Exciter – Transmitter suggestions

[KC9LKE]

OK OK

KA1GZC, Tom, I looked around on the net and only found Tim’s audio mods and not the low power mod. Any info on this would help. 


KE7TRP, Clark, “ The 746 pro is just fine.  Just sit down with a 9 volt battery, A 500k pot and make a voltage divider” ??.
Possibly You didn't know so not to be a Smart A$$, the 756 has a RF level control on the front, so don’t use it?
ALC is better?

The Slab Bacon:
“Why dont you split your final grid biass to partial fixed and then make up the rest with grid leak. This way if you lose drive, you will still have some protective biass to limit the plate current down to a safe level.”

I’ll plan on adding it!! It certainly seems worth the price of the finals. Thanks!

I appreciate everyone’s comments and direction. I am really into this part of the project to learn about the design of interstage coupling. I can read the books, do the math, but want to learn more by bringing it into the real world. I will go with the Ranger carcass and see how it works out, who knows after that. A lot of possibilities. I like the idea of using a transceiver mainly because it has a receive section and I won’t need to buy another receiver.   

Thanks and
Best Regards

Ted / KC9LKE   

[ke7trp]

Interesting.  I will read up on that. 

For now, I need to move the FT450 away from the transmitter and put an extra fan on it to cool. 

C

[KB2WIG]

 T,

I've got a copy of the "west coast handbook" ( 14th Ed, 1956). there's  a few areas that may be of interest. ya can download a 1959 version, fer free. Look for The Radio Handbook William Orr

 
http://www.pmillett.com/tecnical_books_online.htm

[ke7trp]

You cant get 100% mod without the radio pulling back the carrier. The box allows you to run the RF power full up, Then set the carrier with the alc box. Now you can run your audio up to 100% without the limiting action.

C

OK OK

KA1GZC, Tom, I looked around on the net and only found Tim’s audio mods and not the low power mod. Any info on this would help. 


KE7TRP, Clark, “ The 746 pro is just fine.  Just sit down with a 9 volt battery, A 500k pot and make a voltage divider” ??.
Possibly You didn't know so not to be a Smart A$$, the 756 has a RF level control on the front, so don’t use it?
ALC is better?

The Slab Bacon:
“Why dont you split your final grid biass to partial fixed and then make up the rest with grid leak. This way if you lose drive, you will still have some protective biass to limit the plate current down to a safe level.”

I’ll plan on adding it!! It certainly seems worth the price of the finals. Thanks!

I appreciate everyone’s comments and direction. I am really into this part of the project to learn about the design of interstage coupling. I can read the books, do the math, but want to learn more by bringing it into the real world. I will go with the Ranger carcass and see how it works out, who knows after that. A lot of possibilities. I like the idea of using a transceiver mainly because it has a receive section and I won’t need to buy another receiver.   

Thanks and
Best Regards

Ted / KC9LKE   

[KA1ZGC]

Hmmm..  First time talking over an hour on 75 to ww9w,the big Rig had a new problem came up with the exciter.  The FT450 has a system of lowering power as the fan is turned up to cool the radio.  This is obviously dangerous for a class C amp.

If you start out at 36 watts CW to excite the 4-400s at 30ma, You get about a half hour of back and forth use. Then when the rig heats up it turns the fan on and the power goes to 15 watts!    Then, If you keep going and you did not notice the now low Grid Drive, The Rig cuts power OFF, NOT good on a Class C.  Luck for me, I have a breaker in the HV so trip.. But it sill put a good 2 seconds of full slam plate current on the rig before that Tripped.

So Scratch the FT450 as being a good exciter.. There is a menu in the FT450 service list that allows you to adjust this. Then you probably blow the rig up though.. 

"I don't think the Empire had wookies in mind when they designed 'er, Chewie."

That's another downside to running a ricebox (or any sideband rig) as an exciter: they're linear devices (class AB₂ at best), so a 90% conduction angle for the finals (finals get hot), and all that power has to be delivered by the power supply instead of the tank (power supply gets hot).

SSB rigs are designed for 33% duty cycle, and have an efficiency rating of 33% or so. Class C rigs are designed for 100% duty cycle and are 70% efficient at least. The tank does 90% of the work, instead of the PA and power supply doing 90% of the work in a class AB_x rig.

Another good reason to use something designed for constant-carrier duty as an exciter for a Class (C|D|E) big rig.

Manufacturers of SSB rigs only add constant-carrier modes as an afterthought, and only support 25% or so of the max PEP rating for them. You should never exceed 25% of an SSB rig's max PEP rating for constant carrier output, 20% is even better. So if your rig is rated at 100W PEP (which it is), 20W constant carrier should be the most you ask of it. 36W is way too much power.

