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Ham Radio

Journey into Ham Radio and DMR

For years I have hung out with “Hams” and been somewhat interested in the technology.  Guys like ka8jil, w9sn, w9smj, w9cjo, w9abh have all interested in me in ham radio. I remember many years ago, before cell signals were digital, being able to pull up to a car and watching my buddy Tom tune his radio in and listen on the cell conversation going on in the car next to us.  For educational purposes only of course.  It reminded me of the blue  and Red box days of telephone phreaking.  The days of the 300 baud modems and making init strings to make the best possible connection.  For me, and I think I am like many other folks, it wasn’t the draw to the hobby, but rather all of the moving pieces of it which kept me from taking the step into it.  Traditionally Hams have tuned and tuned their radio setups, with many building their own antennas.  I can see where tuning a “shack” to get the best you can get out of it can be a challenging and rewarding thing for many.  Picking the right hardline, connectors, and other pieces takes alot of research, and some trial and error to make it function cohesively.  Tracking down noise, little hums in your transmissions, and other things is a problem solving logic that can stimulate the brain.

repeater
Motorola DMR Repeater wb9arc

But, I am not a true hardware guy.  I am more of a wizard at making it do what I want within the bounds of the software.  If I can make an add on to interface with something existing then thats as far as my interest goes.  This is what we were doing “back in the day” with blue boxes then moving on to the commodore 64. Being able to bypass copy protection, spinning up hardware keys to bypass restrictions, and stretching the limits of what the software could do with hardware add ons.  Then along came the Internet and dial-up modem banks, ISDN, T1s, etc.  All these were technology which could be pushed with “add ons” and “hacks” to something existing.  This is where my attention is really stimulated.  To me, Ham Radio has always been about taking all these different pieces and trying to make something work.  Kind of like getting a total random box of Legos and having to make a replica of the USS Ronald Regan aircraft carrier.  Sure, you can do it, but it’s going to take alot of effort.  Oh and BTW, you have to make it float when you are done. I think there is a large group like me who just wish to put something together from a kit, and then customize from there.

IMG_1196
300 foot tower with ham antennas installed by the author

So now, fast-forward to 2015.  A technology called DMR is really taking off.  Several of my HAM friends are enlisting my help to bring these repeaters live on IP networks and putting them on towers.  After awhile it really clocks with me.  This is kind of like the days of the USR Total Control modem banks.  You have a piece of hardware that does radio to IP conversion along with a few other functions. It communicates with a server over the IP network and an antenna on a tower. DMR is a standard and has set guidelines on how it is supposed to function.  You aren’t inventing the wheel, but optimizing a setup within the bounds of what the repeater is supposed to do.  To me this is a big draw. You have a baseline of how it’s supposed to work, which takes much of the frustration away which can be a very demotivating factor in any endeavor.

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Tower works on a WISP/Repeater tower

There are guys out there who are intrigued and love the RF side of stuff.  It is a science, but you can get so bogged down in it.  If you are making your own antennas you have to make sure all your wire lengths are just right, you use the correct solder, and all these 1000 other factors.  To me, that is not fun.  I admire these folks. It’s not that I want to put in the effort, I am missing the gene that experiences great joy in seeing an antenna I worked 2 months on finally go up in the air and kinda work.  I say kinda work, because I see time and time again having to adjust this or that or replacing this filter, or that connector.  To me that is frustrating. I like spending my time starting with a baseline setup and making that perform the best it can. Some say thats taking what someone else has already put together.  Heck yeah it is.  That is why I admire the tinkerer folks.  They give the folks like me a solid product i can go out and put to use because I didn’t spend those two months doing that piece of it.

IMG_0139
Tytera DMR radio

I know many folks are seeing DMR as the hot and sexy new technology.  I am looking at it as something that is able to be duplicated over and over with minor tweaks.  This keeps things interesting, without having to start from scratch each time.  Instead of focusing on soldering, and programming PLC boards, you can now focus on site installation, and tuning new and existing installations.   On the radio side you have the draw of programming radios to work with repeaters, and talk groups, and the like.  Repeaters have their own software to learn.  Again, you aren’t re-inventing the wheel, rather learning a system.  Within this system you can find ways to do things better, push the boundaries, and be involved in finding bugs and software suggestions.

