Unstable, wide, nasty spur

NC3Z
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Unstable, wide, nasty spur

Postby NC3Z » Sat Oct 27, 2018 12:46 am

On my 7000 I have noticed for a while a nasty spur on 160M. Even with the antenna in terminated it is there. I do run all unused connections into terminators. Here are some screen shots on alive ant and on a terminated antenna.

BTW, the RX antenna is split to another radio and it does not hear/see this. And RX2 also has this spur.

Spur shorted in.PNG
Spur shorted in.PNG (1.08 MiB) Viewed 5085 times


Spur.PNG
Spur.PNG (1.14 MiB) Viewed 5085 times
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Re: Unstable, wide, nasty spur

Postby w-u-2-o » Sat Oct 27, 2018 1:10 pm

Stating the obvious: if it's not coming from the antenna, then it's probably coming from either inside the radio or from the power supply.

The most likely scenario would seem to be the power supply. What happens when you run the radio off of a large battery (preferably), or another power supply?

73,

Scott
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Re: Unstable, wide, nasty spur

Postby NC3Z » Sat Oct 27, 2018 2:13 pm

I should of noted that the PSU was also eliminated. Besides running linear supplies only I did run the 7000 directly off a AGM battery and same thing.

Cold start of the radio the spur is about 1.925 MHz and after a bit settles around 1.945 MHz.
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Re: Unstable, wide, nasty spur

Postby w-u-2-o » Sat Oct 27, 2018 2:34 pm

It would seem you've eliminated all external sources. You may want to consider returning it for service.
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Re: Unstable, wide, nasty spur

Postby Joe-W4WT » Sat Oct 27, 2018 6:00 pm

I use an 8000 board and I have exactly the same spurs you show; the large gnarly one is at 2.0 mhz on my 8000 and the two smaller ones are exactly where yours are so if there is something defective with your 7000 it is also defective with my 8000.

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Re: Unstable, wide, nasty spur

Postby NC3Z » Sat Oct 27, 2018 7:17 pm

Joe, you mean the narrow spurs around 1890 and 1970? Interesting you also see that big fat ugly one.
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Re: Unstable, wide, nasty spur

Postby Joe-W4WT » Sat Oct 27, 2018 8:02 pm

Hi Gary,

Yes, I see both of them at the same frequency and those and the gnarly one are the only ones I see in that bandwidth. Interestingly, these smaller width spurs do not change frequency as the radio warms up. The Gnarly one does change frequency. It goes from 2.004mhz to 2.023mhz after warm-up. It is also moving around a little as you watch it like yours. It is about 4 khz. wide as yours appears to be from the picture.

I also have small width spurs at 1.811 and 2.025. I wonder if you have those too? Starting at 1.811 that spur is reading about -120dbm. The 1.890 spur reads about -122dbm. The 1.970 spur reads about -124dbm and the gnarly one reads about -104dbm. All of these readings were taken in CWU mode and 500hz bandwidth and the meter is set to "signal" mode. Looking and listening to the gnarly spur with mode set to USB and bandwidth of 3.8khz, it reads about -100dbm and sounds something like a shrill hiss. I can record what I hear and send it to you if you like.

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Re: Unstable, wide, nasty spur

Postby NC3Z » Sat Oct 27, 2018 8:12 pm

I have one on 1811 @ -120dB, but other than the other 2 noted my next one is 2048 @ -120dB. But these spurs are not a real issue like the big fat one.
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Re: Unstable, wide, nasty spur

Postby NC3Z » Sat Oct 27, 2018 8:13 pm

I sent a message into the Apache support e-mail about this.
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Re: Unstable, wide, nasty spur

Postby KA1GXR » Sun Oct 28, 2018 12:04 am

Your attenuator is set 0 DB? Try 20 DB attenuation. There are known power supply artifacts in the 8000 although mine may not look like yours. at 20 db it may disappear into the noise.


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Re: Unstable, wide, nasty spur

Postby NC3Z » Sun Oct 28, 2018 12:09 am

Yes I run @ 0dB since my noise is so low on my antenna system. But with -20dB ATT it is still there above the noise but reduced of course.

On a live antenna my 160M noise floor is typically at -135. If I add attenuation via the software it does degrade my sensitivity.
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Re: Unstable, wide, nasty spur

Postby w-u-2-o » Sun Oct 28, 2018 1:18 am

FWIW my 8000 is perfectly quiet on 160.
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Re: Unstable, wide, nasty spur

Postby NC3Z » Sun Oct 28, 2018 11:44 am

I have checked with other 7000 owners on the air and they don't have an issue, but it seems at least 2 of us have.

