.5 amps continuous duty at these voltages.? That is with phase 1 and phase 3 connected out of phase both on primary
and secondary.? Idle current with 240v supply was 0.3 amps. The transformer seems?very happy.?
I calculate the DC voltage to be 2970VDC, 3458 VDC and 3605VDC using a bridge rectifier circuit.? The GU43B is rated at 3 KV, so I think the lowest option will be safest, but wonder would the higher options also be “ok”, as the voltage will fall under load??
What are people's thoughts here??
On a separate note I have this 3cx30,000 3cw 30,000 that I don't need and can't really test. Would anyone be interested in it? If you can test it I would be happy to send it to you and make some sort of a deal? It's maybe more appropriate to start a new topic,
if it's ok to see things on this group?
?
?
Thanks, Des.
|
Re: Building my first amplifier. Where to start?
?Hi guys.?I have pulled out my (big) plate transformer and made some measurements.? For voltage options I have 2100 Vac, 2445Vac and 2550Vac measured with 240v ac supply (today over lunch..) as options to pick from.? The transformer is rated at 3.5 amps continuous duty at these voltages.? That is with phase 1 and phase 3 connected out of phase both on primary and secondary.? Idle current with 240v supply was 0.3 amps. The transformer seems?very happy.?
I calculate the DC voltage to be 2970VDC, 3458 VDC and 3605VDC using a bridge rectifier circuit.? The GU43B is rated at 3 KV, so I think the lowest option will be safest, but wonder would the higher options also be “ok”, as the voltage will fall under load?? What are people's thoughts here??
On a separate note I have this 3cx30,000 3cw 30,000 that I don't need and can't really test. Would anyone be interested in it? If you can test it I would be happy to send it to you and make some sort of a deal? It's maybe more appropriate to start a new topic, if it's ok to see things on this group?
?
?
Thanks, Des.
|
Does anyone verify the meter lamp voltage? I've spent a lot of time on google with no information on the voltage or replacement lamp part numbers. It looks like what Lou said it may be 12 volts but I sure would like to verify this before I get started on it.
Lou, I see 12 volts supply to the meter board?but even that diagram I have does not show the lamps. Bob
Lou, 12 volts? Thanks Bob? W4JFA
On Tue, Jan 9, 2024 at 10:42?AM Louis Parascondola via <Gudguyham= [email protected]> wrote:
Bob, the meter lamps are on the top of each meter.? It’s a plastic removable plate (small) that lifts out with the bulb.? The bulb runs off the control circuitry voltage.? Lou
On Tuesday, January 9, 2024, 10:11 AM, Bob <W4JFABob@...> wrote: Hi all, Just an update, we got the fan job done in my friends AL-80B amp. All is well.
I never noticed that the neither?of the meter lights work. The amp is already? put in it's place so it is a small "project" to get it out. Anyway, the schematic?that I found on line does not show the meter lights and unless I missed it, it doesn't list lights on the parts list either.
Does anyone know where the meter light voltage is picked up from and what is the bulb/lamp voltage?
If I can get this information ahead of time, I can get some LED's ready so we can pull out the amp, install the LED's and back together again.
Thanks and 73, Bob? W4JFA
|
Lou, I see 12 volts supply to the meter board?but even that diagram I have does not show the lamps. Bob
Lou, 12 volts? Thanks Bob? W4JFA
On Tue, Jan 9, 2024 at 10:42?AM Louis Parascondola via <Gudguyham= [email protected]> wrote:
Bob, the meter lamps are on the top of each meter.? It’s a plastic removable plate (small) that lifts out with the bulb.? The bulb runs off the control circuitry voltage.? Lou
On Tuesday, January 9, 2024, 10:11 AM, Bob <W4JFABob@...> wrote: Hi all, Just an update, we got the fan job done in my friends AL-80B amp. All is well.
I never noticed that the neither?of the meter lights work. The amp is already? put in it's place so it is a small "project" to get it out. Anyway, the schematic?that I found on line does not show the meter lights and unless I missed it, it doesn't list lights on the parts list either.
Does anyone know where the meter light voltage is picked up from and what is the bulb/lamp voltage?
