## Saturday, 8 March 2014

### Coax cable loss

Antennas receive the signal, receiver makes it understandable. Between these two coax cable carries said signal, which gets more and more tired the further it travels (coax length) and the bumpier the road (coax quality).
Being tired means you lose energy, so poor signal cannot tell you all the information.
Less info is called signal loss, how much depends on coax cable quality and length,

To improve a signal you can:

1) Decrease the length of coax cable - less travel, more signal
2) Improve coax cable quality
3) Add a preamplifier - this is like an energy drink to signal

### How to calculate signal loss

Coax cable loss increases with frequency. Online resources give this loss in decibels, which is logarithmic, so 3 dB is half the power  - transmitting or receiving makes no difference.
Decibels and logarithmic stuff is complicated, so measure the

length of coax cable, note the writing on it and google this plus "attenuation". Attenuation means weakening of signal in radio speak. So if writing says RG 6, google "RG 6 attenuation".
Get a decibel figure with this online calculator. Enter values on top - results in feet will be on the left, meters on the right, you get a figure in decibels.
To understand decibels in a "this is how much percent of info reaches my receiver ", use this online calculator. It simply converts decibel to understandable percentages, with 1 being 100 % of signal received at the antenna.
Enter number to the left of dB with a minus sign, select energy size on the right, then press calculate.
For example, common RG 58 used at sea in 20 metres 4.4 dB is lost: only 36 percent of signal reaches the receiver.

### Decrease the length of coax cable

More length = more loss.

Use the minimum length of coax required between antenna and receiver; excess lengths will not only lose more signal but will also pick up electrical noise.
Finding an antenna location is a compromise, in an urban setting getting away from household electricity, gadget interference and TV radiation can be challenging.
In the illustration the difference between signal strengths might be small on screen, but that -2 dB means 37 percent of the signal is lost.

### 2) Improve coax cable quality

Better coax will lose less signal. Four times less loss is four times the cost, so selecting a cable is entirely up to your budget.
LMR-400 is commonly used, which is the upper limit in terms of cost and flexibility for mortal souls.
Performance improvents will be only realized with long cable runs, and / or high frequency applications, or if the antenna is used for mission-critical applications e.g. transmission line for life-saving equipment such as mounted VHF on yachts.
Check the table to see the LMR-400 has much lower dB loss figures - but performance comes at a price.

### Use a preamp

For receive - only applications mount a preamp at the antenna to overcome long lengths of coax cable signal loss.
Punters seeking signals above 800 MHZ - such as monitoring trunked emergency comms in the States - or ADSB enthusiasts hunting 1090 MHz will need a preamp with cable runs over 30 feet / 10 metres. Most of these require line of sight / unobstructed view of surrounding terrain hence necessitate long cables to mount antenna on top of the house.
Sailing vessels with antenna on top of the mast are better off using a LNA4ALL powered by nav lights as with tall masts and corresponding excessive cable runs signal loss will be horrendous.

### Significance in marine applications

Highest point on a vessel, usually mast top is the traditional home of antennas, antenna is normally a stainless steel whip.
Antenna higher up - better range due to increased line of sight
Mast height increases with length, Bavaria range as an example, mast heights from waterline in metres:

Cruiser 33 - 14.8 m, Cruiser 37 - 16.8 m, Cruiser 41 - 18.6 m, Cruiser 45 - 20.7 m

33 feet / 11 metres is a popular length for a sailing yacht, use that as an example: to top of mast cable run from navigation station is around 18 metres, to aft rail, cable run is 4 metres.

Cockpit rail mounting enables short lengths of coax to be used, so less signal is lost. And climbing the  mast is not easy...

Commercial marine antennas are normally sold with 20m RG 58 coax cable. I phoned chandleries in Ireland and the UK, RG 58 is the most commonly available "radio cable".
My deepest respect to the few exceptions, but all sellers I've talked with offering life-saving equipment seem to have no clue about technical aspects of radio.
Notable exception is Nevada Radio, a well-known ham dealer also selling marine gear, whom I can recommend for excellent and knowledgeable customer service (no affiliation with them).
Signal loss also affects transmitters, using the above example of 20 metres of RG 58 coax, your 25 W mounted VHF becomes a 9W transmitter.
Note that it is more than enough to establish communications, but results can be improved by using LMR-400.

