Considering 23cm Operation?

The 23cm band is the lowest in the spectrum of microwave bands available to the Amateur Radio operator. With the advent of the new transceivers, it is now possible to make inroads to this band with little difficulty. The power levels of 10 watts are suffient to drive linear amplifiers and more than enough for point-to-point QSOs with reasonable antennas.

The 23cm band is popular for Moon bounce, ATV and Satellite operation and proves an interesting challenge for point-to-point communication.

Unlike the 2m and 70cm bands, it is not enough to put up a vertical colinear and expect miracles on this band. Yagi antennas from 28 element (15.4 dBd gain) to 67 element (19.9 dBd gain) versions are effective and affordable. Because of the short wavelength of the 23cm band, it is possible to produce an antenna with a greater number of elements for and hence a larger gain for a given boom length.

A 23cm Yagi with 70 elements

There are a number of transceivers available with the most recent being the ICOM IC-9700 capable of 2m, 70cm and 23cm. The Kenwood TS2000X was popular and also the ICOM 9100. 

ICOM IC-9700

An alternative to a dedicated transceiver would be a transverter from 28 to 1296Mhz or from 144 to 1296 MHZ.  In many cases it is practical to locate such devices just below the antenna to reduce feeder losses. Transverters are available from SG Labs, Kuhne Electronis and Downeast Microwave. 

SG Labs 23Cm Transverter

DownEast Microwave Transverter with 50W Linear AMP

The Down East Microwave Transverter above is driven by an FT 817 on 28 MHz. Up to 50 Watts output on 1296 MHz

There is no harm in considering a mast-head receive preamp to overcome any signal loss in the coax although it is possible to conduct most portable activities without one.

It is essential that low-loss coax feeder is used for 23cm operation RG 213 is totally out of the question.

Modes of Operation

Obviously SSB, CW and weak signal modes are of major interest as one is seeking DX contacts. Digital Voice Modes will give some stunning results and are worth trying if you are using the ICOM 9700. Experiments were performed with this system using D-Star between two locations with low power on 1296.200MHz and signals just above the noise level. The results were surprising. The signal sounded like a fully queting FM signal coming in at a strength 9.

Propagation on 23cms

It is necessary to have some comprehension of Microwave techniques and the propagation of signals on the 23cm band. 23cms is not confined to line of sight activity and may derive benefit from tropospheric lift conditions due to high pressure weather fronts. During extreme tropospheric ducting, signals may travel further than on VHF. Those living on or near coastal areas may find that some very stable ducts form above the sea alowing considerable distances to be worked. Rapid fading may also be experience in much the same way as experienced on 70 cms.

Tropospheric Ducting

Enhanced conditions will be less frequent on 23cms than on VHF or UHF. The best way to check would be to set the beam towards a known beacon or even a 23cm Repeater where the signal maybe referenced over time.

Hepburn Tropo prediction maps, weather maps and the VHF/UHK DX spot maps can be useful tools. It is worth announcing any trip to a hilltop via a social media channel.

Hepburn Index Tropo Map showing really excellent tropo conditions along the coast of Western Atrica

 Record Breaking contact between EI2FG and EA8CXN via Enhanced Tropospheric Ducting (Photo EI7GL)

Point-to-point communication is possible from high locations, and it will be necessary to have some map reading and compass skills. The beamwidths of 23cm yagi antennas are narrow and, if off by a couple of degrees over a long path, the desired station may be missed. It is worth announcing any trip to hilltops on the ON4KST chat or via the VHF, UHF, SHF Facebook pages.

Tropospheric scattering can occur from pockets of turbulent moist air and are characterised by a rough sounding signal. SSB and CW would be the choice of mode for this type of propagation. Another form of propagation is reflection from objects such as barns, grain silos, aircraft or even passing ships.

Aircraft scatter is one very effective mode of propagation. It is possible to track aircraft and take advantage of reflection from an aircraft traveling a given path adjacent to the two stations. Often this can result is some reasonable signal strengths which suddenly appear and last for a minute or two before they diminish. Such paths of aircraft can be tracked using the program “Airscout” by DL2ALF. Not too long ago, we had an interesting lecture on Aircraft Scatter with audio visual demonstrations, by Anreas Imse, DJ5AR.

