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Gonzo
Intermediate Member
Username: Gonzo

Post Number: 143
Registered: 9-2004


Posted on Sunday, December 19, 2004 - 5:30 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Just posing a question to the amp EXPERTS:
Someone who has used all of these, or has good technical transistor experience

What do you guys think are the cleanest of these RF transistors??
SD1446
SC2290
SC2879
MRF-455

Which can take the most drive?
Which has lowest TVI problems?
Cleanest Audio?
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Tech291
Moderator
Username: Tech291

Post Number: 14
Registered: 11-2004
Posted on Sunday, December 19, 2004 - 5:45 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Gonzo,
it is not so much the transistor as it is the design of the input and output circuts associated with them and also broper biasing.

tech291
CEF#291
kc8zpj
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Bruce
Senior Member
Username: Bruce

Post Number: 1901
Registered: 9-2003
Posted on Sunday, December 19, 2004 - 6:41 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

291

I used 4 sd1446's in my 10 meter class c amp. NO bias problems just drive it hard ( LOL ).
Your right if you bias the transistors so that they are somewhat linear and dont drive them into cutoff they do work well.
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Patzerozero
Intermediate Member
Username: Patzerozero

Post Number: 283
Registered: 7-2004
Posted on Sunday, December 19, 2004 - 11:03 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

the wheels are turning...has gonzo exhausted all his antennas, or is it just the snow outside making you go to amps?!
i don't build 'em, i just use 'em, but i've driven my 2879 amps (2-4-and 8 pill)to where i'd swear they'd self-destruct, and they haven't yet(mostly texas stars, with an occasional davemade or x/magna force thrown in) have overdriven dx250 and dx400's(2290's) w/10w dk and 40 or more swing before i was told it sounded bad. my dx350hd, put magnum S9 into it and had no bad reports. had a customer blow up his new(1446) boomer with stock connex dk7, swing 10, yet i have an old boomer(454's)that i've used w/my S9 with no ill effects. put a 1-455 no name behind grant xl dk2 swing 12+ was fine, behind S9, sounded like $#*@.drive my dx1600 with 2-2290's or 2-2879's obviously more output w/2879's but no bad reports. i'd say 2879's take more abuse/drive. never really asked how my audio in particular was, but if any were overdriven, audio went south, crunch came in...turn down drive & things were fine. as for tvi,(that's why i run power mobile, almost NEVER base) 2290's least, 2879 next, 454,(didn't use any 455 amps base much), 1446 and 1407(?) were bad, old gray 600(mrf422's maybe, don't remember), gave awesome tvi. but i think tvi may be more the quality of amp/drive radio/ant/ground as i can run dx350 base with stock grant lt or pc78 or delta force, cause NO tvi to any tv in my house, yet my ic735 causes nothing to 1, slightly thru speakers of 1, and slight fuzz to picture of 1. S9 is tvi machine, fuzzes picture on all tv's in my house as bad as ft101e when no lowpass used, not as bad but still present w/filter inline.
most (good quality) custom transistor amps are built with 2879's, must be a reason...
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Gonzo
Intermediate Member
Username: Gonzo

Post Number: 145
Registered: 9-2004


Posted on Tuesday, December 21, 2004 - 10:58 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hey Pat I spoke to a Chris unit 210 in your neck of the woods the other night. I am not going to amps for the base, I'm strickly an base antenna guy as you know. However in the mobile........
-----------------------------------------------
Which by the way my mobile is the EXCELLENT Magnum S9 like yours...so any help would be much appreciated. So you recommend 2879's?? This is what I have been hearing. Any particular combo that you think would work well for that radio?, I only want about 3-4 pills.
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Racer X (Unregistered Guest)
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Posted on Tuesday, December 21, 2004 - 5:05 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

This is just a guess, but I think that 2879's are popular because they have the highest ouput per device.

