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Using an SB220 on AM




 
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WA3MJY
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« on: August 18, 2009, 11:10:46 PM »

I recently purchased an used SB220 amplifier. Are there any special modifications needed to allow its use on AM? I intend to drive it with a Johnson Ranger II.
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K5UJ
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« Reply #1 on: August 18, 2009, 11:43:09 PM »

My 2c, you can use a sideband amp in AM service (I'm talking about tube amps in this case) if they are rated at high enough power out to make it worthwhile and you take a few precautions.  desk top amps designed for SSB and CW usually have lightweight plate supplies.  The limiting thing, is the current rating of the plate transformer, usually something like 500 ma CCS.  The other things are the plate dissipation of the tubes, cooling, and the tank circuit (band switch for example).   So you have this envelope you have to operate within and if you know your limits and calculate say, how much current a 200 w. carrier demands, then figure 800 w. when you fully modulate it you get an idea of what the stock plate tranny can do for a few minutes.   you have two 3-500s so you know right away you can dissipate up to 1000 w.  Cooling--most SSB amps are made to be quiet which means their cooling stinks.  One easy mod you can do is get a fan for the 220 that moves more air through it.  Get the highest volume fan you can find that will work in one.  200 CFM isn't too much.  It will be loud but ur amp will love you for it if you operate it in AM.  keeping the plate supply and tubes cool will dramatically extend your transmit time.   I know guys who run the 220 on AM with around 200 to 300 watts but I think they limit their transmissions to just a minute or two.  They don't do a 10 minute buzzard tx b/c it will melt down. 

Or, you can blow all this off and get a high level plate modulated rig which is what I'm trying to do  Cheesy

I think you wrote you have a Ranger exciter?   You need a Johnson Desk  Grin  kidding aside, good luck

Rob K5UJ
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KD6VXI
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« Reply #2 on: August 18, 2009, 11:58:14 PM »

I recently purchased an used SB220 amplifier. Are there any special modifications needed to allow its use on AM? I intend to drive it with a Johnson Ranger II.

My two cents worth:

Add a couple more volts of bias to the bias zener.  Best way is to put a few 6A10 diodes in series, and a largish cap across them (to keep dynamic regulation up).

Directly ground the grids of the amplifier.  This will cause a heapin helpin of people screaming yes and no, but if you do, drive goes down about 20 percent.  If you NEED the extra drive option, keep the chokes and caps from pins 2, 3 and 4 as stock. 

Directly grounding the grids also seems to help with stability on that, and a few other similiar designs.  Of course, this will get the "toaster wire" guys to come up and say it's the best, blah blah blah.  I'm giving you what I've done to mine.

Check the caps in the plate supply.  They are old.  They need to be replaced.

Don't count on the HV resistors to be anywhere near accurate, meaning, don't count on your HV meter being anywhere near 10 percent within tolerance.  Replace the two (IIRC) resistors with 4 or so... They need it, because they are across the entire HV...  If not, you will be replacing them again, when you notice your HV falling off (not really, but the meter will start to read high or (more likely) low, and then it's time to get the HV probe out, etc).

That will get you up and running.  I also go through the tuned inputs on them...  Some will say they are fairly close, but I find that not to be the case.

If you REALLY know how to work on the amp, go through the tank network as well.  Stock, 1150 watts on 10 meters.  After moving the tap on the output coil, and touching up the input, I see 1400++ watts.

It's not hard to get 1600+ on the lower bands, with the tank circuit optimized.  It's not easy, but not hard, as you have to have the "RF Shield" in place when  making the RF deck output 'enhancements'.

Hope that helps.  Total cost should be around 100 dollars + shipping, caps included.  This will give you almost a legal limit amplifer, albeit one that can't be held keydown.

Mine will do 300 watts AM carrier for 5 minutes.  I run QUITE a bit of bias on it, though.  Stock, I'd not go above about 250 for any buzzardliness. 

Hope it helps.

