Monday, November 12, 2018

Clipping the Diode

Two official .gov/.mil organizations hams get involved with are Civil Air Patrol (CAP) and Military Affiliate Radio Service (MARS). Historically, MARS and CAP were allocated frequencies just past the edges of the ham bands, such as 142-144 and 148-150 MHz. Hams in MARS and CAP would use their existing radio equipment on their organizations' frequencies. Typically, there was a jumper or diode on the radio's circuit board that would open up the TX frequency coverage and enable operation outside the ham bands. While CAP has adopted technical standards that preclude the use of most ham equipment for their comms, MARS still allows the use of ham gear. Most radios are still being made with a jumper or diode that will enable transmitting out of the ham bands when clipped. We call this the "MARS/CAP" or "freeband" mod. Most radio places will give a ham the mod info, or perform the mod for a small fee, if they present a MARS or CAP radio license. This would give an HF rig TX coverage from 1.8-30 MHz., and a dual band HT 136-174 and around 400-470 MHz. Some of the Chinese HTs come already opened up, which is what got that Baofeng in hot water with the FCC.

In the early 1990s it was considered a title of passage among radio hackers to "clip the diode" on their recently purchased HT. Many non-hams found themselves bootlegging on 151.625 MHz. and other low-power/itinerant frequencies where there were thousands of licensed users and no one paying much attention. This was before the creation of Part 95 services like FRS and MURS. CB skip shooters would buy a used Kenwood or Yaesu HF rig, clip the diode if not already done, and run 100 watts on 11 Meters and the 27.415-28 MHz range which is still a free for all today.

In regard to modified gear, the following provisions of Part 97 are of interest:


§97.403 Safety of life and protection of property.
No provision of these rules prevents the use by an amateur station of any means of radiocommunication at its disposal to provide essential communication needs in connection with the immediate safety of human life and immediate protection of property when normal communication systems are not available.

§97.405 Station in distress.
(a) No provision of these rules prevents the use by an amateur station in distress of any means at its disposal to attract attention, make known its condition and location, and obtain assistance.
(b) No provision of these rules prevents the use by a station, in the exceptional circumstances described in paragraph (a) of this section, of any means of radiocommunications at its disposal to assist a station in distress.
It is legal for an amateur radio operator to have a ham transceiver that will operate outside the ham bands, and in certain emergencies, it is legal to transmit out of band. Your typical HF-UHF amateur radio station, with the appropriate diodes/jumpers in the radios clipped or otherwise reconfigured, should be able to interoperate on CB, MURS, FRS, GMRS, and conventional analog LMR systems.

While this is legal under §97.403 and §97.405, in reality YMMV and keying up on the local PDs' repeater (assuming they still have an analog conventional system up and running) may result in you getting a rash of s**t if their idea of what constitutes an "emergency" is different than yours. I wouldn't expect the FCC to go to bat for you if that happens. Put aside a couple thousand bucks in case you need to lawyer up.

Realistically, you can expect most 2m radios to stay in original spec from around 140 to 160 MHz., and 70cm radios from ~400 to 470 MHz. Past that you can expect progressively worse transmit power output and receive sensitivity the further you get away from the ham bands. TANSTAAFL. Furthermore, running them regularly on Part 95 or 90 allocations is a regulatory no-no as they aren't "certified" for those services. Again, this is what got that Baofeng in hot water. Yes, I know everyone does it, and for the most part the FCC doesn't pay attention until they get a few complaints.

For what it's worth, my opinion is that if you want to run on Part 95 bands, you should run Part 95 gear as it is generally simpler to operate than Part 90 gear. I've met many a no-code, single test session Extra who despite being able to memorize all three test pools was still unable to program and effectively operate his Baofeng HT. I expect his clueless Aunt Matilda would be even less successful if handed one, and that's not taking into account what might happen if the wrong button was pressed. The simple CBs and FRS handhelds I pass out to non-techies have a minimum number of controls to get confused on, and are simple enough for everyone to operate.

Sunday, November 11, 2018

HTs and Cars

An HT is not the most ideal choice for a first radio, especially if you want to be serious about running simplex, which you should be. A VHF/UHF repeater is an unknown when it comes to reliability in austere conditions, and they have been known to fail when TSHTF. A good rule of thumb however is that ARES/RACES affiliated machines are more reliable in disasters.

Running a stock HT in a vehicle sucks. You start with an inefficient rubber duck antenna, and add the attenuation from transmitting inside a vehicle. I knew a few hams back in the day who would run a 25-50 watt amplifier and external antenna when operating mobile. That setup will give you the equivalent of a regular mobile rig, although the ergonomics won't be as nice.