If you wish to have AIS on board, based on RTL-SDR, use the aft rail to mount the antenna. Less signal loss, less cable required, less hassle and unnecessary to climb the mast - no bruises.

## Wednesday, 26 February 2014

### Antenna Performance Comparison

Selecting an antenna type is always a trade-off between size and performance - quest is finding the best antenna with the smallest footprint, ease of construction and lowest RFI / electrical noise pickup.

### What you need to know

1. Half-wave monopole is best (wrap conductor around one end and you're there) with good noise characteristics.
2. Add one (dipole) or two (as radials) elements to braid to  decrease noise floor in a high RFI / electrical noise environment.
3. Materials make no difference, coat hanger wire still reliably receives VHF signals.
You will get similar results on other frequencies between 100 and 1100 MHz, if you know the frequency you want to hear.
Use results here to construct an antenna for your preferences.

### Importance of wavelength

A specific frequency has a corresponding radio wavelength. To get the wavelength in metres, divide 300 with the frequency in question. For instance, AIS is 162 MHZ, so the wavelength will be 300 divided by 162 = 1.85 metres. Calculations are the same for other frequencies.
Common marine antennas are 0.9 metres, (half-wave) 1.8 metres (full-wave) or 0.45 metres (1/4th wave). Other variations exist such as huge 5/4th wave antennas measuring 2.4 metres, which are solely the domain of larger vessels such as motor yachts and ships.
Antenna types tested are for VHF and up, from broadcast radio to ADSB signals. Use info here to select an antenna for a quick and easy job, lowest noise (Half-wave with 2 radials) or a compromise for size vs performance (Quarter-wave with 2 radials).
Strong shortwave signals are possible to receive even with a rubber ducky. Weaker signals need larger antennas, but shortwave is an entirely different cup of tea.

### Setup

No fancy cables, equipment nor noise reduction measures used to simulate a beginner setup.
Indoor location, antennas taped to floor-to-ceiling windows. If you live in a condo, need a college dorm antenna, or cannot erect an outdoor version, select from the following options. Indoor vs outdoor is a separate question, for reference, comparison at the end of this post.
Nooelec RTL stick, cheapest 20 feet / 6 metres RG-59 coax with no shielding, no noise reduction apart from metal removed from end of USB connector.
SDRSharp 1.0.0.1174 with the excellent Level Meter Plugin, this allows me to measure peak power easily. Same gain, cables and location for all antennas, only variable is antenna to ascertain comparative performance.
Signal: local airport info system, steady signal with the same recorded voice repeated over and over again. Antennas optimised / cut using the above formulas to get full, half and quarter-wave elements.
Distance to signal 2.7 nautical miles / 5 kilometres, no line of sight, signal path over electrically very noisy environment, called "city" in english.
Materials: best available used, 2.5 mm diameter house grounding wire as antenna material just to be on the safe side, not that it really matters: see material comparison below.

### Antenna types tested

Monopole: receiving element connected to center conductor. Full, Half, Quarter and 1/8th wave tested.
Dipole: two elements connected, one to braid and one to center conductor. Half and Quarter Wave tested.
Two radials: one element to center conductor, two to braid, forming a Peace-sign / Mercedes symbol. Half and Quarter wave tested.
Rubber Duckies: common on handheld transmitters and scanners, Icom (FA-S280C, around 20 USD), Uniden (stock, around 11 USD) and Baofeng (upgraded stock from UV-5B, around 13 USD). Adaptors required to connect to BNC shown.

Discone: Skyscan V1300 with 12 feet / 4 metres 50 Ohm cable, around 60 GBP / 72 EUR / 95 USD.
Evaluating performance by received audio is subjective, printscreens are not. Received signal is on the left under red vertical line, this should be as high as possible. Yellow speckles and small waves are noise, lower or less visible is better.

### The Full Picture

Antennas organised by peak signal, gives you an idea what to expect noise-wise.

