Hello all,
Today i’ve installed an 8dBi omni antenna. I’ve had the antenna indoors for a few days and had good reception. Received a lot (24+) of stations in the vicinity. But now, when the antenna is outdoors I can only see a few stations. I expected to receive more stations instead of less.
First screenshot is from the outdoor antenna. The second one is with a separate RX antenna, one for the 70cm band (433MHz). So, not a good antenna for the wireless band. But, RX is much better (more attenuated i guess), just an antenna i had lying around. The antenna’s are at the same height, approximately 1 meter apart.
Is this a known issue, or is something possibly wrong with my setup?
It is not easy for me to put the RB435G near the antenna. But i did try another coax this morning. It’s an Ecoflex 10 with new N connectors. I got the same results. I think the cables are fine.
These are both low loss cables, are you telling me to use a cable with more loss? I will try the antenna at some different locations now.
I’ve tried a location a 10 meters away. Again, a completely red spectrogram in the wifi band, and receiving only 8 stations instead of 20+.
This is what i calculated with http://vk1od.net/calc/tl/tllc.php:
Ecoflex 10 at 2,4GHz and 15 meters long; 3,5dB loss
Ecoflex 15 at 2,4GHz and 15 meters long; 2,5 dB loss
The two connectors and an adapter to RP-SMA will add some loss, but not really much (i guess).
When i read your replies, do i understand correctly, you are telling me to use shorter cables, because i’m losing to much signal? What i see on the spectrogram is opposite, i see a completely red spectrogram in the wifi band. I understand red is high signal strength. When i attenuate the signal i.e. moving the antenna inside or connecting another RX antenna not designed for this band, i get better results. The spectrogram is not completely red anymore, and i receive about 24 other stations.
Am i overloading the receiver? Can i attenuate the signal with the R52Hn?
8dBi antenna, 15 meters Ecoflex10, inside the attic
8dBi antenna, 15 meters Ecoflex10, above the attic roof
with my respect to the numbers above ..but i insist that the secret of your proplem is in the cable..put the routerboard+minipci inside a box ..put the box using 1 meter of lmr cable beside the antenna
You must have that set up in a crowded area. I have some setups like that too.
It may be you are receiving too much. I have seen this when a few busy access points are nearby. My problem was not the signal, it was the hidden nodes of other ap clients “stepping on” the ssids of the other aps. When I increased the gain of the antenna, the number of access points decreased (almost illogical at first), but the spectrum scan of the wifi band was almost solid red, where it had not been before.
I corrected a lot of the problem by using directional antennas.
@laithmikrotik what type of LMR? I don’t have LMR cable in house, so if you name the type, i will order a piece and test it.
@SurferTim, it is a crowded area over here. Surrounded by ~50 houses within a 50 meter radius. Sounds like you’re describing exactly what i see over here. I think i can arrange a directional antenna, and maybe find the source of the strong signal(s)…
I use LMR240 instead of LMR400 for short runs (4 feet or less). It is easier to form into a bend, and I have not seen any deterioration in performance over the LMR400 with runs that short. http://www.l-com.com/productfamily.aspx?id=6491
I agree with normis on the cable length. All but one of mine are 4 feet or less.
Ok, i don’t have LMR cable, but Ecoflex10 with N-connectors rated for 10GHz. I think you all agree that this is also a good cable? See the table below:
dB loss per 100 meters at 2,4GHz
Ecoflex15 = 14.9 dB
LMR400 = 22.2 dB
Ecoflex10 = 22.9 dB
LMR240 = 42.4 dB
I’m using Ecoflex15 for the 15m long cable and only losing at max 4dB including connectors. The antenna is 8dBi and so i would still have around 4dBi gain. But, i have now assembled a 1 meter cable with ecoflex 10. Loss is probably less than 1dB. Please see the photo’s below. Symptoms are still the same… Can we now conclude that the problem is not in the cable? I still think i’m overloading the R52Hn receiver when i stick the antenna outside.
Next step is probably trying 2 directional antenna’s as per SurferTim’s suggestion.
