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Re: Chinese AL-811 / Will nominated as .."project Manager"
On Sep 30, 2006, at 10:46 PM, pentalab wrote:
--- In ham_amplifiers@..., "Mike Sawyer" <w3slk@...>Is the Administrator clueless or what? R L Measures, AG6K, 805.386.3734 r@... |
Re: 4 Tube 811 Amplifier.
On Sep 30, 2006, at 10:46 AM, Jan Erik Holm wrote:
And in the Winter it keeps you warm. R L Measures, AG6K, 805.386.3734 r@... |
Re: Passed 100 total members.... PARASITIC's solved... once and for all !!
On Sep 30, 2006, at 6:01 PM, Bill Turner wrote:
ORIGINAL MESSAGE:chortle. Tom abhors dipmeters because they give false dips -- or so he says when they do not confirm his dicta. R L Measures, AG6K, 805.386.3734 r@... |
Re: Passed 100 total members.... PARASITIC's solved... once and for all !!
On Oct 1, 2006, at 3:09 AM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:I read posts on parasites to check for specious statements.wrote: Agreed, but his groupies know that checking out the leader's dicta ist verboten.### Any RF software program that contains RF skin effect Rauch is full of it.... the softwareG2DAF amplifiers still use the 2-tone test because it produces about 1/11 the distortion products that a human voice produces in a G2DAFfy amp. . I like to debunk taurine feces before some newbies swallow it. Did you get burnedI have never been on a debating team. My bailywick is debating one on one when I am familiar with the subject. When I'm not, I know to shut up and listen to what other folks have to say. ... ... ### Why anyone would wanna leave in the 6 x 200 pf caps + 2 xIt increases the grid resonance freq slightly. By directly grnding the grids you now [a]Grid fusing is somewhat cheaper than tubes. R L Measures, AG6K, 805.386.3734 r@... |
Re: Passed 100 total members.... PARASITIC's solved... once and for all !!
On Oct 1, 2006, at 4:43 AM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:Jim -- A 2500-ohm feedback-path from the output back to the input ofRICH SEZ... The 3cx3000A7 has 0.6 pF of feedback C. That's 6x more a tube with an amplification factor of 200 means nothing to you? IMO... the grid is better grnded on aIt may be but both tubes have more than zero feedback C and more than zero L in their grids. Agreed. Henry parasitic suppressors typically have a Q of >5 at 100MHz. IMO, it's better to keep suppressor Q under 2. (4.8mm / 0.19") grid pins !How long is the 1" strap used to ground 3=500Z socket pins? What is the resonant frequency of a 3-500Z grid when it is so grounded? What is the resonant frequency of the grid in a stock TL-922 or stock SB-220? those who want to employ good engineering practice. All I know is that when you directly strap allNot in my experiences. Increasing the grid's resonant frequency should theoretically allow the grid to better shield the output from the input at higher frequencies -- thereby increasing VHF stability. The fly in the pie is that most of the L that results in the grid's 88MHz or so resonance is inside the envelope. with the OEMUp to what frequency? which also makes for 20-25 w LESS drive power.Perhaps it involves something other than the grids -- such as the Q of the R/L VHF suppressor @ 100MHz? Please describe the VHF suppressors. [thechortle. With 0.3pF of feedback C, it ain't easy to get good stability. The AL-80BXL4Bs are inherently more stable than most other 3-500Z amps because they use less HV to supply the anodes -- and that decreases gain. A glitch resistor is needed to physically limit peak filter-cap### W8JI once modified a small GG metal triode... improved theRICH SEZ.... So why does the AL-1500 - that he apparently designed - current to under 200A during a glitch . Neither a HV fuse nor a typical over-current trip circuit is fast enough or rugged enough to do this job. a FAST HV fuse..a cathode fuse....*** 250V rated? andAgreed, but limiting peak current that severely with a 3kV PS may not be needed. Toss in some fastAgreed Use of aNo delay is needed if the relays are faster than the transceiver. these5mS is typical even if the spedAn RJ-1 or HC-1 makes in c. 1.8mSec with the circuit at: However such speed requires 100 to 150 volts at the other end of the current limiting R. Also, xcvr's like theTurning the mic. gain down to barely any ALC greatly reduces overshoot and usually slightly increases PEP. . Agreed. For an 8171 on 10m, expect 25A-rms. Use a width that will carry the current. I use 4-mil stainless-steel### Here's my problem with Nichrome. It GLOWS ORANGE on the shimstock, cut to the width I need for big ones. It runs so hot... this thermal heat in turn cooksBut you would achieve a lower VHF Q if you used stainless-steel shimstock or Ni-Cr ribbon. ANYNot if it's wide enough. I am aware of this. At 50MHz, 2" nichrome ribbon has c. the same RF resistance as copper ribbon 0.35" wide. However, the DC resistance ratio of Ni-Cr to Cu is c. 50 to 1. Rich, when uThe max frequency will be 22MHz. On 10m, when the band is open 100w is plenty. When 10m isn't open, 10kW is not enough. with a deadcheerz R L Measures, AG6K, 805.386.3734 r@... |
Re: Any idea's on a visual Grid / Cathode fuse indicating device ??
