apache-labs.com

All,

I've encountered a serious spurs problem today on 80 meters band.
Please look at the picture showing the spurs on around 3.510MHz, 3.510 900. However, the spurs disappeared, e.g., on 3.508 800. This is

The firmware of Orion MKII is 2.0b, I think it is the latest. Thetis's version is 2.8.11. My H/W configuration is Orion MKII + Munin3. But the drive level is only 14. The cause of the spurs is not becaus of H/W, but software issue.

Is this phenomenon already experienced by others? Is there a new firmware to remedy it?

73,
Tokio
JA1CCA

Sorry, I forgot to attache the picture.

Post a screen shot of the entire window so we can see all your settings, please.

Hi Tokio

Did you check your computer, monitor and its power supply and your radio's power supply (including the internal switching power supply if any)? When disconnecting your antenna and/or connecting to a dummy load the only spurs getting into the radio would come from one of these sources.
Why do you suspect the software ?
On my radio (Orion Mk 1powered by a linear power supply) the only spurs I experience are on 10 MHz (from my 10 MHz GPSDO connected to all radios and lab gear in the shack) and on 25 MHz (from the crystal reference on the Orion board). All others spikes are way under -135 dBm depending on computer and mostly on the 2 monitors activity.
Try to power your radio on a battery and operate it remotely on your network and chek if the spurs still occur.

Best regards & 73s

FM5GB Phil.

Phil--I think he's saying the spurs are during transmit.

Ok Scott,

I skipped the drive level mentionned by Tokio which is obviously related to a transmit problem.
This might indicate a FW problem, and could be tested by flashing a previous FW version.
Still the timing gremlin ?

73

Phil, FM5GB

Scott, Phil,

Thank you for your comments.
And sorry for getting back late to your posts due to "décalage horaire" and my morning work.

As for the request of Scott, I attache the two screen shots: one is the TUNE on 3.510 900 causing spurs, the other is that of 3.511 900 without spurs. This time the output power of Munin 3 is around 100W. Please disregard the Fwd Power 29W on the screenshots. Alex is checked in the setup panel but it is not connected. So this figure is incorrect. I measured 100W in my Drake power meter.

I could send the setup screen of Thetis. I use OCXO normally, but the result is the same regardless of the use of OCXO/internal TCXO.

In addtiton, I would like to inform you that I use Protocol 2 and the sampling rate is 384Kbps.

I have Hermes, but at the moment this is not cabled. I will check Hermes too for the weekend.

73,
Tokio
JA1CCA

So DUP is ON. But this is apparently a homebrew setup. What is the Orion RX1 looking at during TX? Do you have a coupler at the output of the Munin that is providing a feedback path and a switch that is switching that into RX1 during TX? In other words, are we really seeing the output of the Munin during TX? Assuming there is a coupler, what is the coupling factor in dB?

What does the output of the Orion look like before it goes into the Munin? Is that something that you can measure? Because it is more likely that these spurs are being generated in the Munin.

What is your drive level in Watts (not slider position)? Can you measure that? What happens if you drop that drive level by half (3dB)?

The spurs are below -50dBc which is damn good by any standard.

Hi Scott,

Thank you very much for your input.

> Do you have a coupler at the output of the Munin that is providing a feedback path and a switch that is switching that into RX1 during TX?
--> Yes. We see the output of Munin3. A small relay inside the sampler switches a feedback path to RX1.

>Assuming there is a coupler, what is the coupling factor in dB?
--> I use DC6NY type sampler. This works very fine with my 1KW amp as well as with Munin3 for Pure Signal. So, the coupling factor is around 30dB, then some attenuation inside the sampler. S-ATT during 1kW output is around 4-5dB.

On 3.510 900, I can see the spurs, on the contrary no spurs on 3.5111 900 or other frequencies, but I don't know how extent it is. This is a reality.

The spurs is around 50dB down, then it would be OK for the new spectral purity regulation. However, this kind of spurs would be ameliorated.

Do you have the similar spurs or not on this frequency?

73,
Tokio
JA1CCA

Hi Scott,

S-ATT during 1kW output is around 18dB, not 4-5dB. My memory wasn't correct;
S-ATT for 1K in TX: 18dB
S-ATT for 100W : 7dB.

FYI, the 1KW amplifier is an old TL-922, 2x3-500Z.

Please refer to the attached pictures.

73,
Tokio
JA1CCA

Your results with two-tone and PureSignal on a different frequency are not relevant to your problem with a CW tone on the frequency you are concerned about. That said, the two-tone results look spectacularly good. Performance might even be better if you reduced your coupling path loss by about 6dB in order to achieve a better signal-to-noise ratio on the feedback signal.

Asking again about the original problem: what does the output of the Orion look like before it goes into the Munin? Is that something that you can measure? Because it is more likely that these spurs are being generated in the Munin.

With the Orion MKII in my 8000, and with my amp in standby, and a drive level of about 27W, with TUN spurs are better than -85dBc. With two-tone and PS on better than -70dBc. It did not matter what frequency I used on 80M, results were the same across the band.