--Shane
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W2JBL
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« Reply #3 on: August 19, 2009, 12:34:25 AM »

    I have been running an SB220 on AM for thirty years with little or no trouble at 250-300 watts carrier. I run the amp on 220, in the SSB position, driven by a lightly loaded Collins 32V2 in it's tune position. I also recently acquired a stock SB220 that I run more conservatively on 110. the weak points I found over the years are the fixed loading caps on 75 and 40- I replaced them with rather large "bathtub" style mica caps, and the Zener bias diode. I replaced that with a 50 ohm 50 watt adjustable wirewound resistor and 470 MFD 100 volt cap in paralell and set the resting current to 200 mils. grounding the grids directly defeats a crude inverse feedback circuit and blows the third order IMD spec of the amp all to hell. biasing the amp to a lower resting current also screws the 3rd order IMD spec. I tried it and came out with a dirty amp, so I went back to the RF choke and mica cap from grid to ground, and fairly high resting current. it's cleaner  easier to drive that way, providing you drive it with a clean signal in the first place, otherwise you just amplify the crud from the exciter and add the amp's distortion to that crud.

    a few years ago one of the origional tubes in my older SB220 shorted and took out a lot of stuff. at that time I installed the Harbach power supply board,filter cap block, and hi output fan. I highly recomend all three of those mods. the amp runs cooler, and the issues with inaccurate metering etc are resolved. I did keep my cathode bias setup though. it just works. step back from the amp and take critical a look at the tank circuit and bandswitch before you try to get more than about 1200 PEP out of it (on any mode). the bandswitch WILL melt if you beat on it on the higher bands, as will the tank coil. run it intelligently on AM and you will get years of service from it, even stock. but like all rigs, that extra few hundred watts that most hammy's go for are allways the downfall of most amps. remember- it's a nice green box, but the lable on it says Heathkit- not Harris or Collins.
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« Reply #4 on: August 19, 2009, 12:42:25 AM »

    I have been running an SB220 on AM for thirty years with little or no trouble at 250-300 watts carrier. I run the amp on 220, in the SSB position, driven by a lightly loaded Collins 32V2 in it's tune position. I also recently acquired a stock SB220 that I run more conservatively on 110. the weak points I found over the years are the fixed loading caps on 75 and 40- I replaced them with rather large "bathtub" style mica caps, and the Zener bias diode. I replaced that with a 50 ohm 50 watt adjustable wirewound resistor and 470 MFD 100 volt cap in paralell and set the resting current to 200 mils. grounding the grids directly defeats a crude inverse feedback circuit and blows the third order IMD spec of the amp all to hell. biasing the amp to a lower resting current also screws the 3rd order IMD spec. I tried it and came out with a dirty amp, so I went back to the RF choke and mica cap from grid to ground, and fairly high resting current. it's cleaner  easier to drive that way, providing you drive it with a clean signal in the first place, otherwise you just amplify the crud from the exciter and add the amp's distortion to that crud.

I'd like to see the testing parameters for that.

I have emails galore, as does quite a few others, that show the SB220 with directly grounded grids causes the drive power to drop approximately 20-25 percent Vs. stock SB220.

I can't get the IMD to raise any amount measurable with locals listening a few Kc away from me.  No popcorn, etc.

Keep in mind, this IS for AM use.

Using the stock NFB garbage causes the bias voltage to run up and down, varying with the PEP values of drive.  To me, that's bad engineering.

As to the slide resistor...  You're only using R now, no fixed voltage regulation?  Was this BEFORE or AFTER you played with the grids.

I've been told both possibilities before, and have been involved in quite a few arguments, and listened to both sides. 

Running the SB220 into a single 3CX3000, a 6000 and a 10,000 also showed little to no difference between it and an Alpha for IMD and "crud" in "Crud" out....  This was an SB220 modified as I stated above.

I'd really be interested in what caused your amp to go down the toilet, with the mods posted above... That is, unless, the resistor taking out the fixed voltage regulator for bias was done BEFORE the rest of the mods.  If that's the case, I rest mine.


--Shane
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WA3MJY
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« Reply #5 on: August 19, 2009, 06:05:12 AM »

Thanks guys, you have all given me much to consider. I will consider all of your opinions before I start modifying the amplifier.
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« Reply #6 on: August 19, 2009, 02:18:55 PM »

Quote
I've been told both possibilities before, and have been involved in quite a few arguments, and listened to both sides. 


You spend too much time with the CB and know little crowd on Yahoo Shane
 Grin Youre dealing with the big boys over here.

Ive already posted the IMD degradation results from controlled measurements when the grids are grounded at least twice over there.

I'll take what a HP SA shows over some over the air bozo report any day.

1600W out of a stock 220? Key down? Absolutely impossible at that voltage and xfmr.

