What would be the consequences of adding an amp to
a WHR-HP-G54? I know it already has an internal amp,
but at 9 miles with 24dBi parabolics, the signal is usable
but not great. These still have the stock firmware on them.
Not ever having used DD-WRT, would that help with the
signal strength?
Thanks,
Gordon Montgomery
Living Scriptures, Inc gordon@lsi.com (anti spam - replace lsi with livingscriptures)
(801) 627-2000
>What would be the consequences of adding an amp to
>a WHR-HP-G54? I know it already has an internal amp,
>but at 9 miles with 24dBi parabolics, the signal is usable
>but not great. These still have the stock firmware on them.
>Not ever having used DD-WRT, would that help with the
>signal strength?
Not much. First, you will need to add *TWO* amplifiers, one at each
end. Unless you are trying to deal with the loss of a long run of
coax cable, one amp will probably not be sufficient.
The one detail that I don't know is the coax cable between the
WHR-HP-G54 and the 24dBi dish. What are the coax types and lengths?
The effects of amplifiers can easily be calculated. See:
<http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations>
TX power +25.8 dBm (380mw from FCC data)
TX coax loss ? dB
TX ant gain +24 dBi
Distance 9 miles
RX ant gain +24 dBi
RX coax loss ? dB
RX sens -84 dBm (at 12Mbits/sec connection)
Fade margin (aim for at least 20dB)
You to supply the missing coax numbers. Then plug the numbers into:
<http://www.terabeam.com/support/calculations/som.php>
while watching the fade margin. Adjust the tx power until it's about
20dB and you have the TX power necessary to maintain a minimal
connection.
However, a bit of warning. The numbers generated above are very
ideal. They will not get better, only worse. Antennas never seem to
have the gain specified. The transmitters never seem to put out as
much power as claimed. Receiver sensitivity is affected by just about
everything. Interference and noise will seriously ruin a link.
There's also Fresnel Zone clearance that needs to be considered:
<http://www.terabeam.com/support/calculations/fresnel-zone.php>
For long links, I do a bit of additional testing. Fire up Kismet and
see how many other systems are on the channel and the adjacent two
channels. If there are any really strong signals, find another
channel or move the antenna.
In article <7jmbg3podoj3rn01f2vs6duq30csds4amq@4ax.com>, Jeff Liebermann <jeffl@cruzio.com> wrote:
>gordon@lsi.com (Gordon Montgomery) hath wroth:
>
>>What would be the consequences of adding an amp to
>>a WHR-HP-G54? I know it already has an internal amp,
>>but at 9 miles with 24dBi parabolics, the signal is usable
>>but not great. These still have the stock firmware on them.
>>Not ever having used DD-WRT, would that help with the
>>signal strength?
>
>Not much. First, you will need to add *TWO* amplifiers, one at each
>end. Unless you are trying to deal with the loss of a long run of
>coax cable, one amp will probably not be sufficient.
>
>The one detail that I don't know is the coax cable between the
>WHR-HP-G54 and the 24dBi dish. What are the coax types and lengths?
>
>The effects of amplifiers can easily be calculated. See:
><http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations>
>
>TX power +25.8 dBm (380mw from FCC data)
>TX coax loss ? dB
>TX ant gain +24 dBi
>Distance 9 miles
>RX ant gain +24 dBi
>RX coax loss ? dB
>RX sens -84 dBm (at 12Mbits/sec connection)
>Fade margin (aim for at least 20dB)
>
>You to supply the missing coax numbers. Then plug the numbers into:
><http://www.terabeam.com/support/calculations/som.php>
>while watching the fade margin. Adjust the tx power until it's about
>20dB and you have the TX power necessary to maintain a minimal
>connection.
>
>However, a bit of warning. The numbers generated above are very
>ideal. They will not get better, only worse. Antennas never seem to
>have the gain specified. The transmitters never seem to put out as
>much power as claimed. Receiver sensitivity is affected by just about
>everything. Interference and noise will seriously ruin a link.
