The return of K1JJ

[WA1GFZ]

You guys will observe the solid state inductor is a tad easier to construct.
I agree with you Steve, but Tom Vu has no close neighbors. As far as near field I'm not crazy about being exposed to too much RF.
Chromerics makes some nice Shielded panels you can see through but not sure the low frequency attenuation is all that great.
Maybe he should consider some shielding once he gets things stable.
We like "ding lice is done" but wouldn't want Tom Vu to cook himself.
One of my "around to its" is to build and calibrate a field probe for the shack.

[The Slab Bacon]

With that much stray RF in the shack, he wont need an "off air monitor". He'll be able to hear his own audio ok-fb ringing in his ears and dental fillings!! But Tommy has never been one for doing things in a small way

[WA3VJB]

never been one for doing things in a small way

Not in a small way indeed.

Sure is a good looking machine.
Love your construction standards, right down to the Rastafarian motif.

You'll be able to legitimately play in the Heavy Metal Rally with this beast, Tom, caw ! maw !

[K1JJ]

It warms my buzzardly heart -  I did miss you miscreants dearly.... :-)

OK on the unshielded cabinets, Steve.  Well, I've run unshielded stuff like this for years. I noticed that a large group of 95+ year old radio pioneer/broadcash buzzards died off in the 1990's. They all were overexposed to HF. I don't worry about HF with lifespans like that, esp considering the avg lifespans in the early 1900's.  HF PROLONGS life by killing off the flied lice.

Frank, I would like to hear more about the see thru panels you spoke of. Heck, I could even put aluminum screen over the Plexiglas if needed. I do plan to enclose the entire PDM rig into a Plexiglass display case. There will be no way to get across HV, even if you tried. I figure as an old buzzard, we all become forgetful and need failsafe barriers like that as we get lax.


Steve, I ran the PDM rig up to 1/2 power and had no acoustical ringing at all under normal voice modulation. Frank remembers our old 90's PDM rig's coils doing chin-ups with the bass notes... :-)  I then ran a PDM sideband suppression test: I put 500W into an antenna and listened on an antenna 300' away. The fundamental signal was overloading the receiver, while the sidebands were down almost in the noise. Maybe the house aluminum siding helps to shield the pdm switching noise, I dunno.  The filter attenuation with the series 113kc trap works quite well now.


Joe/BWO - your truck is running beautifully - I'm so glad I bought it from you. Still seems like new.


I picked up a few 4X1's so far. One may be close to new from Stu. That may go into Fabio with the new 833C's.


Paul, what is a RastaBraid?  Is that like a dreadlock? The rig does have a Jamaican look to it, I must admit man.
Yes, details, details. That's what it took to finally get that PDM rig working right. Bypassing, layout, suppressors, etc., it all adds up to stability.


Slab, you have a talent for taking pics of your 4X1's in action. I will get some later as things show some orange color.


Steve/QIX, I built up your new PDM kit generator. That is really a nice quality board with the feedthru holes. It had all the parts present except for one .018 cap. That's not a bad % for a kit, OM.  I'm hoping your new design will be more stable than the one I built using the point to point PCB from 2005.  We'll soon see once tested.


I want to post some pics and latest schematic of KLR's new FET cathode audio driver. I'm telling you, this board may become very popular once guys realize how simple it is to drive ANY modulator cathodes with a 5W fets. Neg feedback and absolute cleanliness.

Also want to post pics of the blown 813 X 813's. There's lots of guys who have built these up and the more pics the better to encourage building. That single 813 using 2500V will put out a fully modulated 500W carrier. The KLR FET audio driver board is the perfect match up for the triode-connected 813 modulators. It is the best sounding plate modulated rig I have built to date. Of course, GirlyMan will sound better with no mod iron to fuss with... :-)

I just hired my first employee - I train him every day, so will be flat out for a while. But hope to finish up GirlyMan once the PDM gen is built and the 4X1's arrive here.