Carl
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Steve - WB3HUZ
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« Reply #7 on: August 19, 2009, 03:58:54 PM »

Another reason why many do not notice any apparent degradation of IMD when modifying amps is that the exciter they are using has an IMD that is worse than the amp they are testing. Many recent SS transceivers have horrible IMD, some as much as 10 dB worse than tube rigs like the Collins S-line and the TS-520s of yesteryear. As you said in another thread Carl, GIGO.
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KD6VXI
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« Reply #8 on: August 19, 2009, 04:46:42 PM »

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I've been told both possibilities before, and have been involved in quite a few arguments, and listened to both sides. 


You spend too much time with the CB and know little crowd on Yahoo Shane
 Grin Youre dealing with the big boys over here.

Ive already posted the IMD degradation results from controlled measurements when the grids are grounded at least twice over there.

I'll take what a HP SA shows over some over the air bozo report any day.

1600W out of a stock 220? Key down? Absolutely impossible at that voltage and xfmr.

Carl
KM1H



Carl, I haven't seen any results posted, from any type of measuring equipment.  Not arguing, as I seem to miss a LOT of posts on it, I'll go through the archives and check.

Making comments about service or people on other reflectors means little.  I know of little to no amateurs running a pair of 20,000s, but still listen to their opinions about high power.  Few amateur operators take weather into account when they are deciding if they will talk on their stations or not, but quite a few "CBers" have to.  Very few amateur operators have a relationship with Reid Brandon where they can call up and have a tube built to spec.  More than a handful of the "idiots" on 11 can.  Big deal.

I never said 1600 watts key down.  That's physically impossible, mine won't do more than about 800 watts KEY, but won't modulate that anywhere near linearly....  I typically run mine (AM service) at anywhere from 75 watts to 300 watts of carrier.  Usually at the 200-300 watt level.  SSB tap, but I use a bit more bias, as well as grounded grids.

My Kenwood 440 exciter has better IMD performance at 75 PEP than it does at 100 PEP.  I don't have test results to back it up, but I can sure see a difference when listening to a rx plugged into a dummy load next to it.  About 10 dB, give or take, depending on the accurace of the S-Meter (1-1.5 S Units lower).  Increasing the gain of the amplifier means if your exciter is running cleaner, GIGO applies.

As I said, I knew my post would stir up a hornets nest.  I'd LOVE to see a pic of the Spec An, a picture is worth a hell of a lot more than numbers being thrown out.... BUT, even then, numbers are nice if that's all you can get.

Regardless, mine is grounded.  I don't have neighbor complaints (with someone living 3 houses down on HF at this QTH) from anything other than front end overload when I didn't realize he was there, and he was in line with my 10 dB gain antenna, and the 10 dB gain linear.  One or the other, I'm fine.  Both, and every time I key up, almost anywhere in the HF region, I KILL his Yeasu 450.

Anywho, guests just arrived at the door, so I gotta run.

If you have some plots of the Spec An, I'd LOVE to see them.  I'd also like to see what your 950's do at 100 and 75 watts, if the xmitters haven't been highly modded....  I know you've hotrodded them quite a bit.

--Shane
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Steve - WB3HUZ
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« Reply #9 on: August 19, 2009, 05:18:34 PM »

You obviously don't know very many amateurs. I can think of quite a few hams right off the top of my head that run WAY more than the power you are talking about. And they are doing it correctly, because they have to - it's a BC station.  Wink

See these guys know what they are doing. That's the difference between them and the CB amp guys. Sure the CB guys can build a big amp. But the specs are terrible. They would never fly in a commercial application. So, you can listen to guys that do it professionally and have decades of proven experience, or you can listen to those who don't.
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N3DRB The Derb
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« Reply #10 on: August 19, 2009, 05:41:17 PM »

the cber's do know one thing better than most hams - how to generate & deliver the juice to hi powered amps. I dont know many hams who can set up 8 to 12 alternators to run 15 to 30 K Bird watts mobile. running 7/8" heliax for feedline.

Their amps may sound terrible, maybe 100kc wide, but they are not made for clean signals. They are made for competition in keydown contests, where you can have thousands of dollars on the line. 

The 2 worlds are so at cross purposes with each other that no valid comparisons can be made.

