Diveristy Reception Adventures...

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W3MMR
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Diveristy Reception Adventures...

Postby W3MMR » Mon Dec 16, 2019 12:26 pm

Just curious how some of you guys have diversity setup in your rigs. It took me a while to get it setup right on my 200D. I have my diversity antenna going into RX2 and using an optocoupler to essentially open the antenna on TX. I was overloading the ADC on transmit for the longest time, but didn't realize the TX Attn was only a 8. So I turned it up to 31 and that stopped me from overloading the ADC. Now, are you guys using a relay on your diversity antennas on TX as well or do you not have the same issue that i am having? It also took me a while to find the noise source so the interfering noise was as strong or stronger on the diversity antenna, and once I did, diversity has been a life saver. I love it. Its great for someone like me living in the city with interference issues. However, you can only null out one noise at a time, but hey, its an improvement!

Perry
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Studio "B" - Heath-Kit DX100, D-104, National NC-303, Hammarlund HQ-140-X
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Re: Diveristy Reception Adventures...

Postby K9RX » Mon Dec 16, 2019 2:02 pm

I've used diversity a good bit. Note there is a check box to ground ADC2 (RX2 it says) on TX, do you have that checked? I don't have any issues with RF getting in.

I've used it with various antennas - primarily where it works is on 15M where I have a 6/6 stack of monobanders and a 4 element custom SteppIR on a separate tower. Going to the west I have this really bad noise - I think it is a plasma TV - it is a large triangular shaped hump that is every 60Khz or something like that. It is about 12 db out of the noise at its peak ... I can point the 4 element north and it still receives this noise well enough - turning on Diversity that noise is completely eliminated and the noise floor goes down about 2 db. It is best if there happens to be a signal at that same point - in that case, only a couple of times that it coincidentally happened that way, the signal went from completely uncopyable (not even knowing it was there) to perfectly copyable.

It is something you have to play with - having the right antennas is a must of course.

Gary
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Re: Diveristy Reception Adventures...

Postby W3MMR » Tue Dec 17, 2019 11:08 am

Where is "Grnd RX2 On TX"? I dont see it in my 200D setup menu anywhere.. There is a "Gnd BPF2 On TX" selection in General>Ant/Filters, but thats only when you have the 7000 or 8000 selected as your radio.

Perry
Studio "A" - Anan 200D, P2 1.9, Thetis 2.6.9c3, Dell XPS 8700 i7-4770k, Samsung EVO 860 SSD, Nvidia GeForce GTX1050ti, 16GB RAM, Shure SM7B, AL80BX
Studio "B" - Heath-Kit DX100, D-104, National NC-303, Hammarlund HQ-140-X
K9RX
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Re: Diveristy Reception Adventures...

Postby K9RX » Tue Dec 17, 2019 1:59 pm

Perry,

Apologies - I am using an 8000 and wasn't aware that the visibility of that parameter would be subject to hardware. Indeed it is BPF2 and not ADC2 or RX2 ... all I know is I don't have any issues.

Actually - thinking more about it - I have my RX array going in to ANT3 (again 8000) as it is a RX antenna. I have it set up not to transmit on ANT3 (a feature I had requested for safety reasons). There is an issue where there is RF present on this which meant that i had to set Key Down Time to at least 30. I posted this elsewhere as well. The bug is that a) RF is present at ANT3 at settings roughly less than 30 and settings much higher than 30 corrupt the CW causing it to be unreadable (at 50 for example).

I have a 6X2 box that allows me to send other antennas to RX2 which I use for diversity. But there is no preamp installed on that line.

Gary
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Re: Diveristy Reception Adventures...

Postby W1AEX » Wed Dec 18, 2019 3:50 am

Perry,

I nearly always engage the so-called "Diversity" function with my 200D on the AM BCB, 160, 75, 60 and 40 meters. I have two 85 foot vertically installed triangular loops that I can switch between to feed the RX2 port. One of the loops favors N-S reception and the other favors E-W reception. With the phasing control to mix the TX antenna and one of the loops I can "steer" my reception and create deep nulls to get rid of noise or stations that are unwanted. The SNR is improved drastically and that's a real treat when operating AM on the lower bands. Note that I use a pair of external relays to disconnect and ground both the RX antennas when I transmit.

As you said, it's really effective for completely eliminating a single point noise source and for dropping the background band noise as displayed by the baseline on the panadapter. A really annoying noise showed up on 75 meters about a year ago and then it mysteriously disappeared after about 3 months. The first video below shows the 20 dB reduction of that noise and a drop of a few dB of the over-all noise as displayed by the baseline. For all practical purposes that towering noise was erased! Not too shabby! The second video shows a 40dB reduction in the signal of WTIC 1080 AM, a nearby clear-channel 50KW AM broadcast station.

Note that in this space Scott will correctly point out that both of these examples are not "diversity" but would more accurately be described as "beam steering". (Thanks Scott!)

Anyone using one of the ANAN rigs with a second ADC is crazy if they are not taking advantage of this feature!

73, Rob W1AEX



"One thing I am certain of is that there is too much certainty in the world."
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w-u-2-o
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Re: Diveristy Reception Adventures...

Postby w-u-2-o » Wed Dec 18, 2019 11:33 am

W1AEX wrote:I have two 85 foot vertically installed triangular loops that I can switch between to feed the RX2 port. One of the loops favors N-S reception and the other favors E-W reception.

