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Author Topic: Mandate from the Tron  (Read 29443 times)
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ka4koe
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« on: December 28, 2014, 02:48:07 PM »

Timtron has deemed my audio acceptable since I reworked the pertinent bits of my Valiant 1. My new mandate from Tron is to "increase my scrote". I feel I have paid my dues and I am ready to take it to next level. Several options come to mind:

1. Build a transmitter (hard/expensive/long term), likely 2x813 modulated by 2x813. Hardest part is locating iron.
2. Obtain a Johnson 500 (expensive).
3. Obtain a Globe King 400/500 (not so expensive).
4. Find a T-368/BC-610 (heavy-must live in garage below).
5. Find a BC TX. See Item 4.

I do not wish to get an AL82 or similar big amp and drive with the Flex. We're talking totally old school. I also do not wish to go Class D/E (solid state).

Advice? Opinions?

FEELEEP
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KL7OF
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« Reply #1 on: December 28, 2014, 02:53:43 PM »

Advice....Stop talking to Timmy.....
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WD8KDG
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« Reply #2 on: December 28, 2014, 03:19:58 PM »

FEELEEP,

AaahhH, the right coast is different from the left. Power/scrote has always been the game on the right. (lived there over 40 years & know) There are more stations on the right coast & the SSB vs AM wars might not be over. This is something the left doesn't understand.

I spend many nights with only the receiver on because the left coast stations live close to each other and get by with 50 watts. Lighting up the filaments on the "500" or Desk KW will not happen for a fading pi** weaker.

#1: Antenna is everything if'n you can do it.

#2:Take care of the little lady of the house & rug rats first!

#3: Be patient and find bigger iron, a GK500 will get the job done.

#4: Had to wait till retirement before the big iron followed me home.

Craig,
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W3RSW
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Rick & "Roosevelt"


« Reply #3 on: December 28, 2014, 03:58:28 PM »

It just sort of happens....
Putting the word out here is a great start.
Don't discount BC610 or BC610 iron.

Surely some good man or woman OP out there has a spare mod xformer?
Plate and choke iron easier to find.
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RICK  *W3RSW*
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« Reply #4 on: December 28, 2014, 05:04:05 PM »

Philip,
         May i suggest roll your own in the form of 812A's modded by 811A's? Basically a GK 400. There's really not that much there to have to scrounge for. You already have an exciter sitting by your fireplace as "room decor". Build a P/S for it, get it running, and use it to drive a pair of 812A's in class C. You can use the P-P 6L6's in there to drive a class B 811 modulator as well. If you never get started, it will never get done. I can email some info for you to smoke over if you'd like.

73, Phil
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Steve - K4HX
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« Reply #5 on: December 28, 2014, 06:57:59 PM »

Iron is not hard to find. Don't let that stop you.
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Todd, KA1KAQ
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« Reply #6 on: December 28, 2014, 08:17:27 PM »

I've got lots of iron here, surrounded by three Collins 21E cabinets. All converted and proven on 75/80m by W2INR. You can have it cheap, too. How big is your garage?
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KA2DZT
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« Reply #7 on: December 28, 2014, 08:24:16 PM »

I like the 813s x 813s.  Good solid xmtr that if build correctly can last forever.  You should be able to get help here on the forum.  Building from scratch is a lot of work and can take a lot of time (unless you're JJ then you can build one in a week Grin).

This could prove to be easier than trying to keep the Valiant up and running.

Let us know when you plan to get started.

Fred
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ka4koe
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« Reply #8 on: December 28, 2014, 09:27:19 PM »

Anything really heavy will go in the garage directly below the shack, eg. 610/368. We've already done the calculations and talked with my Registered Architect friend who told me "NO WAY". Plenty of power available.
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N2DTS
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« Reply #9 on: December 28, 2014, 09:39:06 PM »

I vote for building one.
You can make it easy or hard, one or two bands is very easy, plug in home made coils, a pair of 4x150's modulated by a pair will do 500 to 600 watts carrier easy, low drive, lower voltages.
Or, don't have or want iron, screen modulate 3 or 4 of them for 300 or 400 watts out.
Drive the grids with a ricebox.