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Installing antennas for w9smj repeaters

Many other HAMS tell me since I am a network guy I should love packet radio and technologies similar to that.  Not really, I have that in the interconnected networks called the Internet.  More and more effort is being focused on making connections hardened and resilient that packet radio is more nostalgia to me than anything.  We were doing such things with 300 baud modems in 1987.  Maybe, at one point I will dip my toe into such things.  But, it will have to be in a way that is an add on to existing systems, not starting from scratch.  I would have to have a “packet radio kit” that I assemble and hook into something. the CBRIDGE software that DMR uses really started my wheels turning.  It was not radio related, but it was a piece that I could wrap my head around.  For those of you who don’t know, CBRIDGE is what allows the DMR repeaters to talk over the IP network.  So by learning that piece, it motivated me to learn about DMR in general.  One day my mind said “hey you can use this and not be frustrated because sunspots knock it out for a week at a time.”

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w9smj antenna on a water tower install

So, my advice for anyone looking at HAM radio who is not a tinkering type of person take a look at some of the other aspects of the hobby.  Things like DMR are “easy” to get into in relative terms.  You aren’t going out and buying a base unit, amplifiers, hardline, and spending hours tuning it all.  After you pass your test you can be up and running very quickly without soldering a single connection.  As technology evolves and is incorporated into the hobby, it opens up a new way to get folks like myself interested.

73
kd9emp

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Towers and pricing

One of the more common questions is what does a tower cost me to put up? As many of you know this can vary quite a bit.  We are going to approach this from a single vendor perspective.  What this means is I am going to take what it would cost to buy a commercially available tower from Texas Towers and put it in the air.

Disclaimers
1.I am not endorsing Texas Towers nor am I affiliated with them. They are one of the few tower manufacturers who publish prices.
2.Consumable costs will vary depending on where you are, time of year, state regulations, and maybe even the cycle of the moon.
3.This is geared toward small deployments.
4.Pricing is based upon the information I had available at time of this writing.

  • Texas towers makes a self supporting 100 foot tower (Model HD8-100).  This tower is rated to support 7.4 square feet of load in 110MPH winds. Cost $4,409.
  • The base which goes in the ground costs $225
  • Freight costs vary
  • Concrete. The base for this tower requires 6 cubic yards of concrete. Pricing near me is $95 per yard plus a $30 delivery fee with a 3 yard minimum.
  • If you are doing the 100 foot tower a small 80-100 foot crane can put this up.  The tower weighs around 500 pounds so a small crane is sufficient.  In my area a crane this size would be around $400 for a half day.  Since it’s not a huge crane it doesn’t require special permits in indiana
  • Engineering Fees for the base run around $1000.

So total cost for the tower: $5734 plus freight.

There are some other factors to consider. Permitting, labor to assemble tower, standoffs, etc. But this gives you a good ballpark estimate.

 

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Helpful OSPF times

OSPF can be a mystery to some.  Understanding the default timeouts can be helpful in troubleshooting.  Some vendors change these times so it is very important to realize this stuff if you start mixing vendors in your OSPF domains.

10 Seconds
Default OSPF hello timer on broadcast and point-to-point links

30 Seconds
Default OSPF hello timer on nonbroadcast links

40 Seconds
Default OSPF hold timer on broadcast and point-to-point links

120 Seconds
Default OSPF hold timer on nonbroadcast links

30 Minutes
OSPF LSA refresh timer

60 Minutes
OSPF LSA expiration timer

 

 

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Cambium Releases ePMP v 2.4.3

Software Release 2.4.3 is now avaialbe. 

The release includes the following updates: 

  • L3 Routing on the SM 
  • Multiple User Login on the GUI 
  • 4.9 GHz support under Country Other 
  • Ability to enable and disable management access on the SM from the Ethernet when Management VLAN is configured 
  • Ability to disable the SM’s primary Ethernet port 
  • Ability to disable factory default through power reset sequence

Performance Enhancements 

  • Improvements to UL Latency enhancing TCP throughput under interference 
  • Improvements to Rate Adapt mechanism in ePTP mode 
  • Memory optimization
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Buying IPv4 addresses?

The question has come up about buying IPv4 addresses from other folks once ARIN and others have run out of their allocation pool.  The biggest question is pricing.

Organizations have two options.  The can lease or sell you the IPv4 space.  Selling of IPv4 space needs some clarification.  You can’t just sell IPv4 space like you would a tangible good.  If you truly wish to sell it, as in give up all rights to it, you actually have to transfer it via the Registry.   In the U.S. we typically go through ARIN.  This means if you buy IP space from someone you still have to meet the requirements from ARIN to receive that IP space.