DERB:  Real happy to see you're doing well and getting back on the air.  That BJB avatar is still the best one on the BB... :-)

Later dudes -

Tom, K1JJ   (Known on the east coast as "Ten-Large," caw mawn)

[steve_qix]

Hi Tom,

Very good !!  Although, when I was in broadcasting, I was exposed to RF energy - low frequency (broadcast band) pretty heavily, but NOT strong E/M  fields.  These E/M fields are what will be produced in the PWM filter inductor.  Those fields are not supposed to be good, and there have been regulations developed (many years ago) about exposure limits.  E/M fields are produced by anything with a choke or transformer carrying AC or varying voltages such as flyback transformers (old computer monitors running at very high frequencies), filters, etc.  These high energy transformers/chokes, running at 10s to 100s of killohertz will produce some fairly serious E/M radiation.

Ok on the board kit.  I'll check that part.  I don't do the kitting myself - someone else does it.  I'll check the master parts list and make sure it is there.  Each part on the list is checked off as it is put into the kit package.  With so many parts, it's necessary to have such a system!

Oh, one more thing - very important.  The PWM board you got from me is set up for a higher bandwidth system than you may have.  The solid state modulators have better high switching rate performance at small pulse widths (due to the lower impedance with respect to stray capacitance) than do tube modulators in the same service.  You will probably have to lower the switching rate from the stock 140+kHz to something below 100kHz.  You simply change the value of one resistor, the timing resistor (RT) - part of the SSM2166P PWM generator section of the circuit, to a lower value.  Pull down chip's the documentation form the TI site to see what to do.  It is a very simple change.

Talk later and Regards,

Steve

[N3DRB The Derb]

fo 10 - 10 - large 10 large my nappy headed soul brotha 10 large. I'm workin on my maw workin on my maw workin on my tuna trying to pull myself out of the mud so I wont be a muddy water slappa no mo. I'll have to dress up in my respect suit and pay my respects to the the one an only 10 large in charge when he lay his PDM maw down. I got teh southside covered brothaman and I'll see you in da ghetto real soon now. 

I just got down. 

[K1JJ]

Yo BJB, my Papa-Large Rasta-Braided Bro!

I got ants in my pants and needs to dance.

Been gone so long I've got the laugh to keep from crying blues.

Ten-Large   (Good friend of FiftyCent)

[ka3zlr]

Hi Tom,

 Very much a Master Builder your creations are Inspiring Tom Vu...Awesum....

[Steve - WB3HUZ]

I wouldn't worry too much. The maximum permissible exposure per the FECE is 56.26 mw/cm2 at 4 MHz. You only need to be a bit more than 2.5 feet from a dipole radiator (2.2 dBd gain) with 1000 watts input. Since all the conductors in the transmitter are very short at 4 MHz, I'm assuming their gain will be at least -10 dBd. This means you could run 10 kW and not exceed the radiation exposure limit.

[Bill, KD0HG]

Hi Tom,

Very good !!  Although, when I was in broadcasting, I was exposed to RF energy - low frequency (broadcast band) pretty heavily, but NOT strong E/M  fields. 

What about us 100 KW FM dudes???

Fell off of a ladder and broke my right arm two weeks ago. When they were taking X-rays in the hospital ER they tried to situate a lead-line robe over my nads. Told the nurse not to sweat it, I wuz DONE having kids. LOL.

MoFos set my arm the old western way. No bullet to bite on, no shots of firewater, just a dose of morphine and two docs pulled and twisted the arm until I could hear the bone ends grinding together...GOOD- Hold 'er there..." If I knew better I would have pre-medicated myself from the street pharmacy in downtown Boulder.

[Steve - WB3HUZ]

You're screwed.

Hi Tom,

Very good !!  Although, when I was in broadcasting, I was exposed to RF energy - low frequency (broadcast band) pretty heavily, but NOT strong E/M  fields. 

What about us 100 KW FM dudes???

[K1JJ]

How's it going there Big Country?

OK on the 4 mhz RF. I'm not worried about that.  But how about the EMF Steve/QIX mentioned above?  

There will be square waves and audio going through those coils at 113kc at the same current as the finals.  (The first coil will be 113 kc square waves and the next coil will be mostly audio.)

The coils will be about ten feet away from me when operating.     Each large coil is 10" diameter and has about 600 turns.

I plan to put a large Plexiglas in front of the coil area, but I wonder if I should add a wire screen for shielding too?

T

[Carl WA1KPD]

Tom,
Bit off topic, but I have been meaning to drop you a note and tell you I thought your letter to the editors of The Courant several months  back was well done.

73

Carl/ KPD

[Bill, KD0HG]

You're screwed.