>There's also Fresnel Zone clearance that needs to be considered:
><http://www.terabeam.com/support/calculations/fresnel-zone.php>
>
>For long links, I do a bit of additional testing. Fire up Kismet and
>see how many other systems are on the channel and the adjacent two
>channels. If there are any really strong signals, find another
>channel or move the antenna.
>
Thanks for the reply. I was worried about over driving the radios.
As for the coax, both radios are mounted next to their antenna,
connected with a pigtail. I don't see any writing, but the coax
is at most, 5mm in diameter and probably about 60cm long.
The antenna leads appear to be RG-8/U and about 50cm long.
I was going to try just one amp. I ran this link for 5 years with
some SMC2682W bridges with an amp on only one side, and
had no problems until one of the bridges started locking up
and rebooting for no reason.
Thanks again.
Gordon Montgomery
Living Scriptures, Inc gordon@lsi.com (anti spam - replace lsi with livingscriptures)
(801) 627-2000
That's a real worry. Most amps have AGC (automagic gain control)
which will adjust the levels. However, those are made for perhaps
50mw (+17dBm) and LOWER to compensate for coax cable losses. Higher
power is always problematic. Fortunatly, the power is adjustable on
the WHR-HP-G54 so you probably will not need an attenuator or long
mess of lossy coax to get the levels down to where they need to be.
>As for the coax, both radios are mounted next to their antenna,
>connected with a pigtail. I don't see any writing, but the coax
>is at most, 5mm in diameter and probably about 60cm long.
>The antenna leads appear to be RG-8/U and about 50cm long.
Is the small coax rather stiff? I'll use worst case and guess that
the small stuff is RG58a/u garbage coax and that the combined coaxes
and connectors have a total loss of about 4dB.
Grinding the numbers,
TX power +25.8 dBm (380mw from FCC data)
TX coax loss 4 dB
TX ant gain +24 dBi
Distance 9 miles
RX ant gain +24 dBi
RX coax loss 4 dB
RX sens -84 dBm (at 12Mbits/sec connection)
<http://www.terabeam.com/support/calculations/som.php>
which yields a fade margin of 24.5dB. Anything over 20dB is
considered usable. The link should work as it stands, without a power
amplifier. Raising the tx power with a 1 watt power amplifier
(maximum legal) will only increase the fade margin to about 28.7dB,
which is better, but not sufficiently better than the current 25.8dB
to justify the expense.
My guess(tm) is that something else is happening and that you're
making some assumptions. It might be that the WHR-HP-54G is operating
at reduced power output and needs to be adjusted. It might be some
settings in the routers. It might be water in the coax cables. It
might be a badly assembled antenna (I've seen this all too often with
dish antennas). However, my guess(tm) is that it's interference along
the path or some obstruction in the Fresnel Zone.
>I was going to try just one amp. I ran this link for 5 years with
>some SMC2682W bridges with an amp on only one side, and
>had no problems until one of the bridges started locking up
>and rebooting for no reason.
I recently troubleshot a 2 mile link that had worked just fine for
about 2 years using old 802.11b radios. When I upgraded them to
802.11g, the link kept going up and down. After my usual bad guesses,
I eventually disabled all the wiz bang turbo and super modulation
features, disabled 802.11b compatibility, and locked the wireless
speed to 12Mbits/sec. It then worked prefectly, even with over half
the antenna covered carbon foam absorber. If the old radios worked,
but the new radios do not, I would look for radio problems, not path
problems.
Hint: The more numbers you supply, the easier it is to troubleshoot a
problem.
In article <ijrcg3tocs4r30j0cgnjpek0k1orrn4v9u@4ax.com>, Jeff Liebermann <jeffl@cruzio.com> wrote:
>Is the small coax rather stiff? I'll use worst case and guess that
>the small stuff is RG58a/u garbage coax and that the combined coaxes
>and connectors have a total loss of about 4dB.