It's like saying "well, I axed this guy down in hell and he said this...." vs. "I axed this guy in heaven that, and he said...."

the perspectives you get MIGHT be a little far apart.
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ke7trp
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« Reply #11 on: August 19, 2009, 05:53:25 PM »

Oh brother.. Because Shane is known in the CB world he knows nothing about ham gear?  Give me break.

I have know Shane for 15 years.  If the guy says something you should listen.

As for the SB220.  I think its a waste of time as an AM amplifier.  I have three of them.  Its really only going to do 200 watts AM max. If you try to push it more then that its going to overheat and groan about it. The heat comming off that thing at 200 watts is just silly.  Cherry plates, Power trans that is screaming hot and waiting to blow.. A tuned tank thats about to flash over.

Not a bad little amp for SSB use though.


I have owned 5 of them.  I grounded the Grids on most of them. Makes a Big difference. Does not inrease IMD. I have an HP Spec AN here. The stock config is horrible.  I have plotted the amp with and without grounded Grids. If you say otherwise,  Post your picture of the spec AN showing this.

I also add diodes to the Bias. Really helps for AM use. The last one I built has the Harbach boards, caps and Grounded Grids. Diff bias on that board as well.


T
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ke7trp
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« Reply #12 on: August 19, 2009, 05:55:34 PM »

Ran out of room.

The last one is sitting right here.. Its plugged into a Stiff 240 volt line. It makes 1550 PEP with the original Eimac tubes. Runs Clean on the spec An and never arcs over or gives me trouble.  But I dont like using it on AM much.  I nice old SSB amp that will do full legal pep.  But, A 175 watt AM amp.

Clark
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KC4VWU
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« Reply #13 on: August 19, 2009, 05:59:17 PM »

   I like CB amps. If I can get them cheap enough, some actually have a few good usable parts in them.
Phil KC4VWU
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« Reply #14 on: August 19, 2009, 06:21:41 PM »

Call me uninformed but I always thought the SB-220/1 grid pin circuit was there to counteract lead inductance of the tubes for parasitic suppression. If that is indeed a negative feedback circuit how does if work on all bands?
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Steve - WB3HUZ
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« Reply #15 on: August 19, 2009, 07:39:14 PM »

Quote
Oh brother.. Because Shane is known in the CB world he knows nothing about ham gear?  Give me break.


Who said that he knows nothing? The comments weren't even about him. They were about these mythical people in the CB world with superior knowledge in high power RF to those in ham radio world. I don't know nor ever heard of one CBer who has designed, run or maintained high power RF systems in the commercial world. I know many hams who have. That was my point. I will judge the merits of Shane's (or any one else's comments) on the body of proven knowledge in the field.


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« Reply #16 on: August 19, 2009, 07:40:23 PM »

I ran the SB-220 SA tests in the early 80's when I borrowed one from work at Wang Labs for a weekend. My tests were on a 6M conversion and the Director of the RF Division bought over his SB-221. Both showed a repeatable 2-3dB improvement with the grids as designed. There was no Internet then and GPIB wasnt even available.

The Drake L-4 was designed the same and the designer recently stated that they also saw a 3 dB improvement in IMD.

Both of the above have been discussed on the other group Shane and I doubt if results have changed Roll Eyes However I now have my own SA.
I'll be glad to redo the tests the next time a SB-220 comes in for conversion but that business has been a bit slow recently altho SB-200's keep coming in.

Since the chokes provide some level of degeneration due to their 26 Ohms DC resistance it is easy to see why output decreases compared to direct grounding. It should also follow that the process will also improve linearity. I havent tried the cap across the zener or measuring IMD with a string of diodes. Those are ideas I will try.

Clark, since you have a 220 and SA handy why dont you do as you say:
 
Quote
I have an HP Spec AN here. The stock config is horrible.  I have plotted the amp with and without grounded Grids. If you say otherwise,  Post your picture of the spec AN showing this.


Carl
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« Reply #17 on: August 19, 2009, 08:07:31 PM »


Since the chokes provide some level of degeneration due to their 26 Ohms DC resistance it is easy to see why output decreases compared to direct grounding. It should also follow that the process will also improve linearity. I havent tried the cap across the zener or measuring IMD with a string of diodes. Those are ideas I will try.