If I can get this information ahead of time, I can get some LED's ready so we can pull out the amp, install the LED's and back together again.
Thanks and 73, Bob? W4JFA
|
Lou, 12 volts? Thanks Bob? W4JFA
On Tue, Jan 9, 2024 at 10:42?AM Louis Parascondola via <Gudguyham= [email protected]> wrote:
Bob, the meter lamps are on the top of each meter.? It’s a plastic removable plate (small) that lifts out with the bulb.? The bulb runs off the control circuitry voltage.? Lou
On Tuesday, January 9, 2024, 10:11 AM, Bob <W4JFABob@...> wrote: Hi all, Just an update, we got the fan job done in my friends AL-80B amp. All is well.
I never noticed that the neither?of the meter lights work. The amp is already? put in it's place so it is a small "project" to get it out. Anyway, the schematic?that I found on line does not show the meter lights and unless I missed it, it doesn't list lights on the parts list either.
Does anyone know where the meter light voltage is picked up from and what is the bulb/lamp voltage?
If I can get this information ahead of time, I can get some LED's ready so we can pull out the amp, install the LED's and back together again.
Thanks and 73, Bob? W4JFA
|
Bob, the meter lamps are on the top of each meter. ?It’s a plastic removable plate (small) that lifts out with the bulb. ?The bulb runs off the control circuitry voltage. ?Lou
On Tuesday, January 9, 2024, 10:11 AM, Bob <W4JFABob@...> wrote: Hi all, Just an update, we got the fan job done in my friends AL-80B amp. All is well.
I never noticed that the neither?of the meter lights work. The amp is already? put in it's place so it is a small "project" to get it out. Anyway, the schematic?that I found on line does not show the meter lights and unless I missed it, it doesn't list lights on the parts list either.
Does anyone know where the meter light voltage is picked up from and what is the bulb/lamp voltage?
If I can get this information ahead of time, I can get some LED's ready so we can pull out the amp, install the LED's and back together again.
Thanks and 73, Bob? W4JFA
|
Hi all, Just an update, we got the fan job done in my friends AL-80B amp. All is well.
I never noticed that the neither?of the meter lights work. The amp is already? put in it's place so it is a small "project" to get it out. Anyway, the schematic?that I found on line does not show the meter lights and unless I missed it, it doesn't list lights on the parts list either.
Does anyone know where the meter light voltage is picked up from and what is the bulb/lamp voltage?
If I can get this information ahead of time, I can get some LED's ready so we can pull out the amp, install the LED's and back together again.
Thanks and 73, Bob? W4JFA
|
Re: 144 mhz tuned input for a GG YC-156 ??
Apparently a? 1/2 wave resonator was tried....and works.? 1:1 input swr.
Pegs a 5 kw slug.? 55% eff.? ?A 10 kw slug has been ordered.?
2nd harmonic down 80 db.? 3rd harmonic down 38db.? This is without any external filters applied.??
So far so good.?
|
On Thu, Jan 4, 2024 at 07:27 PM, Jim VE7RF wrote:
KB1SEL got the premade chassis and cabinet from ICA manufacturing in? NJ.? They come completely pre-fabricated and ship flat. All you do is assemble with machine screws. On most of em, they have the outer front panel, and also a 2nd front panel inboard from the outer panel. Stuff like vac caps, verniers etc, is between the 2 x panels.... if you want.?
The pre-made cabinets come in every dimension you can think of.? ?Shipped in the flat pack, the shipping is cheap.? ?ICA runs flat out 6 x days a week.? That's also where the .515" thick teflon chimney for the 10 kw 6m, 3x6 amp came from.
Wow, just checked-out their website... what a great resource!? Thanks for sharing that Jim.? -- 73,
~Alan
|
Metering, Power Supply, control circuitry,? everything from the utility input to the HV of your choice.?
230vac Single phase HV transformer rated at 1 amp continuous at 3000/3500/4000/4500 secondary? ? ?197/208/219/229/240/251 primary??
Currently on 97 Mhz? ?
six meter or two meter conversion or add your favorite tube(s) for 160-10 meters.