I doubt it is RG58, isn't that what TV cables are usually made from?
I dug up the receipt for the pigtails, and they say "195 series cable".
><http://www.terabeam.com/support/calculations/som.php>
>which yields a fade margin of 24.5dB. Anything over 20dB is
>considered usable. The link should work as it stands, without a power
>amplifier. Raising the tx power with a 1 watt power amplifier
>(maximum legal) will only increase the fade margin to about 28.7dB,
>which is better, but not sufficiently better than the current 25.8dB
>to justify the expense.
I've never noticed the power setting before in the setup screens. It
looks like it just gives me percentages, and no where does it
explain what the actual transmit power is. I'll have to do some
digging over the weekend I suppose. ( Again, these are still
running the stock Buffalo firmware. )
>
>My guess(tm) is that something else is happening and that you're
>making some assumptions. It might be that the WHR-HP-54G is operating
>at reduced power output and needs to be adjusted. It might be some
>settings in the routers. It might be water in the coax cables. It
>might be a badly assembled antenna (I've seen this all too often with
>dish antennas). However, my guess(tm) is that it's interference along
>the path or some obstruction in the Fresnel Zone.
The new link does work, but if I run a continuous ping, I'll get 20% to
50% packet loss, sometimes. Sometimes, it is great. That is why
I am assuming weak signal that is getting trod on sometimes. The
two points actually have a small valley inbetween them, so I don't
believe Fresnel Zone encroachment is a problem.
>I recently troubleshot a 2 mile link that had worked just fine for
>about 2 years using old 802.11b radios. When I upgraded them to
>802.11g, the link kept going up and down. After my usual bad guesses,
>I eventually disabled all the wiz bang turbo and super modulation
>features, disabled 802.11b compatibility, and locked the wireless
>speed to 12Mbits/sec. It then worked prefectly, even with over half
>the antenna covered carbon foam absorber. If the old radios worked,
>but the new radios do not, I would look for radio problems, not path
>problems.
>
I believe I have disabled all the whiz bang features, but I'll double check
those as well. I have these running in WDS only mode, because I just
need the bridging component.
Thanks for your helpfulness. I'll be messing with random settings all
week end. ( what...... isn't that how everyone trouble shoots?!? :)
Gordon Montgomery
Living Scriptures, Inc gordon@lsi.com (anti spam - replace lsi with livingscriptures)
(801) 627-2000
On Oct 4, 8:40 pm, gor...@lsi.com (Gordon Montgomery) wrote:
> What would be the consequences of adding an amp to
> a WHR-HP-G54? I know it already has an internal amp,
> but at 9 miles with 24dBi parabolics, the signal is usable
> but not great. These still have the stock firmware on them.
> Not ever having used DD-WRT, would that help with the
> signal strength?
I haven't played with very many consumer grade WiFi units, much less
with third-party firmware, but from what I have read, you can push the
power output levels up to perhaps 200 mW, but the Linksys users
website says pushing it over 100 mW will eventually take out the RF
power amplifier.
Adding a "booster", may it be a one-way transmitting power amplifier
or a bi-directional amplifier, *generally* isn't the way to go if you
use multipoint-to-point, as you run into power output limitations, but
in your case for point-to-point there would be an advantage. On the
receiver side, they typically have 13 dB of gain..and that means the
signal as well as interference will get a 20x boost, so effectively
your signal to noise ratio will be the same. But that 13 dB gain is
misleading as you have to figure in the additional patch cable losses.
At nine miles (and assuming you have a clear Fresnel path), you could
use a diversity like I use for my ten mile plus shots with a 2.4 GHz
and 5.8 GHz link to maintain carrier class reliability.
>I haven't played with very many consumer grade WiFi units, much less
>with third-party firmware, but from what I have read, you can push the
>power output levels up to perhaps 200 mW, but the Linksys users
>website says pushing it over 100 mW will eventually take out the RF
>power amplifier.