Carl
KM1H

Carl,

Here's a ? for ya then.  Would it be "better" to use a different style of choke then, maybe something with BIGGER wire and a core?  That way, you'd get the L you need for NFB, but reduce the ohmic value of the choke.  Bias wouldn't shift with drive level, AND the gain would go back up to the levels we see with the grids grounded.

I undertstand the problems with the core getting hot, and you could semi-negate (no pun intended) that by ensuring it was within the airflow (which it would be)...  Come to think of it, the 220 would cool them fine in stock cooling config, pretty much.

I'd love to find a way to improve the 220.  I LOVE mine.  However, it is a pissweak amp, in comparison to others, and any way to increase performance is OK with me.

As I said, redoing the tank circuit (in and out), made a BIG increase, especially on the upper bands.

--Shane
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« Reply #18 on: August 19, 2009, 08:15:19 PM »

Quote
Oh brother.. Because Shane is known in the CB world he knows nothing about ham gear?  Give me break.

Who said that he knows nothing? The comments weren't even about him. They were about these mythical people in the CB world with superior knowledge in high power RF to those in ham radio world. I don't know nor ever heard of one CBer who has designed, run or maintained high power RF systems in the commercial world. I know many hams who have. That was my point. I will judge the merits of Shane's (or any one else's comments) on the body of proven knowledge in the field.


Steve,

I'm not talking about the handful of US amateur operators that have a job as a broadcast engineer, nor am I talking about the handful that have QRO power AT HOME.  I'm not talking about in the commercial world.

What I'm talking about is there isn't that many amateur operators (if you look at it statistically) that can actually BUILD anything of that nature.  I mean, seriously, are you going to debate that the amateur radio community as a whole is NOT a bunch of appliance operators?  (YES, this is a generalization).

Yeah, we have BE's in the amateur radio ranks.  We also have them in the CB radio world.  I know of 3 BE's that run 15kw plus, 2 FCC engineers (one running my amp) that operate on 27.025, etc., etc., etc.  Who CARES!

My comment was based on the fact that there are people in other services doing QRO.  Just because they don't have an amateur radio license means little to nothing.  Dennis O. can run circles around most "Broadcast Engineers" that I've had the pleasure of meeting, but refuses to use amateur radio.  He now works at Motorola.  Does it mean ANYTHING that he works on CBs to supplant his income?

The problem with the CB'ers coming 'clean' about operating there is the stigmata that goes along with it.  You can't discount, most amateur operators wouldn't even be able to figure out how to build a 75 kw carrier amplifier, much less figure out how to get enough power to it.  They'd rather just pick up an (insert appliance here), throw the G5RV up in the air, and be DONE with it.  Incidentally, these are NOT the types I find here.

IOW, the only place I've found extreme QRO is either VOA Delano, or a couple CBers running water cooled 40,000 triodes.  Me, Ive only got a 30kw water cooled triode, so I don't count in the big boy club Sad  lol

It wasn't bashing anyone, it was a statistical thing.  Lots of hams are engineers.  Doesn't mean any of them are running more than 50 thousand watts out of their house!

--Shane

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Steve - WB3HUZ
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« Reply #19 on: August 19, 2009, 09:14:19 PM »

Quote
The problem with the CB'ers coming 'clean' about operating there is the stigmata that goes along with it.  You can't discount, most amateur operators wouldn't even be able to figure out how to build a 75 kw carrier amplifier, much less figure out how to get enough power to it.  They'd rather just pick up an (insert appliance here), throw the G5RV up in the air, and be DONE with it.  Incidentally, these are NOT the types I find here.

I totally agree. But the same is true of most CBers. So, statistically, it's a wash in that department.

All this is very irrelevant in the realm of discussing an SB-220 or other similarly powered amps, and the relative IMD levels. In this area, I think you will find the amateur population is vastly more educated and experienced than the CB population.
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« Reply #20 on: August 19, 2009, 09:20:31 PM »

Ran out of room.

The last one is sitting right here.. Its plugged into a Stiff 240 volt line. It makes 1550 PEP with the original Eimac tubes. Runs Clean on the spec An and never arcs over or gives me trouble.  But I dont like using it on AM much.  I nice old SSB amp that will do full legal pep.  But, A 175 watt AM amp.

