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Predistortion on OM-Power amplifiers?

Posted: Wed Jun 21, 2023 1:31 pm
by I2NOY
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.

Re: Predistortion on OM-Power amplifiers?

Posted: Wed Jun 21, 2023 2:21 pm
by K1LSB
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 6730 times

Mark

Re: Predistortion on OM-Power amplifiers?

Posted: Wed Jun 21, 2023 2:35 pm
by w-u-2-o
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

Re: Predistortion on OM-Power amplifiers?

Posted: Wed Jun 21, 2023 3:24 pm
by W4WMT
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

Re: Predistortion on OM-Power amplifiers?

Posted: Wed Jun 21, 2023 4:33 pm
by K1LSB
PureSignal doesn't need a directional coupler, so the extra money expended on one of those is wasted on PS.

Mark

Re: Predistortion on OM-Power amplifiers?

Posted: Wed Jun 21, 2023 10:28 pm
by AG5CK
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?

Re: Predistortion on OM-Power amplifiers?

Posted: Wed Jun 21, 2023 11:03 pm
by K1LSB
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

Re: Predistortion on OM-Power amplifiers?

Posted: Sun Jun 25, 2023 3:45 pm
by I2NOY
Many thanks for any suggestion. ;)
Best 73s.