[KA1ZGC]

KA1GZC, Tom, I looked around on the net and only found Tim’s audio mods and not the low power mod. Any info on this would help.

Sorry, I thought this was included in Tim's writeup of all the Ranger mods (look in the tech section of amwindow.org), but having glanced through it again, I see that was a "to be continued" that wasn't. Maybe I'll lean on Timmy this weekend and get him to type something up on the subject. I know he can tell you off the top of his head while snoring, but I can't remember the details.

[KC9LKE]

KA1GZC, Tom, I looked around on the net and only found Tim’s audio mods and not the low power mod. Any info on this would help.

Sorry, I thought this was included in Tim's writeup of all the Ranger mods (look in the tech section of amwindow.org), but having glanced through it again, I see that was a "to be continued" that wasn't. Maybe I'll lean on Timmy this weekend and get him to type something up on the subject. I know he can tell you off the top of his head while snoring, but I can't remember the details.

Thanks Tom

Also

Kevin Found the Orr handbook link.

Thanks
Ted

[WBear2GCR]

Hmmm... what about in CW mode? Can one run an solid state SSB rig in CW mode at full (or nearly so) power output vs. only 25%??

                  _-_-bear

[KA1ZGC]

Hmmm... what about in CW mode? Can one run an solid state SSB rig in CW mode at full (or nearly so) power output vs. only 25%??

Of course you can if you're actually operating CW, since CW is not a constant-carrier mode. Duty cycles are on the order of 20-25%, well within the design criteria. Doesn't matter if it's solid-state or tube. In fact, most rigs allow you to run a bit above the PEP rating because of the lower duty cycle than SSB.

[ke7trp]

I am using CW mode to excite my Class C amp.

C

[KA1ZGC]

I am using CW mode to excite my Class C amp.

...with a constant carrier. That's not CW. CW is an on-off-keyed carrier with a duty cycle of 20-25%. What you're doing is 100% duty cycle.

The fact that the button says "CW" doesn't mean you can follow the ratings for CW operation. Those only apply if you're actually operating CW. You aren't.

Trust me, 25% max PEP rating is the absolute most you'll want to run for a constant carrier, and 20% is better.

[ke7trp]

You love to state the obvious      

I am running the CW postion so I can get the 36 watts I need to Drive the Grids to the proper level.  I moved the FT450 across the room to the operating postion. I installed a small blower fan on the back of the rig. It now runs cool and is not showing the error. I also put a small 12 volt fan from a computer power supply on the back of the Astron 35M power supply. Its ice cold now.

The FT450 is rated at 100 watts constant Data and RTTY, SSTV with no time limit.  I called Yaesu in california to confirm. They told me that I am free to run CW key down at 100 watts no time limit with this radio as long as I keep the rig cool using an extra fan kit or a simple desk fan blowing air towards the rig.. NOT 25 watts you suggested. The guy laughed and said this is a very popular rig for PSK and other data modes because of its features and price point. Thousands run data at 100 watts. THe rig will lower the output and crank the fan up if it needs to protect it self. He went on to say that there are 200 watts of final in the rig which is a low rating.

I left it keyed down at 100 watts for 1 hour with the extra fan and it never timed out.  I think the issue is resolved for now. I am going to put some more time on it tonight and this weekend. 

Moral of the story.. If you are going to use a Solid state Exciter, Make sure to keep it cool, Otherwise, your radio might protect itself and you could loose Grid Drive.

I do see the value in a tube exciter.  If built properly, It wont care about a long key down. However, the added heat in a small room, The size and dealing with Xtals is something I just dont want to do anymore. The SS exciter is working great as of right now.

Thanks!


C

[W1ATR]

Clark, you need to call Yaesu back and ask him if he managed to read the manual before giving bullsh!t information. On both pages 72 and 73 in the manual under basic setup for digital modes, it clearly states if you plan on making a transmission longer than a few minutes, to reduce output power to 1/2-1/3 of the normal maximum. So with that in mind, that means 30-50 watts.

Here's the manual. http://www.yaesu.com/downloadFile.cfm?FileID=3806&FileCatID=158&FileName=FT%2D450%5FOM%5FENG%5FEH024H102.pdf&FileContentType=application%2Fpdf

There's very VERY few solid state radios capable of "balls to the wall" keydown at full power and I've had them all. You said somewhere here that you have a 1000D, use that as it has a 200w final and can handle extended keydown conditions at higher power levels.

[ke7trp]

You missed the line in my post about the extra fan kit for 100 watts Data. Once you have that, Then data goes to 100 watts. I tested it last night using a temp probe. After an old buzzard it was 120F.   It was 85 in the room.

