Using OM-2501 or Alpha 89 - PS “Blows Out”

WR4N
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Joined: Thu Jan 21, 2021 3:29 am
Location: Tennessee

Using OM-2501 or Alpha 89 - PS “Blows Out”

Postby WR4N » Fri Mar 18, 2022 8:19 pm

I originally tried PS using an External Xtronic Coupler with my Alpha 89 (quality coupler and cable, correct SAT, etc.). After two tone, ANAN 7000DLE MKII Black Version would run perfectly for 2 minutes or thereabouts ... and then Flash 12K-20K ... and cease working properly. I specifically bought an OM Amp with Internal Coupler hoping to fix my problem (whatever is may be). Sadly, identical results.

I’ve heard some say this was due to Amp Bias and have even recommended cutting the single bias wire on the OM Amp. Can anyone shed light on this ... share experiences ... offer help?

Thanks & 73
David WR4N
RADIO: ANAN 7000 DLE MK2 (Black Version) Thetis 2.8.11.
PC: HP Desktop - Intel Core i7 (10th Gen) - 16GB memory - 512GB SSD - Intel UHD Graphics 630 - WINDOWS 10 (100% Dedicated to ANAN)
PS: ASTRON 35 AMP (100% Dedicated to ANAN)

Best 73s,
WR4N - David
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w-u-2-o
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Re: Using OM-2501 or Alpha 89 - PS “Blows Out”

Postby w-u-2-o » Fri Mar 18, 2022 9:12 pm

Dave,

Read through Carl's efforts with the OM amp starting with his post on 25 Sep 2018 in this topic:

viewtopic.php?f=20&t=2558

You need to make sure that you are hitting above 0dB ALC reliably. Use the "ALC Group" meter mode to check this.

You need to make sure your feedback levels are good. You need at least a 6dB attenuator on the output of an Xtronic coupler at 1500W. A 10dB attenuator is OK, too. What is your step attenuator being driven to when transmitting? You don't want it up at 31. 20 to 25 is the sweet spot.

How does the data look when using the AmpView display (Linearity > Ampview). Does it look good? A solid, smooth curve, or is it crazy or partial?

Carl had his best performance with 1300W indicated on the amp power meter. The power meter may not be exactly correct. You might be heavily into compression if it shows 1500W.

People generally have the best results with PIN and STBL options turned on and MAP turned off (Linearity > Advanced). If you are running the latest beta of Thetis, also try turning on "Quick Attenuate Response" (same menu).

Remember that anything below -70dBm on the DUP display really doesn't matter.

73,

Scott
WR4N
Posts: 91
Joined: Thu Jan 21, 2021 3:29 am
Location: Tennessee

Re: Using OM-2501 or Alpha 89 - PS “Blows Out”

Postby WR4N » Sat Mar 19, 2022 1:28 am

Thank You❗️
RADIO: ANAN 7000 DLE MK2 (Black Version) Thetis 2.8.11.
PC: HP Desktop - Intel Core i7 (10th Gen) - 16GB memory - 512GB SSD - Intel UHD Graphics 630 - WINDOWS 10 (100% Dedicated to ANAN)
PS: ASTRON 35 AMP (100% Dedicated to ANAN)

Best 73s,
WR4N - David
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w9ac
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Re: Using OM-2501 or Alpha 89 - PS “Blows Out”

Postby w9ac » Sat Mar 19, 2022 2:50 pm

David,

Assuming the sample level is within range and the sampled passband response is reasonably flat, you can try disabling EBS, possibly through your amp's menu. I own an OM Power 2000A+ and EBS can be enabled/disabled right from the front panel menu. I'm not sure about your OM Power model.

With or without EBS enabled, static IM products remain the same, as expected, when engaging Thetis' two-tone IMD test generator. I'm using PureSignal's default values.

However, with EBS engaged, I see a very slight increase in dynamic IMD products with voice, but nothing remotely like the so-called "blow-out" condition. The slight dynamic IMD change is the result of PureSignal's attempt to track changing linearity as the amp changes bias state from full cut-off, to class B during PTT, then to AB1 when EBS fully activates with voice.

For vacuum tube amplifiers, there's no association with memory effect as discussed in the link posted above. I suppose we could call EBS bias changes a form of memory effect as a result of EBS' switched bias states, but as far as I know that term applies only to solid-state RF devices.

See you on 3630...

Paul, W9AC
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w-u-2-o
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Re: Using OM-2501 or Alpha 89 - PS “Blows Out”

Postby w-u-2-o » Sat Mar 19, 2022 4:00 pm

The term "memory effect" can apply to any dynamically changing characteristic associated with linearity. This could be EBS, or more typically transient heating and cooling effects. This latter issue is certainly more likely in a solid-state amplifier.

IMHO "memory effect" is an imprecise term, but if there is some characteristic that causes PureSignal to "chase it", that's a "memory effect".
WR4N
Posts: 91
Joined: Thu Jan 21, 2021 3:29 am
Location: Tennessee

Re: Using OM-2501 or Alpha 89 - PS “Blows Out”

Postby WR4N » Sat Jul 02, 2022 9:24 pm

w9ac wrote:David,

Assuming the sample level is within range and the sampled passband response is reasonably flat, you can try disabling EBS, possibly through your amp's menu. I own an OM Power 2000A+ and EBS can be enabled/disabled right from the front panel menu. I'm not sure about your OM Power model.

With or without EBS enabled, static IM products remain the same, as expected, when engaging Thetis' two-tone IMD test generator. I'm using PureSignal's default values.

However, with EBS engaged, I see a very slight increase in dynamic IMD products with voice, but nothing remotely like the so-called "blow-out" condition. The slight dynamic IMD change is the result of PureSignal's attempt to track changing linearity as the amp changes bias state from full cut-off, to class B during PTT, then to AB1 when EBS fully activates with voice.

For vacuum tube amplifiers, there's no association with memory effect as discussed in the link posted above. I suppose we could call EBS bias changes a form of memory effect as a result of EBS' switched bias states, but as far as I know that term applies only to solid-state RF devices.

See you on 3630...

Paul, W9AC

Should have replied before now. But THANK YOU PAUL! With EBS OFF, Pure Signal does perfect!
RADIO: ANAN 7000 DLE MK2 (Black Version) Thetis 2.8.11.
PC: HP Desktop - Intel Core i7 (10th Gen) - 16GB memory - 512GB SSD - Intel UHD Graphics 630 - WINDOWS 10 (100% Dedicated to ANAN)
PS: ASTRON 35 AMP (100% Dedicated to ANAN)

Best 73s,
WR4N - David

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