Military Communications - From concept to battlefield requirements

By Michael O.Beirne G8MOB

This excellent and comprehensive presentation explored the aims and objectives of military communications, the hierarchy of army command, the different corps, what they do and what sort of communications they need. Also the often-conflicting requirements of speed, security, operational range, HF, VHF and UHF coverage and the physical/environmental requirements of the radios. In addition we were treated to asides and comments from The Crimea War, and the Inns of Court Regiment and its history dating back to the late 16^th century.



The presentation was supported by a selection of radios that Michael had brought along. These included receivers, transceivers and panoramic displays, many of which are included in the following list.


G8MOB’s NOTES ON EQUIPMENT DISPLAYED

HF Receiving

Racal RA3701




Quite extensively used by the military for monitoring and point-to-point links with data systems eg Piccolo. Fully modular with numerous options.

Coverage: 15 kHz to 30 MHz.
Modes: AM, CW, USB, LSB and NBFM, [options for ISB and FSK].
IFs: 41.4 MHz and 1.4 MHz.
IP3: At 20 kHz spacings, +33dBm RF amp out and +25 RF amp in.
1st mixer is a Rafuse type switching quad FETs. 2nd is an IC.
Image and IF rejection better than 90dB (better in fact).
IF Filters: 6, 3, 2.7 U & L SSB, 1kHz and 300Hz. Options for more.

Can be remotely controlled by computer or external Racal controller unit.
One version has two receivers built in (RA3712) and is used in diversity data systems.
Various Racal-Dana frequency standards can be fitted or input from an external source (eg Rb).
Now superseded by the identically looking RA3791 with extensive DSP.

STC STR 8282

Covers 150 kHz to 40 MHz.
IFs: 70.050 MHz and 50 kHz (DSP at 50 kHz).
Modes: AM, CW, USB, LSB, ISB and NBFM.
Measured IP3 at 20 kHz spacing: +23dBm approx.
Measured Ist IF and image rejection: over 100dB.
Measured 2nd image rejection: approx 116dB.
13 bandwidths from 300Hz to 15 kHz.

IF selectivity is excellent. Some specs:

Mode -3dB kHz -100dB kHz
SSB 2.7 4.5 max
CW 0.3 1.5 max
AM/ISB 6 10.0 max
FM 15 25 max

Ultimate IF stop band is > 100dB in all cases. Exceptionally low differential phase distortion in the filters giving a true linear phase response (v important for fast data).

An early DSP receiver (1990s). ADC chip sourced from Tektronics. Very complicated DSP done the hard way.
1st mixer is a Rafuse switched DB quad FET (IC is a Siliconix Si8901Y)
2nd mixer is a most complicated image rejection design using two Si8901Y ICs followed by a complex polyphase network.

Usual provision for computer control and external frequency reference.
DSP output options: In phase and quadrature filtered baseband signals.

However don’t try to find one. Only about 150 – 200 made before STC taken over by Nortel and production stopped to make way for building phone systems. Additionally, there are reliability problems and spares are impossible to source. The fan noise will drive you mad in a quiet room. Most were taken by the “Government listeners”.

HF Transceiver

Philips / MEL PRC 2000

A nifty transceiver of the 1980s using Weaver’s third method of generating SSB. Covers 1.6 to 30 MHz. 20W PEP output. Built in auto ATU and a separate dipole outlet. Has effective voice compression/clipping. Runs off a 15V NiCad.

Can be fitted into vehicles with a mounting tray and external power source.

Not bought much by HMG (since we already had Clansman) but many sales abroad to third world countries.

Has a matching linear amp and auto ATU.

MEL SURF (“Selector Unit RF”)

Used with Clansman VRC321 HF SSB vehicular transceiver as a passive pre and post selector when two 321s have to be used in the same vehicle [eg at a HQ for a squadron/combat team net and the QM’s resupply net].

Spec when fitted to each VRC321:
“Less than 3dB reduction in S/N ratio with a 40W HF transmitter 15% off frequency in the same vehicle with 2 metres antenna separation”. [Ie a whip either side of eg a LandRover].

