The AM Forum

        Summer is usually my radio free period till the cold weather, but a rainy day has me in the shack and reflecting on a disastrous summer. After slicing the knee open with the chain-saw followed by the broken ankle...."other than that how was the play Mrs. Lincoln?"
        I find myself facing a heart catheterization on Monday....Arrgh! I had some minor chest pains and they found I had an abnormal stress test. If they find anything they will be putting in a stint(s). My sister died of a massive heart attack last year, so it behooves me to have this checked out.
        On a lighter note I will be finishing the GS-35 amp project and as I type Steve has found and fixed my modulator for the 24 pill E rig and that will get put back together shortly. Thanks Steve!! It was a very complicated problem and Steve may write up the findings.


Brent W1IA

Man, when it rains it pours...sorry, really sorry, to hear that buddy.

Hard to remember that we're not invincible teens any more, even if we still feel that way.
I'll been working on a number of wellness issues here, nothing major, but darn well
making sure that I don't have something serious happen.

I'll keep you in prayer for the operation and a speedy recovery.
May see you at the fall NEARFest, if not, hope to catch you on the air!
I've been doing a good deal more listening than talking, trying to catch
up on projects.

-Bruce

Hi Brent,

Wow,  does seem like a rough summer! Good luck with the procedure,  and recovery.  Does sound like it IS important to keep an eye on your heart.

73  Good Luck,   Vic

Thanks Bruce..I'm sure everything will be ok.; Otherwise I have to will the 24 pill rig to someone HA! ;D  My basement heating pair of GS-35's will need a new home too.
As long as whomever gets it will make sure they run the Macaroni net for me! ;)
PHHredd will miss me when I'm gone!

Tina

Thanks Vic.....are you part of the west coast gang? I saw a post about internet audio video to my friends on the west coast. Been meaning to check that out.

Brent"Tina"

Brent I worked you last winter on 75 (or 160 but I'm pretty sure it was 75) m.  Funny thing we were just talking about bypass surgery and cardiac tests and such at this months ham club meeting today.  Good luck; I'm sure everything will go well.

Rob

Break a leg!  er, no.  Rip up that treadmill, nah.  Take heart things will get better!  :)

Best wishes. 

Brent, pay no attention to those pains, just smoke two packs of cigs a day and drink whiskey, that's what some hams do?? Just Kidding! I hope you make out well ;D ;D

Brent good luck on Monday with the procedure. Hopefully you won't need a stent, but a friend of mine just had one put in and he claims that now he feels like he's 25 again! Hopefully everything will go as well for you as Steve's repair to your modulator deck!

I happened to be messing around at the bench while you, Steve, and Tom were chatting on 75 meters this afternoon, and recorded a bit of your deck being put to the test by Steve. It sounded very nice. Sound clip attached for your listening pleasure. (Starts out receiving in the 10 kc bandwidth position, then switches to 12 kc.)

Rob W1AEX

Brent,
if the stent is needed you will feel much better.

Be thankful for the medical system in the USA to get you through this. We're considering moving to the Philippines in 4 yrs and the medical may be cheap and pay easily out of pocket BUT certain medical needs and procedures are not reliable here and folks have to go to Hong Kong or back to the USA to get fixed.

Fred

Tina,
        come on down after your procedure, we can chew up a keg of rusty nails, fart sparks, and compare notes!! then we can both comare meds and piss and moan about getting older ;D  ;D

whoever said "life begins at 40" should be tarred and feathered! ! !

Good luck and get well soon!!

Brent-- Those cardiac caths are pretty common these days. We do dozens of them a week here at the Boston VA. The stent(s) sure beat bypass surgery. Good luck; you're due for some.  :)

Roni

All the best to you, Brent, for the procedure on Monday. You'll sure be coming home to some great audio. That clip sounded great!

ldb
K5WLF

Best of luck.

I'm sure you will be running marathon sessions of the gnet soon.

2VeryWeak.

Yo Brent -

Well, that makes three mishaps in a row, so after this procedure you should be on a roll for a long time now... ;D

I'm looking forward to the radio season coming up. From the audio clip, looks like you guys are starting in already.


The discussion gots me interested in doing the mods to the charge pump or whatever needs to be done to my own class E rig.  Let's see if we can axe Steve to document this for existing rigs. Maybe a few scope shots of before and after waveforms showing the ringing will show us what is considered excessive ringing and not.

Anyway, I've been very busy with non-ham related projects every day, but will find the time to give ya a shout soon.

T

Brent manages to create the unusual conditions, that's for sure.  Due to some odd combination of filter, bypass capacitors, lead lengths and other conditions, there was a lot of ringing on the PWM switching waveform on the rising edge.

There is usuall a very small amount of this, but  here, there was a lot of it.  The modulator uses a charge pump to produce voltage for the driver circuitry (which is floating), and normally it is a build-it-and-forget-it type of circuit.  There are some 50 of these operating in the field with no problems whatsoever.  I have 4 of these in my own fleet.

