Predistortion on OM-Power amplifiers?

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I2NOY
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Location: Milano - Italy

Predistortion on OM-Power amplifiers?

Postby I2NOY » Wed Jun 21, 2023 1:31 pm

Hi, is it possible to get a realtime attenuated signal (55-60 dB) from the output of OM-Power or others amplifiers that don't have the output connector carrying this signal?
Any market product available?
Many thanks.
K1LSB
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Joined: Wed Feb 05, 2020 5:25 pm

Re: Predistortion on OM-Power amplifiers?

Postby K1LSB » Wed Jun 21, 2023 2:21 pm

There are any number of market products available, none of which interested me so I built my own 18K-ohm pure resistive sampler that connects directly to the SO-239 jack on the back of my amp.

Disregard the jumble of ancillary resistors and variable pots in the picture, that box was a prototype. The final circuit consists of the six 2-watt Allen Bradley 12K-ohm carbon composition resistors in a series/parallel arrangement that provide 18K-ohm of measured resistance. That arrangement allows PureSignal to function correctly at any power level from a barefoot 25 watts to full legal maximum power.

PXL_20210209_015231793.jpg
PXL_20210209_015231793.jpg (2.45 MiB) Viewed 5525 times

Mark
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w-u-2-o
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Re: Predistortion on OM-Power amplifiers?

Postby w-u-2-o » Wed Jun 21, 2023 2:35 pm

I like the Xtronic units, but HRO never seems to be in stock:

https://www.hamradio.com/detail.cfm?pid=H0-015644

Apparently you are not aware that OM makes their own coupler :D

https://www.arraysolutions.com/index.ph ... t_id=14897

For new amp's OM offers this option:

https://www.arraysolutions.com/index.ph ... t_id=14891
W4WMT
Posts: 330
Joined: Sun Apr 09, 2017 10:12 pm

Re: Predistortion on OM-Power amplifiers?

Postby W4WMT » Wed Jun 21, 2023 3:24 pm

I can personally recommend this one made by a couple of retired Tektronix engineers. It's sort of expensive but built like it came from Tektronix. And for an extra $75 it will come with its own NIST certificate :-)

https://preciserf.com/shop/ddc545-dual- ... l-coupler/

73,
Bryan W4WMT
K1LSB
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Re: Predistortion on OM-Power amplifiers?

Postby K1LSB » Wed Jun 21, 2023 4:33 pm

PureSignal doesn't need a directional coupler, so the extra money expended on one of those is wasted on PS.

Mark
AG5CK
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Re: Predistortion on OM-Power amplifiers?

Postby AG5CK » Wed Jun 21, 2023 10:28 pm

K1LSB wrote:PureSignal doesn't need a directional coupler, so the extra money expended on one of those is wasted on PS.

Mark


It doesn't need it to function, but can puresignal make more accurate corrections if only forward power is being sampled?
K1LSB
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Re: Predistortion on OM-Power amplifiers?

Postby K1LSB » Wed Jun 21, 2023 11:03 pm

AG5CK wrote:
K1LSB wrote:PureSignal doesn't need a directional coupler, so the extra money expended on one of those is wasted on PS.

Mark


It doesn't need it to function, but can puresignal make more accurate corrections if only forward power is being sampled?

Forward power should be the only thing that's being sampled and fed back to PS.

So, on reflection (pun intended) I guess your point is valid! :)

Mark
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I2NOY
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Location: Milano - Italy

Re: Predistortion on OM-Power amplifiers?

Postby I2NOY » Sun Jun 25, 2023 3:45 pm

Many thanks for any suggestion. ;)
Best 73s.

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