Don W4DNR
W4DNR
|
Re: 144 mhz tuned input for a GG YC-156 ??
No but I have the WD7S version, complete with all parts and
instructions. No idea what it is worth.
See
Also, for a picture of a completed board, see
73, Alek VK6APK
On 8/01/2024 9:11 am, Robert W5AJ
wrote:
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THANKS Jim,
GM3SEK web pages are good!???
ANYONE have one of GM3SEK triode control boards/kit for
sale??
73 Robert W5AJ
On Sun, Jan 7, 2024 at
11:24?AM Jim VE7RF < jim.thom@...>
wrote:
On
Sat, Jan 6, 2024 at 05:21 AM, Robert W5AJ wrote:
Jim,?? is there public domain software program that
helps with Pi network design?
?
aka,? I'm looking at 8877 50Mhz project in 2024
73 Robert W5AJ
Don't mess with the PIEL software.? The gold standard is
the GM3SEK? PI / PI-L spreadsheet.? ?It's better since it
factors in everything, like stray C....and also the all
important stray L? Any stray L (intentional or otherwise)
between the anode and the C1 tune cap? will form a step
down L network....which will reduce the plate load Z to a
lower value.? This L network uses the tube's? anode to?
grid C + the extra fractional? uh before the C1 tune cap.?
The GM3SEK software also factors in the parasitic
suppressor if one is used.? ?It also factors in the plate
choke.?
I use the GM3SEK software for all amps? from 160-6m.?
?
I also use it for PI tuned inputs.... but there is a
trick to this.? The software won't match 2 x identical
Z's...so the 'workaround'? is to alter one a tiny bit.?
IE: 50 ohms to 49.999 ohms..... presto, works superb. In
the case of the tuned input, everything else is zeroed
out....( except for the plate choke....enter '9999 uh'?
for the plate choke). .? Where the plate load Z normally
gets entered, you enter 50 ohms..... then enter 49.999
ohms for the load end.
?
You can also tweak the total network Q.? ?Total network Q
= sum of the input and output Q.? Both Eimac and older
ARRL books only used the input Q.? Typ with an amplifier,
with a total network Q of? '12'.? The input Q = 10..and
the output Q? ='2'.
?
On tuned inputs, where both? ends are 50 ohms,? typ a
total network Q of '4' is used....with the input Q =
'2'..and the output Q = 2.
On the high power output tank, (160-6m)? in most cases,
the extra coil has to be installed between the plate block
cap assy...and the C1 tune cap...forming a step down L
network. The plate load Z is stepped down to a much lower
value, low enough that a practical? PI network can be
built, using a much lower Q.... on the highest band? on a
multiband amp.? ?Ditto with any mono band? 12/10/6m amp.?
?With out the extra fractional uh installed, the resulting
loaded Q is sky high, due to the tube's anode to grid C?
(which rises a bunch when tube plugged into the grid
ring..... or grid flange bolted to the chassis).? ?The
extra C comes from the proximity of the lower anode fins
to the chassis below it.? The u can also get even more
stray C between anode to rear / side walls....if tube too
close.? ?All that stray C is easily measured.? ? WE call
that network a L-PI? since it has the extra uh.? ?An?
L-PI-L also works.? I stay away from PI-L networks since
plenty of harmonic attenuation is obtained with the simple
PI (or L-PI) setup.?
?
On the 6M? ?3CX-6000A7 amplifier, the extra fractional uh
was obtained using a 1" wide cu strap in a semi circle,
forming an arc.? ?Main inductance between the vac tune and
vac load caps was done the same way....and both? straps
are at right angles.? Eff is sky high across the entire 6m
band, 72.5%...... and an easy 10 kw CCS? brick on key. By
forming the strap into a semi circle, the strap will
conduct current on both sides. Input swr is dead flat from
50-54 mhz...since it uses a manually tuned, PI tuned
input.? ? Again, it ample harmonic suppression.? If more
is required, a simple shorted 1/4 wave stub can be added,
BUT it has to be inserted exactly an electrical 1/4 wave
length downstream from the C2 load cap.? In the case of
the 3x6 6m amp, the vac load cap is mounted to the inner
front panel, then into the paralleled RJ2B's..... then a
long length of SFT-600? to the rear panel 7-16 DIN
connector.?
