Re: Operating RTTY FSK and Alpha 86
There’s no problem running RTTY on this amp. If you keep the grid current under 40 ma and the plate current under 875ma, you will still make rated power and the tubes will last forever.? If it doesn’t have the optional fan, install it.? ? Jim – KR9U ?
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From: [email protected] < [email protected]> On Behalf Of Ron KK7GO Sent: Monday, September 4, 2023 12:03 PM To: [email protected]Subject: [ham-amplifiers] Operating RTTY FSK and Alpha 86 ? Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: Kenwood TL-922-Need a plate current meter.
I had to do that as well. A little Dremel and a few seconds. Lou does a good job with those replacement meters. Bob W4JFA?
On Mon, Sep 4, 2023, 3:50 PM Jim McPhee < jmcphee@...> wrote: Hi Bob,
You asked that I let the group know how things went. Lou sent the meter, and a soft key module, and both are installed and working perfectly. And the new meter looks just like the original. The one glitch I did encounter is the terminal posts on the new meter are longer than those on the original. As a result, the positive terminal contacted the metal tray that the meter circuit board resides in, preventing the meters from being mounted back in place. I removed the meter and ground both terminals down about as short as they could be and still clamp the ring terminals under the top nut and washer. That fixed the problem. I'd recommend anyone mounting a replacement meter to do? the same before attempting to install the meter.
--
Jim McPhee
Placitas, NM
W5ABA
|
Re: Kenwood TL-922-Need a plate current meter.
Hi Bob,
You asked that I let the group know how things went. Lou sent the meter, and a soft key module, and both are installed and working perfectly. And the new meter looks just like the original. The one glitch I did encounter is the terminal posts on the new meter are longer than those on the original. As a result, the positive terminal contacted the metal tray that the meter circuit board resides in, preventing the meters from being mounted back in place. I removed the meter and ground both terminals down about as short as they could be and still clamp the ring terminals under the top nut and washer. That fixed the problem. I'd recommend anyone mounting a replacement meter to do? the same before attempting to install the meter.
--
Jim McPhee
Placitas, NM
W5ABA
|
Operating RTTY FSK and Alpha 86
Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: 12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 2
Not bad on the switch. Its worth the money For a tube like this.? Input sound standard. Similar to mine but less spacing on caps.? Also not band switched but just 14 taps of inductance from an air dux coil.? If you are going to only run ham bands and never
outside that would be easier to just tap it once for each band.
The big triode thing I don't get. You could use a 4cx3000, 4cx5000 and use the radio as drive.? Grounded screen. Screen keyed. All ya need is a screen transformer, Diodes caps and a relay.? ?
I think the big triode thing comes from CBers.? Then they can over drive the Triode and make more square waves to move the bird meter.? ?Why run and amp into an amp, Now you gotta tune both.? I guess if it was a solid state modern amp that followed the radio
around, it would be ok I guess.??
Are these 3x6's cheap and plentiful?
C
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Type 90 switch is? just under $500.00? ? It's rated at 40 amps @ 20 kv.? ?Scott doubled up on the contacts, and made it into 80 amp switch.?
I used a triple wafer model 88, and paralleled all 3 x wafers.? Modified into a progressively shorting switch by installing? 5 pole? sequential rotors on each wafer.? The 88 is rated at 30 amps @ 13 kv. With 3 x wafers in parallel it's now 90 amps @ 13 kv.
Triple wafer model 85 switches will also work. 30 amps @ 12 kv.? ?90 amps @ 12 kv? with 3 x wafers in parallel.? ?Beware, those current ratings are for 60 hz AC...not RF freqs.? The triple wafer model 85 / 88 are reasonably priced.
Tubing in the plumbing section of Home depot (aisle 16) is dirt cheap.? I silver plate em with the cool-amp glop from Ore.?
The correct? KINTRONICS 40 amp (1/2" tubing)? ?roller coil, new is $1821.00? ? Called a LV19-40.? ( 19 uh).? ? Damned thing is massive,? ? 17.625" long x? 11.625" wide? x? 11.5" tall.? ?Not including shaft out the end. Plus must be mounted on 4 x 6" tall standoffs.?
?Total height is then 17.5" tall. That just kills it for any amp...period.? You need a chassis the size of a dump truck.? I would take the Kintronics roller coil ratings with a grain of salt too.? The actual rolling contact is the weak point on em.? The fixed
tubing Kintronics coils are rated the same as their roller counterparts...which nobody else does.? Everybody else always de-rates the roller versions.? Since the roller is variable, required uh is easy to obtain. BUT the tubing used has to be sized for upper
HF, which means 1/2" tubing.?