Or fix some over priced old stuff all the time..
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KC4VWU
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« Reply #10 on: December 29, 2014, 01:01:14 AM »

Todd's right Philip, with that setup you would be "net control" for the southeast! Nice piece of East Coast Sound to preserve as well. I know if I didn't have so much crap and had the extra room, it would reside here.

Steve, Todd; where you guy's been hiding? Planning on venturing south of Richmond this year?

...Phil
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ka4koe
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« Reply #11 on: December 29, 2014, 07:45:52 AM »

I am the point signal-wise to where I am heard +90% of the time on AM, if I can hear them, that is. I put up the K1JJ recommended limited space dipole, 180' long x 60' high, fed with 600 ohm open wire......so it won't get much better than this aerial-wise unless there is a change of venue.

If'n I put big, and I mean big, iron in the garage below there must be a day or two of cleaning things out. Of course, I'd have to remote the thing from upstairs directly above.
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flintstone mop
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« Reply #12 on: December 29, 2014, 10:44:06 AM »

Feelip
Look at this nice monster.

https://www.youtube.com/watch?v=itlSdNherlI

A member or former member of AMFONE KE7TRP has one of these beauties..

Bigger power like around 500 will mean that you will have to heavy up the antenna system to handle the juice.
A few of the guys in 8 land and VE6PG are running a hundred watts and come booming FB into MOPRADIO on 160.............Cover up static and sound nice. I do not mess around with 75M. I'm working on the Extra class to get below 3.7mhz and changing focus on DX and CW operations.

Fred
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ka4koe
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« Reply #13 on: December 29, 2014, 03:35:59 PM »

Checked 3.7 Mc several times over the holiday and heard nary a word. I guess my timing was wrong. And....160M AM is nearly non-existent...where is everyone?Huh Again, my timing may be wrong.
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steve_qix
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« Reply #14 on: December 29, 2014, 04:03:33 PM »

The cheapest and smallest (physical size/weight) way to go for 160/80/40 is class E.  You can easily build a desktop kW (that's carrier power!) like the one I use at Rattlesnake Island where space is at a premium.

Tube-wise, building is still better than buying (a LOT better), and probably less expensive.

If you have some money to spread around, I would get an Apache Labs SDR and follow it with a big linear.  Unbelievable sound (both transmit and receive)!

You could build the linear and same some money there...
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W1RKW
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« Reply #15 on: December 29, 2014, 05:14:58 PM »

If you want to go with a quad of 813s (2 driving 2), this is a solid design: http://www.amwindow.org/tech/htm/813/813.htm     GORTs innards are made of these.
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Bob
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His fear was when I turned it on for the first time life on earth would come to a stand still.
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« Reply #16 on: December 29, 2014, 06:15:58 PM »

   The thread from Brett concerning both screen modulated 4X150's where 100 watts carrier per tube is possible, and plate modulated 4X150's at 2X that power is pretty telling to me. In the case of screen modulation, a box the size of a SB200 with a remote supply could run legal limit AM.

http://amfone.net/Amforum/index.php?topic=37242.0

Jim
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w8khk
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« Reply #17 on: December 29, 2014, 06:59:31 PM »

  The thread from Brett concerning both screen modulated 4X150's where 100 watts carrier per tube is possible, and plate modulated 4X150's at 2X that power is pretty telling to me. In the case of screen modulation, a box the size of a SB200 with a remote supply could run legal limit AM.

http://amfone.net/Amforum/index.php?topic=37242.0

Jim
Wd5JKO

I really like Jim's idea.  I have been following Brett's thread and I plan to build a screen-modulated 4-holer with a variant of the 4X150.  It is the 7035/4X150D, same specs, but 26 volt filaments at approximately 1/2 amp each.  Got a bunch of these on a surplus buy. 

At a small hamfest in Rome, GA a couple months ago, I picked up a "parts unit" Dentron Clipperton L  for $60.00 and the antenna tuner for $50.00.  (I posted a couple pictures below)  He said it was a parts unit because condition was unknown, but it was complete, so I took a chance.  It has a quad of 572B triodes in grounded grid.  I do not need another linear.  My thought was to yank the glass tubes, and mount a small chassis vertical inside the back to hold the four 4X150 tubes, and use the existing muffin fan for cooling. 

