My new toy. Ultra modulation unit

[ke7trp]

Thanks alot!  I will call napa

Clark

[k4kyv]

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.

Operating phone without a monitor scope is like driving at night with your headlights turned off.

[K6JEK]

Does anybody actually run upside down modulation?  Plenty of us run greater than 100% positive peaks.  I do in just the way Don mentioned, by taking advantage of the asymmetry of my voice.

But is there anyone actually on the air with downward modulation, reverse carrier control, upside down modulation -- 1500W carrier when silent, modulating downward?  Does it drive receivers nuts in practice or not?

Jon

[WA1GFZ]

sure would clear the channel but you need a rig with the BAs to do 1500W CCS

[k4kyv]

But is there anyone actually on the air with downward modulation, reverse carrier control, upside down modulation -- 1500W carrier when silent, modulating downward?  Does it drive receivers nuts in practice or not?

I don't know why anyone would want to put crap like that on the air.

[N2DTS]

I have an ultra mod deck I made 20 years ago, 3 diodes, resistor, power supply.
I had reports I was real wide when it was in circuit so I removed it and put it away.
The circuit shunts the excess audio into the resistor and allows the low voltage supply to power the final, but i suspect its not a smooth transition, maybe like a square wave?

I think one would be much better off running some low level compression and keeping the audio below 100% negitive, you have a much cleaner signal that way.

Brett
 

[ke7trp]

Need manual or more info on the hookup of my UM unit.  The Wires where cut on it.  I have three Shielded wires.

One white that hooks to the junction at the first Filiment Transformer in the unit
Another White that hooks to the junction on the Second Filiment transformer in the unit.

One Red wire that runs to the bottom of a Tube. Marked 2E something.. Cant read it. 

Anyone have the manual?  I have a Downloaded copy of the article for the unit but it does not show three wires..


Clark

[ke7trp]

Ok.. I understand that the 866s are diodes.  I understand that the B+ out of the modulator is sent to the UM unit. I understand it limits the peaks and then sends the voltage on to the final.  What I dont understand is that the UM unit has Two whites and a Red wire. Then, I have the shields for each.

Clark

[Pete, WA2CWA]

Maybe I missed it but who is the manufacturer of this thing?

[ke7trp]

Correction.. I Have been looking over the schematic and opened the unit.


The TWO white wires go to the 866s at the Filament transformers.

The RED wire runs to the Resistor stack.   

Three wires total.

The unit is a commercial grade product.  It was made by UM.  It is for 1KW Class Broadcast rigs. 

UM company.  Red bank NJ.  Model UM4-B.  Serial number 1501

Clark

[ke7trp]

The schematic does not show that.. Or maybe I am blind..

Ok..  I understand that the white wires INTERCEPT the RF B+ out of the modulator deck and to the RF deck.  The RED just goes to the HV source that is NOT RF.  For example, The Feed from the Power supply to the INput to the Mod deck.


Clark

[ke7trp]

I got it..   My mind would not let me figure this out.   What got me was the RED wire on the resistor bank. That one connects to the B+.   The Whites, carry the RFB+ from the mod deck TO the RF deck.. I worked it all out.  I will have it hooked up in a day or two.

Clark

[Gito]

Hi


  Comparing the two circuits  D1 is V1,D3 is V3 ,D2 is V2.

V4,V5 ,6AF6G is part of the indicator when the circuit begins to limit the negative cycle of modulation.

In my opinion,The White cable ,which is written as " connected to mod.amp plate"  must be connected  to the Final amplifier Plate (RF final) like in the "Three diode negative peak limiter."

The other White Cable ,is used when you like to By past this circuit,(negative peak limiter),maybe manually  or with a switch  .interchanged(the two white cable) its connection to the Final Amplifier Plate (RF final).

Gito

[Gito]

Hi

 Sorry ,the white wire that is connected to T1 (filament transformer) is connected to the Modulation transformer, like the circuit diagram,The White cable connected to T2 (filament transformer)is connected to the Final RF tube,

The modulator can has its own B+ or.if the B+ is the same (only one B+),Connect it to the CT of the modulator Trafo (modulator side.) inthis case connected in parallel with the red wire .
Don't connect it to the white wire.

Gito   

[ke7trp]

Thanks for making that Diagram for me. I really thank you for that...

I labled them White 1 and white 2.

Red -  MOD deck B+ input connector.

White 1 -  RFB+ OUTPUT of MOD Deck connector

White 2 - RFB+ INPUT of RF Deck (4-400)

Clark

[ke7trp]

Sure!    I am making up RG58 Belden Poly coax runs for the three wires. Each one will have a Millen connector on it so I can plug this into the GK500C and plug it in to the Dual 4-400 box.  It will be easy to take pictures.

Clark

[ke7trp]

13KV from Beldens website.  Its poly with a High Dielectric.   Its NOT foam which is listed at .3KV


Clark

[Gito]

Clark

It,s the right way to Connect the negative peak limiter unit.