Operating with such a low noise on 160M that I have here it becomes pretty noticable.
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Re: Unstable, wide, nasty spur

Postby Joe-W4WT » Mon Oct 29, 2018 12:25 am

Scott, interesting to hear that you don't have a problem with your 8000. Do you happen to know what iteration of 8000 board you have? There were several produced, it seems. Doug and I determined my board is version 3.2. According to Doug, there was 2.5, 3.2, and 5.0 version board. I believe the version 5 board had the 20db preamp and the 3.2 (mine) has the 14db preamp. Not sure what the 2.5 had. There have been a number of component changes between versions.

This info is a bit old now as Doug and I had this conversation last December. Don't know what iteration they may be on now.

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Re: Unstable, wide, nasty spur

Postby NC3Z » Mon Oct 29, 2018 12:41 am

Just had a text from NJ2US with a 7000DLE (sn 19) and indeed he also has this spur at just above 2MHz. Hmmmmm.
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Re: Unstable, wide, nasty spur

Postby w-u-2-o » Mon Oct 29, 2018 2:14 am

Joe-W4WT wrote:Scott, interesting to hear that you don't have a problem with your 8000. Do you happen to know what iteration of 8000 board you have? There were several produced, it seems. Doug and I determined my board is version 3.2. According to Doug, there was 2.5, 3.2, and 5.0 version board. I believe the version 5 board had the 20db preamp and the 3.2 (mine) has the 14db preamp. Not sure what the 2.5 had. There have been a number of component changes between versions.
Joe--I don't know which revision Orion MKII is in this 8000. I am actually in receipt of two different Orion MKII schematic revisions and one of them shows the 20dB pre-amp. I was confused/concerned by this as I had wanted to update my post here about calculating PureSignal feedback levels. I contacted Abhi directly about this and he told me that ALL revisions in both the 7000 and 8000 utilize the 14dB pre-amp and that the schematic that shows the 20dB pre-amp is in error. This is easily confirmed by back calculating observed step attenuator levels when using PureSignal.

This is my spectrum when operating into a dummy load. The screenshot was taken right now with Thetis/P2 firmware because that's what I have loaded up at the moment, but it is identical to what I see with PowerSDR/P1. I've got a couple of birdies in there. I can't tell you if it's the radio, the power supply (Astron RM50M), or some nasty wall wart in my house. I haven't been sufficiently motivated or annoyed by them to find out because they are almost always below the 160M noise floor when on the antenna.


Image
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Re: Unstable, wide, nasty spur

Postby NC3Z » Mon Oct 29, 2018 11:46 am

Problem with that fat spur is that it is well above the noise floor on live antennas. On 160M my noise floor on the spectrum scope is about -133.
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Re: Unstable, wide, nasty spur

Postby NC3Z » Mon Oct 29, 2018 11:49 am

Well Apache replied with this:

"This spur seems to be originating from the Power Supply, I noticed that you are using 0dB attenuation on 160M, please use at least 20dB attenuation as this extra gain is not needed on this band, this will also significantly reduce the spur level"

Now I made it clear that I am running this off a battery with no reduction. And going to 20dB attn just partially masks it, but it still is well above my noise floor on a live antenna.

Is it still a requirement to use attenuation on 160M even if you have a well designed RX antenna system?
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Re: Unstable, wide, nasty spur

Postby NC3Z » Mon Oct 29, 2018 12:25 pm

OK, so this is what Apache said:

"This spur is a harmonic of the main SMPS used on the Orion MKII card,

The typical noise floor on 160M in a quiet rural environment is -100dBm, this spur is usually below the atmospheric noise once the antenna is connected, however, in your case it seems that the atmospheric noise is lower than usual hence the spur is visible, I am afraid there is not much that can be done to remove this spur"

So I have a local noise floor lower than most so I guess that is why I see it so strong.
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Re: Unstable, wide, nasty spur

Postby w-u-2-o » Mon Oct 29, 2018 2:59 pm

I live in a rural environment and listen to 160M on an antenna that is very quiet on 160M. I rarely use more than 10dB attenuation, and would easily see the spur that you are experiencing.