On this setup, the 2.3 uh coil is 1/2" tubing....and combines the .6 uh pre-coil / L coil and the 1.75 uh 20m coil, all in one coil. 20m Coil tapped for 17+15M. The required uh for 80m is? ?9.25 uh.? 80m coil is just 7.5 uh, since? the 1.75 uh 20m coil is
already in series with it.? 160 required uh is 18-18.5 uh.? ?A simple 9.25 uh 160m coil is on the end of the mess.
Scott got lucky, and has a box full of silver plated 2.3 uh tubing coils, made from 1/2" tubing.? They all came from 13.56 mhz RF generators.?
?
20-17-15m coil is made from 1/2" tubing.? 80-40m coil is made from 3/8" tubing.? ?160m coil is made from 1/4" tubing.?
Any roller...... (or tubing coils in series, and bandswitched)? that covers down to 160m is gonna create grief.? ?You will get the dreaded ....'suck out' on 20-10m every time.? That's why we use a progressive shorting style bandswitch if 160m is involved.?
Multi-tech industries calls those switches.... 'multiple pole rotors'.? ?IE: instead of a single rotor, they use 5 x sequential rotor fingers...that all converge onto the central rotor hub.? ?1st rotor finger does the actual various taps, the remaining fingers
just provide for additional shorts across un-used contacts.? ?You can test for? suck out very easily.? Temp wire a resistor ( = to the plate load Z) between anode to chassis.? Tweak tune and load and roller for 160m..with mfj-259B on output connector for 1:1
swr.? Then sweep the mfj and see what the upper /lower freq is for the 2:1? points.? ?Then repeat on 80m.? On 80m, the 2:1 points should be twice the BW.? And double again on 40m.? And double again on 20m. With suckout, the 2:1 BW is extremely narrow. Temp
short out the last few turns at the 160m end of the roller...and the suckout effect? vanishes.?
?
On a roller that covers 160m, the only option is to use a relay, and it's contacts, to provide for one extra short in the middle of the coil, like where 80m would reside.?
?
Tetrodes are a? pita.? ?The 4x5 has a tiny under fin area? vs the 3x6.? It's dead simple to get 8 kw CCS anode diss from a 3x6. No screen supplies required, nor bias supplies, nor? screen grid protection.? (Lose the B+, with screen V still present, and you
are in for a rude surprise).? ?3x6 is simple resistor cut off bias.? No neutralization required.? ?On my own YC-243, it's a socketless version of a 3x6.? ?Build in grid? flange just bolts to the chassis.? 50 ohm input. Simple tuned input. Fil choke is now
dead simple....just slide on the fair rite oval beads over the pair of power cables.? Simple metering. Sorta like a SB-220 on steroids.
?
Scott already has a 4x15 installed in his aerocom commercial amp.? Damned thing idles at 1000 ma ! (@ 8 kv).? ?Sucks 3 kw on RX....and 10 kw when keyed, on idle....and no drive applied.? And sucks 45+ kw when driven.? 3 x blowers used.?
It uses a 75 kva pole pig configured for 240 input and 5600 vac output.? You need 400 amp service to run it.? ?Totally impractical.? ?It's going up for sale at some point.
?
Sure, a small IPA is required with the 3x6.? ?Everybody already has a 600 watt amp.? 80% of the drive power ends up in the output.
?
Here is the 4x15 aerocom amp.?
Here is the 75 kva plate xfmr that runs it.? ?
?
?The new cabinet is pretty small for this project.? ?It will all just barely fit.? Cab height, from chassis to top is only 9.25".
? Ok, that's the sob story for this week.?
|
Re: 12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 2
Type 90 switch is? just under $500.00? ? It's rated at 40 amps @ 20 kv.? ?Scott doubled up on the contacts, and made it into 80 amp switch.?
I used a triple wafer model 88, and paralleled all 3 x wafers.? Modified into a progressively shorting switch by installing? 5 pole? sequential rotors on each wafer.? The 88 is rated at 30 amps @ 13 kv. With 3 x wafers in parallel it's now 90 amps @ 13 kv. Triple wafer model 85 switches will also work. 30 amps @ 12 kv.? ?90 amps @ 12 kv? with 3 x wafers in parallel.? ?Beware, those current ratings are for 60 hz AC...not RF freqs.? The triple wafer model 85 / 88 are reasonably priced.