Clark

Kinda squares with my experience.  I owned a SB220 -- loved it a lot.  Like an idiot, I sold it when I moved back in '84.  My problem with the SB220 is in how the toobs are cooled.  I wouldn't recommend running "legal" -- with the SB220.  Probably 200 watts would be OK.  Some of the newer designs that allow for proper cooling would work just fine. But the pins have to have air running by them -- a chimney really is necessary if you're going to run the SB220 for the kinda power that AM legal limit runs.  I also had a RTTY station but did NOT run the SB220 with that either.  I had a HB 2 x 813 xmtr for that. The SB220 is a nice SSB linear.  Be sure to run it on 220 VAC

Here's a pic of my old station.  You can see the SB220 in the middle and the HB xmtr on the right.

73, Al VTP


* old w1vtp qsl.jpg (215.99 KB, 964x577 - viewed 878 times.)
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« Reply #21 on: August 19, 2009, 09:27:04 PM »

Black & White QSL? I should talk, I never had any printed. 
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« Reply #22 on: August 19, 2009, 09:35:05 PM »

The BS detector has a lower MDS here.
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« Reply #23 on: August 19, 2009, 10:17:15 PM »


 My problem with the SB220 is in how the toobs are cooled.  I wouldn't recommend running "legal" -- with the SB220.  Probably 200 watts would be OK.  Some of the newer designs that allow for proper cooling would work just fine. But the pins have to have air running by them -- a chimney really is necessary if you're going to run the SB220 for the kinda power that AM legal limit runs.  I also had a RTTY station but did NOT run the SB220 with that either.  I had a HB 2 x 813 xmtr for that. The SB220 is a nice SSB linear.  Be sure to run it on 220 VAC

Speaking of cooling, the original Drake L-4 and L-4B used chimneys and a blower.  The later L-7 (same basic RF circuit with the same PS) uses a fan like the SB-220 except it is a 2 speed thermal controlled model.  I have used my L-7 a couple of times on AM for a local 160 meter net but I keep it at 150 to 175 watts carrier out.
160 is the only advantage the L-7 has over the L-4B but the cooling system is much better on the L-4B.  The cooling system on the SB-220 seems superior to the Drake L-7 given the well perforated case on the Heathkit.

The odd thing is that the T-4 series rigs are controlled carrier and very friendly to linear amplifiers while the TR-7A is a typical SS rig with continuous carrier which generates a lot of heat in the L-7.  I wouldn't use it for lengthy transmissions on AM although it would do fine with the early 4 line gear.

My SB-220 was the first Heathkit I built back in 1976 (and $369 was pretty pricey for a high school student!).  The 3-500Z tubes it came with have a spacer built around the pins so that the tube base/pin seal is elevated a bit for better cooling.  I still have it and use it from time to time and it still has the original finals.  Of course for many years it didn't get a lot of use with all of the time I spent in college and once I finally had more radio time I soon built a new homebrew amp that covered 160 and was better suited for contest use.  But the SB-220 is a pretty well built amp and works great on SSB/CW.  I worked a lot of CW DX with it and a bit of RTTY many years ago.  It does need a standby switch and I implemented that several years ago in the form of an external switch that switched the amp between my SB-102 and Drake C-line with a center "neutral" position.

Rodger WQ9E
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« Reply #24 on: August 19, 2009, 10:36:37 PM »

Yes.. The cooling is the big issue. Thats why I dont like using them on AM.  I did with a ranger and yes it worked. I also used my FT1000D with outboard audio with it. But I would rather fined something that wont cook itself.  Us left coasters tend to key for 5 to 10 minutes a time here on AM.  At Five minutes in an SB 220 is really screaming for mercy.

The Drake is a big step up in my opinion. But it has its own issues.

I have used SB220s for 15 years.  I have used them on every band.  Mine spends most of its time on 40 or 80 as I mainly use the Low bands. No issues with IMD here.  I know, I plotted the amp. I dont have to worry about. Clean in, Clean out.

For years I have heard people bitch about arcing the cap over and how it needs to be changed and how to supress "harmonics".  BS.

Tune the antenna so its flat BEFORE you flip the amp on!  Tune the amp at low power input on the tune postion. Then when its tuned, go to high power and increase drive.. DUH.  I have never had an arc over on an SB220.

Its a neat little KW amp for SSB.  My main complaint really is the band switch is the same size as the tune and load. I have almost hot switched mine several times. I have to stare at the knob and check each time as I am worried about this. Most SB220s have been hot switched and the failed so called "weak" band switch takes the blame.. LOL

Clark
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