linear....really?????

[222DBFL]

If you could just turn the AM power back to get about 1.5-2 watts and a PEP of 6-8 watts max on AM, and anywhere from 8-12 watts pep on SSB, the amp should work fine. Before adding any amp though I would first make sure that my antenna setup was a good as it can be. And I don't mean just a low VSWR (SWR). A good impedance match and little reflect should be obtained as well. This will help the amp to stay cool and also not over drive it as well with too much power. I am speaking of a 2 transistor amp or a 2 "pill" amp. Here are a couple of pics of the 2 x SD1446 amp I have. Supposed to be AB bias but I don't know about all that. Anyways. Keep it clean and like someone else posted here or another thread, garbage in equals garbage out. First things are to have a radio that is tuned and aligned properly. And then also to make sure your antenna setup is at its absolutely best before you add the amp in line. Maybe JMO, but I'm sure others will agree. Here are the pics of my amp. It's a Palomar knockoff of some type I'm sure.
To All, Have a Blessed Day, and God Bless to All.
Sean.

 

[Captain Kilowatt]

I have a 10m amp that is well built with two 1446's. Ran 10w into it with the Kenwood & a dummy load and it reaches full output @ 12.5v.
Think I will stay with that . . .

What kind is it Robb? Is that a REAL 10m amp or is it a "10m" amp. Wink, wink, nudge, nudge. Your 10 watts drive into a pair pretty much equates to my 5 watts into a single so we are not talking much difference if you were talking carrier. I just realized what the difference may be. My amp has an input pad that assures two things. First it helps prevent over driving the amp and second it provides a really low input SWR, typically 1.2:1 or less anywhere in the 10 or 12m bands without having to play with jumpers. Haven't tried it on any other bands except 6m but I had to mod the input/output to make it work there. It made a nice 75 watt amp when driven by the TenTec 1208 transverter at 10 watts. Speaking of the 1208 the input pad of the amp was just like the input pad of the transverter if you are familiar with that. Basically four 220 ohm 5 watt resistors in parallel to ground forming a 50 ohm input with a higher value series resistor feeding the SD1446. Not sure the manufacturer. No name on it that I can see. First and only time I ever saw a "10m" amp with that kind of input. Too bad they weren't all like that. I bought it as a clear out of NOS from a ham dealer called RadioWorld in Toronto many years ago.

 

[redbeast]

Yup, thanks guys and for the link tallman. Got a lot to learn, but nothing worthwhile comes quick OR easy. Would be nice to rig the 25 to talk good barefoot and still switch to feed the mini linear. More to come.

If you could just turn the AM power back to get about 1.5-2 watts and a PEP of 6-8 watts max on AM, and anywhere from 8-12 watts pep on SSB, the amp should work fine. Before adding any amp though I would first make sure that my antenna setup was a good as it can be. And I don't mean just a low VSWR (SWR). A good impedance match and little reflect should be obtained as well. This will help the amp to stay cool and also not over drive it as well with too much power. I am speaking of a 2 transistor amp or a 2 "pill" amp. Here are a couple of pics of the 2 x SD1446 amp I have. Supposed to be AB bias but I don't know about all that. Anyways. Keep it clean and like someone else posted here or another thread, garbage in equals garbage out. First things are to have a radio that is tuned and aligned properly. And then also to make sure your antenna setup is at its absolutely best before you add the amp in line. Maybe JMO, but I'm sure others will agree. Here are the pics of my amp. It's a Palomar knockoff of some type I'm sure.
To All, Have a Blessed Day, and God Bless to All.
Sean.

