Wednesday, 24 April 2013

A.M. CB Days

During the height of cb popularity in the late 70's, I bought my first genuine cb radio. I had a Realistic 2 watt 3 channel walkie talkie, but in 1978 at 14 years of age I became a bona fide AM good budgie. I had been saving my paper round and pamphlet delivery money, and headed to Just CB in Mitcham (suburb of Melbourne) to purchase my first set up. The choice of cheap AM sets was endless in those days, and could be bought almost anywhere, but I decided on a cb shop to spend my money at. The Old Man was with me and he was talking to the salesman when a radio caught my eye. It was a Fanon Fanfare 182 with 18 channels on the dial, and the American channel equivalent on the inside of the Australian 18. What impressed me was the large meter, which the others didn't have, and a variable rf gain, again this feature was not on the other cheap radios. A quick run down from the salesman and I bought it, along with an Arlec power supply, coax and half wave Ringo antenna. I was a few dollars short, and my Dad put in the rest. My Dad also paid for a length of pipe and eave bracket from the local hardware to mount the antenna, and the pipe was delivered the following day.
After setting up the antenna and running the coax through the roof, with my Dad's help, I keyed up for the first time. My neighbor who lived behind us, and was a SSB cb'er, came down to AM to see where this new splatter was coming from. He soon arrived at my front door with a SWR meter and patch lead to tune the Ringo, and I was very happy for his help. Didn't help the splatter, but we both were affected the same, and had to live with it. Before long two more of my school mates had bought cb set ups that lived very close and the splatter was terrible. My poor neighbor who helped me ended up mounting his cb in his car, and was a little annoyed at us AM good budgies, but that was life on the crowded band.
They were great days and great memories. I made some new friends and spent hours on the radio after school. It was the following year that I traded in the AM for a SSB rig, more on that next time. 
Mick 361

Monday, 22 April 2013

DReaM and Journaline

One of the functions of the excellent free DRM program DReaM (besides digital audio) is its ability to receive Journaline - a digital service ( in this case provided by the Bureau of Meteorology ) containing weather warnings and in the example below, earthquake information for our region. In Australia, the frequency is 5954 kHz.
To begin with, HDSDR sees the DRM like this:

The initial DReaM page

The second page showing active link

The third showing a list of earthquakes

The fourth showing details of the New Britain link

 Not bad for a free program. I'm very greatful to those who take the time and make the effort to produce such a great program.

Budget RF amplifier

What do you do when you need to give that weak signal (or in this case all weak signals) a boost and want to spend no money? Well in my case, i had a handful of components, no circuit board and not much solder. I flicked through some of my old books and came across an easy design that would suit perfectly. I drew this diagram using an online designer, so its not perfect, but you get the idea.

 Component list: RESISTORS :  1 x 1.2k, 1 x 47k  CAPACITORS: 1 x 10pf  ceramic, 1 x .001uf  ceramic  DIODE: 1N4002  TRANSISTOR: NPN DS548, SWITCH x 1, BATTERY CLIP x 1 and 9V BATTERY x 1.

 The components were scavenged and i had just enough solder to roughly attach "legs" to them. They are then connected and mounted on a wood base via the same method i used as a child...screws and washers! The end result is not pretty, but signal increase from the multiband and pre-selector is fantastic.

RF amplifier working with the pre-selector

Saturday, 20 April 2013

Base Station 27mhz


This is my home CB set up. A Cobra 142GTL-A, matched with a Turner +3B desk mic, real old school stuff. The Cobra was a cheap pick up for me last year, and works surprisingly well for a 35 year old radio. It's has nice clear receive and all reports on TX are good. It's on frequency and very stable with no warm up required. The only minor issue was the meter lights were not working, so I bought some blue LED's and put them behind the meters. The Turner mic cost me more than the radio, but a good investment and I get great audio reports with it. There are some Cobra 142's brought in from the USA that aren't 240 volt, so worth checking if your considering to purchase one. The 'A' in 142GTL-A shows it to be a unit designed for Australia and have a 240 volt transformer. They can also run on 12 volts and have a standard 3 pin jack on the back. Nice radio and really enjoy using it.
Mick 361.

Friday, 19 April 2013

Utility Monitoring and Decoding

Let me start by stating that i love decoding and utility monitoring. Whether it's chasing numbers stations (of which there are many, considering we live in the age of texting, emails and mobile phones), or decoding something simple like RTTY or Global Wireless or more complex like the STANAG variants. Also on my list fun things are WEFAX, SITOR and the amateur digital modes.

My hardware was basic in the beginning: the small but robust DEGEN 1103. A great little perfomer for a small price. But it wasn't long before i realised that i needed a more substantial receiver to cater to my growing needs.
DEGEN 1103

I had looked around for a while, trying to decide which radio i was going to invest in next. Not suprisingly, many of the shortwave radios that are intended for the serious listener were around the $1000+ mark. Even used radios were $500 - $700. Way too much to even consider. I discussed the matter with a mate, who asked if i had considered Software Defined Radio? "No" i said (having both feet planted firmly in the 20th century). Much Googling and many reviews later, i dragged myself kicking and screaming into the 21st century. Enter the SOFT66LC4. This is my current radio and it's a beauty. Apart from the EXT I/O issue that is now common knowledge amongst SDR users, it is on a par with SDRs 3 or 4 times its price.
The tiny SOFT66LC4

HDSDR locked onto STANAG 4285
It is used in conjunction with Winradio HDSDR and programs such as MultiPSK, FLdigi, DREAM, PC-HFDL and decoding software software such as Ian Wraiths excellent program RIVET. More articles featuring these programs and modes to follow.