The Clipperton runs between 1500 and 1800 volts on the plates.  This could be reduced with an external variac, or the filament winding could buck the plate transformer primary, if needed.  The plate iron checks out OK, should run cool in this mode.  I will pull the entire rectifier/filter assembly and replace with all new components on a far-circuits 8-capacitor board with diodes and equalizer/bleeder resistors; slightly smaller than the module it replaces.

In summary, this approach would eliminate most of the metal work, provide the heavy iron and most of the plate tank components (this one tunes 160 thru 10) and result in a rig that is not too huge or bulky.  All HV would be contained in a single enclosure.  It may or may not be possible to fit the screen modulator components in the main unit;  maybe a separate exciter/driver and audio/screen modulator in a similar size cabinet. 

My suggestion is to research many options, figure out what goal you want to reach, troll the hamfests for the components, then you can see yourself completing the project in a reasonable time frame, and have a rig that you are proud to operate.  GL OM!


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* CAM01106.jpg (1226 KB, 2592x1944 - viewed 355 times.)
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Rick / W8KHK  ex WB2HKX, WB4GNR
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My smart?phone voicetext screws up homophones, but they are crystal clear from my 75 meter plate-modulated AM transmitter
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« Reply #18 on: December 29, 2014, 07:01:25 PM »

"  a box the size of a SB200 with a remote supply could run legal limit AM. "

Be that as it may, I still think that something like a 20V-2 size walk in transmitter is a good thing to have. Someplace to hide from the wife in.


klc
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« Reply #19 on: December 29, 2014, 07:02:20 PM »

Power supply one level down. Pipe high voltage through conduit to RF deck in shack.
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flintstone mop
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« Reply #20 on: December 29, 2014, 07:09:20 PM »

Checked 3.7 Mc several times over the holiday and heard nary a word. I guess my timing was wrong. And....160M AM is nearly non-existent...where is everyone?Huh Again, my timing may be wrong.
Always seems to be a good crowd from the "mid-west",,, 8 land....I am in Western Pa. on 1880 and 1885, 1945, 1980 just about every evening after 7PM. I hear East Coast stations very well from my Western Pa. location. Antenna and power (legal) is in the formula.
3705 gets tricky with SSB that never used to be there, but now there is cuz AMers showed up. So the Extra class guys go to 3.700 or lower to operate and get away from the SSB.  3.880 or 3.885 in the early evening is pretty nice before the chaos sets in.
Fred
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Fred KC4MOP
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« Reply #21 on: December 29, 2014, 07:52:09 PM »

Things to keep in mind:
Screen modulation is easy on the RF deck voltage wise, plate voltage is maximum voltage, so wimpy parts work.
The 4x150 tubes are low voltage tubes, 1500 to 2000 volts is great.
The screen modulator and power supply can be outboard and remote, in a small cabinet with the line level audio equipment, and can work on almost any tube rig at any power level.

 
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ka4koe
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« Reply #22 on: December 30, 2014, 08:26:32 AM »

Now, correct me if I am wrong (no worries on that point), but if you implement screen modulation, doesn't that limit one to 100% modulation and no more?Huh

FEELEEP
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« Reply #23 on: December 30, 2014, 09:04:02 AM »

Absolutely not!

Screen modulation, properly implemented will yield broadcast quality audio. The positive peak headroom is limited only by how you adjust it.

The problem with screen modulation is the efficiency is very poor, but no worse than AM linear operation.  Also, most people really don't implement it correctly.

The screen is a varying impedance load; a nonlinear load also.  Therefore the screen must be modulated using a low impedance device.

The best device for the job is a MOSFET operating as a source follower.

If I had a reasonable power tube RF amplifier lying around here, I'd build a screen modulator as a demo and then document the circuit.   Come to think of it, I do have an old Invader 2000 kicking around (pair of 4-400s) - no power supply for it, but I suppose something could be clip leaded together.  I'll give it some thought.
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Rick & "Roosevelt"


« Reply #24 on: December 30, 2014, 09:43:33 AM »

Duplicate Frank's (AHE's) 4x1 circuit driving your 4 by 1/2's.
 He had to turn down the wick when Riley walked towards us at Gathersburg.  Grin
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RICK  *W3RSW*
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