10m AM Operation

Ignore what recently published 10m band plans may say - 10m AM is alive and well just above 29MHz with most 10m AM between 29 and 29.1MHz.

Many recent band plans talk of 2700Hz wide SSB in the 29 to 29.1MHz slot. This is rubbish written  by people who don't have a clue! Just take a listen between 29 and 29.1MHz next time the band is open and make up your own minds.

Write to your band plan scribes and ask them to actually USE 10m next time before putting pen to paper. I have written to the RSGB to express my displeasure with their latest 10m attempt:  they blame the IARU.  I see on the RSGB website they have made a half-hearted attempt to clarify 10m AM use - a very poor attempt in my view.

28 to 29MHz is plenty of room for narrow-band modes, even when there is a major contest or the band is wide open. There is space above 29MHz for AM, FM and satellites. 29 to 29.1MHz has lots of AM often with beautifully modulated signals: it is a pleasant change.

In a few years time the whole of 10m will be largely quiet again and we amateurs need to use it for local comms, Es, and the occasional N-S DX or risk losing it to CBers and taxis.

There are plenty of 10m projects on my main website.

10m Band Plan - some movement?

The RSGB is seeking views on band plans currently via their website forums (hard to navigate to in my opinion) and the outputs will go to the IARU later this year.

One possible recommendation is the extension of the wider band mode section on 10m from 29.1MHz down to 29MHz. 29 to 29.2MHz is the well used 10m AM sub-band, but changing the bandwidth allowed 29-29.1MHz (i.e no longer 2.7kHz) would mark a great advance over the current confused status of AM on 10m. It would be nice to have the words AM in the bandplan, but this is, sadly, unlikely. As I said before, it would appear the RSGB and IARU believe AM is a dead mode - if only they would actually listen 29 to 29.2MHz in a band opening.

If you have views, please share them on the RSGB's website.

This was John G3WKL's email pointing me to the right place on the RSGB's site. It is not exactly easy to find. The RSGB needs to make this easier if it wants peoples' comments! :

"Roger,

The relevant consultation topic is at

http://forums.thersgb.org/index.php?threads/band-planning.23/

but if you are not registered for this new “forum” application it would be better to go in via

http://rsgb.org/main/rsgb-consultations/active-consultations/iaru-2014-consultation/

as that gives you the “register” link.

You’ll see that Ian has picked up on our earlier discussion concerning 29.1 MHz but you are welcome to post further comments.  Suggestions for new HF topics should be put in

http://forums.thersgb.org/index.php?threads/c4-hf-matters-consultation.11/

and VHF matters in the appropriate topic under “C5 – VHF/microwave Matters”

73 John, G3WKL"

Return to 10m and rubbish band plans

I am concentrating on WSPR currently as it does not require me to use my voice, something I find very tiring with my stroke. Just a few sentences and I get quite exhausted. I am told this is to be expected and it should improve over time.

As 474.2kHz is quite quiet in the daytime, I have QSYed up to 10m where I have already been spotted in LZ, RA3,  DK, PA,  G,  GM and 4X  this morning at 2W. This afternoon, I expect the band will be open to the USA. and Canada.

If my voice was better I'd be trying 10m AM, which despite the absolute rubbish in recent IARU and RSGB band plans is still 29 to 29.2MHz. The band plans, surely written by non-users (?), shows 29-29.1 as for use by modes 2.7kHz wide or less. AM gets  a begrudged and confusing  throw away comment in the footnotes. Reading the band plans it reads as if AM on 10m never happens, whereas when the band is open I regularly hear and work (with real QRP)  stateside AM in the 10m AM window, mainly 29 - 29.1MHz. Sorry, but these poorly thought through band plans ANNOY me.

Why can't the 10m band plan reflect what ACTUALLY happens on the band? 28-29MHz is quite enough space for narrow band modes leaving AM where it is (and SHOUT THE FACT that AM exists and is a good  and fascinating mode on 10m), as well as space downlinks and FM  where they are now. Why do these know-alls have to interfere unless they actually understand what actually happens? Band plans are usually a good idea when they actually help. The current 10m band plan is plain WRONG in my view above 29MHz. Write to the RSGB, ARRL etc.. and tell them. AM is 5-6kHz wide NOT 2.7kHz or less and at 29-29.2MHz this is fine. Just damn well leave AM where it is please. Stop messing about!

