Tuesday, 29 August 2017

Causes of poor radio reception

(This was posted to the SA-Scan group and is reproduced with permission)

As the 2 way radio scene is rapidly changing from analog to one of the many digital transmission
formats available and the SA GRN network will be switching to a full digital system in the near future there is going
to be new challenges in receiving good quality digital transmissions and opinions will always differ, there is sometimes no one singular fix to receive a good quality digital transmission if you are receiving corrupt transmissions in some cases.
This is a guide to possible causes to poor 2 way radio digital transmission reception and is open to many different
opinions, agreements or disagreements and may help fix reception issues you might get with digital transmissions.

The scanner or radio receiver.
The scanner is often the biggest weakness as the majority are not true narrow band receivers by 2 way radio standards.
In Australia the standard bandwidth for VHF & UHF band 2 way radio is 12.5 kHz channel bandwidth with 25 kHz still
allowed in remote locations, most digital transmissions are 10.8 kHz bandwidth with a little spare on the side.

Most scanners have a 30 kHz channel bandwidth which allows for adjacent channel bleed through, this is the most common cause for interference and affecting how well digital transmissions are decoded, now in analog we would hear that interference but as long as we can hear what is being said we tend to ignore the interfering noise, digital on the other hand if that interference is strong or noisy enough it will cause the received digital transmission
to start chopping in and out (breaking up) or not to decode it at all, there is no real fix to overcome this and the problem
is more prevalent when monitoring multi site trunking networks where there is a lot of adjacent channel transmissions,
This is also more common in large metro area's where there is a large amount of 2 way radio traffic and less problematic
in rural but can't be ruled out.

Electrical interference.
This can be caused by many different sources, from poor quality LED lighting to cheap E bay electronic goods
but even quality manufacturers can even have the odd problem product, rooftop solar systems where the manufacturer has used poor quality electronic components that give up in the grid interactive inverter and allow noise in the electrical system.
Earthing faults within the household though rare can happen and earth loop back noise will cause problems.
Most often these can be identified by a buzzing noise when listening to analog transmissions.
Sometimes the interference could be coming from a neighbours house or 2/3 away.

Motor vehicle.
Even in today's modern vehicle electrical interference still happens from alternator, ignition and electronic PWM
ventilation fan speed operation, some vehicles radiator fans are even PWM variable speed control,
poorly manufactured electronic circuits on after market HID and LED lighting is the biggest culprit.
Some alternator voltage regulators can cause noise when under heavy electrical loading.
Also earthing faults within the vehicle is another common fault.
It could also be coming from a vehicle near you while travelling.

The receiving antenna.
In the household environment the most popular type is the discone due to it's wide bandwidth of frequencies it can cover.
It has it's pro's and con's but depending on your location it can either reduce or contribute to RF interference,
this is a tricky one where there will be difference of opinions.
A dedicated frequency band antenna again has both pro's and con's like the discone but limited to the frequency band it's designed for and will perform very poorly outside of that band.
The old height is might saying, it is generally true but again if you are in a heavy RF area it can actually increase interference as the antenna becomes more exposed to RF signals from more sources.
The gain antenna, again more difference of opinions here, it can help but it can be a cause to more interference being received.
On the vehicle either an average frequency trap wide frequency band scanner antenna or a dedicated frequency band antenna not much give here but in heavy RF environments the scanner will suffer no matter what.

Handheld scanners often are provided with either a basic antenna tuned for a centre frequency that the scanner will cover from lowest to highest frequency and not work to well outside of the centre frequency, some might come with a
compromised band trap type, if you are using the scanner at an event where the frequencies you are monitoring are
centralised a frequency dependant band type antenna might be a better option.

Coax cable on a base set up.
Using the wrong cable can possibly lead to interference, also using RG58 over a long run will also cause heavy attenuation of the incoming signal thus creating a cause for poor signal strength and quality at the receiver, also use quality connectors and limit as much as possible the amount of connectors or adaptors used, this always lead to data quality issues as each connection point adds attenuation and in rare cases can be a cause for an interference point to happen.

Do you need to have a look at your existing set up, yes you may have to, what might have been OK for analog might
be an issue to receive good quality digital transmissions, this is to help there is some cases due to your location
you may have interference that you will not be able to eliminate.

There are members on this group who have vast experience in the RF field and no doubt would be willing to help,
never be afraid to ask we all started out green and inexperienced at one stage but there will be difference of opinions on some of the above.

There is most likely other points I haven't covered here but it is a starting point.
Happy Scanning.

Monday, 28 August 2017

Dick Smith Electronics Catalogue 1992

A few pages from back when Dick Smith Electronics was both still open and actually stocked radio related items. Some good memories here.

Sunday, 27 August 2017

Ben Lomond Photos

Recently we went for a day trip to Ben Lomond. Below are some photos and the details of the radio communications sites on this mountain. Ben Lomond is the second highest mountain in Tasmania.

88 MHz Seventh-day Adventist Church (Australian Union Conf.)
433.05 MHz Northern Tasmanian Amateur Radio Club Inc
438.05 MHz Northern Tasmanian Amateur Radio Club Inc
474.125 MHz Warren J Speers
476.475 MHz North East UHF Repeater Association
477.225 MHz North East UHF Repeater Association
479.325 MHz Warren J Speers
853.9125 MHz Bureau of Meteorology
929.9125 MHz Bureau of Meteorology

Thursday, 24 August 2017

Software - TGLogITx

TGLogITx is a custom database program which has been designed and coded using JustBasic. It is based on the "simple database framework" which is included with JustBasic.