Steven Grant
At 08:17 AM 10/1/2006, pentalab wrote:
--- In ham_amplifiers@..., Steven Grant ?* In normal amateur service, i dont see how i could ever drive the amp hard enough to roast the grid ??? even if mistuned (2? 3-500Zs) ???? I dont tune with full power till im close to resonance btw (maybe a 3CX800) ???? I do agree that with the grid open, the tube is off ????? I have seen roasted filament transformers from filament to grid shorts ### simply change out the grid fuse.. and you are back in business. ? * OK, question - will the fuse blow if the tube becomes unstable (parasitic oscillation) ????? ### The grid fuse protects the grid. When the grid fuse ? Steven W4IIV |
Re: Any idea's on a visual Grid / Cathode fuse indicating device ??
pentalab
--- In ham_amplifiers@..., Steven Grant <w4iiv@...>
wrote: bad! ### Say what ? What do u mean "the tube is already bad" ? My buddy has blown the grid fuse about 8 times cuz of misc other problems. The tube is still pumping out 15 kw. Ditto with the grid fuses that have blown in my 2 x 3-500Z linears. ### simply change out the grid fuse.. and you are back in business. [prudent to investigate why the grid fuse blew open in the 1st place.... which could be anything from having a blown HV fuse 1st... in which case the grid current skyrockets. My buddy had an arc over on one of his ant's.... took out one of the HV sandfilled fuses... followed by the grid fuse. Another time, the grid fuse blew from accidental overdrive. STEVEN SEZ... What the grid fuse does is protect the filament transformer IMO
### The grid fuse protects the grid. When the grid fuse opens... their is NO DC path for DC grid current... tube shuts down... can't be driven... and zero watts power output. ### simply change out the grid fuse.. and you are back in business ! ### There is also NO path for dc grid current to flow back into the CT of the fil xfmr.... which then feeds the fil. Extremely high grid current couldn't damage a fil xfmr anyway. The dc grid current flows into the CT... then splits left and right... into each side of the fil, [via the bifilar] The entire secondary.. including the CT... is built like a tank... typ rated for 21-80 A, depending on tube type. later... Jim VE7RF |
Re: Passed 100 total members.... PARASITIC's solved... once and for all !!
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
RICH SEZ... The 3cx3000A7 has 0.6 pF of feedback C. That's 6x more than the 8877 and 4x more than a 3-500Z. At its max-f rating of 110MHz, the 3cx3000A7 has an output to input feedback path with 2500-ohms of XC. ### agreed... so what ?? IMO... the grid is better grnded on a 3000A7... than a 3-500Z. ### In MOST cases... on a HB RICH SEZ...... especially if you just love to repair amplifiers.3000A7... u can just toss the suppressor. ### Build a 3000A7 linear.. and try it yourself. The one turn chrome suppressor from the 8-K is essentially doing...nothing. ### I'm convinced... 98% of stability is how well the control grid is grounded. A 3-500Z has only ONE internal grid pin.... RICH SEZ... It's a 360? cone shaped collet. #### Which in turn splits into 3 x extremly thin grid pins ! They should just fed 1 x WIDE strap from the cone collet.. down to the 3 base pins.... ditto with tubes like 811-A's, 572B's, etc. RICH SEZ...If the 3-pins are grounded directly, the resonance at the grid is in the 80MHz range. If the 3 grid pins are grounded through 200pF caps, the grid resonance is in the 80MHz range. In my experiences it is > better to measure resonance with a dipmeter than to guess at it. ### Who cares ??? All I know is that when you directly strap all 6 x grid pins, with wide strap, to the chassis, the SB-220, SB- 221, TL-922 become rock stable... with the OEM suppressor's.......and that's good enough for me. My only guess as to why it works is perhaps the grids are now really grounded... which also makes for 20-25 w LESS drive power. ### Now the AL-80BX and Ameritron with the 2 x 3-500Z's do have the grids directly