I also feel it is daft having SSTV and FAX channels mentioned in the 2m band plan but AM only gets a (begrudged?) comment in a footnote. 2m AM is a minority interest but surely deserves a "centre of activity" spot on 144.55MHz so AM folk know where to gather? Ex-PMR AM gear is almost given away and AM gear is simple to build and test. When did YOU last hear a FAX station on 2m? At best, the 2m band plan is a mess. Either leave "special interest" channels out or add an AM CoA in please. AM is NOT the pox, but a good and useful mode!

RANT OVER,but these errors do get my goat.

UPDATE 1745z: lots of 10m WSPR spots this afternoon including plenty from across the pond and at good range:

The band closed transatlantic (for me) at 1840z, well after dark with copy of W8QYT. It may have been even later as my PC shut down the WSPR program after doing some updates!

Band Plans and AM - Feb 2013 RadCom

In the new February RadCom that just dropped on my mat at lunchtime there is a copy of the band plans for all bands from 136kHz to 134GHz.  What I fail to understand is why does the RSGB appear so anti-AM?

For many years now there has been a clear choice for an AM centre of activity on 144.55MHz. The RSGB has been made aware of this on many occasions and yet still we have a (begrudging) footnote, just about visible if you look hard, saying this is where to look. Even this comment ends with, "although this frequency is not officially recognised within the 2m band plan". Why not? We have a FAX calling frequency listed and goodness knows how many DV Internet Voice Gateway frequencies listed, yet we cannot be allowed an official AM centre of activity properly listed! AM is not a common mode these days, but those who enjoy the mode need to know where to meet on the band. The RSGB is giving no help at all here.

I also get frustrated with the 10m band plan where AM is again almost treated as a disease. Most AM activity has been in the 29.0-29.1MHz segment for years now: this is THE part of the band where AM users congregate, yet the all-mode section with up to 6kHz bandwidth does not start until 29.1MHz upwards! Does no-one who creates these band plans actually listen to see what actually goes on? In the last 30 years I have had many AM contacts on 10m and not one outside 29.0 - 29.1MHz.

So, next time you consider the band plans, please:

(a) Add an AM "centre of activity" frequency into the 2m band plan - it is 144.550MHz in case you don't know.
(b) Show 29-29.1MHz as the AM sub-band in the 10m band plan.

First on-air testing of the Tenbox TX

This evening, with little sign of F2 propagation, I ventured out to test the range of the 10m Tenbox TX as it is currently. For the TX antenna I used the coax up to my 10m halo as a vertical tuned with the Elecraft T1 ATU. At the RX end, in the car, I used the FT817 with a small base loaded mag-mount.

Tenbox AM TXing with MP3 callsign message on the PC

What I should have thought about was the noise on AM from street lights! When the signal is strong in the village this is no issue at all, but traveling to the next village 3km away there were several spots where the buzz from sodium street lights just killed the little signal. Both antennas are compromised, so another 3-6dB of signal level should be possible with a proper 1/2 wave antenna at each end or with a better car antenna.

Maybe this project, although great simple fun, isn't going to quite meet my needs, whereas a DSB transceiver would?  Receiving the DSB signal as SSB and the improvement over AM will be around 9dB with better noise immunity. However a simple direct conversion RX would not be suitable to use (easily) with a DSB TX, whereas the AM Tenbox would be fully 2-way compatible with another identical AM unit.

Conclusions so far
(a) 6-10dB more may be needed to meet the design objectives with AM.
(b) It is worth repeating the very same test now using a DSB TX with the same power to compare.

The first Tenbox Schematic

The breadboarding of the Tenbox 10m AM transceiver for local cross-town night-time nattering is almost complete now, with just a receiver audio amplifier to drive a loudspeaker to be added. Power output is a conservative 250mW AM carrier (peak power around 1W).  The first schematic draft is shown here, but as always I warn that I may have forgotten to correctly label some parts and the values may change as the circuit is further developed. I hope to road test this over the weekend going out in the car with a mag-mount antenna whilst AM beaconing with the rig from home. As with WISPY, I have paralleled up 4 2N3904 transistors for the PA. This is a very inexpensive way of making a 10m PA stage! The alternative, such as a 2N3866 would be about 5-10 times more expensive.

Tenbox TX progress

Good progress today with the transmit side of my Tenbox 10m AM transceiver.

