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Author Topic: Brand new Expert 1.5K-FA pre-distortion test  (Read 1173 times)
I4LEC
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Posts: 14




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« on: November 30, 2017, 11:17:13 AM »

Following to my previous post on the Expert 1.5K-FA, as happened for the 1.3K-FA, I had a chance to have one unit in transit for a little bit, long enough to run some test.

Contrary to the 1.3K-FA model, the unit comes only with the built in ATU and it uses a single MRFX1K80H module, supplied at 55V with a nominal output power slightly exciding US limit.

Since the manufacturer introduced the -60dBm built in coupler, I thought to focus on the pre-distortion, thus, I used my ANAN 10 as a driver along with the Pure Signal (PS) option.

Two tone tests were performed at the maximum available drive (10W) for an average output power, among the various band, corresponding to 83% reference to the US limit.

Attached find the link to the screen shots with and without pre-distortion, these were taken on 20m, chosen as representative mid band, aside from a two tone test, the SSB signal was also checked with PS ON and OFF.

2T IMD3 no PS = 29dBc (35dB pep)
2T IMD5 with PS = 60dBc (66dB pep), incredibly good ! And the third order was even slightly better

On the air, made several contacts on various bands and modes, with good overall reports, had also a nice screen shot from a US station, showing the strait shoulders of my 40m signal.

Where needed (WARC bands), checked the ATU performances, it behaved as expected, tuning the 80m sloper system to a perfect match on all three bands (3rd, 5th and 7th harmonic) given the average SWR around 1.8-2.2:1

Efficiency was also figured out, it went from a bit less than 60% to over 75% on a couple of bands.

Each band linearity was also checked at step of 1W up to 10W drive, it turned out to be very homogeneous among the bands, including the extreme ones as 6m and 160m.

Editor’s note
Seems the perfect companion to my ANAN 10 rig, as you end up with a fully automated Solid State QRO station with built in ATU delivering a very clean signal!

Disclaimer
The reported values where taken directly from the PowerSDR mrx PS GUI, two tones test ran from the built-in test set.

73, Clay

https://drive.google.com/file/d/1oVYSQmqTQumgvpUriFAaxGFrCLRnU5Pf/view?usp=sharing

https://drive.google.com/open?id=1N-xaZP7H8iu6PWUmtWAdHxXAdSbqsHub

https://drive.google.com/open?id=1bihMaQPebsb49IV_563FRWLedhd7TVCY

https://drive.google.com/open?id=1bz4uwRI3x0C5J0O2hMNoY63_TFMvNHJO

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KW7Y
Member

Posts: 2




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« Reply #1 on: December 02, 2017, 10:10:31 AM »

How level was the gain from band to band?

- Paul  KW7Y
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K6AER
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Posts: 4686




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« Reply #2 on: December 02, 2017, 11:02:09 AM »

When you took the measurements what was the power out for 10 watts in?
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I4LEC
Member

Posts: 14




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« Reply #3 on: December 03, 2017, 02:13:31 AM »

Paul,

you can find band by band details in your mail box.

Michael,

the average output power among the bands was 1250W

73, Clay
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K6AER
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Posts: 4686




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« Reply #4 on: December 03, 2017, 02:38:24 PM »

Very impressive.
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NO9E
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Posts: 720




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« Reply #5 on: December 04, 2017, 09:24:43 AM »

A few questions...

Is predistortion computed automatically or does it have to be set up? If so, how long does it take on a single frequency?
How much is it frequency dependent within band?
If the setup is done wit the amp cold, how much heating affects the predistortion?
Is there any mechanism to prevent overdrive? 

1.5k is advertised as a 1.5 KW amplifier. What is the max power at a reasonable IMD3 limit, say -40db

If it is all automatic and works well, ZENKI can retire.

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I4LEC
Member

Posts: 14




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« Reply #6 on: December 04, 2017, 11:24:35 AM »

Glad to read focused questions, even if don't know whether I can answer to all of them, I'll try anyway

1) Pure Signal (PS) just need to be turned on, I have it on all the time, no setup required, its feedback level needs to be about 7dB below clipping, if properly selected, the internal attenuator (31dB at 1dB step) will automatically adjust the attenuation to meet the specified target, in the case of the 1.5K-FA, which has a pickup level around -60dB, turned the auto attenuator to 21dB. On a daily basis I do use an external coupler (a strip line tuned on 10m),  it has a 20dB variation from the upper to the lower band, this is easily compensated by the auto attenuator.

2)No frequency dependency within the band

3) PS is adaptive and it compensate heating changes to a big deal

4) It does not prevent overdrive but up to a certain extent, it avoids excess of distortion introduced by the overdrive.

5) I did not make it to full legal, given the 10W drive,  but close on a couple of bands, I do not expect much difference from the posted values anyway, without PS, «only» -35dB pep, I guess ZENKI is still on business then, and he better be as I checked my driver at full power (-41dB pep), if instead would it be driven by something else, figures might be rather different, as we all know the motto of sh.. IN sh.. OUT.

73, Clay
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NO9E
Member

Posts: 720




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« Reply #7 on: December 04, 2017, 12:23:54 PM »

Clay,
Thank you for the answers. So predistortion correction is pretty much automatic. Perhaps with some modification to software, overdriving  can be eliminating automatically by reducing input power when nonlinearities are too big to handle.

Ignacy, NO9E
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I4LEC
Member

Posts: 14




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« Reply #8 on: December 06, 2017, 08:35:37 AM »

Ignacy,

Yes it pretty much automatic, please check the little clip I made while I was testing the function, it takes just the pressure of PS-A push button (on the upper left an side)

73, Clay

https://drive.google.com/open?id=1Hx0nBhH9bh7zhrAQqAaxrmKaA01cogS4
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KB6DYA
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Posts: 41




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« Reply #9 on: December 07, 2017, 01:36:05 PM »

This is a great post. Thank You for sharing your findings. It is sad that not many hams responded,this is the future of ham radio. I guess most hams do not give a crap about IMD. Run the same old boat anchor junk and not in vest in new technology.
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