i have a 2x sd1446 palomar amp or similar, i know the sd1446 are rated at 75 watts. my meter shows it keying up with a 2 watt carrier going in at 80, 150 , 250 watts for low med high power, is this possible? i fairly certain the meter is accurate at least at the lower readings because i know my radio is set to 2 watts on low power and its is right on the reading. ( not to say thats an accurate way to judge my meter buts its all i have)
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power output question about the sd1446
- Thread starter cjruger
- Start date
Unfortunaly that's only possible if your amplifier is unstable and oscillating. This transistor is only rated for 10db gain. That means whatever drive you give it, the transistor will try and make 10 times that as output. With the 2 watt carrier the amp should only be keying about 20 watts.
For it to be over 200 watts output with 2 watts drive means the stage would have to have 10 times the gain it actually does or the more likely possibility is it's self oscillating. Check you SWR when it says this power and there is a strong change they will be high. Another key sign something is wrong.
For it to be over 200 watts output with 2 watts drive means the stage would have to have 10 times the gain it actually does or the more likely possibility is it's self oscillating. Check you SWR when it says this power and there is a strong change they will be high. Another key sign something is wrong.
So your telling me that this amp should only key up at 20 watts with 2 sd1446 abd 2 watts in? That doesnt seem right
And yes the swr is higher with the amp than with out it, stock radio swr 1:3 and with amp its like 1:7 swinging down to 1:4 or 1:5.
So there is a problem with this amp? It has worked really good for me over the past year or so. There was a small capacitor ( i think) ratteling around inside when i aquired the amp, that was totally smoked, i could find anywhere where it should go and wrote it off as something left in there from assembly. Also i thiught it was a palomar 250 which i thought ment 250 watts out.
And yes the swr is higher with the amp than with out it, stock radio swr 1:3 and with amp its like 1:7 swinging down to 1:4 or 1:5.
So there is a problem with this amp? It has worked really good for me over the past year or so. There was a small capacitor ( i think) ratteling around inside when i aquired the amp, that was totally smoked, i could find anywhere where it should go and wrote it off as something left in there from assembly. Also i thiught it was a palomar 250 which i thought ment 250 watts out.
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Sorry, I was looking at the VHF spec for this part. At 30 MHz. the gain is better. With 2 watts in you should see close to 70 watts out on high power. The 250 watts you're seeing still sounds troubling. Did you check the SWR with the amp on?
Yes swr with amp on is higher but swings down. 1:7 dead key swinging down to aroundd 1:4
With amp off around 1:3
If the SWR was going to swing in any direction, it should be up if power is increasing with modulation. The fact it swings down is another indication the amplifier may be oscillating. Higher drive levels tend to swamp out the self oscillation.
The 70 watts min spec simply means that's the least amount of output you should expect in a properly built and driven circuit. The 10db min is the least gain the part will have around 85 MHz. Gain determines the power input to output ratio. The higher the gain the more output for the same drive.
The 70 watts min spec simply means that's the least amount of output you should expect in a properly built and driven circuit. The 10db min is the least gain the part will have around 85 MHz. Gain determines the power input to output ratio. The higher the gain the more output for the same drive.
Don't get all caught up in that spec sheet, it's 50mhz at 12.5 volts. When run at 13.8-14.5 the numbers go up. So for 11m purposes a 1446 is a 90 watt final.
If I read what you are saying correctly, a 2 watt input carrier is giving you a dead key out of 80, 150, & 250? If so you have some problems there, you would be lucky to see 150-220 peak watts with say 20 watts PEP input.
You might try a different watt meter, it's acting like you are dead keying too much wattage in. Next would be the amp is damaged. Strange problem there.
If I read what you are saying correctly, a 2 watt input carrier is giving you a dead key out of 80, 150, & 250? If so you have some problems there, you would be lucky to see 150-220 peak watts with say 20 watts PEP input.
You might try a different watt meter, it's acting like you are dead keying too much wattage in. Next would be the amp is damaged. Strange problem there.
Ya thats it. Not sure what to do now. I do have another watt meter ill try but im not sure how high it goes.
Could be that the 2950 even at 2w dead key is still putting out too much PEP power into this amp? Might check the PEP with an accurate meter and see. These amps really don't like anything more than 20w PEP - tops. More like 12w PEP is best.
Had to fix one of these amps for a local who just insisted on using a 2950 radio up too high for the amp. Try 1w dead key if the radio will go that low. Same is true for SSB; too much power can fry the 1446's. Keep in mind that the 2950 is a dual final radio; not a single final radio. Weren't these amps built for single final radios?
Overdriving this amp will be its destruction - IMO
Great little amp if you can keep it alive and not trying to squeeze every single last watt out of it. Tried it out with my Kenwood on SSB after adjusting radio output to just 10w. Got 160w out and squeaky clean too. Looked great on a scope . . .
Had to fix one of these amps for a local who just insisted on using a 2950 radio up too high for the amp. Try 1w dead key if the radio will go that low. Same is true for SSB; too much power can fry the 1446's. Keep in mind that the 2950 is a dual final radio; not a single final radio. Weren't these amps built for single final radios?
Overdriving this amp will be its destruction - IMO
Great little amp if you can keep it alive and not trying to squeeze every single last watt out of it. Tried it out with my Kenwood on SSB after adjusting radio output to just 10w. Got 160w out and squeaky clean too. Looked great on a scope . . .
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2watts is as low as she goes. The radio does swing a lot. The meter shows it swinging up in the 300's on higher power. I have been running it for quite a whil now with good reports all over. I guess im cooking those pills? But they keep on working.
Im looking to upgrade the amp anyway, the issue im dealing with in taht is my power supply is 36 amp 40 peak. Base amps are out of my price range so im looking for a mobile that will stay within the 36 amp limit, any suggestions?
A guy here has a texas star 350v for sale im considering that
Im looking to upgrade the amp anyway, the issue im dealing with in taht is my power supply is 36 amp 40 peak. Base amps are out of my price range so im looking for a mobile that will stay within the 36 amp limit, any suggestions?
A guy here has a texas star 350v for sale im considering that
If your meter is showing 300w from this amp; then I don't trust your meter.
The only way it might do that is if the amp is being fed too much voltage. Check the voltage on the pwr sup with a DMM when you key up; sometimes RF from the amp can affect the voltage regulator in you pwr sup and cause it to lose regulation. If this happens move the amp's output coax away from the power supply and re-check.
Best to run the amp with the voltage set to the specs of the 1446's are spec'd at. 12.6v if your pwr sup is adjustable.
The only way it might do that is if the amp is being fed too much voltage. Check the voltage on the pwr sup with a DMM when you key up; sometimes RF from the amp can affect the voltage regulator in you pwr sup and cause it to lose regulation. If this happens move the amp's output coax away from the power supply and re-check.
Best to run the amp with the voltage set to the specs of the 1446's are spec'd at. 12.6v if your pwr sup is adjustable.
300's on high at pep not dead key.
It is adjustable, its set at 13.8, ill check later tonight if voltage moves when keying up
Since the 2290 & 2879 are also "rated" the same I don't see it as realistic or necessary to turn the voltage down on a power supply to 12.6 volts. If it was then we all would have to do the same with say out Texas Star 250 & 350's. I don't see running 13.8-14.5 volts as part of this guys problem.
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