The series  modulator was breadboarded a few days ago, so today I built the 3rd overtone oscillator, the buffer and the modulated PA stage. Results were as expected with around 50-60mW of clean well modulated AM available at the output. With a single linear amplifier with around 10-13dB gain (easy at 29MHz) this will take me into the 500mW-1W carrier level, which is my design aim. As I did not have a suitable 29.05MHz crystal (anyone know where these can be obtained cheaply?) I used a 28.500MHz one on a dummy load. With this frequency, any range tests will have to be done at night to avoid QRM to SSB stations.

When the linear is added , maybe even before then, I'll do a local "drive around" test with the TX on "speech beaconing" mode (using an MP3 file on the PC) and with the RX attached to a mag-mount antenna on the car. This will establish the useable local coverage.  Assuming this power level is OK, I'll then complete the full design on a tidy breadboard and publish the initial schematics on my blog and website. After that, a PCB may be in order and a neat enclosure.

This project is great fun: a simple, straightforward and easily reproducible design and a project that will be useful at the end. Much more fun than working DX with 400W and a 5 el beam in a contest with a £5k commercial HF transceiver.  Honestly, I'm having a real ball with this.

10m local range?

With the 10m AM Tenbox design coming along nicely I'm reminded of the fun we had in the early 1980s with 10m FM using converted CB rigs here in the UK. Using a converted CB radio with 4W FM into a vertical half wave antenna I was usually able to make contact with similarly equipped stations up to around 25-30 miles away pretty regularly. Certainly within a 5 mile radius signals were fully quietened, even to mobiles.

So, I am wondering how I'll get on with 0.5W of 29MHz AM? My expectation is that with a similar antenna (1/2 wave vertical - I currently use a horizontal halo) I should be able to cover 3-5 miles without too much problem. I'm wondering what sort of ranges people achieve with AM CB radios (WITHOUT add-on PAs!) where this mode is legal?  Running a few dB more power is no problem if required of the Tenbox design.

When 10m is wide open it is possible to work thousands of miles on FM but I always found that the competition was too great and therefore the mode is not well suited to DXing. The aim of the 29MHz AM Tenbox is just for very local communications and definitely not for DX working. In my mind I see the Tenbox being a modern version of the old Heath HW19 (the Tener) rig - see the image and data on the Rigpix page

Tenbox 10m AM rig - a bit more

Although I had little time today, I experimented with adding varicap tuning to the Tenbox AM transceiver's RX section. Only problem was I had no varicaps, so tried using a few different diodes and a transistor as a varicap. 1N4148 and a Germanium diode reverse biased hardly produced any change in capacitance going from 2-12V. I know a 1N4007 works quite well but could not find one. Then I used a 2N3904's base-collector junction and got a few pF of change. In the end I just did as I did in the Sixbox and used a fixed capacitor in series with a 365pF polyvaricon tuning capacitor. This moves the RX frequency as much as I need at around 2MHz maximum.

10m QRP (2W) AM DX QSO

The excellent conditions on HF today

Just worked K1IED in Connecticut when using 2W AM to my halo antenna. The 10m AM segment is busy with some good signals from the US and Canada. When 10m AM is like this you just know 10m is wide open.

Although K1KW was an excellent AM signal I was unable to get through the pileup on AM to work him.

The very poor quality video below shows K1IED's 10m AM signal a few minutes after I worked him.

10m AM DX QSO today

Today I had a nice solid AM QSO across the Atlantic to K2WF in Long Island on 29.010MHz when I was running just 4W to the halo antenna. My report was 55 and I gave Alan 57. He was running 25W carrier. This is my first 10m DX AM QSO in about 10 years and very welcome too.

29MHz AM Signals

For the first time in several years I am hearing 10m AM signals coming through from across the Atlantic between 29 - 29.1MHz. Good signals from N1GKX and KA1CU amongst several others including UA and G. For me, 10m AM is like a time warp, reminding me of how the HF bands used to sound in my youth back in the early 1960s. Yet to work any DX AM this season.

Sunspots

At the moment we seem to be seeing quite impressive sunspot numbers, at last. See http://www.solen.info/solar/ . This bodes well for this coming autumn and winter which should see 10m well open to the USA on a regular basis by October. Such conditions offer the chance of transatlantic AM QSOs between 29-29.1MHz even with quite low power. In previous sunspot maximums it has been possible to work AM DX with just a few watts to a mag-mount on the car. AM makes a change from SSB.