Approx 0.75dB loss on transmit and receive.


VHF receiving

Nems-Clarke 1303

1960s vintage, all valved. 24 valves.
Tunes 55 to 260 MHz in a single band using the American-made Mallory “Inductuner”
Modes AM and FM
F/E valve is a tiny ceramic planar triode for minimum noise. Measured the average noise figure at about 3.8dB. This compares with the latest Watkins-Johnson 8611 with a spec of 7 to 11dB. Front end module is of silver-plated brass. Each bandwidth has its own IF strip.

Separate meters for signal strength and centre tuning. (These are expensive products made by Honeywell)

Gives exceptionally low demodulated distortion. Had great difficulty in measuring the distortion on WB – well below 1% THD.

Used extensively by US Govt agencies, particularly NASA for telemetry for the Mercury and Apollo missions.
Factory price: $2,700 in 1963.
Several other versions made, some with two tuners fitted.
Has an optional add on panoramic adaptor but is exceptionally rare.


Norlin SR209-C EW receiver

Transistorised receiver of the late 1960s/1970s used primarily by US Govt bodies. Used in USN submarines.
Separate plug-in tuners cover 30 MHz to 12 GHz (I have four which cover 30 MHz to 1,000 MHz). Frequency display on a long film scale.

Modes: AM, CW, NBFM and WBFM
Many choices of bandwith from 10 kHz to 4 MHz; each comes on a PCB containing the entire IF strip and demodulator.

Separate meters for signal strength and centre zero tuning.

Modules for panoramic display and a digital display with DAFC (a “huff & puff” system).
Very similar to the WJ8730 series (using v similar plug-in tuners and the same Mallory Inductuner). Both factories in Gaithersburg, Maryland, not far from Washington DC.


Racal MA2313E Panoramic Display



Input: 21.4 MHz.
Display span from 100 kHz to 3 MHz.
Can switch IF inputs and audio from 2 receivers.
Matches the Racal RA1795 receiver (20 to 1,000 MHz) but will match any receiver with a panoramic output (ie prior the main IF filtering) of 21.4 MHz.


Eddystone 1061A/1 Panoramic Display

Inputs: 1.4 MHz and 100 kHz (switched internally)
Display Span: 1.5 kHz to 15 kHz
RBWs: 50, 100, 250 and 500 Hz.

Switchable log or lin display with up to 40dB switched attenuation to expand the screen log display range of 40dB. Made in the 1980s and 90s but dated now.
***
It is simply not possible to do justice to Michael’s fascinating presentation, which by any standards covered an extremely wide selection of pretty specialist equipment, and we are very much indebted to him for providing such an unusually interesting and entertaining evening.

John Longhurst G3VLH

NE602 History

This short history of the famous NE602 chip posted on soldersmoke:

http://soldersmoke.blogspot.com/2009/06/na5n-on-ne602.html?showComment=1263270417170#c2188916935597814880

Stewart/G3YSX

Meeting Cancelled Wed 13th January

Having taken soundings about conditions near the club I think that we should be prudent and cancel the club meeting again tomorrow night.

I am told there will be a thaw over the weekend, so hopefully things will be back to normal on Sunday, but we will issue an update nearer the time.

I suggest that we meet up on GB3WS again tomorrow night (Wed 13th) at 2030GMT.

73

Stewart/G3YSX

G3NZP's Snowy Antennas

Here are some more pictures of snowy antennas, this time from Malcolm (G3NZP). The first is his HQ-1 mini beam and 2 metre SSB Yagi the day after the heavy snow fall.



This second picture is his HF 160 metre Carolina Windom which was in a similar state but later snapped under sheer weight of ice.



If anyone else has any seasonally interesting antenna pictures that they think CARC members would enjoy seeing, then please send then to me, and I will load them onto the blog.