RB435G, 1 meter cable and 8dBi antenna.
Antenna connection, connector is rated for max. 10GHz.
This is with antenna inside the attic, receiving 24 stations.
This is just above the attic roof, receiving only 13 stations.
there are somethings strange in your issue ??!!
1- do you put the outdoor antenna nearby something like electrical cable?
2- you sure of your wireless settings?
3- you sure of your cable between the routerboard and powersupply?
1- do you put the outdoor antenna nearby something like electrical cable?
Not really, but is a few meters away from a 28MHz quarter wave antenna (short wave), a dualband 145/435MHz antenna. A few meters down there is a 14MHz half wave end fed wire antenna. All antenna’s were not transmitting during the tests.
2- you sure of your wireless settings?
Yes, i’ve even reset the settings to default. RX/TX is on chain 0.
3- you sure of your cable between the routerboard and powersupply?
Well, there is obviously a cable from an adapter that provides the correct voltage and amperage, and 3 ethernet CAT5 cables connected to an HP Procurve 1810g-24 switch.
I’ve ordered a directional panel antenna with 30dB front/back ratio, and 19dBi gain. When i have the antenna, i will sweep it around and we will see what happens. I Hope i can localize the interference, or source of high signal strength.
Working in a very crowded spectrum like the 2,4Ghz in an urbanised area needs a strong (high gain) antenna setup and directional antenna’s at the clients.
If you need to server several client in a circular there is hardly anything else to use than a good omni or when you only need to serve 1 - 3 clients you can think of directionals on the AP pointing to them.
By using directionals you basically try to make your clients ‘listen’ only in the direction of the AP and trying to avoid as much as possible receiving signals from unwanted radios.
Only when you can arrange your AP-client connection to have signals that are really outstanding a 20dB from the rest (which from a point of your setup view is noise) you can achieve some stable connection between these.
So, the higher the gain the better, but more important, the more focused the directivity the better.
Overall the fact that many households nowadays have 2,4Ghz routers will mean in urbanised areas that lots of signals from these will be picked up if you choose to work in the same band.
I have one 2,4Ghz AP in an urbanised area that easy picks up 30+ AP’s only! Spread over all channels but most concentrated on the 6th channel.
The only reason I can still serve notebooks etc. is that my signal is probably the strongest a client will hit and due the high gain antenna I am also able to pick up and distinguish the clients signal from the noise.
It also has some importance to have both AP and client tuned-in to each other. Meaning you force the AP to only accept the clients you want (access list, encryption, management protection, or NV2) and the client has to be forced to listen only on the frequency of the desired AP (wireless freq. scan) and the desired AP (mac address and/or SSID in the ‘connect to’ list or anything similar in other brand client products).
If you serve fixed antenna client one thing you could do is use horizontal polarization. Or use the 5Ghz band. (But in time you’ll have the same problem here…)
@pd0b: Let me know what you find. I am interested if that works for you also.
If you think wifi radios are the only interference, you are in for a surprise. I had an odd encounter with one of my customer/condo owners last week. He was having a TERRIBLE time staying connected. He would connect for a few minutes, then disconnect for “no reason” as he put it. I saw nothing on my end to cause the problem. Good signal strength and low noise on my end.
But there was a reason.
His condo had a cordless telephone. It is on 2.4GHz. It took a while, but we finally figured out that it was in fact the phone. As long as he stayed off the phone, he could stay connected. If he picked up the phone, immediate disconnect until he hung up.
I’ve installed this antenna: http://www.elboxrf.com/PL/p31/TetraAnt_2_19_20_RSLL.html. When rotating this antenna, there was not a single spot that has the most signal/interference. As seen in red on the spectrum history. Makes me think the omni antenna did indeed receive too much AP’s from all around. Connectivity is much better in the direction of the antenna. Cable length is/was not an issue here. Yes i lose a few db’s but this is not meant for a long distance connectivity where you want to get every db you can.
So i’m happy with this, thanks for all your suggestions!