grnded.... and STILL spit, arc, etc. [the guys on the east coast em.. the "firecracker's " ]. The AL-80BX is a poorly built amp imo. My buddy had so much trbl with his brand new one... he tossed it... and bought a used L4B... I modified the L4B.. with the usual mods... 100% reliable. ### W8JI once modified a small GG metal triode... improved the grid grnding... and built the worlds only [as far as I know] 160- 6m linear.... with NO parasitic suppressor !! RICH SEZ.... So why does the AL-1500 - that he apparently designed - have a reputation for sudden 8877 failures? As I see it, an amplifier that appears to be stable during an hour or so of testing is not guaranteed to be stable in the long run. ### dunno. I do know a lot of amateur's with the AL-1500.... and they run flawlessly... some pound out 2500 w PEP on ssb.... for literally 5 hrs every night.... and almost 365 days a yr... for the last 4 yrs. IMO,Perhaps some simple protection would help... like adding grid fuses, high speed grid + plate overcurrent protection.. a FAST HV fuse..a cathode fuse.... and a real 50 ohm, 50-100 w glitch resistor. Toss in some fast high swr protection, and also dump the stock mech T/R relay scheme.. and replace it with a high speed vac relay. Use of a digital delay for cw + ssb will help immensely..... these modern xcvr's crank out globs of RF instantly... even if the sped up vac relay does operate in < 2msec. Also, xcvr's like the ICOM's.. will have peak overshoots. That's easy to fix...... just use fixed dc volatge.. fed to the ALC jack at all times ! till the parasitic goes bye bye. If using a real small globar... and u run outa room.... reduce the width of the strap. RICH SEZ... Smooth move. Reducing the width of the strap increases RF- resistance, which lowers the L/R suppressor's VHF-Q, which in turn lowers VHF gain and reduces the chance of VHF oscillation. #### Whoa nellie ! Believe me... plan A was to use 1" wide strap.... which would mean using a 6" long - 150 w CCS globar... which I didn't have on hand. At 15 kw... on the high bands, the RF current is just unreal through that suppressor strap !!! Another way of increasing RF-resistance is to choose a conductor that is more resistive than copper. Example -- The 8169 / 4cx3000A amplifier at: appears to have no parasitic suppressor whatsoever, however the anode to blocking-cap connector strap, as well as the connection to the Bruene-bridge neutralizing cap is made out of a nickle- chromium alloy. ### Here's my problem with Nichrome. It GLOWS ORANGE on the higher bands. It runs so hot... this thermal heat in turn cooks the plate blockers !!! IMO, nichrome belongs.... in a toaster oven. Use wide copper strap on globars = zero problems. ANY SP type Globar will handle 350 deg C heat CCS... and when used with copper strap... run just fine. Even a big metal triode/tetrode will never get hotter than 225 deg C.. when maxed to the peg. ### Stainless steel is bad too... it will turn BLACK. ### Rich, on the high bands, the tube C makes up a huge chunk of the total C1 tune cap... which means extremely high RF currents on 17-10m......... all flowing through the parasitic strap material ........which is NO place for nichrome. Rich, when u finish ur 4 x 10... fire it up.... on 10/12m... with a dead cxr.... for just a few seconds.... then report back to us. I wanna know whether the bagel came out right.... or charcoal ! According to (W6HW) - a friend who worked for Collins Radio Co. - the 30S-1 amplifier used the same technique. ### Called "L-101" on my 30S-1 schematic. Later...... Jim VE7RF |
Re: Any idea's on a visual Grid / Cathode fuse indicating device ??
Steven Grant
What we are not seeing is when this fuse goes, the tube is already
bad!
toggle quoted message
Show quoted text
What the grid fuse does is protect the filament transformer IMO Steven W4IIV At 05:29 AM 10/1/2006, pentalab wrote: --- In ham_amplifiers@..., R L Measures wrote: |
Re: Passed 100 total members.... PARASITIC's solved... once and for all !!