Thanks everyone for the good input. Rob-the unit had the power and ground wires wired in parallel with a cobrastyle power plug right at the back of the amp, so im guessing youre spot on there about the 13.8-14.2 volts to run it. 222, sounds right about squaring away the antenna, and having the radio right. Tallman, what are the numbers you would see on a stock untouched 25, 4watts should be the limit but what about pep? What im hearing from you guys is that this linear can pretty much work with stock input power. Bear in mind Im not setup or knowledgable enough at this point to mess with tuning. Point taken also about not overdoing the 25, so sounds like best plan at this point would be tune the 25 stock and add the amp in for ""power"". So with 5watts drive this little guy should put out about 80? Again, my bad about the transformer/pill thing, makes more sense now, and forgive my oversimplification on operating stuff, justtrying to relate using auto background. Again, sounds like general opinion is this guy can be safely driven with stock radio without letting the magic smoke out of the "pill"?

 

[Tallman]

Again, sounds like general opinion is this guy can be safely driven with stock radio without letting the magic smoke out of the "pill"?

I don't think running full 4 watt dead carrier will hurt the amp at all. First thing I would like to point out is tune the antenna with just the radio and no amp. If the SWR is good at 4 watts it will still be good a 400 watts. You aren't tuning to the power just the out put frequency. When you add the amp in only check the SWR with the amp off. If your radio is putting out some harmonics those will get amplified and appear as increased SWR. And all radios put out some harmonics. The linear is not very selective as to what gets amplified since it does not have tuned circuits. If you don't over modulate the carrier you should be fine.

 

[Tallman]

The SD1446 will produce a tad over 100 watts output with 7 watts of drive at 30 MHz. according to the datasheet. Five watts drive makes about 90 watts out.It can take 12-15 watts pep driving it easily. I ran a single SD1446 for years on 11m with such operating drive levels and had nothing but good reports.

Hey Red Beast just a heads up for you, Captain Kilowatt in my opinion is "The Expert" that the experts will take advice from. So what he says in the above quote I would take that advice and run with it.

 

[Captain Kilowatt]

Hey Red Beast just a heads up for you, Captain Kilowatt in my opinion is "The Expert" that the experts will take advice from. So what he says in the above quote I would take that advice and run with it.

Nope. I do not claim to be an expert at all but thanks for the confidence. I just read the data sheet and apply the numbers. I believe in running something within specs and doing so has never failed me yet. The SD1446 is speced at 50 MHz and as such gain figures will be higher on 11m. The datasheet will show the gain over a wide frequency range.

 

[Robb]

What kind is it Robb? Is that a REAL 10m amp or is it a "10m" amp. Wink, wink, nudge, nudge. Your 10 watts drive into a pair pretty much equates to my 5 watts into a single so we are not talking much difference if you were talking carrier. I just realized what the difference may be. My amp has an input pad that assures two things. First it helps prevent over driving the amp and second it provides a really low input SWR, typically 1.2:1 or less anywhere in the 10 or 12m bands without having to play with jumpers. Haven't tried it on any other bands except 6m but I had to mod the input/output to make it work there. It made a nice 75 watt amp when driven by the TenTec 1208 transverter at 10 watts. Speaking of the 1208 the input pad of the amp was just like the input pad of the transverter if you are familiar with that. Basically four 220 ohm 5 watt resistors in parallel to ground forming a 50 ohm input with a higher value series resistor feeding the SD1446. Not sure the manufacturer. No name on it that I can see. First and only time I ever saw a "10m" amp with that kind of input. Too bad they weren't all like that. I bought it as a clear out of NOS from a ham dealer called RadioWorld in Toronto many years ago.

Ahh . . . but in my test it was in SSB mode.
I ran that 'amp' into a dummy load for testing purposes (as I still do not use amps, although I do have a few) following the datasheet power input requirements.

 

[Captain Kilowatt]

Ahh . . . but in my test it was in SSB mode.
I ran that 'amp' into a dummy load for testing purposes (as I still do not use amps, although I do have a few) following the datasheet power input requirements.

