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Author Topic: My new toy. Ultra modulation unit  (Read 52160 times)
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ke7trp
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« on: July 06, 2009, 03:36:31 PM »

Here is my new toy.  Going to use it with the Globe king 500C.  Should be fun!

Anyone ever use one?





* !BVL3)-w!2k~$(KGrHgoH-CUEjlLl1UPiBKROSqR6Gw~~_1.jpg (22.54 KB, 400x300 - viewed 823 times.)
* 5610027[1].pdf (282.97 KB - downloaded 676 times.)
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N3DRB The Derb
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« Reply #1 on: July 06, 2009, 06:03:53 PM »

nope. Thats the first commercially available unit (not a homebrew) I have ever seen. Glad a gangsta got it. I posted it in the ebay section.  Cheesy
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W2PFY
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« Reply #2 on: July 06, 2009, 06:13:03 PM »

I've been watching it on ebay and it shows that it didn't sell???
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ke7trp
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« Reply #3 on: July 06, 2009, 06:23:09 PM »

The owner is a good friend and elmer, I went over and he said it did not sell... So I purchased it from him. 

Its a good working unit complete with cover. I need to get Shielded HV wire somewhere to hook it up. I guess spark plug wire will work..

Also..  They dont want you to run it with a Tetrode with a seperate Screen supply.  My Globe king 500C has a seperate 400 volt screen supply.  Screen current runs around 30 to 40 MA depending on how I load it.

I have figured out I need 35K at 56 watts for the screen Dropping resistor.  To go from 1800 to 400 volts for the screen:


1800 volts (might be more like 2000 as I am solid state and have not measured the actual voltage.
400 volts needed at 40 MA

I came up with 35K at 56 watts.   Sound correct? 

If I could just find an adjustable 75 watt resistor, I will be good to go!  THen, Just attach it inline with my B+ lead and off to the 4-400 screen.  I can fine tune it to 400 volts in my situation.  I will just yank the Screen supply Rectifier tube and leave the rest there so it can be changed back later.  Simple and I get a modulated Screen Smiley

Anyone have a big adjustable resistor lying around???  I am dieing to plug this thing in and give it a go! 

This unit is rated for the 1kw broad cast rigs.. Its the larger of the two they made so I have no worries there! I am even going to leave the 866s in it so it glows blue sitting there next to the king!

Clark
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W2PFY
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« Reply #4 on: July 06, 2009, 07:47:21 PM »

I would use RG8X for shielded HV wire unless you have some old shielded military spark plug wire. RG8X should be good for better than 25KV. I forgot how that thing is supposed to work?  Anywho, it looked very nice.
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ke7trp
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« Reply #5 on: July 06, 2009, 07:53:12 PM »

Ok. I have RG8X. That will work out nicely.. I attached the PDF document on the original post if you want to see how it installed ect.. THis one is a commercial built unit but its identical to that article.

I just need to find a tapped/variable resistor now!

Clark
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flintstone mop
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« Reply #6 on: July 06, 2009, 09:05:04 PM »

Let's sing the "Shaft" song. That's gonna be a mean mutha...........shut yo mouth!!

Good find. It should really wake up the bands

Fred
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ke7trp
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« Reply #7 on: July 06, 2009, 10:15:36 PM »

I had the idea of using a large variable resistor for the screen dropper.  That way, I can attach a Volt meter to the screen and adjust it for my actual B+. 

I called W0VMC Robert and he said he probably had the resistor I need... So thanks to Robert!

I do have two 20Ks at 100 watts.  I could series them for 40K, Drop it in and test it out. 35K to 40K is what I need at 56 to 60 watts.  I think the ultimate would be to have the adjustable one from Robert so I think I will wait.

ITs going to be a big change getting the King setup with modulated Screen and plate. Then with the UM unit hooked inline it should be fun:)

I just wish I could get a little more B+ on the 4-400!   1800 Volts is just not enough to really fire things off. But hey.. Its an old Globe king...

When I find time to get the Big rig working, this is going to get interesting. That unit has two 810s running up at 2600 volts with two 4-400s.  I will make up cables so I can use the Ultra mod unit with that machine also!

I would like to hear from people that have used these or have listened to them. 

Clark
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KB2WIG
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« Reply #8 on: July 06, 2009, 10:30:41 PM »

  "" Ok. I have RG8X. That will work out nicely..  ""

Just to make sure.........


Don't use pl259's fer the HV connectors......



klc
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Bill, KD0HG
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« Reply #9 on: July 06, 2009, 10:35:14 PM »

I would use RG8X for shielded HV wire unless you have some old shielded military spark plug wire. RG8X should be good for better than 25KV. I forgot how that thing is supposed to work?  Anywho, it looked very nice.

Nooooo!

Do NOT use foam coax of any kind! RG-8X included!

It does NOT have near the voltage rating of solid poly coax. It's only good for 300 volts, max!

And don't use PL-259s, either! They're only good for 500V, max.

Use RG-213 solid poly coax and leave at least 2" to 3" of uncovered shield at each end for a good 'crawl'. RG-8 and RG-213 SOLID poly are good for maybe 13 KV.

DO NOT even try using RG-8X foam. Or any other foam coax, for that matter! Solid poly is the only way to go.

Please! I don't want to see you smoke it out! Or hurt yourself.

I have built several ultra-mod units...One is currently use in my big rig. You are talking at least 2x to 4x your static PA plate voltage if it's working properly. WAY more than 300V. Maye 10x that!

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ke7trp
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« Reply #10 on: July 06, 2009, 10:45:14 PM »

That makes total sense...    I guess I will just use Copper center spark plug cable.. I dont want to run RG213 sized coax to and from this unit.. Heck it has unshielded wire on it from the factory.. About 18 Gauge!   