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
wrote: statements can, things will definitely be less entertaining.such as the laws of AC circuit analysis do not apply to VHF RICH SEZ... Why read it more than once? ### One has to be either a complete nutcase or bored.... to read thousands of postings on.. "parasites" RICH SEZ ..before I started the grate parasite debate with Tom I was warned by a Ham in Manhattan that he wins debates in the eyes of his groupies by never backing down, even on issues that, to a RF-savvy person, make him look the clown. In my opinion, this is probably something he picked up from his father, Charles Thomas Rauch, Sr. - editorial - If I go to my grave with a bunch of newbies believing Tom's statement that Ni-Cr alloys have reverse RF skin-effect, VHF resonances can't ring, et cetera, I will not be resting in peace and that's for damn sure. ### Any RF software program that contains RF skin effect analyis... for doz's of different alloys... at any freq will tell one... in seconds flat.... that NI-CR alloys DON'T have reverse RF skin effect. Rauch is full of it.... the software just said so. Gee, that took all of 3 seconds to punch it into the software analyis.... what's next... how no commercial manufacturer of SSB gear is even allowed to use 2 x tone tests for IMD testing anymore ? [ 2 x tone testing is flawed, by juggling the freq of the tones about... you can easily hit a sweet spot where IMD drops, in the real world, nobody uses it] ### Rich, I think you are a.. " #5 " on the Energram personality trait book [#5's love to argue]. Did you get burned in the high school debating team ?? The grid resonance with the grid pins strapped to ground isThe grid resonance in a stock TL-922 is in the high 80MHz range. typically about 1MHz lower. How does this make the amplifier more stable at the 120MHz resonance in the anode circuit? ### Well, this IS the $64K question for sure. I don't have a clue. All I know is... when the 6 x grid pins are strapped directly to chassis.. with wide strap... on a SB-220/SB-221.. TL- 922... some Henry amps....... they become rock stable.... WITH the stock OEM parasitic suppressor's !!! ### Step 1 is to strap all 6 x grid pins to chassis. Now... IF a parasitic still occurs.... THEN add either [a] nichrome.... or [b] add a real suppressor... made from a globar wound with strap... and just enough turns to kill the parasitic. ### Why anyone would wanna leave in the 6 x 200 pf caps + 2 x chokes is beyond me. By directly grnding the grids you now [a] drive the amp with 20-25 watts LESS power on ALL bands or [b] really drive the crap outa the amp with the SAME drive power as b4.... and... [c] eliminate all parasitic problems.. and leave in the stock oem suppressor's ..... and [d] do the 160m mod easily, since the grids are now bonded to the chassis..... otherwise you gotta ADD another 1000 pf ..PER socket...plane nuts. Jim VE7RF Rich, AG6K |
Re: Any idea's on a visual Grid / Cathode fuse indicating device ??
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
### Not quite. The GRID RING is bonded to the chassis !! This fuses"is not a case like Rich using 1/2 watt resistor's as "grid which WILL leave the grid floating] RICH SEZ... Tony -- Have you ever blown a grid fusing R and observed what happens? ### WE are talkin bout a metal triode... complete with either a socketed grid ring... or a YC-156/YC-243... with a built in grid ring.... NOT a SB-220... with 1/4 or 1/2 watt 30 ohm resistor's installed between one grid pin and chassis. ## IF the 30 ohm resistors explode open... tube shuts down.... nothing happens.... except it's now a pain in the butt to change out the 30 ohm resistor's........ hence a rear panel 3agc fuse holder... with a fast 3agc grid fuse... installed between grid shunt and chassis..... takes 4 seconds to replace. In that above Rich modified SB-220... the grid is left floating in a vac....which isn't gonna harm anything... and no, the anode is not gonna arc to a now floating grid... then arc to the cathode. 73 Jim VE7RF |
Re: Any idea's on a visual Grid / Cathode fuse indicating device ??