Stewart/G3YSX

Harwell Rally

Sunday 14th February 2010

HARWELL AMATEUR RADIO SOCIETY are holding a Radio and Electronics Rally at Didcot Leisure Centre, Mereland Road, Didcot, from 10.30am-3.30pm. There will be radio, electronics and computing trade stalls, secondhand stalls, Special Interest Groups displays etc. Refreshments will be available all day. Entry £2.00 (children under 14 free). Details from Ann on 01235 816379 or see www.g3pia.org.uk

South Essex Amateur Radio Society's 25th Annual Radio Rally

South Essex Amateur Radio Society's 25th Annual Radio Rally will be held on Sunday 7th February 2010, at the Paddocks Community Centre, Long Road, Canvey Island, SS8 0JA.

This venue is at the southern end of the A130. Look for a mini roundabout on Long Road at the entrance to the Paddocks access road. There is plenty of free parking and wheelchair access. Doors open at 10.30am. Entrance fee is £2.00.

Bob's Snack Bar will be providing bacon rolls, tea & coffee etc.as usual.

Note: There is no "Bring & Buy" table but tables may be hired by the hour at £3.00 or for the day at £15.00. Payment in advance on the day. There are a few tables left so early booking is advised.

Rally Organizer : Mr Dave Speechley Tel 01268 697978. Email : g4uvj@btinternet.com

Traders who have booked to date are listed below but please check our web site at: http://www.southessex-ars.co.uk/trader.html for the latest information.

B. Bowden
Camsecure
Chelmsford. ARS
J. Cook
M.Duce
Essex Repeater Group
F.Greenwood
Harrison Electronics
G.Howard
K.Kelly
D.Lindop
Pro Whip Antennas
D. Penny
R.N.A.R.S
Rigfix
RSARS
Silverthorn Radio Club
Surpleletronics
P.Shepherd/ RAIBC
J.Tansley
Waters & Stanton
B.Welling
The Sweet Stall

More Snow News

Richard, G4ANN and I ventured up to Hut 18 today to check whether there was any risk of the cold weather causing water damage in the club house due to frozen pipes bursting. It was definitely 4x4 territory up there, with the paths only just withing the capabilities of my RAV4.




There was one car in the main lane that was being pushed by its passengers as it was stuck in the snow. Although there were tracks up near the huts there were no other cars up there and a few dog walkers cars parked near the edge of the main track.

Even without heating the hut was a reasonable temperature presumably due to the residual heat from the shack. The pipes were all in good shape, but we turned the water off at the main and drained down as much as we could.



The antennas got a pretty thorough covering with snow but seemed in good shape. However we noticed that the beams seemed to be swinging in the wind rather more than we would have expected and we will need to check the rotator out when we manage to get back up there again.

I think that ground conditions are going to have to improve considerably before we can resume out regular meetings, but until that happens we will continue to organize a variety of nets and other social gatherings outside Tilgate.

Stewart/G3YSX

When All Else Fails There is Always WSPR (tm)

We woke up on Wednesday 6th of January to the aftermath of the worst period of snow since 1981, though we may we may be set for a winter that challenges 1963. Not surprisingly some of us had to revert to Internet TV or a poor analogue signal.



As Wednesday is a club night we QSYed from Hut 18 to the airwaves. Our initial attempt was to work each other on 80m, but skip conditions such that most stations were very weak, indeed Derek, G3GRO one of the most powerful stations on the net was barely audible at G3YSX (Merstham) and was only 50% copyable in Crawley Down (G3VLH). However we did QSY to GB3WS where we had a most enjoyable net for about an hour. Indeed this was so enjoyable that a number of members have suggested trying again to establish a club net.

After the session on GB3WS a number of us tried again on HF, this time on 20m. Again the paths losses were unacceptably high. It will be interesting to try this again when there is less snow on the ground (and on the trees) and when the antennas are less covered in ice to see how much effect the weather was having on the signal paths.

The pictures below show the ice buildup on my antenna systems.



The VHF antenna did well considering the amount of ice that coated it. Note that the long wire used on 80m and 20m was also iced up earlier in the day.



This is the ice on the long-wire at the top of the vertical feed.



... and this is the ice on the bottom. The remote ATU lives in the dustbin to give it additional weather protection.