What makes it confusing ,is that in the diagram ,its is written that the white cable from T2 is connected to MOD.AMP PLATE ,

Actually it must be Connected to the PLATE OF THE FINAL RF TUBE.(Its the B+ of the Final RF tube)

Thanks

Gito.

[ke7trp]

Yes.. I was very confused..  Lucky for me, I have you guys and others to help me 

I think the Belden will be fine.  The stuff they used from the factory is much smaller with very little insulation.


Clark

[Opcom]

But is there anyone actually on the air with downward modulation, reverse carrier control, upside down modulation -- 1500W carrier when silent, modulating downward?  Does it drive receivers nuts in practice or not?

I don't know why anyone would want to put crap like that on the air.

The statement might be a reference to the practice of using unprocessed voice signals, which can be non-symmetrical in the voltage domain, and instead of phasing the mod to where the taller voice peaks point upwards, pointing them downwards and raising the carrier to the level where there is no negative overmod. It can work only if a person's voice wave is not symmetrical WRT peak levels.

It's been covered in writings and there is at least one members'? website showing this principle.
The summary is that one eschews processing and sets the big voice peaks to negative side of the mod and raise the carrier to avoid spaltter.

symmetrical voice normal use:
voice voltage peaks +2.00, -2.00 relative  level
carrier  = 375W
PEP=1500

non symmetrical normal use:
voice voltage peaks +3.00, -1.00 relative level
carrier = 187.5W
PEP=1500

non symmetrical inveted use:
voice voltage peaks +1.00, -3.00 relative level
carrier = 1312.5W
PEP=1500

this is what was being illustrated I believe. For those who have a voice that gives a fairly symmetrical voltage waveform, there won't be much difference. But for those who have large peaks one way or the other, they can either turn the mike polarity so that the 1500W PEP limit is hit when the high peaks are "up", resulting in having to reduce the carrier, or, they can turn the mike polarity around so the big praks point down, and run a thick carrier. It will sound the same at the other end, and there is not negative overmodulation in either case. The advantage is a more powerful carrier to get rid of noise in the over-the-air path.

Unfortunately those with a very unsymmetrical voice will always be faced with a modulation cycle "duty cycle" far away from 50% and the "volume" of the voice on the RX end will appear weak. So instead the best thing is to process the voice somehow either with a clipper, balanced compressor, or phase rotator, or a combination of various techniques.

[ke7trp]

Ok restoration and repair of this UM unit is complete. Bad tubes and caps.  Made a new harness out of Poly RG58 covered in a RGU braid.  I put millen connectors on the end so you can interface it with the King 500C. 

Fired it all up and found that the King cant make enough audio to see much action. I can adjust it to limit negs to about 95%. Positive is 100%.  No noticeable difference on the air of course. I need more audio power.  With out the unit, I can go 125 up and 125 down.. But with it, just wont make it. I can just start to see the Negs limited.

I wish I had the smaller unit they made. This one is made for the KW broadcast rigs.  Four 4-400s ect.. The 811s just cant kick it into action much.

It looks great, It fills the room with a nice Blue glow with super bright when I talk. A really neat piece of gear I will save for my Big rig... I am sure with the 810s into the 4-400s It will work a bit better.

Thanks for all the help on this project!

Clark

[KD6VXI]

Fired it all up and found that the King cant make enough audio to see much action. I can adjust it to limit negs to about 95%. Positive is 100%.  No noticeable difference on the air of course. I need more audio power.  With out the unit, I can go 125 up and 125 down.. But with it, just wont make it. I can just start to see the Negs limited.

Clark

Since that unit is only supposed to work on negative peaks, I guess I wonder why it won't hit 125 percent with it inline on pos peaks?

Odd, but...  Maybe you should just do a 3 diode limiter, if you are that worried about your neg mod peaks???


--Shane

[ke7trp]

Or, I can study the schematic and try to figure what I need to change to get it to act at lower power..  I think Its just the lack of audio power shane. I only have about 350 watts of audio power.  If I had 600 then this would be loud as hell on the air.. But I dont.

Clark

[ke7trp]

Here is picture of it with me talking into the mic.  Its working.. But Not the action I want.  The resistor is a 10K. The tap is near the 866.  If I move the resistor tap like they say, I get lower audio pos and neg.  Maybe Try changing that resistor?


Clark

[ke7trp]

This must be working.. The Eye tube is not though.. Its nice and bright but it never changes from full on modulating. I will have to find out why.

I unhooked the unit.  300 watt carrier on easy tune up. Talk and get 325 RMS.. So a slight bump in RMS on the Bird.  Plate current stays the same with a slight wiggle down.

Hook up the unit,  Adjusted Tap to 6000 ohms.. Thats the plate load of my 4-400a.   Load to 300 watts on bird meter. Talk and it takes out the 500 watt slug hard to the side. Back it off a bit and it talks around 450 rms. Plate current jumps UP when I talk.  Scope is not showing Flat topping or over mod at 450 RMS when I talk.  Really clean looking.

The NEG limiter 866 glows bright as hell.  The Peak about half as much.  Maybe when I get on the air and they guys ask me to turn it down, I will know its working.  BIG increase in RMS talk power.

Clark