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
a little current begins to flow, the tube cuts off. My modified SB-220 and TL-922 do this, and if a tube ever happens to short, nothing is damaged. #### Partially agreed. When a grid fuse [inserted between grid meter and chassis... (or between grid shunt and chassis on a multimeter)... AND the grid fuse is shunted with a 100 K resistor..... AND the grid fuse opens, one would think the grid current [600-900 ma on a 6000A7] flowing through the 100 K resistor would create enough bias to cut off the tube ? It sorta does..... fact is.... with 800-1000 w of drive..... you still get 1/4 pwr output . We simply REMOVED the 100 k resistor across the grid fuse.... and now all is well. Now when grid fuse blows open...... zero DC grid current.. zero watts outa the amp. [where the 800+ watts of drive goes is beyond me. It either stays in the cathode.. or cooks the grid.... or both ??? ] ### On one of my L4B's a few yrs back [this one was unmodified], It was still using the +130 V scheme for cut off bias on RX. The contacts on the 3PDT t/r relay were bad... and the +130 v was still being applied on TX !! You could STILL get power output... [now in class C] ! Fix was to replace relay.... then rewire with a 100 K in the CT.... and relay contacts shunt the 100 K on TX.... end of problem. RL Drake's... and later Heath's "brilliant idea" of using +130vdc for cutoff bias on RX... was one of the stupidest moves ever...... 2nd only to using 6 x 200 pf caps + 2 x rf chokes on the 6 x grid pins !! ### BTW, the 100 w + 1 kw contacts of the bad T/R relay were perfectly intact. It's the center contact [with the +130 V} that goes bad eventually. When this center contact is in mid air... you have opened the cathode up for a split second.... and the cathode will want to assume full plate V ! RICH SEZ... - note - In a stock SB-220 or 922, a shorted tube can destroy the filament transformer in short order. ### say what ?? IF the fil xfmr draws too much current on it's sec,...... the fuse/small breaker on the PRI of the fil xfmr should blow ! Oh, I forgot.... in it's infinite wisdom... neither the SB-220 or the Drake L4B even had fil xfmr pri fuses........ they relied on the ..'big momma' 20 A slow blow ckt breaker in the 240 V pri!!! Fix... install a fil xfmr primary fuse. ## The L4B has an extra winding on the fil xfmr ... after being run through the 1/2 wave rectifier [ one diode, one cap.... how CHEAP could they have gotten ?] u get +27 vdc... to run the T/R relay. Fix is.... either change to a FWB..[+27 vdc]... OR change to a doubler. The doubler will put out +63 vdc.... and a resistor is simply inserted in one leg of the stock T/R relay's coil..... and presto.... you have a fast sped up mech stock relay.... not qsk... but faster VOX. The + 63 vdc ocv can [and is] be used also for a speed up circuit for a RJ1-A. ## Either way... this extra smaller sec... used for the T/R relay... should be FUSED. Fix... install a 3agc fuse holder... with the appropriate sized fuse. .... end of problems.... like as in this small sec ever shorted out..... you don't melt the fil xfmr [ "fused" with a 20 A breaker in the 240 V pri] RICH SEZ... With 3-500Zs, 1k-ohm will limit anode current to about 25mA when the fuse opens. ### when WHAT fuse blows? A cathode fuse ? If so, I agree.... and it should be increased to a 20-100 K unit..and complete cut off will /shoiuld occur. RICH SEZ - A 250v-rated fuse in a circuit operated by 3000v is not good engineering practice. ### the 250 V rated cathode fuse is NEVER gonna see 3000 V across it... and here's why. The worst case senario will be a HV to chassis short.. or a anode to grid flashover, etc. With reverse connected safety diodes [ I use a pair of paralled 6A diodes pointed one way... and a 2nd PAIR, pointed the other way] .. connected between CHASSIS and B-.... the fault current simply flows from chassis through the diodes... and back to B- ... completing the loop... and presto... the sand filled fuse in the B+ blows.. every time ! Also use reverse connected 6A diodes across BOTH the grid and plate current meter's. You will NEVER arc across the 250 V rated fast blow 3agc CATHODE fuse !! ##### Question is... what's an easy way to obtain a visual TONY SEZ... If the cutoff bias is high enough, a neon bulb with aindication /led/neon/etc.... to let us know said fuses are series resistor could be used as an indicator. RICH SEZ. It takes c. 90v to light neon. A LED takes c. 1v. Also, with 1k=ohm and 3-500s, 25mA means the fuse is open, so one does not need an idiot light. ####### When the big amp is 30' away... in a garage or a workshop, etc...."idiot lights" def are needed ! RICH SEZ...Also, when the grid-I meter deflects backward, a tube has a filament that is shorting to the grounded-grid. ### agreed. And the fix is to install reverse connected diodes across the grid meter/shunt.... then the diode will conduct.... instead of deflecting ur grid meter backwards. #### For some added protection... we are thinking of an adjustable spark gap between load cap ...and chassis..... set to fire at a V higher than the normal low swr V.... and a point well below the rating of the 5 kv vac load cap. I think Rich may have done this ? RICH SEZ ..Correct ### I don't want the expensive ceramic vac load cap to ever internally arc. RICH SEZ.... Spark gaps are good! However, adding a rugged low-ohm low-L resistor in series with the spark gap helps to limit peak-I during a glitch. ### Huh ? This is HIGH RF voltage across the spark gap [across the vac load cap]. What do u suggest.... a 50-500 ohm 90/150 watt globar ??? There's already a heavy duty glitch R in the B+ of the HV supply. Adding R in series to any spark gap may well slow down how fast the grid/cathode/ sandfilled HV fuses blow ??? Later......Jim VERF |
Re: Chinese AL-811 / Will nominated as .."project Manager"
pentalab
--- In ham_amplifiers@..., "Mike Sawyer" <w3slk@...>
wrote: weren't looking. A little wind may restart the kindling again. Will is a good choice, he's a little more subtle than me;>)######## Nice try Mike.......... it sure as heck didn't make it. Now, W8JI et all... has pissed off HSU.... somebody should tell HSU to move over here. HSU seems like a nice fellow.... now he's having to defend his country. The very latest post is.... "the administrator" has reprimanded all of em ..again ! Later Jim VE7RF |
Re: Passed 100 total members.... PARASITIC's solved... once and for all !!