Very nice! I didn't realize that was your setup, Rob. That should be quite flexible for use with this function.

As you said, it's really effective for completely eliminating a single point noise source

Yes it is!

and for dropping the background band noise as displayed by the baseline on the panadapter

Not really. "Diversity" can NOT remove random noise, i.e. atmospheric or "band" noise. Sorry to jump on this Rob, and I know you tried to qualify your statement by saying "as displayed on the panadapter", but I don't want anyone to think they can use diversity, which is really coherent beam forming, to reduce random noise.

You provide a perfect example of this in your first video. In that video you suppress an interfering signal quite effectively. And, while the noise floor appears to be reduced, the desired signal level is also reduced by approximately the same amount. This is because the resulting antenna pattern was one of overall low gain with a deep null in the direction of the interferer. I.e. in order to form that deep null you had to give up about 10dB of overall antenna gain. That's why the noise, and signal, level dropped, not because it was "suppressed". If you added that 10dB gain back in with a preamp the noise would come right back (but not the interferer). SNR was never significantly changed.

Another way of saying this is that you can improve signal-to-inteferer ratio, but not signal-to-noise ratios with "diversity".

People reading here can find more info on this topic in this thread.

The second video shows a 40dB reduction in the signal of WTIC 1080 AM, a nearby clear-channel 50KW AM broadcast station.

That really is very impressive, and shows just how flexible your antenna array is for exploiting this feature.

Anyone using one of the ANAN rigs with a second ADC is crazy if they are not taking advantage of this feature!

But to take advantage of it fully you need to have a really great dual antenna setup like Rob. Two verticals spaced appropriately would be great for this.
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Re: Diveristy Reception Adventures...

Postby KA1GXR » Fri Dec 20, 2019 1:32 am

W3MMR wrote:Just curious how some of you guys have diversity setup in your rigs. It took me a while to get it setup right on my 200D. I have my diversity antenna going into RX2 and using an optocoupler to essentially open the antenna on TX. I was overloading the ADC on transmit for the longest time, but didn't realize the TX Attn was only a 8. So I turned it up to 31 and that stopped me from overloading the ADC. Now, are you guys using a relay on your diversity antennas on TX as well or do you not have the same issue that i am having? It also took me a while to find the noise source so the interfering noise was as strong or stronger on the diversity antenna, and once I did, diversity has been a life saver. I love it. Its great for someone like me living in the city with interference issues. However, you can only null out one noise at a time, but hey, its an improvement!

Perry
W3MMR



Perry: What how do you use for on optocoupler on RX2 ? I am dealing with too much rf leakage on a 200D and an 8000DLE on RX2 during transmit damaging my amplified receive Magnetic Loop antenna Amp. I tried a DX Engineering RTR1A relay box that switches in 4 milisec. to ground the rx and that attenuates RX line further but a large spike in CW intermittantly gives as much as +5DB of RF briefly. I captured this on a spectrum analyzer using peak hold.
Thanks for any info on the optocoupler for RF device.

Tom
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Re: Diveristy Reception Adventures...

Postby ki4z » Sun Dec 29, 2019 7:04 pm

I have an ANAN 100D and a 200D. Any way to sync the two rigs with 4 receive antennas to get some serious Receive Diversity/Beam Forming/Gain effects? How about sync two ANANs on Transmit with two antennas and adjustable phase shift between them to achieve phased transmit gain? Is it legal to use multiple transmitters on the same frequency driving multiple antennas? Possible gold mine here!

KI4Z Mark..
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Re: Diveristy Reception Adventures...

Postby w-u-2-o » Sun Dec 29, 2019 9:32 pm

Mark,

That would be very cool. Imagine driving a four square array with no phasing harness. Or driving a pair of stacked Yagi's to get an infinitely adjustable beam elevation ("take-off") angle. Although you would need separate amplifiers for each antenna so it would start to get expensive!

Unfortunately, neither the available hardware, nor the available software, supports what you suggest, but the theory is sound, and multi-element phased antenna arrays, for both receive and transmit, are in use everywhere. The most common example these days is "MIMO", a cellular and Wi-Fi term of art. MIMO is nothing more than a multi-element phased array, either on transmit, receive or both. Why they had to make up a new name for it I can't imagine.

It would probably be possible to modify a couple of ANAN units to share a single set of clock references between both of them. That is the hardware requirement: everything must be referenced to the same set of clocks. That's the easy part. The hard part is writing the software to make it all work. Not that it is intrinsically hard. Multi-element phased array math is well understood. It just will take longer than making the hardware mod's.

73,

Scott
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Re: Diveristy Reception Adventures...

Postby ki4z » Mon Dec 30, 2019 11:17 am

Scott.. hardware mods should be minimal (maybe none?).. using the 10mhz reference inputs to sync the clocks, then adding a sync pulse between rigs (GPS PPS?) should be adequate. The rest is some serious software/FPGA code for sure.

KI4Z Mark
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Re: Diveristy Reception Adventures...

Postby w-u-2-o » Mon Dec 30, 2019 5:50 pm

Unfortunately, the design uses a separate oscillator that is not phase locked to the 10MHz for the ADC/DAC sample clocks. That would need to be shared, distributed and/or phase locked between each chassis. Why they did it that way I can't say.

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