Use the Dosy as you see fit, but Astatic simple power meter can only go to low-power outputs - so between the amp and radio it goes...
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Amp swings lower power?
- Thread starter Cutlass327
- Start date
Ok, when power is small signal - the amp can take it in...without "dropping" - or I can also look at this a flat-topping or a saturation.
So, if both amps are this way...I find it kinda odd that both swing backwards when they are put into this arrangement - unless you got all this in one package and you have to figure out what to do from there...
I got the amps at different times, from different sources.
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Connected the Astatic mini meters in, the 88HL drops output.
Connected the 939, low power reads around 1.2W, swings to 3, highest is 4 swings to 6.
Antenna SWR is 1.2, dummy is 1.3 without amp in system.
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What is the chances of it being a power supply (p/s) issue? The battery I am using is one that you would use in a backup p/s type setting, lead acid but you can turn it at any angle like a gel cell.
This is the 30A p/s I was using. It has 3 B+ and 3 B- screws, so I tied all 3 (+) together and all (-) together, to insure I had full output available. It is adjustable, turned voltage up to 14v. Still had issues.
Click here \/ \/ \/ \/ \/ \/
Amazon product ASIN B00D7CWSCG
^^^click this line^^^
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So, if it was an issue with the radio clipping/saturation, would the power supply amps still drop? I know amps are load related, so I would think that if the radio was putting out solid power, amp demand would not drop.
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SWR between amp and 939 radio on dead key (DK) is 1.2 with amp on and off, and also on high and low power. This is with radio on lowest power. Full output puts it to 1.5.
If I whistle into mic, amp on, SWR goes to 3:1. Never tried this on other setups, always checked at DK only. Output on 939 was full. When I tried this with Amp off it stayed at 1.5:1 even with whistle.
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Connected the Astatic mini meters in, the 88HL drops output.
Connected the 939, low power reads around 1.2W, swings to 3, highest is 4 swings to 6.
Antenna SWR is 1.2, dummy is 1.3 without amp in system.
--------------------------------------------------------------------------------------------------------------
What is the chances of it being a power supply (p/s) issue? The battery I am using is one that you would use in a backup p/s type setting, lead acid but you can turn it at any angle like a gel cell.
This is the 30A p/s I was using. It has 3 B+ and 3 B- screws, so I tied all 3 (+) together and all (-) together, to insure I had full output available. It is adjustable, turned voltage up to 14v. Still had issues.
Click here \/ \/ \/ \/ \/ \/
Amazon product ASIN B00D7CWSCG
^^^click this line^^^
-------------------------------------------------------------------------------------------------------------
So, if it was an issue with the radio clipping/saturation, would the power supply amps still drop? I know amps are load related, so I would think that if the radio was putting out solid power, amp demand would not drop.
----------------------------------------------------------------------------------------------------------
SWR between amp and 939 radio on dead key (DK) is 1.2 with amp on and off, and also on high and low power. This is with radio on lowest power. Full output puts it to 1.5.
If I whistle into mic, amp on, SWR goes to 3:1. Never tried this on other setups, always checked at DK only. Output on 939 was full. When I tried this with Amp off it stayed at 1.5:1 even with whistle.
Odd, I inserted a link, but it doesn't' show anything. Put your mouse between the "Click here"s and a line appears, you click anywhere in that area and it opens to an Amazon page.
The above test is why I presumed you had a power issue with the radio. But to remove all doubt - we had to take on all the different amps and see the results.
I'm curious to know what mods were done to the 939...
And you did do this test with a battery too right? You mentioned that Gel cell - although great for E-backups and UPS systems - they have an internal "resistance" to them that limits the amperage capacity or amps per hour.
Ok, here's the reasoning...power draw in a radio that "swings forward" would naturally pull more power in to make that power appear to go up on the external meter.
The radio seems to be turned down - or even have a bad part or two - causing this low-power issue - where; when you demand more power by adding in audio - the thing simply will not...
The amps themselves seem to have their own issues but do not appear to be the problem.
So back to the 939 we go.
It think it's time you went into the 939 and took a look around to see what has been done. Especially around the AM Regulator - it would be on the side panel - near the power jack - rear quarter panel area.
I wonder too, if the radios' board number - see if you can find it - again by the right rear quarter section, by power jack, and near the side panel location of the Audio amp chip - and the AM regulator located on that same side panel - towards the rear of the radio - by the power jack.
It would help immensely if you took a pic or two so we can see the work...
Why?
I have a fear of this...
Someone may have goofed around and did mods not yet known...the above should be your board - its the schematic and look for the EPT069611A silkscreened on the board somewhere...
Because if they defeated a part, that's one thing but if they made a change and didn't like it, so they tried to undo it and put it back the way it (was) and goofed that up...the above is the best I can offer you...
I'm thinking they may have over done the tune up and you may need to get in there and realign it, try this again after that alignment, then if all else fails, we have to go part to part and match them up.
I'm curious to know what mods were done to the 939...
