A modern 50 KW AM BCB transmitter

[Bill, KD0HG]

Thought these pix I took today would be of interest. It's a new Nautel 50 KW transmitter. The size is amazingly small, like a large refrigerator. No more taking up half a room. Just incredible.
The internal 700# power transformer takes up 1/3 of the cabinet. It'll do 55 KW and 140% positive modulation at the same time (into a dummy load, of course!)
Eat your heart out, JJ.  

There is an active touch-screen monitor on the front. Not only traditional stuff like modulation % is displayed, but there's also an active Smith chart and spectrum analyzer. The blue line on the spectrum analyzer is the legal mask that the transmitted spectrum must comply with. The little 'boxes' on the left and right of the carrier are to accommodate the IBOC subcarrier. You can see that at 40.8 KHz above the center, the transmitted crud is 76.12 db down. Move your finger across the display to wherever you want to measure. The Smith chart is showing that at 910 Hz above the carrier, the antenna load is 49.525 ohms resistive with only a tiny amount of reactance. Cool stuff! This is what my next homebrew rig should look like- LOL

The tubes on the floor behind me are a pair of 4CX35000s a retired transmitter once used.

[Bill, KD0HG]

And here's the Smith chart:

[ke7trp]

Awesome Bill!   I had a chance to see one of these on my W7TFO tour of the mountain.  It was not up and running when I was there but I was very impressed with it.  Probably pays for itself in the power it saves.

Nice pics!

C

[WA1GFZ]

Bill,
WE need information. I wonder if it is a digital like the Harris DX50?
Schematics, final part numbers, And most of all. How about information on the combiner.

[Bill, KD0HG]

Bill,
WE need information. I wonder if it is a digital like the Harris DX50?
Schematics, final part numbers, And most of all. How about information on the combiner.

Yes, it is of course solid state digital.
I'll look up how many pills it incorporates and other details once I grab the manual. Give me a few days. It's all new to me. It contains a very complex piece of software, and it's all Linux.

We do have a Harris DX-50 on site, which is now the backup transmitter, and it's been a workhorse but this new rig is insane with what it can do. It's a fraction of the size of the DX-50. I'll bet it could do 100 KW out if the software allowed it. Got a peak power meter in it, I've seen 300 KW PEP out of it while testing into a load, maybe 55 KW and 130% modulation.  Brought a big grin to me. That pretty much maxes out the 3" rigid line it feeds. Damn, it isn't much bigger than an old timey KW-1.  Inside the box, it's about 1/3 power supply, 1/3 RF and 1/4 computer.
The combiner is internal to the cabinet. The final matching net is made of paralleled 3/4" copper pipes, one big sucker of a coil. The 700# power transformer came shipped on casters, uncrate it, roll it into the back of the cabinet with a pry bar and bolt down the cables. IIRC, it's about 90% efficient. With electric bills running ~$4,000/month, it probably does pay for itself over a few years. Hang on, I'll be back.

There's a couple of dozen of these things on the air around the US now.

I wonder if it could be retuned to 1885...? Into the big stick? You can set the carrier frequency in a video screen operating the exciter, LOL.

How technology has evolved.

[K5WLF]

The capabilities of that transmitter are simply flat, freakin' awesome!

But, you know, I'd still rather have a Collins 20V-2 or a Gates BC-1J with those magnificent 833As glowing through the window in the front.

I admire the myriad functions of the new gear, but I'd rather live with an old hollow-state rig any day of the week.

Just like vehicles. I enjoy driving my pickup even though it has a computer in it. It's a '93 Dodge Dakota -- not overly computerized but still not fully mechanical. All things considered, I wish I was still driving my '66 Chevy 3/4T with a 325 HP 327 CID 'Vette mill in it. Not a computer in sight and I could keep it running with bubble gum and baling wire.

The above opinions may well be a result of the fact that I turn 60 a week after Friday.

ldb
K5WLF

[flintstone mop]

The Smith Chart is an amazing piece of valuable info.

Fred

[WA1GFZ]

Bill,
A number of us would be interested in any combiner information you have for the DX50. I had a look at the manual years ago but didn't get a good look at the combiner design.
The DX50 used old FETs, I bet the newer devices work a lot better.
I think the DX50 ran 85% so making the jump to 90% is quite impressive. 

[flintstone mop]

hey Bill
Are you working in an A.M. station playing music?? That would be an outrageous sound.
I hope the processing will make maximum use of the allowable bandwidth for great TX audio.
fred

[W2ZE]

Bill,

That bandwidth measurement looks pretty good considering you're down at 850. Did you do any work to the stick to have it optimized? When Nautel came out with this box last year, I asked if the Smith Chart was a true representation of what was going on or was it just a reference, and they assured me that it was the real deal. Spectral regrowth looks pretty good too;it looks like it just meets mask, but most are close anyway. The best spectrum shot I have ever seen was WOR's in NYC. TR has his regrowth down -72dB! Looks exactly like the AM output right out of the exciter.
Good luck with that TX, but you won't need it,that box will give you years of service!

Mike

[ka3zlr]

Thought these pix I took today would be of interest. It's a new Nautel 50 KW transmitter. The size is amazingly small, like a large refrigerator. No more taking up half a room. Just incredible.
The internal 700# power transformer takes up 1/3 of the cabinet. It'll do 55 KW and 140% positive modulation at the same time (into a dummy load, of course!)
Eat your heart out, JJ.  