Tubing in the plumbing section of Home depot (aisle 16) is dirt cheap.? I silver plate em with the cool-amp glop from Ore.?
The correct? KINTRONICS 40 amp (1/2" tubing)? ?roller coil, new is $1821.00? ? Called a LV19-40.? ( 19 uh).? ? Damned thing is massive,? ? 17.625" long x? 11.625" wide? x? 11.5" tall.? ?Not including shaft out the end. Plus must be mounted on 4 x 6" tall standoffs.? ?Total height is then 17.5" tall. That just kills it for any amp...period.? You need a chassis the size of a dump truck.? I would take the Kintronics roller coil ratings with a grain of salt too.? The actual rolling contact is the weak point on em.? The fixed tubing Kintronics coils are rated the same as their roller counterparts...which nobody else does.? Everybody else always de-rates the roller versions.? Since the roller is variable, required uh is easy to obtain. BUT the tubing used has to be sized for upper HF, which means 1/2" tubing.?
On this setup, the 2.3 uh coil is 1/2" tubing....and combines the .6 uh pre-coil / L coil and the 1.75 uh 20m coil, all in one coil. 20m Coil tapped for 17+15M. The required uh for 80m is? ?9.25 uh.? 80m coil is just 7.5 uh, since? the 1.75 uh 20m coil is already in series with it.? 160 required uh is 18-18.5 uh.? ?A simple 9.25 uh 160m coil is on the end of the mess.
Scott got lucky, and has a box full of silver plated 2.3 uh tubing coils, made from 1/2" tubing.? They all came from 13.56 mhz RF generators.?
?
20-17-15m coil is made from 1/2" tubing.? 80-40m coil is made from 3/8" tubing.? ?160m coil is made from 1/4" tubing.?
Any roller...... (or tubing coils in series, and bandswitched)? that covers down to 160m is gonna create grief.? ?You will get the dreaded ....'suck out' on 20-10m every time.? That's why we use a progressive shorting style bandswitch if 160m is involved.? Multi-tech industries calls those switches.... 'multiple pole rotors'.? ?IE: instead of a single rotor, they use 5 x sequential rotor fingers...that all converge onto the central rotor hub.? ?1st rotor finger does the actual various taps, the remaining fingers just provide for additional shorts across un-used contacts.? ?You can test for? suck out very easily.? Temp wire a resistor ( = to the plate load Z) between anode to chassis.? Tweak tune and load and roller for 160m..with mfj-259B on output connector for 1:1 swr.? Then sweep the mfj and see what the upper /lower freq is for the 2:1? points.? ?Then repeat on 80m.? On 80m, the 2:1 points should be twice the BW.? And double again on 40m.? And double again on 20m. With suckout, the 2:1 BW is extremely narrow. Temp short out the last few turns at the 160m end of the roller...and the suckout effect? vanishes.?
?
On a roller that covers 160m, the only option is to use a relay, and it's contacts, to provide for one extra short in the middle of the coil, like where 80m would reside.?
?
Tetrodes are a? pita.? ?The 4x5 has a tiny under fin area? vs the 3x6.? It's dead simple to get 8 kw CCS anode diss from a 3x6. No screen supplies required, nor bias supplies, nor? screen grid protection.? (Lose the B+, with screen V still present, and you are in for a rude surprise).? ?3x6 is simple resistor cut off bias.? No neutralization required.? ?On my own YC-243, it's a socketless version of a 3x6.? ?Build in grid? flange just bolts to the chassis.? 50 ohm input. Simple tuned input. Fil choke is now dead simple....just slide on the fair rite oval beads over the pair of power cables.? Simple metering. Sorta like a SB-220 on steroids.
?
Scott already has a 4x15 installed in his aerocom commercial amp.? Damned thing idles at 1000 ma ! (@ 8 kv).? ?Sucks 3 kw on RX....and 10 kw when keyed, on idle....and no drive applied.? And sucks 45+ kw when driven.? 3 x blowers used.?
It uses a 75 kva pole pig configured for 240 input and 5600 vac output.? You need 400 amp service to run it.? ?Totally impractical.? ?It's going up for sale at some point.
?
Sure, a small IPA is required with the 3x6.? ?Everybody already has a 600 watt amp.? 80% of the drive power ends up in the output.
?
Here is the 4x15 aerocom amp.?
Here is the 75 kva plate xfmr that runs it.? ?
?