At the same 27W out into a KPA500 to achieve 500W, with TUN I'm seeing close in spurs, all within 400Hz, down about -45dBc. This is irrespective of frequency or the state of PS on 80M. With PS on, using two-tone under the same conditions, I'm seeing -60dBc spurs. In my case the amp is clearly the limiting factor, and it is not sensitive to frequency.

Hi Scott,

Thank you very much for your reply.

1) As for Pure signal, to get more performance of pre-distortion, my current feedback level could be increased by reducing the coupling. That means S-ATT for 1KW should be 24dB(6dB up), as well as for 100W S-ATT be 13dB reading. I'll try to get more feedback level for the weekend.

2) About the spurs, since this is my first concern, I'll check the output of Orion MKII by using a spectrum analyzer, not by using DUP of Thetis.
I noted that your measurement of the spurs level is -85dBc at the drive level 27 on 80meters band at any frequency.

73,
Tokio
JA1CCA

Scott,

I measured the output of Orion MKII and also that of Munin3.
You are partially right. Since there are no spurs at the output of Orion MKII nor Munin3.

I tested as follows;
Step 1: I confirmed the spurs on Thetis DUP by TUNE on 3.510 900. We can see the spurs as attached picture.

Step 2: I measured the output of Orion MKII as well as that of Munin3. No spurs as shown the attached picture. There is one screenshot because the result is not difference except the reference level.

My conclusion is that Thetis DUP panadapter is not showing the Munin3 amplifier output spectrum. The << spurs >> behavior is strange. We can see the spurs on 3.510 900, but on 3.511 900, they vanish. If I have some spurs from other devices, one kilohertz change doesn't affect the spurs.

Any comments would be much appreciated.

73,
Tokio
JA1CCA

Tokio,

I notice now that your S-ATT setting when using TUN is 31dB, and the tone power is -15dB. That means the power level at the Orion RX1 input is +16dBm, which is far too high. Indeed, anything over +13dBm is potentially dangerous. You may be seeing IMD occurring in the receive path. So instead of taking some attenuation out in the coupled/switched path, you may actually want to be putting some in.

This is a bit strange, however, because with two-tone at 1KW you are only seeing an S-ATT of 18dB. This implies an RX1 level of +7dBm (total of both tones, each tone by itself 6dB less) and a total loss in the coupled/switched path of -53dB. And, of course, the values at 100W are almost exactly 10dB less, just as expected. Under those conditions you should be unconditionally safe for any power level 1KW and below, and at 1KW a CW signal (not two-tone) would have an power level 6dB higher.

What is different about the TUN cases?

73,

Scott

Scott,

Thank you for your question and advice.

1) Sorry, I didn't pay much attention on S-ATT 31dB case. Yes, it is very strange. But, I couldn't remember exactly the set-up situation.
I check again the 100W output case where it was 31dB S-ATT.

2) The actual S-ATT for 1KW is around 18dB that I confirmed. So for me, there is 6db margin to increase the feedback level. I'll try this for the weekend.

73,
Tokio
JA1CCA

Scott,

This evening I checked the spurs on 3.510 900 which was shown in the previous screenshot. You mentioned 31dB S-ATT on the picture.

31dB is set because that ATT on TX is set to 31dB in the setup panel << General->Ant/Filters->Antenna >>. In addition, this is TX by TUNE. In TUNE transmission Puresignal is not active, even PSA is enabled. Though, I set PSA disabled as in the picture.

One thing I found strange about this option is the following:

I changed the value from 31dB to, e.g., 25dB. Then I clicked TUN button. S-ATT is 31dB, then I see this option. The value becomes 31dB.
Maybe there is some tip to keep this value to 25dB in the setup panel. But it is beyond of my experience.

Hope my post will clear your question.

73,
Tokio
JA1CCA

Hi Scott,

According to your advice about feedback level, I increased it by 2dB this time. My sampler uses 2 stage ATTs after Tandem match, 23dB, and 2dB. I removed 2dB ATT. For 23dB, I use 56 ohms 1W chip resistor (56 - 330 - 56: 23dB pi ATT) . To get 4dB increase, I have to replace this 23dB ATT by using other values. But I haven't the appropriate ones, such as 61dB 1W resistor. So I have to be satisfied for the moment with this feed back level.

As you can see the attached picture, the improvement of Pure Signal is evident. S-ATT becomes 20dB from 18dB for 1KW. I try to change the value in due course .
Thank you very much for your good advice. BTW, it would be very much helpful to understand the Pure Signal, if you could explain why this feedback level is needed to get the good result?

73,
Tokio
JA1CCA

Tokio,

The "tacked" topics here:

viewforum.php?f=20

Will answer that question, and more.

73,

Scott

Hi Scott,

Thank you very much for your prompt reply.

I'm following the URL you mentioned.
You are very competent pathfinder I really appreciate.

73,
Tokio
JA1CCA