Hi Tom,

Very good !!  Although, when I was in broadcasting, I was exposed to RF energy - low frequency (broadcast band) pretty heavily, but NOT strong E/M  fields. 

What about us 100 KW FM dudes???

Thanks, Steve.

To think I sacrificed myself for "Don't fear the Reaper..."

[Steve - WB3HUZ]

Ola, 10-Large! Howzit hanging?

The exposure limit at 113 kHz is 100.00 mw/cm2. Even with 5000 watts into a full-sized dipole (imagine how big that would be) you only need to be 5 feet away to be below the limit.

Forget shielding. The field is magnetic. You would need eighth-inch or quarter-inch thick steel or mu-metal to do any real shielding.

Bill:





The limit at 100 MHz is 1.00 mw/cm2. If you are 190 feet away with 100 kW and a dipole, you are OK. Most FM arrays have more gain than that, but not at a negative 180 degree angle!

How's it going there Big Country?

OK on the 4 mhz RF. I'm not worried about that.  But how about the EMF Steve/QIX mentioned above?  

There will be square waves and audio going through those coils at 113kc at the same current as the finals.  (The first coil will be 113 kc square waves and the next coil will be mostly audio.)

The coils will be about ten feet away from me when operating.     Each large coil is 10" diameter and has about 600 turns.

I plan to put a large Plexiglas in front of the coil area, but I wonder if I should add a wire screen for shielding too?

T

[WA1GFZ]

You guys ain't seen nuttin. The PDM rig Tom Vu built in '91 makes this look QRP.
Back then the power supply was too far away and he couldn't buy the parts he needed to make it hang in. Tim will remember the day of the Jacob's ladder modulating through the arc with a nice echo through the forest. I remember getting on the portable and telling him what he was doing. Then I had to ask. " how does the rig look making such a big arc across the feeders" He came back with " plate current is down a bit"

Tom,
Get yourself some metal window screen and put it against the Plexiglas it will work just fine and a heck of a lot cheaper.

[steve_qix]

Right, for magnetics, steel or mu-metal will do it !  I'm probably just being a bit paranoid.  After working at Digital in Electro-Magnetic Compliance for about a year (before going into development), I got sensitive to the whole thing    If you read the European regulations about this sort of thing, you'd think everyone who used an old-fashioned TV set or monitor was going to get cancer  

[K1JJ]

OK on the E/M data, Big Country.  Looks like no problem.  But as Frank says, putting a steel screen against the big display Plexiglas might be a good idea anyway.


Carl - Tnx, OM.  You never know who's reading the newspaper... :-)   Yes, I saw enough careless people running their dogs on the ice - I had to say something about it. As you know, dogs have no idea that they can fall through and get trapped. It happens more in the late fall and early spring when the ice changing a lot...

Man, uploading speed has slowed to a crawl here in the last month or so. Comcast cable. Uploading a picture has become a real task. The video/movie downloaders are taking up all the bandwidth.... sigh    I also have trouble sending out an email with attachments > 100K.
The next commodity/energy shortage? = Internet Bandwidth.


T

[WA3VJB]

Tom, haven't you heard ?

Comcast has taken its cue from the ARRL and has imposed a Bandplan on Bandwidth.

http://blog.wired.com/monkeybites/2007/09/comcast-custome.html

[Todd, KA1KAQ]

You guys ain't seen nuttin. The PDM rig Tom Vu built in '91 makes this look QRP.

Ah, yes....the BIG PDM rig of the early 90s. Wasn't that the one used frequently by Sgt. Anderson?   

Looking forward to the return, T - maybe it'll get some of these signals offline and on the air.  The BJB has been on a few times, good sigs with 15 watts large.

[N3DRB The Derb]

i got the amp almost done - just needs a internal coax cable toobs put back in and some wiring checkout. I'm feeling a bit better today, I might go get at it.

[K1JJ]

"I'm as pretty as Fabio... and smell sweeter too, don't ya think?"

Yaz III

[K1JJ]

"And I'm smarter than Fabio too."
- Yaz


The Blown 813's under glass  -     (One 813 X 813's, plate modulated with new WA3KLR designed FET cathode audio driver)

[N3DRB The Derb]

Tom Vu sure love the plexi. Never known him to have rig with metal screen - makes his modulation xtal clear. (cum awn)