Quater-wave dipole and half-wave monopole same length, dipole needs twice as much (two) electrical connections. The single greatest cause of electrical problems at sea is connectors, hence the monopole recommendation.
Monopole - stock is the supplied telescopic antenna that comes with the RTL stick.
Ducky refers to rubber duckies, separate comparison against a monopole below.
Full-wavelength antennas in any form will be a challenge to mount, as 1.8 metres for marine band (156-162 MHz), and 2.5 metres total length for airband (118-134 MHz).

Adding one or two elements (same length of wire as receiving wire) to braid reduces noise pickup, resulting in better signal-to-noise ratio.

### Rubber Duckies

Common on transceivers, noise pickup is significant in an urban environment. Included here for reference, recent testing confirmed previous findings (See Marine AIS antenna post above) that with antenna at 3-4 metres above sea level e.g. cockpit mounting reliably picks up AIS signals out to around 3-4 nm.
Compared to a simple half-wave antenna the performance difference is striking, the lower noise floor is evident side-by-side.

### Indoor vs Outdoor

All antennas taped to a window: this 1) simulates  common scenario when you can not erect an antenna outside, and 2) heavy rain and gale force winds outdoors.
Here's a direct comparison with a discone:

1. Outdoor means antenna 1 metres from window. 10 dB increase visible means 100 times more signal received.
2. All antennas, especially discones, should be outdoors. The concept of an indoor discone is a heavy compromise, buying a 100-dollar antenna then placing it in the corner is pointless.
3. If you cannot have an outdoor antenna, add two radials and tape antenna to window. Lower noise floor than a discone, better signal-to-noise ratio.

### Materials

Same lengths, from top to bottom: Commercial telescopic antenna with BNC connector, stock telescopic, antenna from a radio, 2.5 mm diameter solid copper grounding wire, 1 mm multi-stranded copper wire, 220 V power cable.
Click on the image below to check they aren't the same, no difference whatsoever by ear.

Doubtful? Repeated test with quarter wave antennas from: Grounding wire, 220 V power cable, and gym locker hanger, all cut to the same size. Center conductor wrapped around wire, as basic as possible.

Note that signal height is the same in relation to noise floor, same performance on-screen and by ear.

## Thursday, 6 February 2014

### Shootout: Shortwave for 50 dollars

Disclaimer: I purchased all products in this review from my own funds, no manufacturer involved.
Shortwave Listening (SWLing for short) is still a popular pastime: a simple 50 dollar receiver and turning a dial results in a cacophony of foreign broadcasts and exotic tunes.
Using a software defined radio makes finding stations easier, as you actually see the signals.
An RTL-SDR and Upconverter combo is around 50-60 dollars, a mid-range portable, such as the Eton G8 can be also had for around 50-60 dollars.
Apples to oranges? Absolutely. The RTL setup has a steeper learning curve, but rewards with more settings available to fine-tune the signal, the portable requires 3 AA batteries and your finger to find a station.
The real question is: should you get an upconverter or a portable shortwave receiver? How to spend 50 bucks? Usability, portability and personal preferences aside, the bottom line is: listening to shortwave stations.

### In the standalone corner: Eton / Grunding G8 Traveler II Digital

A palm-sized receiver with mostly positive reviews from the ham community, digital frequency readout with 1kHz tuning steps, alarm, more details in the user guide.

### In the Software Defined Radio corner: Ham-It-Up Upconverter from Nooelec.

Probably the most widely used upconverter, as alternatives are more expensive. Same cost SDR UP 100 is out of production, and as I had good customer service from the manufacturer, I'd recommend this.