But, Brent's filter ringing was such that the charge pump diode was switching in the low mHz range rather than the 160kHz range which is the normal switching frequency.  The charge pump diode would get very hot switching at the ringing frequency, and would fail after about 10 minutes (sometimes less) of operation.

The solution was 2-fold.  First, I applied a bypass capacitor to the power supply line coming into the modulator,
and 2nd, I put a small inductor in series with the charge pump diode along with another diode (as a damper), and a capacitor and a resistor back to the high voltage supply, to remove the unwanted high frequency components from the charge pump.  I will document the change (which is simple to make), however since no one else has reported any problems with their modulators at all (and I know of no other incidents where charge pumps were failing), this may be an isolated case.  However, because it is possible to happen elsewhere, I will certainly document the change.

Regards,

Steve

That is a big diode and surprised it failed. There must have been some interesting layout issues.

Hi Frank - well, the diode isn't THAT big   :)  - it's a 3 amp 600 volt diode in a normal 3 amp diode-size package with leads on each end.  The device dissipation might be 1 watt tops.

I don't exactly know what combination of factors lead to the ringing components - I've never seen any such thing anywhere else - just with that modulator.  But, I was able to cure it with some bypassing on the HV coming in, and I added the charge pump filter for good measure!

Here is the section of the PWM output with the charge pump, showing the original circuit and the modified circuit.  Components L1, D520, C520 and R520 are the additional components.  Essentially, inductor L1 will remove any high frequency components that might appear on the PWM waveform (ringing, etc) and keep them from getting into D500, the charge pump diode.  D520 is necessary to damp L1.  C520 bypasses the damping current from D520, and R520 is a protection resistor to protect the low voltage power supply from excessive current should the transmitter be operated with the high voltage supply turned off.

So, that's it!!

(http://www.classeradio.com/charge_pump.jpg)

Steve, I suspect it was also due to C500 not a good HF bypass.
Brent, good luck with the pen spring installation. Pen springs are great devices and are used to make great power valve blow out preventers in Holley carbs.

Steve,

Thanks for posting the mod.

Could you also post a pic of what a maximum "tolerable" ring looks like in the PDM output?   I haven't had any problems like Brent's, but want to see if my small amount of ring is acceptable before doing the mods.

I already did a lot of bypassing and shielding changes - and shortened lead lengths back in the shake-down phase and was hoping maybe I didn't need to change anything else...

T

a 3 amp diode can haul big time transients for a short time. I suspect 100 amps would not hurt it. Yes long leads cause series L and ringing. Maybe a big bulk C at the input of the board in parallel with HF bypass. This would shunt the long lead back to the supply inductance. The filter input is inductive so a longer lead is ok. Also look at the ground on the damper diodes and make sure any extra bypass is connected to the damper diode ground. 

That would have been nice ;D   It was the first thing I looked at, and had nice, clean DC there.  Turns out the ring on the PWM output waveform was turning the charge pump diode on and off - it was that significant.  There was a lot of current flowing in that circuit - C500 and C503 were quite warm when Brent was having the problem.  Now they are cold.

This is a good improvement to the circuit, but I wouldn't bother retrofitting existing modulators unless there is excessive heating of D500.

Tom, I'm sure you would have seen a problem before now if you had a ring issue.  You could take a pic of your PWM waveform and I'll have a look at it.

I accidentially left my transmitter (it's almost identical to Brent's) on for more than *4 hours* once, at full power.  No probs whatsoever.  Got to see how much (or how little) things actually heated up.

The pulse modulators are ultra-efficient.

Regards,

Steve

"The pulse modulators are ultra-efficient", but very layout critical
I bet the filter is some distance from the switch to get that big ring to swing below the boost voltage and conduct the diode. Sounds like there is a transient issue with the filter response to set things in motion. Also could be ground related.

Thanks for all the kind words guys! The catheterization is more of a preventative maintenance due to my sisters demise and I have another surgery scheduled later this fall (unrelated to the heart). The doctors would not preform the surgery unless my heart was in tip-top shape. I feel great all things considered. I am back on the air with the 24 pills now that the modulator has been fixed by Mr. Qix

See you on the air and at Boxboro this Saturday! ;D

Brent"Tina"
W1IA

Brent:

The best of luck with your health. I know you'll do well.

This radio stuff is a distant secondary concern (other than providing a good escape to life's difficult times).

Dan

Yep, you said it, Dan.

Yesterday I was on a ladder leaned up against a round tree (big mistake) and the ladder rotated and I took a spill. I hit the ground with my left foot first, at a weird angle and got a bad ankle sprain. Lot's of swelling.  I've been trying to get around on one foot lately. It's so easy to take simple things, like walking around, for granted. Right now it's a major adventure just to get up the frickin stairs... YAz watches me in Bizzaro-world wonderment.;D

T

My masta  Kung Fu es piss weak

Amen to that. I was helping the YL build a shed and was standing on a crosspiece about 3 feet off the ground that let go and dumped me. My left foot hit the sill of the shed with my toes up on the sill and my heel striking the ground 6 inches below. Bye bye Achilles tendon! After the screaming and red haze receded, I at first I thought it was just a bad sprain, but after a couple of days gimping around with a floppy foot and a doctor visit, I learned my whole summer was trashed. Surgery followed by 6 weeks on crutches, then a walking boot, etc etc. What an eye opener in terms of how limiting an injury impacting mobility can be! 2 years later, it still reminds me that all is not as it was before.