I believe I read somewhere once that they are only clean up to 80 watts and then start spewing spurious emissions. Kenwood used to use a pair of them for their HF rigs so they were only doing 50 watts per device. I don't know what they currently use, but I know they were used in the TS140, TS680, and TS450 - probably others too.
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Patzerozero
Intermediate Member
Username: Patzerozero

Post Number: 286
Registered: 7-2004
Posted on Friday, December 24, 2004 - 3:45 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

hey bill, i spoke to a triple zero in your neck of the woods last nite...sounded just like you! and my final QTH was about 5 miles closer to you then when i started(gotta keep the locals guessing)but still a fair distance for my rinky dink skiptalking mobile to talk local.
don't know chris, but but then i don't get off 6 or 835 much either...
the way my XL talks mobile and the fun i have with the S9 in the house, nearly 4 months gone by & i still can't get the darn thing in my truck permanently!
obviously the custom amp builders are looking for power more then worrying about tvi, but you did say mobile! definitely 2879's, and with the S9 your choices are 2 or 4 pills, a 3 pill has a builtin driver stage which probably won't be too happy with the 40 watts swing from the S9.
was just looking over post on another area here re: the 1 watt dead key myth...having spoken with sam lewis direct re S9 and his texas star dx500hdv recommendations, i am going to experiment with my S9 and a (2879) dx350hdv and raise the S9's dead key to see the results. also may have a 4-2879 davemade for a few days next week, he told me to HAMMER his 4 pill w/40 watts dk and 100+watts swing, can't do it with the S9, but will definitely go with the 10 watts dk the S9 does & see how that compares to the 2pill 350hdv and see if i can put my S9 in a friends truck with his 4pill 500hdv and see what results i get. still debating how to hard mount my predator 10k or (new!) astatic 3kl then i'll mount my S9 in my truck and go either 4 or 2+8 & hope my airbags stay put!!
hopefully i'll get to do my comparison testing this coming week, & i'll be sure to let you know my results!!
pat
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Gonzo
Intermediate Member
Username: Gonzo

Post Number: 148
Registered: 9-2004


Posted on Friday, December 24, 2004 - 5:32 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Great Pat thanks.
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Patzerozero
Intermediate Member
Username: Patzerozero

Post Number: 299
Registered: 7-2004
Posted on Sunday, January 02, 2005 - 12:54 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