### Testing setup

Test is purely about shortwave reception capabilities, so please no comments on either system's perceived advantage over the other; same money on the table after all, the rest is personal bias.
"SDR setup" in this text refers to Nooelec RTL 2832 820T stick + Ham It Up; "G8" refers to the Eton / Grunding G8 Traveler II Digital.
Built-in antennas: for indoor testing, the SDR setup has no antenna so I connected a telescopic antenna via adaptors to the ANT IN of the upconverter.
External antennas: two identical longwires thrown outside, lengths 20 feet / 6 m. Longwire directly connected to antenna input for the SDR setup, and wrapped around the G3's telescopic antenna base. No preamp.
Note on antennas: no-frills setup, no antenna isolators nor electrical noise reduction of any kind.
RFI: Both receivers equal distances from laptop (same electrical noise pickup), in front of a window, wire led outside and swinging 10 feet off the ground.
Audio setup: Laptop's built-in speakers and G3's speakers equal distance from listening position. Identical sound level ensured by tuning to broadcast FM station and measuring sound pressure level at the listening location; two free apps installed on two smartphones and a tablet utilized as I have no SPL microphone, the resulting six different readings gave identical SPL levels, so any difference in audio level or quality is due to the actual receiver system.
Gain: Gain, digital noise reduction and filter bandwidth used in SDRSharp to find best compromise between signal to noise ratio and intelligibility; no gain nor DX / local switch available on the G8.
Timeframe: both setups tested for several days, side-by-side, night and day.
Your operating enviroment will be different from mine; I devoted the largest part of my book to electrical noise reduction, as 1) simplest, 2) cheapest and 3) most effective way of improving reception. No noise reduction used in this test, because using 100+ dollar worth of cables, antenna isolators, stubs, or a better antenna system will yield better results.
The question is: should you get an upconverter or a portable shortwave receiver? How to spend 50 bucks?
This test tries to simulate an average user connecting a longwire to either receiver hoping to listen to a station of his/her choice.

### Test Results

Sorry, no video this time, I made one but no audible difference with major stations / strong signals, weak signals are noise interspersed with voice, not video material.
If you can clearly see the signal in SDRSharp the G8 can receive it without any problem.
If you have to strain your eyes or play with contrast - G8 will receive it 1kHz below indicated SDRSharp frequency. Faint, but still audible.
Indoors: same performance. No surprise here, placate wife and neighbors, erect an outside antenna.
20 feet / 6m outdoor antenna: Major broadcasters - government propaganda, religious and foreign  language programming all booming in. No difference between Ham It Up and portable shortwave for enjoyment factor.
20 m (around 14.2) CW and SSB chat caught on Ham It Up, indistinguishable with the G8.
Ham It Up is very slightly better with lots of software tweaking, gain and digital noise reduction is your friend. The difference is there, but really, really small. More often than not, you end up with voice fading in and out.
Weak signals are a hit-and-miss with either setup, at least with the RTL setup, play with contrast,  gain and digital noise reduction and click on the faint waterfall. Many minutes later you might get a voice from the other of the globe. Or not.

### Recommendations

1. You will be better off with a portable shortwave receiver. Easier to use. Better to listen to.
2. The Ham It Up needs a preamp. Badly. When I got tired of noise I plugged in the LNA4HF.

The Ham It Up is slightly better in terms of reception capability, added software features make it an enticing proposition. But if you're hunting weak signals (read: love to listen to hissing noise) a proper antenna, noise reduction tricks from the book and a preamp is a must.
The "better to listen to" part is impossible to explain. Live music will be always better than recorded, and to my ears, the portable is better for listening.

For shortwave listening spend your hard-earned money on a portable.

### If you enjoyed this article, or wish to support this blog,

... go to Amazon and buy my book.  Tips and tricks in the book will save time and money, reduce frustration with computer settings and help you build the best antenna system from shortwave to microwave. Detailed and illustrated step-by-step descriptions on easy-to-do antennas, from shortwave to microwave.
Basically all you need to know to enjoy radio.

## Tuesday, 28 January 2014

### LNA4HF Review

Affordable, portable and works, this is a must-have for upconverter owners and shortwave listeners.

### What is it?

The LNA4HF is a low-noise amplifier (also called signal booster) for long -, medium -, and shortwave reception, amplifies signals 80 - 100 times between 0.15 MHz and 30 MHz.
It will let you hear more signals with your RTL-SDR plus Ham-It-Up setup, and can be also used for standalone receivers.