That's true for the WRT54G v1 thru v4. 100mw is safe. 250mw is
maximum. Everything in between is subject to anecdotal horror
stories, including one of mine. One of my customers fried his
WRT54Gv4 at 250mw, probably by cooking the PA.
That's not true for the Buffalo WHR-HP-G54, which is FCC type
certified at 380mw for 802.11g and 280mw for 802.11b. See previous
discussion at:
<http://groups.google.com/group/alt.internet.wireless/msg/5acd2fef5f836d1b>
Ugly spectrum analyzer photos. Note how dirty the waveform looks at
250mw which is another reason to not turn it up to maximum.
<http://explorer.cyberstreet.com/wrt54g/WRT54g-spectraloutput.html>
Incidentally, the latest 2wire wireless routers at type certified at
400mw.
>I doubt it is RG58, isn't that what TV cables are usually made from?
>I dug up the receipt for the pigtails, and they say "195 series cable".
That's LMR-195. 0.62dB/meter loss at 2.4GHz. Drop my 4dB coax losses
down to about 2dB total. That will yield a fade margin of 28.5dB for
the 9 mile link. If here are no obstructions or water in the coax, it
should work just fine, even and higher speeds. You don't need an
amplifier.
>I've never noticed the power setting before in the setup screens. It
>looks like it just gives me percentages, and no where does it
>explain what the actual transmit power is. I'll have to do some
>digging over the weekend I suppose. ( Again, these are still
>running the stock Buffalo firmware. )
I have no idea. I never use the stock Buffalo firmware. As soon as I
get a case of them in the office, I do production line BIOS
transplants with DD-WRT v23 SP3.
For a clue of what's in DD-WRT, see the online emulator at:
<http://www.informatione.gmxhome.de/DDWRT/Standard/V23final/Wireless_Advanced.html>
Note that the default power out is 28mw. Methinks you have some room
to work with on the power output.
>The new link does work, but if I run a continuous ping, I'll get 20% to
>50% packet loss, sometimes. Sometimes, it is great.
Show me. Download fping 2.17 from:
<http://www.kwakkelflap.com/fping.html>
and run:
fping ip_address_of_router_at_other_end -c
for about 100 lines and email the results to me at jeffl @ cruzio dot
com. I wanna see the numbers. Make sure there's no other traffic
going across the wireless when running the test. (I'm too lazy to
write another disertation on how to interpret wireless ping results).
>That is why
>I am assuming weak signal that is getting trod on sometimes.
It's almost for sure getting stepped on. What you probably don't
realize is that cranking up the power isn't going to help. Once
another signal gets in between the packets (inter-symbol
interference), you're data is trashed.
Also, it doesn't have to be wi-fi interference. See shopping list at:
<http://wireless.wikia.com/wiki/Wi-Fi#Interference>
See if any of these are possible culprits.
>The
>two points actually have a small valley inbetween them, so I don't
>believe Fresnel Zone encroachment is a problem.
Perfect. No Fresnel Zone problems assuming the valley is deep enough.
For 9 miles, you need at least 68 ft radius clearance around the line
of sight at mid span. Do you have this much clearance?
<http://www.terabeam.com/support/calculations/fresnel-zone.php>
>I believe I have disabled all the whiz bang features, but I'll double check
>those as well. I have these running in WDS only mode, because I just
>need the bridging component.
WDS has some overhead, but not much. When you load DD-WRT, you might
look at the "client bridged" mode.
<http://www.wi-fiplanet.com/tutorials/article.php/3639271>
>Thanks for your helpfulness. I'll be messing with random settings all
>week end. ( what...... isn't that how everyone trouble shoots?!? :)
Nope, at least not for me. Numbers and calcs first. Then I tinker.
If I have time, I RTFM.
Tinker settings:
<http://www.informatione.gmxhome.de/DDWRT/Standard/V23final/Wireless_Advanced.html>
CTS protection mode: disabled
Frame Burst: disabled
Preamble: short (only if you have 802.11b compatibility mode off)
Afterburner: off
WMM (QoS) support: off
>On Oct 5, 5:12 pm, gor...@lsi.com (Gordon Montgomery) wrote:
>>The antenna leads appear to be RG-8/U and about 50cm long.