Project 5 : N4UJW Multiband longwire

I found this antenna some years ago and i always wanted to have a crack at building it once i had the time and materials. The design i followed is by N4UJW and can be found here :
The original design required speaker line or even fencing wire as options. I went for plastic coated clothes line wire as i needed something more durable that would stand up to the winds we get here. So, 140 metres of line divided thus: 1st element: 43.891 meters (90 and 31 M bands), 2nd element: 36.149 meters (75 and 25 M bands), 3rd element: 28.011 meters (60 and 19 M bands) and 4th element: 24.171 meters (49 and 16 M bands).
original design
The mounting was fairly straight forward with the exception of the insulators/spacers that i just could not get to function correctly. As stated in the image, the premiss is that each element will support the one above. In practice, no matter what material i made them from (including bamboo), they offered no support. In the end i reverted to tying each element individually to the support mast.
Mounted on the mast, showing the co-ax/element harness

I have been testing this antenna for a couple of days now and it beats my old faithful longwire hands down. It is used in conjunction with my homebrew pre-selector (see previous project) and a 9 volt, single transistor RF signal booster circuit i built. This antenna is perfect for the utility monitoring and signal decoding i do with my SDR and programs. Build time was a couple of days.....on and off.

Tuesday, 16 April 2013

2 Element V-Quad for 27mhz


This is my first article, and I am a keen 27 mhz CB operator. I started out in the 70's during CB's most popular time, when it was legalized. While absent from the scene for many years with family life, I've been back into it for a few years now and really enjoying it. There is something about the 11m band that brings operators back, and brings in new operators for the first time. It's low cost and simplicity could be a factor, and also it's lack of pretense. Doesn't matter what equipment or experience you have, someone will always say G'day and have a chat with you. There are a few clowns out there like anywhere in life, but most just enjoy the hobby. My call is 361, or BSB361, as I'm a member of the Bendigo Sideband Club.
To the subject. I was looking for a beam antenna a couple of years back, as I enjoy DXing or chasing skip. There isn't much else, as local operators are thin on the ground. My needs included a tight budget, limited space and a low mounting position. After looking at a 3 element yagi, I decided that wasn't an option due to space and the need to have it at an elevated position to maximise it's potential. I then looked at a cubical quad, but again mounting would be a problem for me because of the height needed. The boom is central in the antenna and a high supported mast or tower would be required. Then I hit pay dirt, the V-Quad or Delta Loop. It has the boom at the base of the antenna, perfect for my low mounting requirements. It's low angle of radiation makes it ideal for this type of install, whereas a yagi needs height to perform at the same level. After looking into it, and costing, I decided on a 2 element V-Quad made by Shockwave Antennas in Melbourne. The price was right, and construction is very robust.
After picking up the antenna and getting it home, I quickly put it together, very easy and made sure the metallic jointing paste was used for conductivity and corrosion prevention. I bolted it to the pole and clamped it to my pergola. Connected coax and excitedly checked SWR, which was 1.3, good enough. Radio check, and working beautifully. Rotating the antenna is easy, via the armstrong method, and the noise level was very low compared to my vertical. Signal strength is about 2 'S' points higher compared to the vertical, and similar on transmit. Couldn't be happier with the 'V' performance.
SWR is easy to adjust, via the gamma match. I had to adjust SWR after a big storm passed through here, which caused some damage around the area. A tree in my backyard broke in half and had blown onto my garage roof, making a large hole through the tin roof. My vertical bent like a banana, but didn't snap thankfully. The 'V' looked in perfect condition, no bends or breaks, but I was worried watching it in the wind. Checking the SWR the next morning and it was at 3, which confused me a bit because it was still in the correct shape after the storm. Thinking about this for a while, I figured the only possible way the SWR had changed is by the gamma match moving. I adjusted the gamma match out and SWR dropped to 1.5.  Bingo, I found the cause of high SWR. The flexing and bending of the driven element in the storm had caused the gamma to close about an inch. Another adjustment and the SWR was flat, no movement on the meter at all. The first time ever I've had an antenna achieve this, I was very happy. I will note also that Pete from Shockwave Antennas advised against sealing the gamma with silicone, and said vaseline is better because it waterproofs and allows for future adjustment. Great advice which I followed.
I've had countless contacts on the CB with the V-Quad, and rarely use the vertical these days. Being only 2 element, it has a good range of coverage to the front, I would say 120 degrees is about right. Though for weak signals a better directional adjustment is needed to boost the signal. By and large, if skip is running into Victoria, I can point it NE and get Eastern Australia, New Zealand, Hawaii and mainland USA without needing to move the antenna. If channels 35 and 38 are clogged with overseas and local skip, a flick to the official call channel, 16, can bring surprising results as quite a few still operate there. Also many Pacific Islands use 30-33usb, so always worth checking.  I have read recently there are some trying to push 27.255usb as an international call frequency, as opposed to the 27.555 which is outside the Australian, and most countries, legal operating band. I encourage operators to support 27.255usb, or channel 23, to avoid crossing paths with the ACMA and staying within the legal band.
Enjoy the hobby and good DXing,
Mick 361.   

27MHz Author

A big welcome to our new author mick! Who will be looking after our 27MHz section. Welcome mate!