ok, bill, and anyone else interested. spent all afternoon testing. the results were definitely not what i expected. spoke to several BIG TIME amp builders and customizers and worked this test with the assistance of one. sideband and AM being 2 different animals, i was basically told i would not get optimum results on an amp that worked on both, but get an acceptable result using an amp such as texas star. these are all AM ops/builders, and they all profess knowledge and desire of building amps that, on AM will deliver the maximum, true, usable wattage. i was told, Am or SSB, forget peak watt readings, use the rms scale ALWAYS, whether AM or SSb, more avg watts with less swing is more productive then low key and lots of swing. ok, i've believed that, just all the hype about the magnum, including what i've seen with mine...well we'll get to that. i also was told to chuck my cb wattmeter for any ACCURATE readings, no matter what the manufacturer claims. all measurements were done with their bird 43, MY diamond sx100, and their dosy 3 meter. the bird was used with a 50 watt, 100 watt and 1000 watt slug, the diamond and dosy just switched scales. 2 trucks, my 99 durango, stock alt and optima battery with astatic 3kl on triple magnet/ball mount, and a 99 S-10 with HO alt (95amp??) and 2 diehards, with a 5' skipshooter on a thru the roof ball mount. all tests on channel 11AM & SSB, durango swr on grant xl swr meter was about 2x needle width past left of scale, same for cobra 29 in S-10,(so probably less then 1.3-1). we estalished that my sx100 on 30 watt avg scale reading variable wattage of my XL and S9 was close to the bird, considerably lower then pep readings, and readings when on 300w scale. XL varied less then 1w to 5.5 watts dk, and swing was maybe 9-9.5 all on avg scale. i was reminded not to waste my time with peak readings when i asked. yet if i put sx100 on 300w scale it showed 8-9w dk and 18-20 w swing. on bird w/50w slug, XL did 1-5dk and 9 swing. cobra, no vary dk just over 3 and swing 10-11 on bird. now, my S9 varied 2-7.5 and swung 15 on bird, 1-8dk and 16 on SX100 30w avg scale, and 1-10 and 21 swing on 300w avg scale. S9 starting to NOT look so impressive. dm452 on S9, astatic 575 on XL and stock mic on 29, my son on my ar3500 @ base approx 4miles away. all keys, i said 'five-five-five' and my keydown partner said "one-one-one', with the intent being to give me the edge each time. he said XL & 29 were pretty much equal, MAYBE an edge to XL but calling(yelling) to a dx station, he felt it was equal. 1w dk on S9 vs 29, he said the cobra had it hands down. hmmmm. 3w dk on S9 son said was pretty much same again w/cobra. 7.5w S9 dk gave edge to S9 over cobra, but if anything, barely. so as loud and impressive as i've been told the S9 sounds, it really didn't fare any better then a stock cobra or uniden in real world comparisons. that's not good. none of the amp builders i spoke with had ever seen an S9, much less know anything about them. they all use 29/76's or 148/grants and preferably older ones. when i told them how they work, topgun, 1w dk w/40w swing from 2-1969's they were all skeptical to say the least of it's true output and efficiency as an AM skiptalker. our tech from ***** amps tried not to say i told you so, but i know he was just biting his tongue. he was impressed with the rcv quality of the S9 though. as a sometimes sidebander, he said he may actually consider one, though in his chevy van with the large steel tube, he plans on sticking with his cobra 29. i can't get the davemade amp i was hoping to borrow til next week, and my friend with the S-10 is going back to fla on monday, so we did what we could do to test amps with what we had between us. now, the 2 amp builders that were most helpful in answering my questions, plus the tech we had with us, all said, on AM to go with a 5 pill whether it be the dave, texas star, or whatever, as long as the driver stage is a 2290 or 2879, when using the S9. now, this contradicts what i was told by sam of magnum. he said NO driver stage. these amp builders told me on SSB w/dual 1969's they'll MAYBE overdrive the amp, so unless i was to turn the mic gain down to back off some of the swing the S9 would be better suited to a straight 4 pill. we used my TS dx350hdv (2-2879's and variable) in my truck, and a TS dx667v(1-2290 driving 4-2879's variable) in the S-10. XL in my truck, 120dk and 240 sw on bird, 150dk and 285 swing on SX100 300w scale, and 250dk and 425 sw on SX100 3kw scale. so much for accuracy. now, the S9 dk3w on bird on the dx350 keyed 125 and sw 250 on bird, almost identical to my grant !!!??? 150dk 300sw on sx100 300w scale, and 200dk and 450sw on sx1003kw scale. compare S9 & XL readings on SX100. strange. and my son said XL sounded clearer(understandable) but S9 was louder, though no carrier difference between the 2. 29 on bird w/667 dk 250w and sw 400w (always avg scale!) and needless to say smoked XL and S9 on dx350. he varied the 667 to 240w sw & it dk 175 or 125dk & sw was 200-was pretty much neck & neck with both XL & S9. now, i never mentioned the dosy's readings, we didn't try it but a couple times, and the readings were so outrageous it wasn't funny-the 29 & 667 was keying 500w and swinging 1000, come on, i knew to give it up when the S9 dk15 & sw 65! the conclusion here was, on AM at least, with S9 dead keying the same as cobra 29 or grant XL, and ROUGHLY the same output from 2 different amps, they all were equally matched-no clear cut advantage to the S9 with all its hype. now, when we put the S9 on the 667, w/3w dk, on bird, it dk 260w & sw was 480, more then 29 on 667. would it have made a difference? don't know, but at that power, a couple watts won't. the S9 on SSB sounded overdriven with both amps at 4 miles, and, ssb output on bird rms was 18w, with dx350 was 275w and on 667 barely 400. XL was 14w, 250w on dx350 and 400 on dx667. backed down mic gain on S9 to get 667 to sound better, and saw no loss in output, but with rf gain on ar3500 almost all the way down, the grant & S9 were pretty much equal. i know, an apples to oranges comparison all the way around with the amps, but the best i could do. i have everything written down, so when i get hold of the dave 5 pill next week, i'll at least be able to compare output watts to see how it does. not that anybody has ever given the S9 a bad signal or audio quality report, but it just didn't give itself any advantage over a stock cobra 29 or grant XL. i honestly expected to see more from the S9 then i did, even after 2 amp builders and a couple of big amp users told me otherwise. to keep from getting bummed, i keep telling myself that for double the price of the XL, i have more channels and a freq counter along with talkback and endless echo. it didn't get beat by either radio, but it sure didn't outtalk them either. and, no, i really didn't get to test SSB real good, as my friend , the tech with us, and the builders i spoke with are all AM guys, and weren't real interested in testing SSB.
the general consensus here, was, 2879's are always the way to go, and on AM at least, forget about swing, 1:4 ratios, etc. set your radio at the wattage that gives the highest dead key with forward swing. in this case, with 2 texas stars, 3 watts deadkey produced the highest dk with the most swing, any more dk, and the swing was less. and, by the way, the dx350HIGHDRIVE showed NO difference with 3 watts drive or 8 w drive (from the S9).
great way to spend a 60 degree new year day!
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Racer X (Unregistered Guest)
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Posted on Sunday, January 02, 2005 - 2:48 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Sounds about right to me.