What are some common pricing to expect?
There are several brokers out there, but very few publish pricing on recent sales.  Since this is basically buying real estate it can be highly negotiation and sales driven. Given the current state of ARIN allocations this will only drive the price up.

One site that publishes data is ipv4marketinggroup

$12.50 per IP address for a /22
http://ipv4marketgroup.com/broker-services/buy/

 

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OSFP and areas

OSPF areas are one of the more common topics I am asked about as networks grow.   Before we dig into this, we need to understand the reasons why OSPF areas were created in the first place.  Next, we will go into how to apply areas to modern network designs.

Why did areas come into being?
Let’s rewind to a time where RAM in routers was very expensive.  Processors were expensive.  One of the biggest reasons OSPF areas came into play was ram limitations. Every route in your routing table takes up ram.  The more routes you have the more ram that is taken up in each router to hold that table.  Also, in order to calculate these routes processor power is used up.

So what do areas do for me?
OSPF areas have many advantages.  However, in most WISP and ISP networks they serve two purposes.

The first purpose is they group similar devices into logical groups.  These groups can have filtering policies applied to them.

The second purpose is more important.  Implementing areas reduces the size of the routing table.  By doing this your routers spend less time calculating routes, and less time updating the database during a topology change. By reducing the routing table you also speed up what is called convergence time.  This is the time the entire network needs to agree on the current routing topology.   If a major backbone link is flapping your routers could be spending a fair amount of their resources calculating routing tables.

An important thing to note with implementing areas is you must have a good IP network design.   This means your sites/pops/towers should have a logical design which allows for easy route summarization and consolidation.  If you are looking into areas make sure you can summarize your routes in that area easily.  The following examples illustrate why this is important.

ospf1

 

In the above example we have created “Area1”.  Since we have a good IP network design we can summarize our routing table in and out of area1 into a few different ways.  If we want to reserve the whole 10.5.0.0/16 for future expansion then we can.  Or if we want to break this down into 10.5.0.0/20 or even smaller we can.  Part of this depends on growth plans.  With areas you have to keep in mind every area needs to touch the backbone (area 0.0.0.0) directly.  Now, you can use Virtual Links to have one non-backbone area traverse another non-backbone area.  However, even though is a standard, is a workaround at best.  There are many disadvantages to virtual links.

Now, back to our example.  If we create an area the 10.6.1.0/24 and 10.6.2.0/24 routers are the “in roads” to Area1.  These are known as area border routers (ABR).The main function of ABRs is to summarize sub networks found throughout the OSPF network. It stores many copies of its link-state database in memory when one of the stored copies shows an area where the actual router is connected. The ABR holds a minimum of two copies of the routing tables.  One from the backbone area, and one from each area it is connected to.

But, I thought areas were supposed to cut down on ram and CPU usage? Well, everything has a tradeoff.  This is where the philosophy side of things come into play, and probably the reason you have read this far.

When, how, and should I implement areas?
In today’s modern world with fast ram, fast links, and fast processors OSPF areas are needed less and less.  Routers today have more ram than even 5 years ago.  This means they can hold larger routing tables and do more calculations.

If you are thinking about implementing areas the first thing to look at is your IP design.  In order to take the best advantage of areas you should have a logical, and congruent design.  What I mean by this is your towers should be able to summarized as much as possible.  If you can fit 20 towers into a single route statement that is one good place an area would make sense.  If those 20 towers are not able to be summarized then adding an area is not going to be much of a benefit to you.

Network size does not necessarily dictate the need for OSPF areas.  If you have a neatly summarized IP network the need for areas is lessened.

What about if you are trying to join two different networks?
Say you purchased a neighboring ISP and want to join the new network with your own.   If you have overlapping IP space then things might not mesh together well, even with areas.   Most times you are better off running BGP with the two separate networks.  This allows each network to have it’s own space, own routing policies, but still be able to share bandwidth and other resources.  You simply don’t announce any overlapping space to each network until things are re-numbered.

One question I get in this scenario is my router can’t handle BGP.  BGP is a fairly lightweight protocol.  The issues arise when you start pulling in full or partial internet routing tables.  This is the same concept as mentioned above with the OSPF routes.