This program has been developed by myself over the past few years for the purpose of logging trunking radio talk groups associated with our local EDACS trunking radio system. While it has been designed for this purpose, it can also be used for logging talk groups of any trunked radio system. With some minor changes it could also be used for logging more general radio scanning related data such as frequencies and channels.

TGLogITx is freeware and freely distributable, please note that I can accept no responsibility for how it is used and any issues it might cause on your computer as setups and configurations vary so much. TGLogITx is self contained in it's own folder and does not write any files outside it's own folder or reg keys, this means it is totally portable and will happily run off a USB key.

As my interest is logging talk groups against sites, I have the following fields.
Talk group / Name
Date / Site

To protect your loggings I have the program password protected, the password is scanning

The main screen is shown below, in this example I have a few "sample" loggings.

AFS2DEC is a small freeware program which is used for converting EDACS talk groups between AFS and decimal formats.

By default TGLogITx opens in "read only" mode, you can search / view all records but are unable to add, edit or delete.

To enable add, edit and delete, click "edit mode". This will display a warning message and then reload in edit mode. To close this, simply close TGLogITx.

Entering a new record.

Editing a record.

Deleting a record.

Searching can be done against any of the three fields, when results are shown they will also save to a report file once each record is highlighted.

Search by talk group or name.

Search by date

Search by site

Search my notes

To exit, file -> exit, or click the cross.

Download TGLogITx

Sunday, 20 August 2017

News on VK7RAA Interference from the WIA News

This is something I have heard myself, to the point that I have had to "avoid" this frequency due to to it locking up my scanner.

“We have recently been experiencing intermittent interference on the VK7RAA 2m repeater. It seems to be originating from aircraft transmissions possibly in the Devonport area or adjacent to Mt Arthur. As the originating signal is AM, when received on an FM receiver it sounds distorted.

From investigations carried out so far, it seems to be from one particular aircraft. Flights involved occur about 3 times a day to Launceston and Devonport, however, it is not always the same aircraft being used. Aircraft also may have two or three transceivers which makes the job of identifying the source even more complicated.

This interference is being investigated by several amateurs in the Launceston area.

In the meantime, please do not attempt to reply on the repeater to distorted calls which do not seem to be by amateur operators."

Tuesday, 15 August 2017

Radio Go Case - August 2017

Over the years, while involved in the radio scanning / amateur radio / ultralight DXing hobbies, I have used a number of different bags and cases for carrying my radios and associated bits and pieces. Some of these bags and cases have worked very well, others have not for various reasons.

I have again returned to my love of portable operation, this has meant finding a suitable carry case or bag for my radios to undertaken these activities in parks and other locations.
Based on my experience in the past, I decided to move away from a soft bag like I have used recently and started looking around for a hard case. This needed to be big enough to hold my Uniden UBCD436PT, aerials, chargers, USB cable and ear phones. The "lunch box" case I have been used has served me well but I wanted something stronger and with better protection.

Jaycar sell a number of ABS cases, based on the size I needed I decided on this model "ABS Instrument Case with Purge Valve MPV1". I was lucky enough to get this on special for $31.95, saving $8 off the RRP. The foam that comes with them is not great so I removed this and instead installed a divider which is wrapped in bubble warp, providing a good level of protection to my UBCD436PT. I also installed some bubble wrap in the base and used double sided tape to secure the top lid foam.

The below photos show my final setup, this works well, provides great protection to my UBCD436PT and is still small enough to travel with me in my back pack.

Friday, 11 August 2017

UBCD436PT Key Press Codes

CHAN MOD + 1 = LCD / Keypress test
CHAN MOD + 2 = LCD Contrast Adjustment
CHAN MOD + 4 = Tone Out Test
CHAN MOD + 9 = Clock Reset
SYSTEM + 1 = Close Call Test (Knob controls band)
SYSTEM + 2 = USB Serial Test
SYSTEM + 4 = Load Test Data 144MHz
SYSTEM + 5 = LCD Brightness
SYSTEM + 6 = Load Test Data 163MHz
SYSTEM + 7 = Trunking Test
SYSTEM + 9 = Load Scan Test Data

Tuesday, 1 August 2017

Upper Burnie Lookout

Braddons Lookout

Today I was down the North West for work. On the way I stopped at Braddons Lookout to see how many EDACS control channels I could hear. Below is the list, this would have to be close to the most you could hear from any location.

865.1125 = Transend Site COMPANION HILL TAS 7321
865.1625 = Wynyard Transport Site TABLE CAPE TAS 7325
865.1875 = Ericsson Site GARDNERS RIDGE TAS 7304
865.2125 = Radio Terminal KELLYS LOOKOUT TAS 7303
865.2375 = Hydro Electric Commission Site KELCEY TIER TAS 7310
865.2875 = Air Services Australia Tower MT BARROW TAS 7259
865.4625 = Vodafone Site Off White Hills Road SULLOCKS HILL TAS 7316
865.4875 = Telstra/Ericsson Site MONTUMANA TAS 7321
865.5125 = Council Community Site ROUND HILL TAS 7320
865.7625 = HECT Site MT CLAUDE TAS 7306
865.8375 = Weather Radar Site WEST TAKONE TAS 7325