It's odd that some folks have this and some don't.
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Re: Unstable, wide, nasty spur

Postby NC3Z » Mon Oct 29, 2018 4:06 pm

I have had a couple of hams send me videos of the same exact spur, and others that do not see it at all like you, so it appears that not all Orion II's have this issue with the internal power supply. At least Apache confirmed what the issue is.

It's unfortunate investing in such a very low noise RX antenna only to have it out run the radio ;)
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Re: Unstable, wide, nasty spur

Postby Joe-W4WT » Mon Oct 29, 2018 7:56 pm

My 160m USB, 2.7khz daytime noise level with the meter on sig avg runs -107/108dbm on my RX antenna system. The gnarly spur is around -98 for this mode and bandwidth so it is easily heard as it is about 10db above the noise level. Fortunately, my spur is out of the band so it doesn't matter to me.

I also run my attenuator at 0db because of my low noise antenna and when working CW I will typically run the filter at 25hz. My noise level with that combination is -136/-137dbm. If I ran with 20db of attenuation, I wouldn't be able to hear some signals under these conditions so saying we should be running 20 db is just not true for all installations.

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Re: Unstable, wide, nasty spur

Postby NC3Z » Mon Oct 29, 2018 8:46 pm

Joe-W4WT wrote:My 160m USB, 2.7khz daytime noise level with the meter on sig avg runs -107/108dbm on my RX antenna system.

My noise level with that combination is -136/-137dbm. If I ran with 20db of attenuation, I wouldn't be able to hear some signals under these conditions so saying we should be running 20 db is just not true for all installations.


My numbers here are almost identical to yours, with the spur about 12dB above the noise floor. Likewise, I can find stations that are difficult to copy with 20dB attn on, but at 0dB they are Q5. So likewise I am confused by Apache saying I should be running at least 20dB attenuation on 160M. For me it just does not make sense. Unless someone can enlighten me to why 20-30dB attn on the lower bands is more beneficial, I am all ears.

But it does seem that these spurs are something we will need to live with as Apache has no solution. At least it is a known quantity.
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Re: Unstable, wide, nasty spur

Postby W2PA » Sun Nov 18, 2018 1:51 pm

Just noticed this thread and wanted to chime in...

My 8000 has the spur at 1972. It seems to move around slightly, about a kHz or so over time, and wobbles in place a few hundred Hz or so. The peak is around -107dBm with 0db attenuation. It's about 3kHz wide. Interestingly, the peak decreases to about -113dBm with the antenna connected and some band noise.

It's noticeable even with an antenna connected under relatively quiet conditions - like now in November in a semi-rural area. So it's not something that can be ignored.
73,
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Re: Unstable, wide, nasty spur

Postby w9ac » Sun Apr 21, 2019 2:14 pm

For those not seeing the wide spur on 160m with Orion MKII, expand the display a bit to 2100 kHz. Mine occurs at 2020 kHz, outside the 160m band. The root switching fundamental appears to occur at approximately 400 kHz. Switch the band selector to "L/MW." With the antenna disconnected, look for even and odd harmonics of the switching frequency (e.g. 800, 1200, 1600, 2000 kHz and up).

I'm nearly certain the culprit is U36, a very high-current switching regulator on Orion MKII. Ain't no easy means of getting around it without kludging in a separate high-current supply. Just my opinion, but Orion is too delicate of a place for this kind of experimentation. Here are the ominous notes from the datasheet:

"Note 4: The switching frequency is programmable for 400kHz to 750kHz.
Note 5: LTM4628 device is designed to operate from 400kHz to 750kHz"


https://www.analog.com/media/en/technic ... 4628fe.pdf

Additional filtering on the board likely won't help, even if there was ample real estate. Referring to the Orion MKII schematic, notice how many parallel caps are already used to drive down effective ESR on the power rails. Because the receiver is so sensitive, its awfully difficult to knock this stuff down.

Same issue with with Flex. I owned a 6700 and there's substantial switching ingress from a DC-DC converter. Flex uses a Faraday cage around the SCUs. If even one of the conducting finger stock makes poor contact, high level switching spurs are seen.

In time, the problem got worse to the point where I had to fashion an expanding post made from two Delrin cylinders with a common screw that applied pressure between the Flex 6700 SCU cage and the side frame. Crazy, but it worked. Soldering the finger stock together would eliminate the problem -- but then the SCU becomes unserviceable!

Paul, W9AC

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