I suppose but remember that datasheet states gain figures and drive requirements for 50 MHz. Gain goes up as does the ability to handle more drive and get even more power out of them at 30 MHz. and below. The SD 1446 will produce 70 watts out with 7 watts drive at 50 MHz with a Vcc of 12.5 volts. Drop to 11m and with 12.5 volts you will get a little more than 100 watts.......still within spec. That's my point.......specs at 50MHz can be exceeded when operating below that frequency without detrimental effects. That's the beauty of using a VHF Lo transistor on HF. They are even more rugged than the apparent design specs. I have used Motorola VHF Hi transistors rated to 300 MHz on 6m and even UHF transistors on 2m and in ever case you could drive them harder and get more power out than what the datasheets called for and not have distortion, flat topping, or splatter. Unfortunately the ubiquitous 2SC2879 is only rated to 30 MHz and exceeding the specs quickly results in spectral purity issues.

 

[Robb]

I suppose but remember that datasheet states gain figures and drive requirements for 50 MHz. Gain goes up as does the ability to handle more drive and get even more power out of them at 30 MHz. and below. The SD 1446 will produce 70 watts out with 7 watts drive at 50 MHz with a Vcc of 12.5 volts. Drop to 11m and with 12.5 volts you will get a little more than 100 watts.......still within spec. That's my point.......specs at 50MHz can be exceeded when operating below that frequency without detrimental effects. That's the beauty of using a VHF Lo transistor on HF. They are even more rugged than the apparent design specs. I have used Motorola VHF Hi transistors rated to 300 MHz on 6m and even UHF transistors on 2m and in ever case you could drive them harder and get more power out than what the datasheets called for and not have distortion, flat topping, or splatter. Unfortunately the ubiquitous 2SC2879 is only rated to 30 MHz and exceeding the specs quickly results in spectral purity issues.

Seem to remember awhile back your mention of this device's properties.

As far as this amp is concerned, it has an input filter and simple biasing. Seems to run pretty clean from what I can tell from tests. Gonna put in a bias supply, and give it real biasing.

 

[redbeast]

Hey Red Beast just a heads up for you, Captain Kilowatt in my opinion is "The Expert" that the experts will take advice from. So what he says in the above quote I would take that advice and run with it.

Tallman....Thanks for all the help, &"the Capn'" as well. Think ill give it a shot on the stock 25, but first going to have to do a little wiring work on the power side. Projects, projects. Right now colder than a welldiggers butt up here, and holidays on us.....so it will be a bit, ill post up when i try it. Again, thanks for all the input from everyone, like to get some thoughts before using unknown stuff. Merry and a safe Christmas to all...gotta go-mails gotta move. 73

 

[redbeast]

Been working weird hours, so havent been on in a while. Update on baby linear.......rigged it behind stock cobra 25, and my rat shack 3way meter reads about 12 watts out. Going thru sirio 5000 with swr @ 1.05:1 channel 1, 1.1:1 channel 40, about 1.15:1channel 19. Reports ive gotten is that its clear and louder, one hand said barefoot was better, but he was close. Last time i used it i was talking to a base about 15-20 miles away in serious hill country.
Not sure how accurate my rat shack meter is, seems like 12 watts is kinda low. Guessing probably close, would lowering deadkey actually increase output? Not using it constantly, as per your advice not to blow transistor. Yup, the preamp switch is definitely for increased rx signal, had forgotten about thay feature on my other unit. Is it worth setting up the 25 for a lower deadkey to run into the amp? Get good reports on the 25, and as far as i know its never been touched.......time for a good peak and tune. Input and advice always welcome, sorry i havent posted in a while

 

[9C1Driver]

The amp pictured in the very first post is only doing 12 watts? What radio are you driving it with? Sounds like it's broke. I tried to catch up on this thread but got so lost. I assume you discovered it's a one pill amp then?

 

[redbeast]

The amp pictured in the very first post is only doing 12 watts? What radio are you driving it with? Sounds like it's broke. I tried to catch up on this thread but got so lost. I assume you discovered it's a one pill amp then?

Yup, its a one pill amp. Further talk with the original owner turned up it was a handmade amp, cost him $60 to have made, the guy isnt a real knowledgable source. I dont guess but what that kind of $ for parts and labor and profit would bring it anywhere close to a small palomar!!!! Hey, it was free, and it works(kinda)....gift horse, right? Dont know if it could be tweaked or not, suggestions?