 Showing reception of a Beacon over distance via Aircraft Scatter

Reflections from objects or structures, such as a barns or grain silos, can often result in an enhanced and unexpected path especially if operating at lower elevations. 

In one instance it was possible to reflect a signal from a passing cruiser resulting in a contact between two Spanish Stations who would not normally be in a line of sight advantage.

23cm signal Reflected from a passing Cruise Ship (Photo EI7GL)

There is much scope for experimentation on the 23cm band using different antennas, power levels, and portable locations. Provided you have a number of local operators to assist and give reports it will pave the way for DX operation at later stage. Even a small 2-watt transverter with a good antenna system will suffice and provide some excellent results into a 56 element beam. We are fortunate that there are at least eight operators capable of running equipment on 23cms in the Galway and Mayo areas. If you have the equipment contact the Galway VHF Group or Mayo VHF Group.

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EI4GCG Galway Allstar Gateway

Galway 4 Metre Allstar Gateway Parameters

Frequency .................................... 70.425 MHz        

CTCSS Encode and Decode ....... 77Hz 

Power Output .............................. 20 Watts  

Antenna ...................................... 1/2 wave vertical

AllstarLink is a worldwide network of Repeaters, Remote Gateways and Personal Hotspots linked together via the internet and/or private IP networks. AllstarLink can run on a dedicated Linux computer or Raspberry Pi hosted at home or a remote site. Allstar is open source GPL software free for anyone to use.

Allstar Link has become popular on a worldwide basis and yet only one station existed in the Republic of Ireland with a further four located in Northern Ireland. The UK is well populated with Allstar Nodes and many are connected to the Supernode, UK HUBNET, which, in turn, connects many Repeaters and Gateways throughout the UK.

The quality of audio from the Allstar system is excellent and it is a user friendly system without too many commands.

Worldwide Distribution of Allstar nodes

There is a good distribution of Allstar Nodes around the world so a contact is always possible

There is a wide distribution of Allstar Nodes in the UK, however, very little in Ireland. The Galway Node only recently went on the air.

One excellent feature is the Bubble Connection map showing the node with all of its connections.

As illustrated there is a huge number of connections to the UK HUBNET node which is shown by the blue shaded bubble in the centre of the diagram. No excuses for no QSO after a call into this system.
 

The Galway 4 metre Allstar Gateway 

The Galway 4 Metre Allstar Node was easy to build using a M0AQC modified CM108 fob fitted into a plastic case. This connects, via a USB lead to the Raspberry Pi. A second lead connects to the radio bringing audio levels to and from the radio plus the PTT line and Carrier sense.

The TX Audio, RX Audio, COS, and PTT lines are brough out to a 15 pin accessory plug for connection into a Tait radio.

 

A Low Band Tait TM8110 was programmed for use on the Gateway. The radio was easy enough to program for one channel only with CTCSS Decode and Encode tones, power level of 20 watts and the various outputs and inputs from the accessory pins.

It is important to organise a cooling fan for the radio. The heatsink does get quite warm with a heavy duty cycle. Unfortunately radio amateurs do waffle on a bit!

The Asterisk Program, the controlling software, can be downloaded from the Ham VIOP Webpage where all the instructions for setting it up are included. 

Setting it up was not easy but if one follows the instructions from Ben Topham, G5REV, it is a good starting point. In this YouTube Video one will be 99% of the way to completion. Allstar Set Up The only other stumbling block is the set up of the Internet Router.

This is the completed set up which needs to be in a small rack with a coooling fan to force air across the heatsink. 

Prior to building the 4 Metre Allstar Node, a 70 Cm Personal Node was acquired from M0AQC, mainly to find out what activity can be found on  Allstar.

The only difference between the Allstar 4 metre Gateway was that a 70cm Baofeng 888S was modified to output a few milliwatts from the Driver Stage with the PA stage removed. This will give a good range around the home QTH. The Raspberry Pi was configured almost exactly the same way as for the Gateway. I used DCS Squelch on this systems as I was getting spurious transmission using CTCSS. This was courting some snotty remarks from the users of HUBNET and quite rightly so.

Ben Topham, 2E0BMT/G5REV, produces a complete kit of parts to build a 70cm Allstar personal Node. He also produced a 6 part YouTube video series showing a step by step build.

