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marekm
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6GHz products not working well at >=6300 MHz

Tue Dec 19, 2017 6:59 pm

Ticket#2017110422000917

I see sudden signal level drop between 6295 and 6300 MHz. Latest response from support (after a few back-and-forth to upgrade RouterOS and try various settings, with not much effect):
"The output power and the receive sensitivity can vary on the upper frequencies and there is nothing we could do about that as that all is happening inside the wireless chipset."

It's very disappointing, in my opinion if the product is advertised for the range 5.9-6.4 GHz then it should work well over the whole range. I did expect some variation, but it is common practice to specify frequency range at -3 dB loss, not about -20 dB which I see here (about -73 dBm signal on a 750m link between two SXT6's at 6375 MHz).

I was hoping for a 3km link between SXT6 (AP) and DynaDish6 (STA) but below -80 dBm it is just unusable at the frequencies available to me (near end of the range).

Has anyone looked inside, if the product really operates the wireless chipset directly at such high (out of spec) frequencies? I would expect to see some up/down-conversion circuits inside, perhaps the change at 6300 MHz has something to do with frequency range switching.
 
p3rad0x
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Re: 6GHz products not working well at >=6300 MHz

Wed Jan 03, 2018 5:03 pm

Hi,

What kind of signal level are you seeing at 5.9-6.1Ghz?
There you go then you touched something ;-) : it only takes a change in wind direction to screw with your nat :-)
 
HaQs
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Re: 6GHz products not working well at >=6300 MHz

Wed Jan 03, 2018 7:40 pm

I tested dynadish 6.
And confirm that.

Its look like as very bad antena design ?
sigal is ok to 6200MHz, but at 6300 and above it is unusable (signal very bad on low distance at >=6300MHz).
 
p3rad0x
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Re: 6GHz products not working well at >=6300 MHz

Thu Jan 04, 2018 10:55 am

I tested dynadish 6.
And confirm that.

Its look like as very bad antena design ?
sigal is ok to 6200MHz, but at 6300 and above it is unusable (signal very bad on low distance at >=6300MHz).
I have a feeling that the dyna-dish 6 and sxt 6 is using the exact same antenna as their 5ghz models.

only way to know is to open them and check inside
There you go then you touched something ;-) : it only takes a change in wind direction to screw with your nat :-)
 
marekm
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Re: 6GHz products not working well at >=6300 MHz

Thu Jan 04, 2018 8:05 pm

The sudden change of signal and noise floor levels between 6295 and 6300 doesn't look like antenna characteristics, more like some band-switching or up/down-converter circuit active at 6300-6500 MHz.

Compared at the same distance (about 3 km):

1. AP (RB922UAGS-5HPacD) + Cyberbajt 6GHz 16dBi/120deg sector -> STA (NetMetal5) + ElboxRF 6GHz 23dBi panel @ 5975 MHz
STA Tx/Rx signal: -48/-48 dBm, Tx/Rx rate: 144/144 most of the time (forced N, more stable than AC in our noisy environment), Btest UDP average 30/32 Mbps

2. AP (SXT6) -> STA (DynaDish6) @ 6095 MHz
STA Tx/Rx signal: -58/65 dBm, Tx/Rx rate: 86/104, Btest UDP average 2/12 Mbps

Both links with some other traffic so results not very accurate, but you can clearly see which one works better.
Second link was unusable (below -80 dBm) when I tried to change the frequency to 6375 or 6405 MHz.
So, the high channels are only really usable for short distances (so short that should be good for LHG 60 too...).

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