### How much?

Costs 27 USD / 20 EUR / 16 GBP including shipping, available from Adam, the manufacturer via his webpage. You pay for the item when it arrives, no shipping worries.
Contact the seller, Adam directly via email for orders: adam9a4qvwashington@yahoo.com. Remove the capital of the USA to get his real email: name (4letters) and callsign (5 characters).
Disclosure: I received my sample for free for testing. Thanks. This is the second product I receive from the manufacturer for testing, and like before, no instructions nor "please write this". Adam simply answered my emails and updated his product blog with answers to my questions.

### Size and power

Measures 25x25 mm, or one square inch. Small enough to be placed in an electrical box.
Signal connectors are SMA female.
Wide range of power options:
1) 6-12 V via supplied red and black cable.
2) 5V supply by soldering a piece of wire onto the board, so power from the the Ham-It-Up can be used. This is great for those who wish to install the LNA in an enclosure, close to the upconverter.
3) 13.8 V (car battery), place a 470 Ohm resistor in line on the red (positive) cable.

Fine tip solder and advanced soldering skills needed for 5V modification (components are the size of an ant's head), 470 Ohm resistor costs around a dollar.
I simply used six AA batteries in a cardboard tube, taped wires to batteries, and ran them to the board power supply.
After providing power to its brother, the LNA4ALL with screws, seeing chunky red and black wires
in the bubble wrap envelope was a relief.

### Low-pass filter

Interference from signals above 30 MHz (Broadcast radio etc) are reduced due to a low-pass filter at the antenna input. The bypass switch will be rendered useless on the Ham It Up - no signals above 30 MHz, shortwave only.
Tested efficiency by tuning to strongest boadcast station, gain up to 42.1 dB, LNA4HF made an audible and visible difference when inserted into the signal chain.
Disable the low pass filter and get a preamp covering 0.15 Mhz - 2000 MHz by cutting the electrical connection as per Adam's instructions, as I already bought a preamp for VHF (and hate to solder) it's not tested.
"Simple modification" is not the first expression I'd use for any modification involving soldering on this board, the 2-euro coin in the image above is slightly larger than a quarter dollar coin - SMA connectors look huge in comparison. The option is provided, which is great, but if you want a preamp for 30 plus MHz buy an LNA4ALL, that works with car batteries out of the box.

### Placement

Preamps should be placed right after the antenna for optimum performance, so electrical noise picked up by antenna cable will not be amplified any further. In theory. Daily practice is to place any preamp indoors, where I can easily provide power and won't have to worry about waterproofing.
A cheap and cheerful solution is to place the preamp and power supply in an electrical junction box, add a switch for On/Off, place the preamp right at the antenna, and turn on power when you need it. This is a tried and tested solution with a 9V battery for field trips and / or maximum performance.

### Performance

Works as advertised, signal height is 20 dB higher in SDRSharp. Audible difference.
Tested on four shortwave frequencies with an outdoor discone, same settings in SDRSharp, only removing the LNA4HF for comparison.
Beginner setup, no elaborate noise reduction measures, only a modded USB cable connecting a R820T stick, pigtails between Ham-It-Up and LNA4HF, 10 foot coax to discone. Urban location with significant FM, pager and UHF interference.

Utilizing the performance potential can be only achieved with an optimized antenna system - a proper shortwave antenna and noise reduction measures will make a huge difference.
Still, even with this VERY basic setup the improvement is clearly there.

Shortwave aficionados will love this preamp - the low pass filter reduces local interference whilst simultaneously amplifies signals.
An Icom IC-R5 (handheld wideband receiver, about 70-80 USD on eBay used) easily received the same stations used for testing the LNA with an upconvrter - why not connect the preamp to the Icom?
Connecting the preamp between the antenna and the receiver resulted in better signal quality - see video below. Same antenna and same volume settings, Band Scan.

Note 1: the shortwave receiver and antenna above is a far cry from a dedicated shortwave receiver and proper antenna, included here for comparison purposes only.
Note 2: video above with a discone, a longwire plus preamp will possibly overload and damage an Icom IC-R5, this hasn't been tested.