?The new cabinet is pretty small for this project.? ?It will all just barely fit.? Cab height, from chassis to top is only 9.25".
? Ok, that's the sob story for this week.?
|
12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 3
Here the manually tuned,? tuned input is installed.? Typ a pair of 4? section broadcast caps are used for this application...and has been used several times in the past. (17-540 pf per section, and all 4? x sections strapped in parallel.....=? ?68- 2160 pf ). With a pair of 4 x section caps used, they only have to be padded on 160M.? ?In this case, the 4 section broadcast caps are too long.
Plan B.? ?A pair of 2 x section broadcast caps are used (load cap used on a SB-220).....and padded on 160M and 80M).? Each section of the 2 section caps are 15-450 pf...and again, both sections are strapped in parallel.? The progressively shorting bandswitch is from the kw tank circuit of a TL-922 amp.
The bandswitch is used to change taps on the (aprx) 3.5 to 4 uh coil seen in the video, and also add padding to each 2 x section cap on 80m, and 160m.
Each air variable gets it's own 6:1 vernier reduction drive assy.? A small 2" diameter turns counter drives each 6:1 vernier.? Each cap only rotates 180 degs to get from min to max (1/2 rev).? ?With a 6:1 vernier installed, it then requires 3 full revolutions to get from? min to max C.? With the mini turns counter installed, (0-99 increments per rev) it's then 0-300 tiny increments to get from min to max C.? This will provide for the ultimate repeatable.... 'dial? it up by the numbers'.? A simple cheat cheat is then made up for several parts of each band.?
In normal operation, it's just change the bandswitch to the correct band, and dial up both caps to their respective pre-sets...done.? Then the input SWR is always 1:1? across each band.? In the past, when using the same manually tuned, tuned inputs, we also have to factor in the tube's stray C (grid to cathode) as the tube C is directly in parallel with the C2 cap of the tuned input.? We also have to factor in the stray C from each fil lug to chassis, as there is more stray C at the hot end of the fil choke.? ?We also have to factor in the length of coax from IPA (intermediate power amp) to input of the tuned input.? We also have to factor in the bias used (fully adjustable), drive level, (also adjustable).. and also B+ used...(can be altered? by varying the taps).? We also have to factor in the length of coax from tuned input to the cathode.? Ideally, you want the C2 cap as close to the cathode as possible, esp on upper HF, but that is not always possible. Typ eff will suffer on 10 + 6m, with 50 ohm coax lengths > 1' on 10m, and even less on 6M.? Typ 'fixes' include using paralleled? 50 ohm coaxes ( which effectively adds C to the cathode), or adding C to the cathode (cathode to chassis)
In the past, we tested the manually tuned, tuned input by applying a 800 watt? cxr for 10 mins on each band. Done with wattmeter's on both sides of the tuned input....then into a 50 ohm DL.? ?The 3CX-6000A7 (and also the smaller 3CX-3000A7)? have a 50 ohm input Z.? With input swr tweaked for 1:1 we get max drive applied to the cathode...and also max grid current.
Trying to design and fabricate 5-9? separate, bandswitched / relay switched PI tuned inputs....that will each handle 800 watts CCS? cxr, is an exercise in futility.? Arco compression trimmers are only good for 200 w pep...and also have to be padded on 80 +160m.? Correct sized toroid's and magnet wire are a non issue. Been there, done that.? If fixed caps are used, they have to handle the current, and you need a box of em to arrive at the final tweak...pita.? ?Then either a 2 x wafer bandswitch is used, or a small single wafer bandswitch is used to activate a mess of relays.? You end up with a convoluted, complicated mess on your hands....and even more complicated if the tuned input bandswitch is mechanically ganged to the 10 kw output bandswitch.
The dead simple, manually tuned, tuned input is far simpler, and bullet proof...and fast to design and install.? ?With 800 watts into 50 ohms, it's only? 4 amps into 50 ohms, and only 200 V rms (283 V peak).? Those broadcast style caps typ have .032" spacing, and rated for 1.1 kv.? With older, dirty ones, toss em into the dishwasher....(with plates un-meshed), and they come out squeaky clean.....and hi-pot test to an easy 1.5 kv.?
We intentionally don't mechanically gang the manually tuned, tuned input bandswitch with the 10 kw output bandswitch.? In normal operation, it does not take long to change bands, with the 2 x bandswitches and 4 x caps, using cheat sheets for both the input and output tuning. (< 1 min from 15m down to 160m).?
|
Re: 12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 2
Looks great. I like the drives for the caps mounted vertically.? Neat idea.?