>
>RG8 52 ohm cable is about half inch diameter, RG-58 is about quarter
>inch.
Nope. The impedance of the cable is dependent on the ratio of the OD
of the center conductor, the ID of the shield, and the type of
dielectric. Both 50 and 75 ohm cables come in all manner of different
diameters ranging from 0.085" semi-rigid, to monsterous 4.5" heliax
used for broadcast xmitters.
>> I doubt it is RG58, isn't that what TV cables are usually made from?
>> I dug up the receipt for the pigtails, and they say "195 series cable".
>
>TV cables use RG59, 75 ohm, RG58 is 52 ohm.
Sorta. Most TV cable is RG6/u. RG59/u is suitable for short patch
cables and not much more due to higher losses than RG6/u. For less
loss, but a larger diameter, there's RG11/u. Lots more types
depending on size and application.
For 2.4Ghz, the LMR series of cables are quite popular because of low
loss, decent connectors, and high quality.
<http://www.timesmicrowave.com/wireless>
Most common is LMR-400 which is .405 OD.
Some dish and panel manufacturers use cheezy RG8/u for pigtails
between the feed and the coax connector. This is possible because
although the RG8/u is rather lossy, there isn't very much coax
involved, so the losses are minimal. I would prefer something that
doesn't wick water into the braid and has 100% coverage, but cheap is
cheap.
On Oct 5, 10:20 pm, Jeff Liebermann <je...@cruzio.com> wrote:
> nevtxjus...@gmail.com hath wroth:
>
> >On Oct 5, 5:12 pm, gor...@lsi.com (Gordon Montgomery) wrote:
> >>The antenna leads appear to be RG-8/U and about 50cm long.
>
> >RG8 52 ohm cable is about half inch diameter, RG-58 is about quarter
> >inch.
>
> Nope. The impedance of the cable is dependent on the ratio of the OD
> of the center conductor, the ID of the shield, and the type of
> dielectric. Both 50 and 75 ohm cables come in all manner of different
> diameters ranging from 0.085" semi-rigid, to monsterous 4.5" heliax
> used for broadcast xmitters.
While the coax impedance is ratio defendant, the topic was about RG-8,
RG-8, and RG-59...so my answer still would be correct, "RG-8 52 ohm
cable is about half inch diameter, RG-58 is about quarter inch."
> >> I doubt it is RG58, isn't that what TV cables are usually made from?
> >> I dug up the receipt for the pigtails, and they say "195 series cable".
>
> >TV cables use RG59, 75 ohm, RG58 is 52 ohm.
>
> Sorta. Most TV cable is RG6/u. RG59/u is suitable for short patch
> cables and not much more due to higher losses than RG6/u. For less
> loss, but a larger diameter, there's RG11/u.
In the context of comparing RG-58 and RG-59, my answer is definitively
still correct. However the standard is to not use RG59 for anything
longer than a patch cable.
In article <84tdg35arda1fhn82t5k22n3i90efgkob8@4ax.com>, Jeff Liebermann <jeffl@cruzio.com> wrote:
>Show me. Download fping 2.17 from:
><http://www.kwakkelflap.com/fping.html>
Done. I tried different channels until I found one that seemed
to do better that the others. ( oddly enough it was 9, not the
usual 1, 6 or 11 )
>Perfect. No Fresnel Zone problems assuming the valley is deep enough.
>For 9 miles, you need at least 68 ft radius clearance around the line
>of sight at mid span. Do you have this much clearance?
Definately plenty of clearance at mid span. I am a lousy judge of
distance, but I would say at least 100 ft or more.
Gordon Montgomery
Living Scriptures, Inc gordon@lsi.com (anti spam - replace lsi with livingscriptures)
(801) 627-2000
Adding an amp .... 
Linear Mode