### If you enjoyed this article, or wish to support this blog,

... go to Amazon and buy my book Tips and tricks in the book will save time and money, reduce frustration with computer settings and help you build the best antenna system from shortwave to microwave. Detailed and illustrated step-by-step descriptions on easy-to-do antennas, from shortwave to microwave.
Basically all you need to know to enjoy radio.

## Monday, 13 January 2014

### Review: Baofeng UV-5R

... also known as Baofeng UV-5R Plus Qualette.

Review primarily for mariners, secondarily for all interested in a cheap, portable and altogether excellent walkie-talkie.

### What is it?

Handheld radio covering 137-174 MHz and 400-520 MHz, costs 55 USD / 40 EUR / 34 GBP including  external speaker microphone, USB cable and protective cover, free shipping from Hong Kong took 2 weeks to Ireland.
Transmits and receives on Marine Channels, Personal Mobile Radio, Amateur bands, Family Radio Service, GMRS, practically any analog frequency used by ordinary folks.

### Useful features

Weight 244 g / 8.62 oz with battery and protective cover, fits in your palm, size equivalent to a digital camera. Icom lists the M87E as "compact and lightweight", this is 36g lighter and about the same size.
Quality feel, first impression is "heavy, well built". Fit and finish is good, pushing buttons and rotating knob feels positive and reassuring.
Flashlight: LED on top, dedicated button for continuous light or strobe. Surprisingly strong light and usable torch, one less item to carry on duty.
FM radio: Listen to Broadcast Radio from 65 to 108 MHz. Automatically muted if incoming transmission detected.
Loud: 1000 mW audio output power. Fills a room easily.
Alarm: flashing white light, siren and automatically transmits on last selected frequency.
Display: standby / receive / transmit glows in different colours, user selectable. Alphanumeric display, so instead of 156.800 you can enter CH 16.
Dual watch, monitor two frequencies at the same time.
External speaker microphone: keep the radio in your pocket, speaker mic on shoulder. No armpit rope, no fumbling on your belt.
Power: selectable Low 1W and High 5W, independent reviews confirmed 10% less in real life, still on par with radios costing minimum 2-3 times more.
Computer programmable: via free software.
Long battery life: standby over 2 days, full charge in 4 hours. Half charge in 2 hours.
Cost: radio only 30 dollars. Dropped, overboard, destroyed - 30 dollars gone. You can even buy the old UV-5R for 20 dollars (shipped) which will be 80% identical cosmetically and offers exactly the same performance.

### Yachting use

Any scenario when you need communication with crew members, or as an emergency radio.
Man overboard: Lone helmsman in the drink has at least a chance to call for help and / or direct rescue operations. GPS capable, buoyant Marine VHF e.g. Icom M91D is over 400 dollars.
Crew ashore: lounge on the beach and listen to local tunes, monitor two frequencies at the same time, port captain calls with clearance, crew member surfaces from nightclub, crew finished provisioning in supermarket 2 miles away - you will know that you're ready to go, no need to carry expensive (or yacht property) Marine VHF or second walkie talkie.
Party time: audio ear-shatteringly loud at 1000 mW output power, previously mentioned Icom only offers 700mW. In comparison: your laptop's built-in speakers maxxed out is probably quieter than this radio.
And a lot more, small size, high power output and low cost makes for a versatile radio.

### Different versions - which one to buy

Recommended: UV-5R Plus Qualette Yellow. Easier to find in the dark and deep cupboards.
The original UV-5R, introduced few years ago revolutionized the handheld ham radio transceiver market due to low cost and usefulness; update added more interior metal, better antenna and firmware updates, most recent incarnation called the UV-5R Plus, subject of this review.
Latest models can be spotted from the antenna: taller with square top, no grooves on the bottom, superior to the original (first version) antenna.
BEWARE: Ebay sellers feature the old antenna, often showing images with the new and old antenna side by side. Confirm antenna type before ordering.
Same brain, different body: UV-5R2 loses Band button, UV-B5 has rotary channel selector instead of flashlight, larger body and worse display. "Qualette" designation means radio comes in yellow, blue, camo and
red colours. UV-5RA looks better, rounded curves, less compatible accessories.
As long as the radio features the new, improved antenna and comes with firmware 297 it is the latest version.
Whilst you're on Ebay order SMA female - SMA female barrel connectors for 1 dollar each, enables industry standard antennas and adapters to be used.