And you did do this test with a battery too right? You mentioned that Gel cell - although great for E-backups and UPS systems - they have an internal "resistance" to them that limits the amperage capacity or amps per hour.
Ok, here's the reasoning...power draw in a radio that "swings forward" would naturally pull more power in to make that power appear to go up on the external meter.
The radio seems to be turned down - or even have a bad part or two - causing this low-power issue - where; when you demand more power by adding in audio - the thing simply will not...
The amps themselves seem to have their own issues but do not appear to be the problem.
So back to the 939 we go.
It think it's time you went into the 939 and took a look around to see what has been done. Especially around the AM Regulator - it would be on the side panel - near the power jack - rear quarter panel area.
I wonder too, if the radios' board number - see if you can find it - again by the right rear quarter section, by power jack, and near the side panel location of the Audio amp chip - and the AM regulator located on that same side panel - towards the rear of the radio - by the power jack.
It would help immensely if you took a pic or two so we can see the work...
Why?
I have a fear of this...
Someone may have goofed around and did mods not yet known...the above should be your board - its the schematic and look for the EPT069611A silkscreened on the board somewhere...
Because if they defeated a part, that's one thing but if they made a change and didn't like it, so they tried to undo it and put it back the way it (was) and goofed that up...the above is the best I can offer you...
I'm thinking they may have over done the tune up and you may need to get in there and realign it, try this again after that alignment, then if all else fails, we have to go part to part and match them up.
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Well, I did find a ceramic cap on the side of the chassis soldered from chassis to something that was cut. I soldered it back in. Looked like it would have been a filter of sorts. It was by a 'chip' bolted to the chassis for a heat shrink.
I also just talked to a local guy that has a shop, have heard him chatting every night on the radio to others, sounds pretty knowledgeable and trustworthy from things they talk about when tuning... said he'd check it out for me, check alignments and such. Thinking I'll give him a shot at it and see how his work is. He has a spectrum analyzer among his tools that look respectable, so doesn't seem like a hack.
I also just talked to a local guy that has a shop, have heard him chatting every night on the radio to others, sounds pretty knowledgeable and trustworthy from things they talk about when tuning... said he'd check it out for me, check alignments and such. Thinking I'll give him a shot at it and see how his work is. He has a spectrum analyzer among his tools that look respectable, so doesn't seem like a hack.
Easy answer, maybe.
Note the power level it swings "down" to with modulation.
Turn the carrier down to that level.
73
Note the power level it swings "down" to with modulation.
Turn the carrier down to that level.
73
The finals of your radio have been tuned for "GHOST WATTS."
That is the harmonics that will push your dead key up and make you think you have a hot radio and you just have a splatter box.
That is the harmonics that will push your dead key up and make you think you have a hot radio and you just have a splatter box.
@Cutlass327 - after a good tuneup...
Locate JP10 - lift one, unsolder one leg of it.
Does swing return?
The section hi-lited in blue and boxed in brown - are potential suspects.
R270 and R271 form a voltage divider - and power is obtained from AM Regulator output - thru D103. This forms a 1/2 supply rail from the AM Regulator output.
The other part of the source power arrives from the OUTPUT of the AM Regulator control Q53, the part that has both audio and BIAS that goes into the Darlington pair Q55 and Q54 - which SUPPLIES D103 the power for that divider.
What the circuit is supposed to do is, when you have a low-level carrier with high levels of audio applied, Q56 senses this and because of the DC power placed on the BASE of Q56 - it's potential rises and power flows from the base towards and thru D108 into the RF POWER control. D108/D107 are steering switches. This RF POWER pot area receives power from the Collector at Q53, Q55 and Base reflects it - if there's more power in audio than in Carrier - this affects the RF power control so the audio will "compress" onto the carrier because the audio presence is greater than the bias - so it sees a power drop. C242 helps control this by smoothing the now rectified Audio and Bias power the Base has because of the power the Collector and Emitter have, is greater than what is being send thru D107/D108 - so it smooth's it into a control signal for envelope.
IN doing so, it pulls power from the collector - thru the base - into the Emitter in an effort to keep or tries to keep the circuit stable - RF power and audio drop - but due to the voltage divider R270 and R271 - this is a mid-point for the "trigger" that Q56 uses - so it always keeps a 50% up - 50% down level control of envelope - by STARVING the junction of Q53 into Q54 using it as a means to pull power to keep the envelope modulated equally.
By lowering RF power, you prevent a cutoff and saturation event using this circuit. Looks like the bad tuneup and changes made to the RF TX strip are what has made Q56 act like a zealot and steal all the joy of swing the radio could have.
IF you wish to defeat it (Remove Q56) or modify it - that is up to you - but what it seems to be doing is correct from a standpoint of power presence. However, when the bad tune up is done to lower the carrier and increase the audio (swing mod) - this circuit prevents asymmetry skewing and distortion. IT is better to modify this circuit than to remove it - you have several options including changing the ratios R270 and R271 have - even jumpering D103 to provide better recovery.
Locate JP10 - lift one, unsolder one leg of it.
Does swing return?