Bill Turner
ORIGINAL MESSAGE:
On Sat, 30 Sep 2006 05:21:57 -0700, R L Measures <r@...> wrote: even on------------ REPLY FOLLOWS ------------ Word is he's still out there with his grid dip meter looking for series resonances. :-) Bill, W6WRT |
Re: Any idea's on a visual Grid / Cathode fuse indicating device ??
On Sep 30, 2006, at 10:53 AM, Tony King - W4ZT wrote:
R L Measures wrote:Nothing happens. ... R L Measures, AG6K, 805.386.3734 r@... |
Re: Chinese AL-811 / Will nominated as .."project Manager"
Mike Sawyer
¿ªÔÆÌåÓýHey folks,
??? I just planted the seed over there when the 'moderators'
weren't looking. A little wind may restart the kindling again.
??? Will is a good choice, he's a little more subtle than
me;>)
Mod-U-Lator, Mike(y) W3SLK ----- Original Message -----
From: pentalab
Sent: Saturday, September 30, 2006 3:22 AM
Subject: [ham_amplifiers] Re: Chinese AL-811 / Will nominated as
.."project Manager" --- In ham_amplifiers@ |
Re: Any idea's on a visual Grid / Cathode fuse indicating device ??
Tony King - W4ZT
R L Measures wrote:
<snip> nope, no grid fuse if the grid is bonded to the chassis directly ;)### Not quite. The GRID RING is bonded to the chassis !! ThisTony -- Have you ever blown a grid fusing R and observed what happens? I was referring to B- floating off ground but if it isn't, then there isn't an issue. 73, Tony W4ZT |
Re: 4 Tube 811 Amplifier.
R L Measures wrote:
Amen!! So true so true.I suppose you require the same deal onWith multi-tube indirectly-heated cathodes, adding cathode RF-NFB is a piece of cake, but with directly-heated cathodes it's a bucket of snakes. Thats why I built a 8171! At one point Rich also gave me some help,I remember building a 2 x 4-1000 amp... with two ofSmart move. If one needs more suds, go for One tetrode with handles. now it runs like a charm! 73 Jim SM2EKM |
Tuned Plate Tuned Grid Oscillators
Bill Turner
On the "other" reflector a statement was made about TPTG oscillators
and I posted a follow up question about the time of the Great Migration to this reflector so I never did get an answer. I'd like to ask it again here. The 'Gentleman From Georgia' (you know who) made the comment that a TPTG oscillator will not oscillate if the grid tank is tuned higher in frequency than the plate tank. Under that condition, apparently the phase of the fed-back voltage is wrong and oscillation can not occur. Since this is essentially what a VHF parasitic oscillator is, it caught my attention. Is this statement true? If so, then it would seem that all one has to do to achieve VHF stability is to make the two resonances meet the above requirements. Can it be that simple? TPTG oscillators - the intentional kind - have not been used in ham circles for decades so I wouldn't be surprised if knowledge of them has been pretty much lost. All comments welcome. 73, Bill W6WRT |
Re: 4 Tube 811 Amplifier.
On Sep 29, 2006, at 4:16 PM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:That's the awful reality of adding cathode RF-NFB with thoriated tungsten tubes in parallel I suppose you require the same deal onWith multi-tube indirectly-heated cathodes, adding cathode RF-NFB is a piece of cake, but with directly-heated cathodes it's a bucket of snakes. Smart move. If one needs more suds, go for One tetrode with handles. Just trying to trbl shoot a 4 x tubeAmen, Jim. Dennis Had is reportedly now in the AF amp business -- which is where he pretty obviously should have gone in the first place. R. L. Measures, AG6K, r@somis,org, 805-386-3734 |
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