A picture of the completed G5REV kit

In this kit, one has to modify the CM108 fob and bring out leads for the Audio in and Audio out, PTT, and Carrier sense (COS). The Baofeng CM 888-S is stripped down and modified for low power use. Subsequent videos in the video series will cover the software set up and parameters to be set up in the Router.

Allstar Commands

 Mandatory Commands

*1 Disconnet from Link

*2 Connect to Node in RX Mode only

*3 Connect To Node in Transceiver mode

*4 Command Mode of Controlling node

 Optional Command codes

*80 Forces system ID

*81 Say System Time

*980 Say app_rpt Software version

*75 Link connect (Local Monitor only)

*72 Last Active node (System-wide)

* 71 Disconnect All links (Macro)

*74 Reconnect all links (Macro)

Note to connect to a node Always - *3##### where ##### is the node number to connect to

To Disconnect from a node Always - *1##### where ##### is the node number to disconnect from

Once one has successfully set up the parameters and software there is very little to operating Allstar. The audio quality is excellent although some operators do tend to over or under drive their audio levels. Make sure you have yours set right! This system is more active than EchoLink. It is possible to add Echolink to the software but it would be a retrograde step

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Activating the 4 Metre Band

The Four metre band was always referred to as the "Gentleman's Band" due to the relatively small community of operators who were on first name terms with one another. These were real radio hams as they either built their own equipment or modified existing ex commercial equipment. During VHF NFD, the norm was to work all the stations in CW during the first half of the contest and then in voice for the second half.

Until recently the Four metre band was not hugely popular in Ireland mainly because there were very few commercial black boxes and it was "just another VHF Band". For the more serious and dedicated operators, there was the option of a transverter, allowing SSB and FM operation, and, for general use, many would delve into the innards of Low Band ex-commercial equpment and align it onto the Four metre band. Some resourceful operators converted existing Six metre equipment for use on Four metre band, whilst many others designed and built their own transceivers. Twiddling with radios on the bench is primarily what we do, as radio amateurs, because it is part of the hobby and is cost effective. 

Many operators from the 60s - 70s would have modified the old Pye Cambridge AM version although it did come in an FM version also. The Pye Cambridge would have been in use by the Police and Taxi Services. They had a great receive audio and were reasonably sensitive.

Many Commercial radios such as Pye, Tait, Motorola, Maxon, Kyodo, Cleartone, Ascom, Simoco, and Philips, to name but a few, were ideal for conversion. 

Two old favourites - Top ASCOM SE-550 and bottom the Philips FM-1000

 

In the last few years, more and more countries have allowed operation on the Four metre band although the actual band allocation varies in some countries. As a result of this, the amateur radio manufacturers have offered radios which include the Four metre band. Anytone, Wouxun and Retevis have produced some dedicated Four metre transceivers which perform admirably on the band.

 

Retevis have recently introduced the RT9000D to the market and several YouTube videos have given it good reviews. Recently, three operators in the West of Ireland purchased the RT 90000D and there have been others on the IRTS Facebook page who took an interest.

 

Some countries do not have the Four metre allocation but will operate cross band from 6 metres and receive on 4 metres.

The ICOM 7100 was probably the first transceiver to offer 4 metre operation as standard. They have more recently included Four metres in their ICOM 7300 and the ICOM 9700. There is an added bonus of D-Star in the ICOM range. Subsequent ICOM models included Four metres. Nowadays, Yaesu have included the 4 metre band in their newer models. Obviously SSB and CW operation will give excellent results.

The Irish allocation for Four metres is 69.9 - 70.500 MHz although ComReg opened up a huge chunk of spectrum of which there is a band from 54 - 69.9 MHz. Many of the dedicated Four metre transceivers will cover from 66 - 70.500 MHz.  The segment from 66 - 69.9 MHz is permitted as a result of the recent allocation by ComReg.

The Propagation characteristics of the Four metre band make mobile operation more interesting as the distance covered is generally superior to Two metres. Auroral, Sporadic E and Tropospheric Propagation often result in some vast DX openings. Sometimes a DX station will appear on the operating channel out of the blue.

Normally Sporadic E season is noticeable from the end of April until the end of August. Recently there have been strong openings around 9 am Local time. Moving into the Summer Sporadic E is most noticeable around 5pm. 