How much are those Type 90 switches?? ?I recognize it.? I have one inside my outdoor antenna switch.? Its stepper driven. I can't remember who made the switch and console. I got it at a ham fest many years ago.?
I would think a nice kintronics Roller would just be easier for this. But I am sure it will actually work better band switched. The coils can be optimized for each band.
I know you guys like those triodes, but I would put a 4cx5000 in that amp in a heartbeat.
C
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Ceramic Vac tune and load caps? mounted vertically, both with right angle drives below chassis.? ?Between the front panel and sub front panel,
they will both feed a sprocket assy, so the actual turns counters will be above the chassis.? Multi-tech industries Model 90 bandswitch has been modified, such that there is now 40 amp contacts on both sides of the single wafer. Contacts on both sides to be
strapped in parallel. There is a pair of multiple pole rotor assy's, (aka progressively shorting type bandswitch).
Neither vac cap has to be padded on 160M.
|
12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 2
Ceramic Vac tune and load caps? mounted vertically, both with right angle drives below chassis.? ?Between the front panel and sub front panel, they will both feed a sprocket assy, so the actual turns counters will be above the chassis.? Multi-tech industries Model 90 bandswitch has been modified, such that there is now 40 amp contacts on both sides of the single wafer. Contacts on both sides to be strapped in parallel. There is a pair of multiple pole rotor assy's, (aka progressively shorting type bandswitch).
Neither vac cap has to be padded on 160M.
|
12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 1
Ok, new project started.? 160-15M amp using the 3CX-6000A7. I re-designed the 160m coil, made from 1/4" tubing, so it's shorter, but bigger diameter, so it will fit.? 80-40m coil already made...from 3/8" tubing. 20-15m coil made from 1/2"? tubing.? ?The whole thing is a tight fit.
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Re: TL-922 47pF Capacitor
On Sun, Aug 27, 2023 at 02:14 AM, Alek Petkovic wrote:
That would be an interesting exercise. I use my nano vna all the time too but I don't think I'll bother in this case, as it seems to work fine with the cap in place. I'll let sleeping dogs lie. I'm just finishing off some mods for a local ham, which were started many years ago and the guy doing them got ill and sadly passed away.
I saw a reference where Rich Measures mentioned the addition of a small cap around this size from the normally closed I/O relay to ground, to improve the through SWR on 10m when the amp is bypassed. Why anyone would ever operate with the amp bypassed is beyond me.???
73, Alek, VK6APK
It's typ only 10-15 pf at most, for a cap...from either NC contact to chassis.... to flatten the bypass swr on 10m.? Typ used on a SB-220. Not required on my L4B's...and dunno abt the TL-922.? In this config......Lou is correct. It will just increase the min C on every bands by 47 pf.?
|
Re: TL-922 47pF Capacitor
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On 28 Aug 2023, at 7:35 am, Alek Petkovic via groups.io <vk6apk@...> wrote:
?
Yes. A silly activity.?
Alek. VK6APK
On 28/08/2023 7:08 am, HaL Mandel
wrote:
Dear Alek,
?
My thoughts on seeing the word “bypassed”
lead me to believe
“running barefoot.”
?
?
Hal Mandel
W4HBM
|
Re: TL-922 47pF Capacitor
Yes. A silly activity.?
Alek. VK6APK
On 28/08/2023 7:08 am, HaL Mandel
wrote:
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Show quoted text
Dear Alek,
?
My thoughts on seeing the word “bypassed”
lead me to believe
“running barefoot.”
?
?
Hal Mandel
W4HBM
|
Re: TL-922 47pF Capacitor
Dear Alek,
?
My thoughts on seeing the word “bypassed” lead me to believe
“running barefoot.”
?
?
Hal Mandel
W4HBM
|
Re: TL-922 47pF Capacitor
Yes. That was my observation too. Maybe VC2-1 was marginal on 40m
and the 47pF was selected so that it provided that little bit of
extra capacitance without messing up 10m with too much
capacitance.
73, Alek.
On 27/08/2023 5:41 am, Louis
Parascondola via groups.io wrote:
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That 47 pf cap basically would add 47pf to the total of the entire
value of the load cap. ?Usually load padding is switched in and
out rather than hung on there forever. ?That’s a relatively small
amount compared to the value to the cap.
On Saturday, August
26, 2023, 4:48 PM, HaL Mandel <hmandel@...> wrote:
?