?
The only time u can insert the shorted 1/4 wave stub
directly on the output of an amp, is if it's PI-L config.
( or a L-PI-L).?
|
Re: 144 mhz tuned input for a GG YC-156 ??
THANKS Jim,
GM3SEK web pages are good!???
ANYONE have one of GM3SEK triode control boards/kit for sale??
73 Robert W5AJ
On Sun, Jan 7, 2024 at 11:24?AM Jim VE7RF < jim.thom@...> wrote: On Sat, Jan 6, 2024 at 05:21 AM, Robert W5AJ wrote:
Jim,?? is there public domain software program that helps with Pi network design?
?
aka,? I'm looking at 8877 50Mhz project in 2024
73 Robert W5AJ
Don't mess with the PIEL software.? The gold standard is the GM3SEK? PI / PI-L spreadsheet.? ?It's better since it factors in everything, like stray C....and also the all important stray L? Any stray L (intentional or otherwise) between the anode and the C1 tune cap? will form a step down L network....which will reduce the plate load Z to a lower value.? This L network uses the tube's? anode to? grid C + the extra fractional? uh before the C1 tune cap.?
The GM3SEK software also factors in the parasitic suppressor if one is used.? ?It also factors in the plate choke.?
I use the GM3SEK software for all amps? from 160-6m.?
?
I also use it for PI tuned inputs.... but there is a trick to this.? The software won't match 2 x identical Z's...so the 'workaround'? is to alter one a tiny bit.? IE: 50 ohms to 49.999 ohms..... presto, works superb. In the case of the tuned input, everything else is zeroed out....( except for the plate choke....enter '9999 uh'? for the plate choke). .? Where the plate load Z normally gets entered, you enter 50 ohms..... then enter 49.999 ohms for the load end.
?
You can also tweak the total network Q.? ?Total network Q = sum of the input and output Q.? Both Eimac and older ARRL books only used the input Q.? Typ with an amplifier, with a total network Q of? '12'.? The input Q = 10..and the output Q? ='2'.
?
On tuned inputs, where both? ends are 50 ohms,? typ a total network Q of '4' is used....with the input Q = '2'..and the output Q = 2.
On the high power output tank, (160-6m)? in most cases, the extra coil has to be installed between the plate block cap assy...and the C1 tune cap...forming a step down L network. The plate load Z is stepped down to a much lower value, low enough that a practical? PI network can be built, using a much lower Q.... on the highest band? on a multiband amp.? ?Ditto with any mono band? 12/10/6m amp.? ?With out the extra fractional uh installed, the resulting loaded Q is sky high, due to the tube's anode to grid C? (which rises a bunch when tube plugged into the grid ring..... or grid flange bolted to the chassis).? ?The extra C comes from the proximity of the lower anode fins to the chassis below it.? The u can also get even more stray C between anode to rear / side walls....if tube too close.? ?All that stray C is easily measured.? ? WE call that network a L-PI? since it has the extra uh.? ?An? L-PI-L also works.? I stay away from PI-L networks since plenty of harmonic attenuation is obtained with the simple PI (or L-PI) setup.?
?
On the 6M? ?3CX-6000A7 amplifier, the extra fractional uh was obtained using a 1" wide cu strap in a semi circle, forming an arc.? ?Main inductance between the vac tune and vac load caps was done the same way....and both? straps are at right angles.? Eff is sky high across the entire 6m band, 72.5%...... and an easy 10 kw CCS? brick on key. By forming the strap into a semi circle, the strap will conduct current on both sides. Input swr is dead flat from 50-54 mhz...since it uses a manually tuned, PI tuned input.? ? Again, it ample harmonic suppression.? If more is required, a simple shorted 1/4 wave stub can be added, BUT it has to be inserted exactly an electrical 1/4 wave length downstream from the C2 load cap.? In the case of the 3x6 6m amp, the vac load cap is mounted to the inner front panel, then into the paralleled RJ2B's..... then a long length of SFT-600? to the rear panel 7-16 DIN connector.?