What bias were the amps? I would imagine that as heavy AM users they were class C for higher efficiency, while they SHOULD be AB1 for AM and SSB definitely needs AB1.
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Patzerozero
Intermediate Member
Username: Patzerozero

Post Number: 301
Registered: 7-2004
Posted on Sunday, January 02, 2005 - 9:01 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

texas stars, as TS states on their website, should've been AB1, allowing them to work equally 'so-so' AM & SSB, as per the big boys, and i guess that was the result. the davemade we'll get our hands on next week (hopefully) will be a hands down no holds barred built for AM machine, class C.
the dave will be a 5 pill, 1-2290 driving 4-2879's, and i should have access to another truck with a TS 500V (sam @ magnum's reccomended amp for the S9), a class AB1 amp. the big boys agree w/sam regarding the 500 & S9 on SSB, but not on AM. as our testing showed, the S9 might be a bit more hype then performance, and they say that my findings confirm the S9, on AM at least will work fine w/ an amp with a driver stage. obviously dead key can't be S9's 9 watts, but 'claimed' swing of 45 IS hype, and, on the davemade at least, will cause no ill effects, and for that matter, the S9 sounded fine on AM on the TS dx667(1x4), just a tad much on SSB, but again, that was at a 4 mile distance, and even to touchy ears, the topgun sounds scratchy/compressed when too close.
on a phone call with the tech that was with us yesterday, he reiterated the claim, that for AM, you want carrier power, not swing, 350w dk swinging to 375 watts should 'generally' be considered preferred to 150watts swinging to 600, with decent audio, the carrier power being 3db (or double) plus some. of course, not taking into consideration variables, such as line losses, antenna gain, etc. this info is coming from guys who build 4-5-6 THOUSAND and more watt transistor amps, (and 20 THOUSAND plus watt tube amps), and so far, with small watts, their point is proven. he did have a few more questions for me regarding the S9, he'd like to HEAR one again, rcv & xmit, as he was impressed with its rcv as he does talk SSB sometimes w/ a grant XL at his base, barefoot.
as for AM, he wasn't impressed with it at all.
this test was for me to see just how good the S9 is and which amp to put with it, mobile, in hopes of having THE setup. so far, i'm disappointed with the S9. i'll just have to see how it goes with these other 2 amps.
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Gonzo
Intermediate Member
Username: Gonzo

Post Number: 149
Registered: 9-2004


Posted on Monday, January 03, 2005 - 5:56 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks Pat for your excellent work. As you know I am on SSB most times even in the mobile, and have ordered a TS500V to go with the S9 in the mobile. I ordered it before your report, so I am glad some people agree with me that this would be a good SSB combo.

I also agree that swing is highly overated and on AM you want carrier power not swing, otherwise your a mudduck for sure.

The dave-made and the TS667 appear to have the same transistors..a driver and 4 SC2879's, outputs should be close. Without having to buy a different amp for AM, I am sure the S9 can be modified to provide more AM carrier. Mine appears to put out 25 watts of AM carrier with swing to 40, this is with a Bird 43. I also have the SX100 meter, which other than the Bird is fairly accurate. This is probably still not enough a driver transisitor/amp would no doubt be better. Although the difference in signal strenght between 400 watts and 500 watts, is just about zilch, so maybe you can drive them a little lower and save your audio and your amp.

The TS667 is nothing more than a TS500 with a driver transistor, otherwise its the same amp, so the S9 should be able to work fine on AM with a little tweaking.
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Gonzo
Intermediate Member
Username: Gonzo

Post Number: 150
Registered: 9-2004


Posted on Monday, January 03, 2005 - 6:39 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

PAT
Do you know Man O' War?? He has a breakfast break around here, all the local ch 6 freaks are there, next one is in March. Lots of wattage here, I will keep you posted (by radio)if you are interested.

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