AmateurRadio.com

Partly because bandwidths are very low,  there has been a revival of interest in NBTV systems similar to the early TV transmissions by Baird in the 1920s and 1930s.

There is even a Televisor kit available for about £40 delivered (in the UK) with a CD with some still and moving images and its own test card generator. I am quite tempted!

The televisor kit is available for £35.94 + shipping from http://www.mindsetsonline.co.uk/Site/Home (search for televisor). This is compatible with the 32 line standard of the NBTV Association.  The NBTV Association home page is at http://www.nbtv.wyenet.co.uk/index.htm .

Bandwidths are audio only, so a tape recorder or CD are fine. Over the air transmissions only require audio bandwidths too. Of course, with just 32 lines don’t expect brilliant images!

Is the end in sight for Motorola?

See http://www.bloomberg.com/news/articles/2015-02-06/motorola-solutions-said-to-explore-sale-of-87-year-old-company .

When I was at work (I retired 7 years ago) Motorola was our greatest rival. Since coming into existence in the early years of this century, my own company Sepura has been in profit every year. The demise of Motorola is a salutary lesson never to be complacent. How the mighty have fallen.

Recently, I wrote to the “Last Words” column in Radcom. I very much doubt my letter will be published. The main thrust of the letter is the (very negative) attitude of the RSGB to the AM mode.

My letter (as sent) is reproduced here. I’d be interested to hear your views.

At the present time G6ALB is experimenting with very low cost 70cms AM modules as the heart of a possible short range (3km) voice transceiver. We have had some success already.

“Thank you for publishing the latest Band Plans in the February 2015 RadCom. Although because of my poor voice (stroke) I tend to use digital techniques, I still enjoy the occasional outing using AM. Like many, I have worked transatlantic AMers on 29-29.1MHz with real QRP and simple antennas.

Yet again, one could be forgiven for thinking AM, especially 28MHz and up, is a dirty word at the RSGB.  AM gets no mention on 28MHz and 50MHz and gets a (begrudging?) comment as a footnote only in the 144MHz Band Plan when other modes get “centres of activity” mentions. For the avoidance of any doubt, AM is alive and well in the 29-29.1MHz sub-band. AM on the 144MHz (2m) band can be found on and around 144.550MHz. There has been AM on 29-29.1MHz for years and years and years! Yes, this is the all-mode section, but why not say this is the 28MHz (10m) AM sub-band? Also, why are 144MHz AM users asked to “consider adjacent channel activity”? AM should easily fit in 6kHz!!

Sorry, yet again, AM is being treated as a dirty and outdated mode. May I remind readers that ex-PMR AM rigs ripe for use on VHF can be picked up for virtually nothing and that there is room for AM on all bands from 28MHz upwards. AM has its enthusiasts on other bands too, but yet again the RSGB seems hell bent on killing off this mode. Why?

73s
Roger Lapthorn G3XBM”

At around 9PM on May 31, 1978 were the first KNOWN transmissions of Packet over Amateur Radio. The location was Bill Wong’s Restaurant in Montreal, Canada.

The Montreal Packet Net Group C/O:

Bob Rouleau VE2PY; Norm Pearl VE2BQS; Fred Basserman VE2BQF; Bram Frank VE2BFH; Jacques Orsali VE2EP; Ted Baleshta VE3CAF; Ian Hodgson VE2BEN; among others not mentioned.

They operated on a single 220Mhz channel using start-stop ASCII with the Ethernet CSMA/CD protocol. The protocol was modified for amateur applications by Robert T. Rouleau, VE2PY, and implemented by Fred Basserman, VE2BQF. Montreal Packet Net (MP-Net) Operated at 2400 bit/s using home-built modems.

A detailed description of the Montreal Protocol and hardware used in the experiments is given in the TAB book #1345 “PACKET RADIO” by Bob Rouleau and Ian Hodgson published in 1981. An interesting note is that the Montreal Modem design used the Exar XR-2206/2211 chip set. I am told that a sample of the Montreal Modem was sent to the Vancouver group (VADCG) in the fall of 1978 and it is probably no coincidence that the same chip set appeared in the TAPR TNC modem of which Doug Lockhart of VADCG had a hand in designing.

After an initial spurt of activity in amateur packet, Bob Rouleau and several others in the group turned to commercial applications for packet radio. The resulting company, DATARADIO Inc, today is building and marketing commercial packet radio systems around the world. A typical application is the Canadian Weather Radio packet service introduced some years ago using DATARADIO equipment specially designed for the application.

Bob was inducted in the CQ Magazine Amateur Radio Hall of Fame in 2003.

See http://www.southgatearc.org/news/2015/february/ht_of_the_future_at_orlando.htm#.VNi6BC4WKPc .

Southgate News reports that Bruce Perens K6BP will be demonstrating a handheld platform that can cope with many modes at VHF/UHF at the Orlando Hamcation in Florida. This looks like a demonstrator at 100mW RF. With SDRs, quite a flexible, and low cost, architecture is possible.

I wonder which of the “big names” will be first to market with a real SDR design? This could enable them to sell very low cost units, but maybe they would rather shaft us and make big profits?

As I have mentioned before, I am a rare repeater user, partly because my voice is so poor currently and I don’t find operating through repeaters that satisfying. Each to his/her own and if this helps you enjoy the hobby go ahead!

At the moment it is far from clear which form of digital repeater will win: there are several competing digital standards and all have their advocates. For now I shall sit back and wait. A bit like the video standards war in the 1980s, the best system may not win. Let’s see. Up to now I have only used FM repeaters.

When I do use voice I use SSB, FM and AM. All modes have their places on our bands. SSB is good on the crowded HF bands, FM useful for nets on VHF, and AM rigs simple to build and there is space on all bands from 10m upwards for all analogue voice modes. A well designed AM rig should occupy less than 6kHz, far less most FM transmissions on our bands. 10m AM, just above 29MHz, is a great mode. I have worked quite a few stateside stations on 10m AM. And I have only used QRP AM.  Let no-one tell you AM is a dead mode!

Today I checked the sensitivities of my FT817 and FT817ND using a loaned signal generator. Although about 10dB deaf at 472kHz (expected) both were easily able to copy down to -127dBm on CW on all bands to 70cms. -127dBm is as low as the generator would go.  I could have added a 10dB attenuator, but did not.  I also managed easy access of GB3PY and GB3OV 70cms repeaters at the 500mW level into the V2000 vertical.  My conclusion is things are OK at my end and I wonder if G6ALB has some additional cable loss at 70cms at his end (water in the feeder?).  My antenna has been up for about 2 years whereas his has been up for around 20 years.