Brent, good to hear you on the last couple of days, and good luck on your procedure Monday. We'll be keeping good thoughts for you.

Yikes!!  That is some injury.

It's so frustrating cuz it happens so fast and goes really bad in an instant. There's no way to turn back the clock.  I've made a lot of changes in my life lately, mostly protection-safety related. I need to do a full review of standard working/falling and walking stuff ASAP.  

Tendons, having little blood to work with, can take months and sometimes over a year to heal.  In contrast, muscles heal quickly.  I've been taking too many chances when working around here. It's funny that I've never been injured climbing these towers after hundreds of work hours. It's usually the stupid stuff like ladders and stairs, or not taking the time to figure out a safe approach, that gets us.

T

Tendons, having little blood to work with, can take months and sometimes over a year to heal.  In contrast, muscles heal quickly.  I've been taking too many chances when working around here. It's funny that I've never been injured climbing these towers after hundreds of work hours. It's usually the stupid stuff like ladders and stairs, or not taking the time to figure out a safe approach, that gets us.

T
[/quote]

I used to run up and down my 80' tower (big tower...I climb up the inside) like it was nothing.  I would go up and down the thing 3 or 4 times a day and really not think much about it.  Then.....something called arthritis, commonly associated with old buzzardness, set in.  I can still climb up there, but unfortunately, I seem to pay for such exploits with a painful aftermath that can last for weeks....consequently...don't do much climbing anymore.  Trouble is...it is really difficult to get anybody to do antenna work around here.  You end up having to pay somebody (commercial contractor) a healthy hourly rate and they don't feel compelled to give "amateurs" a break.  I'm not denying that their time is valuable and the risk can be high, but it makes antenna projects a lot less affordable.

Tom...my crazy tower safety story goes like this:

I was installing a huge 60' boom yagi for 20 and 10M.  Had to hoist the heavy beast sideways up to the top of the tower utilizing a jeep with a winch and cantenary wires up to the top.  Got it up there...and clamped it to the 4" mast pipe.  The boom had an overhead guy system supporting it with a center angle and guys going out to points on the boom.  I, of course, was up inside the tower when a gust of wind caught the boom spinning it slightly and clamping me inside the tower between the boom and the tower itself.  Fortunately...a neighbor saw my plight and was able to pull on a rope, still attached and moved the boom far enough that I was able to crawl out the top and down the outside of the tower.  A little bruised, including my ego, but very much in one piece.  Scared the heck out of me...but I turned around and went right back up the tower to finish the job.  Kinda like getting back on the horse that threw you.  Anyway...ever since that little adventure, found myself being a lot more careful.


By the way Brent...hope everything goes super with your procedure and you are feeling great soon!!!

73.  Jack, W9GT

Your not kidding Tom. I was finishing up the floor job putting the last few courses against the wall in the bedroom. I went to stand up for about the hundredth time on a weird angle with tools in my hand. I pulled a muscle in my leg that is just starting to feel better after 3 weeks. I finally stated walking again this week.
Heck, this is still better than sitting in front of the boob tube with a remote in my hand. Too many people call that a life, we don't

[quote/]
By the way Brent...hope everything goes super with your procedure and you are feeling great soon!!!

73.  Jack, W9GT


[/quote]
Thanks Jack,
I love your page on QRZ! And your right "Life is to short for QRP"
Nice wood platform tube rigs.

Brent

just make sure the 24 pills stay in your transmitter and not in your daily regimen!

Best wishes brother Brent!!

I was carrying 2 sheets of 1/2" plywood the other day and sneezed.
Pulled a muscle in the lower left back that anchors at the left butt cheek.
4 days later it's just now starting to feel better.

Lotsa power in a sneeze!!

" Lotsa power in a sneeze!! "

New meaning to the phase, "put some ass into it"


klc

Hey Brent. This sure explains why you have been quiet.

My dad who passed last May had a 3xbypass in '86 and stents and other bits of services since, made it to 81. This is from a line of men in the family who never made it much beyond the late 50's in age! All will be well.

Hope you feel better soon.

Brent,
I hope things are going well with your procedure today.  I am sure it will go well and you will be in good shape for the follow-up operation you were talking about.   
Speedy recovery!
Regards,
Joe, W3GMS

Everything is FB guys! Other than being on a cold table and drugged up on phyntenol...I was on the table when the doc got called into the ER for someone having a heart attack...Rrrr! Made me uneasy. An hour later they injected the dye and pronounced everything clear. YAY! I home still doped up on meds...phew!

Nothing like a sixties moment :P

Brent

Excellent! Nothing like getting *good* news from a doctor to make your day.

Awesome !!!!  I guess you'll be a-strapping for quite a few more years  ;)  Glad the results were positive.

Great news Brent!  Strap On!

73,  Jack, W9GT