One of the most reliable tools for establishing Ionospheric Conditions in the Ionogram. The Chilton Ionogram can be accessed from >> Here<<.

 

A good indication of a Sporadic E opening is shown in the Ionogram above. A dense area of Ionisation at approximately 100 Km above the Earth's surface is a good indicator that there will be exceptional conditions from the 10 metres - 4 metres.

Consulting DXmaps.com >>Here<< will show the the MUF over the European area. A typical opening from this site is illustrated below.

 

 

The squares are colour coded: the Green squares show propagation from 30 - 50 MHz, the lighter green from 50 - 70 MHz, the Yellow from 70 - 90 MHz, the Orange from 90 - 110 MHz, the darker Orange from 110 - 130 MHz and a Red colour from 130 - 150 MHz.

Another display can be obtained from >>Here<< which plots uploaded logged contacts between stations giving a good representation of activity. 

As illustrated, Sporadic E can produce some excellent results. By selecting different tabs, contact paths may be shown for 10, 8, 6, 4, 2 metres and 70cms. Forget those silly Ham Prop programs as the Ionogram and DxMaps is by far the best indicator for serious VHF operators. 

Many years ago Dick Madigan, EI9Q from Waterford, used to be heard in South East London as regular as clockwork around 7 pm on Four metres CW. This was due to the SPoradic E openings at that time of the evening. Remember the Spanish TV interference on RTE1 (Band 1 TV)

Four Metres will produce good DX via tropospheric propagation. Aircraft scatter is particularly noticeable on this band with sharp rise and falls of signal strength. My home QTH in the UK was on the flight path into Heathrow so this was noticeable almost every day. 

The Four metre band shares many characteristics with the neighbouring Six metre band. However, as it is somewhat higher in frequency it does not display the same propagation mechanisms via the F2 ionosphere layer normally seen at HF which occasionally appear in Six meters, leastwise not at temperate latitudes. However, Sporadic E is common on the band in summer, tropospheric propagation is marginally more successful than on the Six meter band, and propagation via the Aurora Borealis and meteor scatter is highly effective.While Sporadic E permits Europe wide communication, it can be a mixed blessing as the band is still used for wide bandwidth, high power FM broadcasting on the OIRT FM band in a declining number of Eastern European countries. Although this has lessened in recent years, it can still cause considerable interference to both local and long distance (DX) operation.

Antennas

A quarter wave antenna for this band is approximately 108 cms long which is a convenient size for mobile operation. Most amateur radio retailers now stock Four metre band mobile antennas, however a homebrew version should be easy to make. For base station use, a variety of beams and verticals are also available from retailers, but once again, a homebrew beam or vertical should prove easy to construct and even easier on the wallet.  

Consider making a Halfwave Vertical or a Slim Jim Antenna which will only cost a few Euro to make and will give as good a result as any of the commercially made verticals.

Local Operations

Tests were conducted on many bands, by members of the Galway VHF group, especially in Connemara which has a very rugged and mountainous terrain. Bands from 70cms to 10 metres were included. Surprisingly, as VHF Bands go, the Four metre band actually gave the best signals over distances. 4 metres managed to circumvent many obstacles. It was concluded that the 4 metre band would always give better results whilst mobile in most areas. Tests over a given path from Salthill (3m Above Sea level) to Headford found a greater signal strength for a given power level over a fixed path on Four metres vs Two metres. Not surprising really, as the wavelength is longer than Two metres. From Salthill, there appeared to be a slight “flutter” noticeable on the signal. After much thought and ruling out the presence of aircraft in the area, it was decided that this may be due to reflections from the traffic on the M6 motorway. 

In conclusion, the Four metre band is likely to give surprising results due to the unpredictable nature of the Sporadic E opening. Some interesting results can be obtained via Tropospheric propagation. One instance often quoted was a cold frosty morning with a light mist at ground level. One operator maintained a QSO with another in Ballyhaunis whilst driving from Castlebar, Co Mayo to Shannon Airport.  

With the availability of more transceivers which include Four metres, it is certain that he level of activity will increase.  Put out an occasional call on 70.450 and 70.2625. These are both calling channels so please QSY once the contact is established and do try not to hold nets on recognised Calling Channels. Park the car on a high location and put out a call - you will not be disappointed as the Four metre community is growing.

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