?
The only time u can insert the shorted 1/4 wave stub directly on the output of an amp, is if it's PI-L config. ( or a L-PI-L).?
|
Re: 144 mhz tuned input for a GG YC-156 ??
In Europe Capton or Mica were used as insulation material on broadcast amplifier tubes and capacitors by companies like Plisch, R&S, Siemens, SEL etc..
?
I used Teflon with my YL1056 to insulate the tube from the copper tubing of the coaxial output circuit.
I built that amp in 1988 and never had any problem with the insulation.
?
73
Peter DJ7WW
?
?
?
?
-----Original-Nachricht-----
Betreff: Re: [ham-amplifiers] 144 mhz tuned input for a GG YC-156 ??
Datum: 2024-01-07T18:53:19+0100
Von: "Jim VE7RF" <jim.thom@...>
An: "[email protected]" <[email protected]>
?
?
?
On Sat, Jan 6, 2024 at 09:44 PM, Steve wrote:
I could tell I was beating a dead horse when all the HFers ignored my earlier comments about plate bypass capacitors made of two metal plates with an insulating sheet between, and then when they kept talking about pi-nets while purporting to discuss V/UHF amplifiers. Some folks seem enamored by the view of lumped constants arranged and connected willy-nilly. But Hank, W6GGV, raised me knee-high on stripline design, and I've never forgotten the difference, nor how easy they are to design (not necessarily to build, however!). They'll just have to learn the hard way, I spose, just like I'm having to learn how to make holes in this desert cliche for tower bases.
I can just imagine one of these characters looking upon a typical V/UHF amplifier tank circuit and wondering "just HOW the hell can this thing possibly work?!?! How do you calculate the inductor in the output tank, fer Gawd's sake???"? 8-)
Steve, K0XP
?
Guess what the #1 component that fails in FM broadcast is ?? ?It's always the teflon plate block assy.? ?I just saw one, this time made from polyimide? cut loose 6 months ago, ruptured, blew up.?
?
Years ago, I tried a hb plate blocker by 1st wrapping the entire circumference of the anode with teflon sheeting....then a wrap of wide copper strap ( narrower than the teflon sheet).? ?Problem is.... the total C is formed by the entire circumference,
but the rf current exits the blocker at only one point.... so it's all concentrated at one point of the circumference.? ?You can also get imperfections (air pockets) between the anode and teflon...and also between teflon and copper strap.? That's when the corona starts up..... and you can't see it.? I experimented with it, using a YC-243 tube, with it's 6.125" OD anode cooler / 19.24" circumference? ( socketless 3x6)? for 2 months...then gave up, went back to a conventional assy, using paralleled? HT-57's.?
?
In the older arrl books, and also orr books, they both depict 8877 being used on 144 mhz...and also 220 mhz..... and both used a T network for the tuned input.?
?
Years ago? I had buddy try a T network? ( series coil, shunt C, series coil)? ?on his 2 x GS35B? 6m amp.? ?After a week, gave up, went to a pi net, with small air caps and one coil.... end of problem.?
If a simple T / PI network will work as a tuned input......mounted right at the cathode.....and is fully adjustable, what is the advantage of a strip line config ???
?
My issue with any tuned input is...... change anything, like drive level, bias, B+, length of coax to xcvr (or ipa), etc, and it always has to be re-tweaked a bit.? That's why a fixed tuned input was not used on the 3x6? 6m amp.? Besides, we needed something? we can slam 500-700 watts? CCS? drive level......on data modes.?
?
On these multiband? GG triodes,? I was not about to construct 5-9 separate PI tuned inputs...all bandswitched.? 2 x broadcast caps ( padded on 160m) and a simple 4 uh tapped tubing coil works superb.? We tested it on every band by stuffing a 800 w cxr though it on each band for 10 mins...then into the 2nd bird meter, then the 50 ohm DL.? ?6:1 verniers on both caps..then the 0-100 scale.? Then it's just...'tune by the numbers'.?
?
On my next amp, I'm going to 1st experiment with a new 0 - 4.4? uh roller coil ( multronics / cardwell...now called Viking).? It's wound with 8 ga wire. Then I can experiment with changing the Q on any band..... the idea is to see the effects of IMD? vs tuned input Q, and other parameters.?