### Accessories

Radio comes with battery, battery charger, wrist strap, FBI style earpiece, and belt clip. Belt clip screws on, strong enough for all-day use. Charger and adapter takes up little luggage space, important for international travel.
Package prices will be cheaper than purchasing accessories separately, do yourself a favour and buy a USB cable for PC programming.
Digital camera cases or a phone pouch can be used as radio is tiny.
Since the radio is around for a while, large range of accessories available. None of the newer models offer this diversity of accessories.
Speaker Mic: around 10 dollars, comes with clip, functions as a speaker (listen to received audio) and as a microphone (press the button and talk into it). Standard Kenwood-style two pin connector.
USB cable: 6-10 dollars, enables programming with computer, free software available.
Rubber sleeve: 6-8 dollars, protects from scratches and bumps.
Cloning cable: Copy frequencies and settings for 5 dollars in a few seconds between two radios.
High-capacity-battery: standard is 1800 mAh, 3600 mAh for 20 dollars.
Battery case: operate with six AA batteries, 9 dollars for the privilege. As standard battery is 7.4V presumably radio works with rechargeables, I haven't tested this.
Battery eliminator: 12 V (read: standard boat or car) supply, replaces battery pack, 9 dollars. Note that the charger adapter outputs 10V DC, I cut the adapter cord and hooked up to a 13.4V battery - charged the radio fine. If you need tethered operation stay safe and spend 9 bucks, charger might overheat from extra voltage.

### Connectors

Radio comes with detachable antenna, SMA - Female
connector, looks like regular SMA connector turned inside out, signal pin inside,  rest of metal visible = ground.
SMA female barrel adapter required for regular SMA antenna connection, SMA male - BNC female for antennas featuring BNC connection.
Other adaptors (N-type shown) can be used to connect to mast-mounted antennas, as N-type connector is most often used in professional radio applications.
All antenna cables shall be 50 Ohm aka "radio coax". Ask for RG 58 cable, or LMR 240, LMR 400 for less cable loss or for long cable runs.

### Antennas and performance improvements

For normal operation stock antenna is perfectly fine.

For maximum range or better performance on VHF (Marine Channels) you must buy a longer antenna. Nagoya 771 or 773 around 10 dollars, Diamond handheld antennas 20-30 dollars. Looks like a horsewhip, 15-20" / 30-50 cm lengths. I have a Nagoya 773 on order as it's collapsible, will report back on performance.
To improve performance of any handheld antenna use the following:
Tiger tail, rat tail, counterpoise, same stuff, piece of wire connected to antenna ground: metal surrounding the center pin around the antenna socket.
Length should be 75 divided by MHz of interest, for maximum efficiency on marine channels use 20" / 50 cm length wire - if no measure available roughly three palm's length, wrist to elbow distance or shorter and longer side of regular A4 paper together.
Above 400 MHz use 7" / 17.5 cm length of wire, palm's length, safe bet.
Connect the wire to metal base, round wire connectors shown are a perfect fit. Plastic surrounding the socket needs to be cut, screw the antenna on and mark at the back of the radio first.
If using non-standard antennas, due to gap tiger tail is not flush and moves around, washers needed for a tight fit.
Tiger tail effectiveness: 50 % to 100 % improvement on both transmit and receive.

### Computer programming

Definitely order a USB cable to use free software called CHIRP, setting up the radio with Marine and PMR channels takes 10 minutes.
You will need to download USB cable driver, CHIRP, then follow the detailed guide available on the miklor site.

IMPORTANT: Fully plug in the USB connection cable, small plug to small socket and larger plug to larger socket, last few mm makes a difference, repeat: fully plug in connection cable.
You may delete or edit channel settings individually, explore Radio - Import From Stock Config options.

### Online support and resources

Sort of cult following for the UV-5R, lots of info on the web.
Factory helpline, chat and support does not exist, but any and all of your questions will be answered by subscribing to the UV-5R Yahoo Group mailing list.