{SNIP}
I have a question regarding what appears to be an added
47pF/3kV blue ceramic capacitor in the output tank
circuit. It goes from the output contact of the
bandswitch to ground, as seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your
question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0
MHz),
and the Stop Frequency, (again, more than likely
30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on
the input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various
amplifiers
he’s attempting to renovate, and has uncovered
mistunings because
of incorrect padding, incorrect choking, incorrect
input tuning, etc.,
and has become astute with the small instrument enough
to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA.
It came
with clips and a small PCB with bits so I could set the
machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
|
Re: TL-922 47pF Capacitor
Thanks Hal.
That would be an interesting exercise. I use my nano vna all the
time too but I don't think I'll bother in this case, as it seems
to work fine with the cap in place. I'll let sleeping dogs lie.
I'm just finishing off some mods for a local ham, which were
started many years ago and the guy doing them got ill and sadly
passed away.
I saw a reference where Rich Measures mentioned the addition of a
small cap around this size from the normally closed I/O relay to
ground, to improve the through SWR on 10m when the amp is
bypassed. Why anyone would ever operate with the amp bypassed is
beyond me.???
73, Alek, VK6APK
On 27/08/2023 4:48 am, HaL Mandel
wrote:
toggle quoted message
Show quoted text
?
{SNIP}
I have a question regarding what appears to be an added
47pF/3kV blue ceramic capacitor in the output tank circuit. It
goes from the output contact of the bandswitch to ground, as
seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0 MHz),
and the Stop Frequency, (again, more than likely 30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on the
input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various amplifiers
he’s attempting to renovate, and has uncovered mistunings
because
of incorrect padding, incorrect choking, incorrect input
tuning, etc.,
and has become astute with the small instrument enough to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA. It
came
with clips and a small PCB with bits so I could set the
machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
|
Re: TL-922 47pF Capacitor
That 47 pf cap basically would add 47pf to the total of the entire value of the load cap. ?Usually load padding is switched in and out rather than hung on there forever. ?That’s a relatively small amount compared to the value to the cap.
On Saturday, August 26, 2023, 4:48 PM, HaL Mandel <hmandel@...> wrote:
?
{SNIP}
I have a question regarding what appears to be an added 47pF/3kV blue ceramic capacitor in the output tank circuit. It goes from the output contact of the bandswitch to ground, as seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0 MHz),
and the Stop Frequency, (again, more than likely 30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on the input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various amplifiers
he’s attempting to renovate, and has uncovered mistunings because
of incorrect padding, incorrect choking, incorrect input tuning, etc.,
and has become astute with the small instrument enough to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA. It came
with clips and a small PCB with bits so I could set the machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
|
Re: TL-922 47pF Capacitor
?
{SNIP}
I have a question regarding what appears to be an added 47pF/3kV blue ceramic capacitor in the output tank circuit. It goes from the output contact of the bandswitch to ground, as seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0 MHz),
and the Stop Frequency, (again, more than likely 30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on the input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various amplifiers
he’s attempting to renovate, and has uncovered mistunings because
of incorrect padding, incorrect choking, incorrect input tuning, etc.,
and has become astute with the small instrument enough to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA. It came
with clips and a small PCB with bits so I could set the machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
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Re: TL-922 47pF Capacitor
Alek, FWIW, mine has it as well. Attached picture is my 922. That extra circuit board you see is the "Kessler" electronic bias board. 73, Bob? W4JFA
G'day all.
I am currently working on a couple of TL-922 amplifiers and I
have a question regarding what appears to be an added 47pF/3kV
blue ceramic capacitor in the output tank circuit. It goes from
the output contact of the bandswitch to ground, as seen below.
Both amplifiers have this capacitor and the above picture was
from Google.
Does anybody know what the purppose of this capacitor might be?
It definitely looks like an addition.
I'm happy to leave it in place but I'm wondering what it does.
Thanks and 73, Ale, VK6APK.
|
G'day all.
I am currently working on a couple of TL-922 amplifiers and I
have a question regarding what appears to be an added 47pF/3kV
blue ceramic capacitor in the output tank circuit. It goes from
the output contact of the bandswitch to ground, as seen below.
Both amplifiers have this capacitor and the above picture was
from Google.
Does anybody know what the purppose of this capacitor might be?
It definitely looks like an addition.
I'm happy to leave it in place but I'm wondering what it does.
Thanks and 73, Ale, VK6APK.
|
Bob
HaL Mandel