?
Jim? VE7RF
?
|
Re: 144 mhz tuned input for a GG YC-156 ??
Yes, it is a 2m amp with YC-179.
The quarter wave stub is a notchfilter for harmonic supression.
The amplifier is built and used by a friend.
?
73
Peter
?
?
?
?
?
-----Original-Nachricht-----
Betreff: Re: [ham-amplifiers] 144 mhz tuned input for a GG YC-156 ??
Datum: 2024-01-07T17:52:04+0100
Von: "Jim VE7RF" <jim.thom@...>
An: "[email protected]" <[email protected]>
?
?
?
A pi-circuit
?
73
Peter, DJ7WW
?
##? I don't get it.? You already depict a PI network, with adjustable pair of caps and small coil.? ?How exactly does the heliax fit into the overall scheme ?? ?Is this? 144 mhz amp with the YC-156 ???
?
|
Re: 144 mhz tuned input for a GG YC-156 ??
On Sat, Jan 6, 2024 at 09:44 PM, Steve wrote:
I could tell I was beating a dead horse when all the HFers ignored my earlier comments about plate bypass capacitors made of two metal plates with an insulating sheet between, and then when they kept talking about pi-nets while purporting to discuss V/UHF amplifiers. Some folks seem enamored by the view of lumped constants arranged and connected willy-nilly. But Hank, W6GGV, raised me knee-high on stripline design, and I've never forgotten the difference, nor how easy they are to design (not necessarily to build, however!). They'll just have to learn the hard way, I spose, just like I'm having to learn how to make holes in this desert cliche for tower bases.
I can just imagine one of these characters looking upon a typical V/UHF amplifier tank circuit and wondering "just HOW the hell can this thing possibly work?!?! How do you calculate the inductor in the output tank, fer Gawd's sake???"? 8-)
Steve, K0XP
?
Guess what the #1 component that fails in FM broadcast is ?? ?It's always the teflon plate block assy.? ?I just saw one, this time made from polyimide? cut loose 6 months ago, ruptured, blew up.?
?
Years ago, I tried a hb plate blocker by 1st wrapping the entire circumference of the anode with teflon sheeting....then a wrap of wide copper strap ( narrower than the teflon sheet).? ?Problem is.... the total C is formed by the entire circumference,
but the rf current exits the blocker at only one point.... so it's all concentrated at one point of the circumference.? ?You can also get imperfections (air pockets) between the anode and teflon...and also between teflon and copper strap.? That's when the corona starts up..... and you can't see it.? I experimented with it, using a YC-243 tube, with it's 6.125" OD anode cooler / 19.24" circumference? ( socketless 3x6)? for 2 months...then gave up, went back to a conventional assy, using paralleled? HT-57's.?
?
In the older arrl books, and also orr books, they both depict 8877 being used on 144 mhz...and also 220 mhz..... and both used a T network for the tuned input.?
?
Years ago? I had buddy try a T network? ( series coil, shunt C, series coil)? ?on his 2 x GS35B? 6m amp.? ?After a week, gave up, went to a pi net, with small air caps and one coil.... end of problem.?
If a simple T / PI network will work as a tuned input......mounted right at the cathode.....and is fully adjustable, what is the advantage of a strip line config ???
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My issue with any tuned input is...... change anything, like drive level, bias, B+, length of coax to xcvr (or ipa), etc, and it always has to be re-tweaked a bit.? That's why a fixed tuned input was not used on the 3x6? 6m amp.? Besides, we needed something? we can slam 500-700 watts? CCS? drive level......on data modes.?
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On these multiband? GG triodes,? I was not about to construct 5-9 separate PI tuned inputs...all bandswitched.? 2 x broadcast caps ( padded on 160m) and a simple 4 uh tapped tubing coil works superb.? We tested it on every band by stuffing a 800 w cxr though it on each band for 10 mins...then into the 2nd bird meter, then the 50 ohm DL.? ?6:1 verniers on both caps..then the 0-100 scale.? Then it's just...'tune by the numbers'.?