Running a mobile antenna is probably the easiest way to increase the performance of your HT when operating from a vehicle. Since most amateur radio mobile antennas use a PL-259 connector, you will need an adapter to connect it to the BNC or SMA antenna connector on your HT.

Here is a Weierwei V1000 2m amateur radio HT, one of the higher-tier radios coming out of China. Opening it up, we were pretty convinced its design was "borrowed" from an EX600 or Visar.

Looking at the antenna connector on the radio, we discovered it was an SMA male, which is pretty typical for commercial LMR and Chinese ham radio HTs.

The HT with a generic dual-band (2m/70cm) cellular look-alike magnet mount antenna. It's a quarter-wave on VHF and 5/8th wave (or so) on UHF. Cheap hamfest find. It uses a PL-259 connector, so we need an adapter.

SMA female to SO-239 adapter cable. I prefer using cable adapters as they place less strain on the HT's antenna connector.

Everything all put together and ready to go.

You can expect a noticeable increase in communication range with this setup because you are eliminating attenuation from transmitting through a vehicle body, and running a higher-gain antenna than the stock rubber duck on the HT.

Saturday, November 10, 2018

Finding Your Local VHF/UHF Net

So you just passed your Technician class license, and bought one of those <$50 HTs that covers the 2 meter and 70 cm bands. Your next step is to check into a VHF/UHF net on a local repeater (network). This is useful because it lets you know that your radio is working well enough to reach something, even if the repeater is doing most of the work for you.

First you have to find a repeater you access. In New England, we have the excellent New England Repeater Directory which you can reach at http://www.nerepeaters.com/. For other regions, you can try https://www.repeaterbook.com/, https://www.artscipub.com/repeaters/, or a search engine.

To get into a repeater, you will need to program in the receive frequency, transmit (TX) offset (which is usually +/- 600 KHz. on 2m or +/- 5 MHz. on 70 cm), and probably a PL/CTCSS tone. For example, my local repeater in Terryville, CT is on 147.315 MHz. with a TX offset of +600 KHz. (147.915 MHz.) and a transmit PL tone of 88.5 Hz. It is also part of a networked repeater system.

For ninety percent of you, finding which repeaters are active is simply a matter of doing a little OSINT research, and performing a point search on a few frequencies. If you are living someplace that lacks the proper OSINT material, then a band/sector search of 144-148 (2m) and 440-450 (70 cm) MHz. over the course of a few days will find what you need.  Even when idle, most ham repeaters will identify themselves every 10 minutes or so.

Once you have some repeaters identified, program the specifics into your radio, key up, wait a second or two, and simply say "<your_call> testing." If successful, you will hear a carrier from the repeater, maybe a courtesy tone, and maybe someone will come back to you with a signal report. If you want to rag chew a bit, just key up, wait a second or two, and say "<your_call> listening (or monitoring)." You usually don't call CQ on a repeater. if someone is listening and wants to chat, they'll come back to you.

So now that you've found a local machine or three, you need to find out when the nets are being held.  The ARRL has a net directory at http://www.arrl.org/arrl-net-directory, and there are, as always, search engines to help you. Usually VHF/UHF (repeater) nets are held in the evenings after dinner. Some nets may not be listed in the ARRL Directory. My local repeater's swap net (Fridays at 8PM) is not. I found it by listening.

When the net starts, listen closely for instructions from net control. Nets all have different check in procedures, and the net control station will tell you everything you need to know. For example, the WyoComm (Wyoming) weekly net on Sunday evenings does check-ins by region (Wind River, Big Horn, et al). The Donkey Dusters (CT) Swap Net takes Echolink check-ins first. RACES/ARES nets usually take emergency and low power (QRP) stations first.

Nets are a good source of information about the local amateur radio community, and something you should participate in even if only by listening. They are also good for setting a specific time to check your equipment.  I'm not normally a VHF/UHF repeater operator, yet among the first things I did  after moving back to New England was dig out an HT, program in the local repeater frequency and start listening.  Last night I heard the swap net start, checked in, and after the net had a quick QSO with a friend who lives in central Massachusetts and can also reach the same repeater network.  When I get some HF gear set back up, and try a sked with the same friend, we'll probably coordinate our HF comms on the same 2 meter repeater network.

With that said, the same local repeater network also has 10m and 6m nodes. When the bands start opening up, feel free to jump on and toss your call out.

Tuesday, November 6, 2018

Connecticut Intro Class - January, 2019

We'll be doing a one-day intro to communications and SIGINT class next January in Watertown, CT. Cost will be $100. More specifics once we finalize the date.

Sunday, November 4, 2018

Gab Deplatforming

What is the one thing that I've said since starting Sparks 31?

Never trust anyone else's infrastructure.

The recent deplatforming of Gab is the latest reason why.