The section hi-lited in blue and boxed in brown - are potential suspects.
R270 and R271 form a voltage divider - and power is obtained from AM Regulator output - thru D103. This forms a 1/2 supply rail from the AM Regulator output.
The other part of the source power arrives from the OUTPUT of the AM Regulator control Q53, the part that has both audio and BIAS that goes into the Darlington pair Q55 and Q54 - which SUPPLIES D103 the power for that divider.
What the circuit is supposed to do is, when you have a low-level carrier with high levels of audio applied, Q56 senses this and because of the DC power placed on the BASE of Q56 - it's potential rises and power flows from the base towards and thru D108 into the RF POWER control. D108/D107 are steering switches. This RF POWER pot area receives power from the Collector at Q53, Q55 and Base reflects it - if there's more power in audio than in Carrier - this affects the RF power control so the audio will "compress" onto the carrier because the audio presence is greater than the bias - so it sees a power drop. C242 helps control this by smoothing the now rectified Audio and Bias power the Base has because of the power the Collector and Emitter have, is greater than what is being send thru D107/D108 - so it smooth's it into a control signal for envelope.
IN doing so, it pulls power from the collector - thru the base - into the Emitter in an effort to keep or tries to keep the circuit stable - RF power and audio drop - but due to the voltage divider R270 and R271 - this is a mid-point for the "trigger" that Q56 uses - so it always keeps a 50% up - 50% down level control of envelope - by STARVING the junction of Q53 into Q54 using it as a means to pull power to keep the envelope modulated equally.
By lowering RF power, you prevent a cutoff and saturation event using this circuit. Looks like the bad tuneup and changes made to the RF TX strip are what has made Q56 act like a zealot and steal all the joy of swing the radio could have.
IF you wish to defeat it (Remove Q56) or modify it - that is up to you - but what it seems to be doing is correct from a standpoint of power presence. However, when the bad tune up is done to lower the carrier and increase the audio (swing mod) - this circuit prevents asymmetry skewing and distortion. IT is better to modify this circuit than to remove it - you have several options including changing the ratios R270 and R271 have - even jumpering D103 to provide better recovery.
Some radios when you turn down the front power knob actually underdrives the amp and I have seen this cause strange issues such as this as well.
Maybe try setting a 3w dk using the variable power knob vs the 2w and retest.. my 0.02 worth
Also, how does just the radio due on power output with no amp inline??
Maybe try setting a 3w dk using the variable power knob vs the 2w and retest.. my 0.02 worth
Also, how does just the radio due on power output with no amp inline??
I tried it with the radio on lowest setting and on the highest. There was a very small amount of drop barefoot, too.
I have them sitting in the car ready to go to the shop Tues. I have my DX44V hooked up to the same TX250, and it swings high as it should and it is also putting out full potential, where before I never hit 100W out. I'm thinking my 2 radios are needing some medical help, and they both have the same issues.
Handy Andy, Once I get back Tues, I'll see how it goes, as he will be tuning them up properly and straightening the filters as much as he can to eliminate the ghosts... Gonna see if he'll let me get a couple pics of the spectrometer before and after.
I have them sitting in the car ready to go to the shop Tues. I have my DX44V hooked up to the same TX250, and it swings high as it should and it is also putting out full potential, where before I never hit 100W out. I'm thinking my 2 radios are needing some medical help, and they both have the same issues.
Handy Andy, Once I get back Tues, I'll see how it goes, as he will be tuning them up properly and straightening the filters as much as he can to eliminate the ghosts... Gonna see if he'll let me get a couple pics of the spectrometer before and after.
Well, bringing this back..
Had them checked out, he fixed that coil in the back of the 939, said they all check out good. Something about the 88HL crystal is off a touch, but otherwise all ok.
Noticed something since I started trying out the side bands. It swings forward like it should on side band, but still not on the AM. Think my meter is needing a look over?
Handy Andy, I haven't tried those tests yet. Thinking of taking my meter over to the shop and have him check it out for issues. It is a good 20 years old....
As for power, some may have seen my other post about power supplies and batteries - I have a 100A PowerMax unit coming, should be here Wednesday. See how things go with 100A to it all.
Had them checked out, he fixed that coil in the back of the 939, said they all check out good. Something about the 88HL crystal is off a touch, but otherwise all ok.
Noticed something since I started trying out the side bands. It swings forward like it should on side band, but still not on the AM. Think my meter is needing a look over?
Handy Andy, I haven't tried those tests yet. Thinking of taking my meter over to the shop and have him check it out for issues. It is a good 20 years old....
As for power, some may have seen my other post about power supplies and batteries - I have a 100A PowerMax unit coming, should be here Wednesday. See how things go with 100A to it all.
You do know that a Dosy can not test Peak Power I guess? It least not PEP since it has no PEP circuit. It is an Average reading wattmeter & all of that bouncing around is just that. My old test center made a great target at the Gun Range when I got my 2nd Autek WM-1 wattmeter. I would blame the wattmeter having 1st hand experience with that same model but that's just one opinion.
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