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Mikrotik Router OS 6.29 released

The fastTrack improvements are a big improvement for those of you doing such things.

What’s new in 6.29 (2015-May-27 11:19):

*) ssh server – use custom generated DH primes when possible;
*) ipsec – allow to specify custom IP address for my_id parameter;
*) ovpn server – use subnet topology in ip mode if netmask is provided (makes android & ios
clients work);
*) console – allow ‘-‘ characters in unknown command argument names;
*) snmp – fix rare bug when some OIDs where skipped;
*) ssh – added aes-ctr cipher support;
*) mesh – fixed kernel crash;
*) ipv4 fasttrack fastpath – accelerates connection tracking and nat for marked
connections (more than 5x performance improvement compared to regular slow
path conntrack/nat) – currently limited to TCP/UDP only;
*) added ~fasttrack-connection~ firewall action in filter/mangle tables for marking
connections as fasttrack;
*) added fastpath support for bridge interfaces – packets received and transmitted
on bridge interface can go fastpath (previously only bridge forwarded packets
could go fastpath);
*) packets now can go half-fastpath – if input interface supports fastpath and
packet gets forwarded in fastpath but output interface does not support fastpath
or has interface queue other than only-hw-queue packet gets converted
to slow path only at the dst interface transmit time;
*) trafflow: add natted addrs/ports to ipv4 flow info;
*) queue tree: some queues would stop working after some configuration changes;
*) tilegx: enable autoneg for sfp ports in netinstall;
*) health – fix voltage on some RB4xx;
*) romon – fix 100% CPU usage;
*) romon – moved under tools menu in console;
*) email – store hostname for consistency;
*) vrrp – do not reset interface when no interesting config changes;
*) fixed async. ppp server;
*) sstp – fixed router lockup.
*) queue tree: some queues would stop working after some configuration changes;
*) fixed CRS226 10G ports could lose link (introduced in 6.28);
*) fixed FREAK vulnerability in SSL & TLS;
*) improved support for new hEX lite;

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What is AirMax priority?

From UBNT:

airMAX Priority is a setting which can be changed on station devices in an airMAX network. This option can be found on the airMAX logo tab.

It defines the number of time slots (or amount of airtime) assigned to each client. By default the AP gives all active clients the same amount of time. However, if the clients are configured with different priorities, the AP will give clients more or less time, depending on the priority. For the best performance, an airMAX network whose clients have the best signals should receive the higher priorities, while clients with poorer signals should have less/no priority.

Note: airMAX Priority only functions when multiple clients have it enabled.

airMAX Priority options include:

–  High 4 time slots (4:1 ratio)
–  Medium 3 time slots (3:1 ratio)
–  Low 2 time slots (2:1 ratio)
–  None 1 time slot (Default setting for clients; 1:1 ratio)

Clients with a higher priority have access to more of the AP’s airtime, providing higher possible throughput and lower latency when sharing with other active clients.

For example, if there are 3 clients, 1 set to None, 1 set to Medium, and 1 set to High, the None client will get 1 time slot, the Medium client will get 3 time slots, and the High client will get 4 time slots.

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Protecting your Mikrotik from DNS Amplification

There are several reasons and benefits to using your Mikrotik as a DNS caching server.  Queries to the client are just a tad faster, which makes the overall user experience seem snappier.  It also allows you to quickly change upstream DNS servers in the even of an outage, attack, etc.

There are two main avenues to think about when protecting Mikrotik from DNS.

The first is the incoming port 53 requests to the router.  You only want your customers to have access to query the Mikrotik.  In a simple scenario we have this:.

basic

ether1 is our upstream ISP connection.  Customers are other ports.  In this case if we want to block all port 53 requests from the outside world we specify the WAN interface to drop in the following code:

/ip firewall filter
add chain=input in-interface=ether1 protocol=udp dst-port=53 action=drop
add chain=input in-interface=ether1 protocol=tcp dst-port=53 action=drop

This will still allow your Mikrotik to send out DNS queries because they are sourced from a non reserved port. We are simply blocking the Mikrotik from not answering port 53 requests on the external interface.

In a later post we will talk about what to do if you have multiple wan interfaces or multiple exit paths on your router (say running OSPF)

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American Tower Webinar for WISPS

An advertisement on the WISPA list. Useful for any WISP looking at deploying on American Tower Towers or Cell towers in general.

https://attendee.gotowebinar.com/register/7229015539956879618