C

[KA1ZGC]

You love to state the obvious      

...said the joker to the thief. I'm not the one who almost burned up his big rig because he was burning up his ricebox.

Mock me if you want, we'll see who laughs when your Yaesu goes the way of your flashbox.

[ke7trp]

True. I dont know what I am doing. I am just a kid.

[KB2WIG]

.

[W2ZE]

I have used a solid state rig for years to drive the 2x833's by 2x833's. The secret is to add an IPA state that runs very conservatively. The easiest way to do this is to add a GG stage, and a dropping resistor off the B-puss. I use a sngle 813 GG, using a T-network input tune. Plate resistance I wanted to run wasabout 4K, so I added a 2K 100 watt resistor, gives me about 1500vdc, and only requires about 15 watts of drive. simple stupid, with drive to spare. Drives the pubes well into class C. I prefer to run boatloads of drive, and if ricebox breaks, I have about -105vdc of bi-ass to cut the amp off.

I have used both a stranger1 and a ricebox for drive. I have to repair the ranger 4 times, each time requiring a cabinet removal. I got sick of that real quick. A ricebox is the way to go, bar none. You can give me all the usual crap about using a ricebox bolted to a pube rig, and how I don't support th good ol' US of A by using a 50 year old POS, I want to turn the rig on, and not have it warbluate or drift up and down the band.

My 2 pennies.

Mike, 2ZE

[K1JJ]

 A ricebox is the way to go, bar none. You can give me all the usual crap about using a ricebox bolted to a pube rig, and how I don't support th good ol' US of A by using a 50 year old POS, I want to turn the rig on, and not have it warbluate or drift up and down the band.

Mike, 2ZE

    Tell it like it is, Mister Mike. (That's quite a message!)

BTW, good idea about the GG 813 as an IPA driver.  See, that redeems you back into the good ol boy tube driver club.

Are you on any bands now?  Hope to hear that muddy water slapper whirlwide this season.

T

[W2ZE]

Are you on any bands now?  Hope to hear that muddy water slapper whirlwide this season.

I'm currently on slopbucket with a wounded ant damaged by the neibors tree falling last winter. I am currently in aquisition and shack cleanup mode. Ant's need erecting, and rigs need assembling, but making progress. Da muddy water slappa' should be back this winter to a 75 meter channel near you pluggin' up your earhole.

Hijack over; over....

[w1vtp]

I'm considering two options: first would be my EICO 722 VFO driving a 720.  The screen / plate HV circuit will be controlled using a FET circuit.  Could use a variac but the FET will be much more compact.  Second, use my FT-301 (YES! a  rice box)  it served me well over 30 years ago with the same application so I expect it would do well in the next build.

The EICO really wouldn't be a problem tuning up as far as I'm concerned - should be second nature.

Al

[KM1H]

Back when I was building amps to order and needed a bit more of AM or CW/SSB drive for a couple of GG 4X1's I rigged up 4 6LQ6's in GG driven by the CE-100V, those tubes were cheap in the 70's.

BTW, that old 100V is coming back to daddy at Nearfest so expect to hear some classic phasing rig DSB AM fairly soon; I might even switch over to phase modulation so it sounds like a DX-100 or Globe King

[KC2ZFA]

hello all, new guy here, just thought this may be of interest:
I'm just about done wiring the attached circuit in my "millen
exciter" rendition.

If you see anything funny in the circuit please let me know. The
xtal oscillator is from the Orr book (it can also do 160 per
the mods mentioned in the book).

[ke7trp]

I did some more work on the 4-400 transmitter with solid state driver.  After a friend came over to talk about his new rig, We decided that I was still using alot of Drive.  That brought up the accuracy of the Grid meter I have in place.

I wrapped a wire around the Grid pin on one of the 4-400s then used a 2.5 choke to my volt meter. At an indicated 15 ma (per tube) I was showing 47 watts of Drive.  This was in reality -350 volts!  I backed it down to -240 which is a bit more then the eimac suggested -220.  Power out shot from 500w to 750 watts.  I then loaded the amp back down to 500.  The Grid meter shows 10 ma now. I am not sure if its wrong yet. I have not tested it which will require RF deck removal. 

Is this ok to go on the voltage rather then current for the Grid?

If I go less, PA current goes up.  If I go more, Then P-out goes DOWN.  -240 volts and an indicated 10ma is right at that balance of current and power out. 

The Solid state exciter is now ice cole as only 24 to 30 watts is required depending on band.


C

[KB2WIG]

Anyone care to comment?  these things are still around ....

klc