Are we in agreement that Spark plug cable will work?   Henry has the larger diam stuff at a decent price.. I can just order 10 Ft of it and be done.

Clark
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Patrick J. / KD5OEI
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« Reply #11 on: July 07, 2009, 12:07:01 AM »

outdoor neon wire is cheap and good-sized guage.
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N3DRB The Derb
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« Reply #12 on: July 07, 2009, 01:12:35 AM »

theres a guy on ebay selling RG400 teflon double shielded silver braid jumpers. Rg 58 size but lots better voltage breakdown and shielding. do a search on rg400, you'll find him.
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ke7trp
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« Reply #13 on: July 07, 2009, 01:28:54 AM »

derb,  Send me the item number.   I got lost in the search. 

Clark
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k4kyv
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« Reply #14 on: July 07, 2009, 01:52:07 AM »

Hate to rain on your picnic, but you will most likely be disappointed with the results unless you substantially beef up the G-K modulator.  Ultramodulation works on the assumption that you have enough undistorted audio power available to modulate up to about 150% or more in the positive direction.  With an unmodified G-K you are lucky if you can achieve 90% positive or negative.
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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

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ke7trp
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« Reply #15 on: July 07, 2009, 01:55:08 AM »

Of course..

I have that covered Don.  I can go 125% now Smiley

Its a toy.. I will play with it. If i dont like it, I will not use it... Either way, I will have fun!

Clark
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N3DRB The Derb
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« Reply #16 on: July 07, 2009, 05:09:24 AM »

http://cgi.ebay.com/RG-400-Silver-Plated-Shield-Coaxial-Cable-Up-to-12Ghz_W0QQcmdZViewItemQQ_trksidZp3286Q2em20Q2el1116QQhashZitem45ecf7f719QQitemZ300328417049QQptZLHQ5fDefaultDomainQ5f0QQsalenotsupported

not the same guy I got mine from, but the length is 3 ft, about what you need.

I you dont like him, look for others.
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K5UJ
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« Reply #17 on: July 07, 2009, 06:49:19 AM »

You can get 6 foot pieces of h.v. wire from rf parts

http://www.rfparts.com/hvconnector.html#wire

I've wondered about 100 v. 130%.  I can go up to 130% and I prefer to do that but I've read that guys using the older rx that don't have product detectors get distorted audio.  When I get my outboard plate supply built I should be able to run a 350 w. carrier at 100% but I'd still rather run around 300 w. at 130%.

Rob
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flintstone mop
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« Reply #18 on: July 07, 2009, 09:25:14 AM »

You're right Rob,
130% Positive is about the max before a receiver starts distorting.
During the wild experimental days, before the 1500 P.E.P. fiasco, the ultramod and a P.E.P of 5kw was an outrageous signal. There was a thread recently here about a Ham who had a room for a very big transmitter using ultra mod.

Fred
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Fred KC4MOP
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« Reply #19 on: July 07, 2009, 10:36:30 AM »

Quote
Do NOT use foam coax of any kind! RG-8X included!

UGG, Me not know that  Huh
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W2PFY
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« Reply #20 on: July 07, 2009, 10:44:47 AM »

How does this differ from the three diode keep alive circuit by WA1QIX?

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k4kyv
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« Reply #21 on: July 07, 2009, 01:01:38 PM »

With good, undistorted audio from mic to modulated stage, you don't need any kind of negative peak clipper or negative cycle loading to achieve 130% or so. Most human voices are naturally asymmetrical.  Just make sure the audio polarity is correct so that the peak with the greater amplitude excursion goes in the positive direction.

Steve's circuit and negative peak limiters are best used to protect from occasional breaks in the base line on negative modulation peaks.  This can potentially destroy modulation transformers and cause splatter, although I have never noticed a tremendous amount of splatter from slight overmodulation on occasional negative peaks if the signal is otherwise clean.  Most  heavy splatter comes from the speech amp going into oscillation, rf parasitics in the modulated stage or distortion/self-oscillation in any leenyar that follows.  Even with gross overmodulation, more splatter is likely to come from spurious distortion products that originate elsewhere, than from the overmodulation itself.

If the transmitter flat-tops on positive peaks, that produces exactly the same kind of splatter as overmodulation on negative peaks.  A large percentage of slopbucketeers do that every time they use an amplifier, particularly since modulation monitor scopes have become virtually nonexistent within ranks of the "new" amateur community.
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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

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Patrick J. / KD5OEI
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« Reply #22 on: July 08, 2009, 01:11:10 AM »


A large percentage of slopbucketeers do that every time they use an amplifier, particularly since modulation monitor scopes have become virtually nonexistent within ranks of the "new" amateur community.

That could acount for slow sales of $1 CRTS at the hamfest.. If someone is too ignunt to build a modulation scope.. probably too ignunt to adjust the SSB leenyar correctly and too cheap to buy a scope as well.
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ke7trp
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« Reply #23 on: July 08, 2009, 01:13:29 AM »

I agree. I am shocked to see so many hams not using scopes.  I use the Yaesu YO-100s on alot of my AM stations and some of my SSB stations. Its a nice compact easy to use Scope.

C
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« Reply #24 on: July 08, 2009, 12:18:11 PM »

At one time neon signs used Packard 440 spark plug wire. Belden still sells it in 25 foot spools. I bought my last spool at Napa.
Shielded is best so good soild dielectric 1/2 inch coax is good RG213 or RG11 gith plenty of spacing between the end of the shield and center conductor. A few inches will be fine. Strappers would use RG393 or RG141, RG400
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