There is an active touch-screen monitor on the front. Not only traditional stuff like modulation % is displayed, but there's also an active Smith chart and spectrum analyzer. The blue line on the spectrum analyzer is the legal mask that the transmitted spectrum must comply with. The little 'boxes' on the left and right of the carrier are to accommodate the IBOC subcarrier. You can see that at 40.8 KHz above the center, the transmitted crud is 76.12 db down. Move your finger across the display to wherever you want to measure. The Smith chart is showing that at 910 Hz above the carrier, the antenna load is 49.525 ohms resistive with only a tiny amount of reactance. Cool stuff! This is what my next homebrew rig should look like- LOL

The tubes on the floor behind me are a pair of 4CX35000s a retired transmitter once used.

One word....Awesum....

[Bill, KD0HG]

I'll pull the manuals for the DX-50 and Nautel and detail the combiner arrangements, I just don't have the time to do that right now.

Fred, the station is newstalk format, no music at all, except for that talk show that plays the Pretenders song for an intro- LOL.

Mike, the tower is 5/8 wave, 666' tall, matched with an L network so it's going to be fairly broadband. Never changed a thing when we originally went IBOC with the DX-50. We made the customary bandwidth measurements and it was good. The whole ground system was redone some 5 years ago, 120 new 700 foot radials of #6 copper. The old radials are still in place, a few might be damaged, so there could be actually be 200-some radials in place now.

If it was me, I'd never put up a 666' tower; that's why it gets hit by lightning.  

[W2ZE]

the tower is 5/8 wave, 666' tall, matched with an L network

Ahhh, that explains it. Being 5/8 wave, the selective fading must wreak havoc on the IBOC, and the analog for that matter, about 20 miles out at night.

[WA3VJB]

Nice to see a picture of you man, you're lookin' good.

[k4kyv]

Mike, the tower is 5/8 wave, 666' tall, matched with an L network so it's going to be fairly broadband. Never changed a thing when we originally went IBOC with the DX-50. We made the customary bandwidth measurements and it was good. The whole ground system was redone some 5 years ago, 120 new 700 foot radials of #6 copper. The old radials are still in place, a few might be damaged, so there could be actually be 200-some radials in place now.

What's the point in IBOC if it is all talk and no music?

[NE4AM]

I'm pretty sure the Nautel tx uses a PWM modulator.  The PWM is digitally derived, hence their claim of 'digital' modulation.

The high power Harris transmitters have a series combiner, with each individual PA on a toroid transformer, with the secondary a single turn, a copper pipe down the middle of all the toroids, like beads on a string.

[flintstone mop]

[

What's the point in IBOC if it is all talk and no music?

Hey Don
It's just nice to have it. If Rush moves his head on the stereo stage you'll hear it!!!!!LOL
News/Talk network. No personality radio. The new broadcast industry....A lot more players......more diversity.......less music........no giants.

And I guess with the computer screen display there are no meters to see dancing around?? The should be some serious current changes with solid state circuitry.

Fred

[k4kyv]

What's the point in IBOC if it is all talk and no music?

It's just nice to have it. If Rush moves his head on the stereo stage you'll hear it!!!!!LOL
News/Talk network. No personality radio. The new broadcast industry....A lot more players......more diversity.......less music........no giants.

Rush and all the other politico-talk windbags could just as well broadcast on slopbucket, and the average listener wouldn't even tell the difference if he didn't have to know how to tune it in.

[WA1GFZ]

agree since most of the wind is coming out the 6

I would be surprised that a PDM rig could hit 90% overall.

[Steve - WB3HUZ]

Yep, same goes for the windbags on NPR. Living off the taxpayers and blowing hot air. SSB would be too good for them.

[Detroit47]

The tubes on the floor behind me are a pair of 4CX35000s a retired transmitter once used.

The transmitter is nice but I'd rather have those 4CX35000's.That is a true work horse.

N8QPC

[DMOD]

According to the Lit, it is a high sampling-rate Class D transmitter

http://www.nautel.com/Resources/Docs/Brochures%20&%20Spec%20Sheets/HD%20Radio/NX%20Series/NX50_w_b_1.2.pdf

with 20 RF/modulator modules producing 2.5kW carrier each.

I would think it would be capable of 325kW PEP for 150% modulation.

Phil - AC0OB

[KX5JT]

I LOVE the bumber music that George Noory plays on Coast to Coast AM. 

Even talk radio stations have SOME music to consider.

[W9GT]

Wow Bill, that new xmtr is impressive.  Here is a glimse of what is used to take to do 50KW.  Quite a contrast.

http://historyofwowo.com/tech.html

73,  Jack, W9GT

[k4kyv]

Yep, same goes for the windbags on NPR. Living off the taxpayers and blowing hot air. SSB would be too good for them.

Like it or not, whether you pay taxes or not, you are paying out of your pocket for the mindless garbage on commercial radio and TV whether you watch and listen to it or not.  For example, if you pay medical insurance premiums or purchase prescription meds, you are subsidising the TV broadcast industry.  Who do you think ultimately finances the "ask your doctor" commercials?