However the Wednesday 6th January was a period of special activity on 80m for WSPR, and I always try to take part in these special activity sessions. The poor results on the club net HF net struck me as being an interesting contrast to the results I was getting that day on 80m using WSPR. For this activity I was running about 2.5W from my FT-817 to the same long-wire antenna and ATU.

Here is the 24hr plot I got for 80m WSPR taken at 1317 the following day:



The best DX (that heard me) in the log was W5OLF (7720 Km), KV6O (7633 Km) and AL2F (7401 Km). However there were close in contacts for example M0JEK (57 Km), G3THQ (34 Km), and G8VDQ (30 Km) which were at a comparable distance to the CARC evening net. The G3THQ contact ocuring about an hour before the club net. There were just over 190 contacts in the log. By sorting the contacts into distance order and assuming that the pairs at the same distance represent a two way contact (a very rough, but reasonable accurate approximation) I estimate that I made 71 two way contacts.

I know that this is an apples to oranges comparison, but the antenna was the same (including most of the ice) and the power WSPR power (about 2.5W) was about 19db down on my SSB signal, and it is interesting to compare the relative effectiveness of the two modes.

Stewart/G3YSX

September Meeting “D” Star - What It Is & How To Use It

by David Lake G4ULF



In his short but pithy article in the February 2009 CARC Newsletter David wrote- “ Experimentation has always been at the heart of Amateur Radio, and the latest digital linking system, D-Star is debatably the most wide reaching innovation in Amateur Radio since the introduction of SSB. Whilst currently dominated by one manufacturer, the majority of the D-Star transport protocols are open and published, ripe for a sport of reverse engineering”. Since the publication of this short article David has been working on both the hardware and software elements of D-Star.

On Wednesday 16th September we were treated by David G4ULF to a rundown of the D-Star system. D-Star has been developed in the last few years by Icom in conjunction with JARL (Japan Amateur Radio League) and is gradually being taken up by VHF and UHF users as a means of providing worldwide communications.

The worldwide aspect is achieved by employing the Internet as the bearer for long distance linking of amateur V/UHF repeaters and reflectors. Prime movers in this D-Star community enterprise include Robin Cutshaw AA4RC.

This ability to couple a local repeater into the Internet means that potentially worldwide communications is possible, with the repeater at each end of the link providing the local V/UHF radio communications hub. D-Star uses Gaussian filtered Minimum Shift Keying (GMSK) as the modulation method. This is an effective and relatively simple approach to digital modulation for wireless data transmission.

The particular relevance of D-Star to CARC and Ashdown Forest Repeater Group members is of course that it is one of the modes now operational on our local GB7MH repeater located at St Leonard’s Church, Turners Hill. So, why are we implementing D-Star at this time?

The D stands for digital and, as it is digital, the signal from your D-STAR radio is converted from its original analogue format into a series of zeros and ones. Along with your digitized voice, the data stream contains addressing and routing information - what radio it is coming from, what radio it is going to, and how it is getting there. There are similarities to email in that without the addressing information, the mail won't go.

These concepts will sound familiar to packet radio users and D-STAR does in many ways work like packet e.g. MyCALL (who you are), UrCALL (who you're talking to), RPT1 C and RPT2 C. Even working simplex, your radio needs to know "Who it is" and "Who it is calling"… again, it’s a digital thing. When you transmit a digital voice (DV) signal, the radio's codec digitizes your voice and addressing information is added. In receive mode, your radio runs the data through the codec and turns it back into something we humans immediately recognise and use, analogue sound.

So, Digital Voice is a digital mode, and while it may sound like analogue FM coming from the speaker on your radio, the way it all happens is quite different. Being digital, there are a lot of interesting things we can do... such as sending your traffic to the local 70cm port and 1.2 GHz port. Or sending your traffic to the local 2 metre port and a "Reflector" somewhere across the world, such as the USA... all at the same time!

In the past few months David G4ULF has produced some major D-Star software implementations and he, together with Malcolm G3NZP, Richard G4ANN and Paul Phillips have collected, modified as necessary and installed the necessary equipment to get GB7MH up and running under D-Star protocol. This is a major achievement and whilst still classified as work in progress those equipped with D-Star mobiles or hand portables can now connect in to the D-Star network.