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On my next amp, I'm going to 1st experiment with a new 0 - 4.4? uh roller coil ( multronics / cardwell...now called Viking).? It's wound with 8 ga wire. Then I can experiment with changing the Q on any band..... the idea is to see the effects of IMD? vs tuned input Q, and other parameters.?
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Jim? VE7RF
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Re: 144 mhz tuned input for a GG YC-156 ??
On Sat, Jan 6, 2024 at 05:21 AM, Robert W5AJ wrote:
Jim,?? is there public domain software program that helps with Pi network design?
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aka,? I'm looking at 8877 50Mhz project in 2024
73 Robert W5AJ
Don't mess with the PIEL software.? The gold standard is the GM3SEK? PI / PI-L spreadsheet.? ?It's better since it factors in everything, like stray C....and also the all important stray L? Any stray L (intentional or otherwise) between the anode and the C1 tune cap? will form a step down L network....which will reduce the plate load Z to a lower value.? This L network uses the tube's? anode to? grid C + the extra fractional? uh before the C1 tune cap.?
The GM3SEK software also factors in the parasitic suppressor if one is used.? ?It also factors in the plate choke.?
I use the GM3SEK software for all amps? from 160-6m.?
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I also use it for PI tuned inputs.... but there is a trick to this.? The software won't match 2 x identical Z's...so the 'workaround'? is to alter one a tiny bit.? IE: 50 ohms to 49.999 ohms..... presto, works superb. In the case of the tuned input, everything else is zeroed out....( except for the plate choke....enter '9999 uh'? for the plate choke). .? Where the plate load Z normally gets entered, you enter 50 ohms..... then enter 49.999 ohms for the load end.
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You can also tweak the total network Q.? ?Total network Q = sum of the input and output Q.? Both Eimac and older ARRL books only used the input Q.? Typ with an amplifier, with a total network Q of? '12'.? The input Q = 10..and the output Q? ='2'.
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On tuned inputs, where both? ends are 50 ohms,? typ a total network Q of '4' is used....with the input Q = '2'..and the output Q = 2.
On the high power output tank, (160-6m)? in most cases, the extra coil has to be installed between the plate block cap assy...and the C1 tune cap...forming a step down L network. The plate load Z is stepped down to a much lower value, low enough that a practical? PI network can be built, using a much lower Q.... on the highest band? on a multiband amp.? ?Ditto with any mono band? 12/10/6m amp.? ?With out the extra fractional uh installed, the resulting loaded Q is sky high, due to the tube's anode to grid C? (which rises a bunch when tube plugged into the grid ring..... or grid flange bolted to the chassis).? ?The extra C comes from the proximity of the lower anode fins to the chassis below it.? The u can also get even more stray C between anode to rear / side walls....if tube too close.? ?All that stray C is easily measured.? ? WE call that network a L-PI? since it has the extra uh.? ?An? L-PI-L also works.? I stay away from PI-L networks since plenty of harmonic attenuation is obtained with the simple PI (or L-PI) setup.?
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On the 6M? ?3CX-6000A7 amplifier, the extra fractional uh was obtained using a 1" wide cu strap in a semi circle, forming an arc.? ?Main inductance between the vac tune and vac load caps was done the same way....and both? straps are at right angles.? Eff is sky high across the entire 6m band, 72.5%...... and an easy 10 kw CCS? brick on key. By forming the strap into a semi circle, the strap will conduct current on both sides. Input swr is dead flat from 50-54 mhz...since it uses a manually tuned, PI tuned input.? ? Again, it ample harmonic suppression.? If more is required, a simple shorted 1/4 wave stub can be added, BUT it has to be inserted exactly an electrical 1/4 wave length downstream from the C2 load cap.? In the case of the 3x6 6m amp, the vac load cap is mounted to the inner front panel, then into the paralleled RJ2B's..... then a long length of SFT-600? to the rear panel 7-16 DIN connector.?
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The only time u can insert the shorted 1/4 wave stub directly on the output of an amp, is if it's PI-L config. ( or a L-PI-L).?
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Bob
Alan - W5ARM
Robert, W5AJ