David has produced some notes on the D-Star system, which can be found at http://carc.org.uk/downloads/CARCTalk.pdf .

John G3VLH

Individual Access to the CARC Shack

At the last AGM we put forward the possibility of allowing member to have access to the club shack outside the normal meeting hours, or other special club events. Having discussed the matter in committee, the committee propose the following access policy. We will table this as an agenda item at the 2010 AGM with a view to requesting ratification of this policy:

1) Access to the club and use of the club shack on Wednesdays and Sundays would continue as before and would not be changed by this policy.

2) The priority for the committee in taking any decision with regard to the implementation of this policy would be the well-being of the club as a whole.

3) All club sponsored activities will take priority over individual access.

4) Access permission will be at the discretion of the committee and would only be granted to fully paid up club members who have shown regular club attendance for at least two years.

5) Access permission would be withdrawn in the event of abuse of the facility or operating outside the terms of the license, and keys would be required to be returned immediately. In the event of a failure to return keys, the individual concerned would be responsible for the costs of changing locks.

6) Damage other than normal wear and tear would be the responsibility of the member concerned, who’s access rights would be withdrawn until the matter was resolved to the satisfaction of the committee.

7) Before being granted access to the club shack the member would need to demonstrate their operating skills, particularly whist working HF stations, and would need to produce evidence of possessing and Intermediate or Advanced license.

8) Foundation license holders are not eligible for out of hours access to the club shack.

9) Operation would at all times need to conform to the Club license conditions, or the license conditions of the operator which ever was stricter. For Intermediate Licensees this would mean using their own callsign and an output power of 50W or less.

9) Usage of the club shack out of hours would need to be recorded in the out of hours log, together with a note of any equipment malfunction or other abnormal event.

10) Since the club will incur real costs associated with providing this facility, the member will be required to pay an additional club fee over and above their normal club membership fee. This value of this fee will be decided at the AGM.

11) No pro-rata or concession would be granted against the out or hours fee.

12) Presence of any guest who was not a club member would require the prior permission of the committee. Authority to grant such permission may from time to time be delegated to one or more members if the committee.

13) Individual use of the club shack would be on a first come first served basis and in the event of a member waiting to use the facility the members concerned would be expected to come to a reasonable accommodation with each other.

As per the proposed policy we will agree the fee at the AGM. A fee of £30 pa is proposed by the committee.

Comments before the AGM are welcome.


Stewart/G3YSX
Chairman CARC on Behalf of the CARC Committee

Virtual Club Meeting Sunday 10th January

In view of the forecast of further bad weather conditions throughout the weekend, the club meeting on Sunday 10th is canceled.

The committee will review the situation on Tuesday and make a decision about the Wednesday evening meeting,

However we will meet up for another club get together on Sunday morning at 10.30 on WS. If WS is down this due to another power failure we
should use the OUTPUT frequency for WS (145.750) as an alternate.

If WS has a lot of traffic from mobile users we will QSY down to one of the simplex channels.

- Stewart/G3YSX

What make GB7MH tick

Previous posts have shown the details of the now famous flagtenna that radiates the signal from GB7MH. Malcolm G3NZP has now provided some photographs of the repeater equipment cabinet



... and of the 3G router that is providing the connection to the Internet.



Stewart/G3YSX

Happy Birthday Sir Isaac Newton

As Google have just reminded me that it is Sir Isaac Newton's Birthday with an apple bouncing Google Doodle, I thought that I would remind readers that he had another career after his time as Mathematician, Physicist and Alchemist. He was Master of the Royal Mint. There is a very good book, part biography, part detective story that I am just finishing reading and which I would recommend to others: Newton and the Counterfeiter by Thomas Levenson. Also it's worth looking at the author's video on the the Amazon site.

For those club members who don't have time to read the book, it was a Radio4 book of the week and I am sure the audio is still out there in the webverse.

Stewart/G3YSX