Testing the Tenbox on 10m AM today

Today I wanted check how good the Tenbox 10m AM receiver (part of the intended transceiver) was in real use as opposed to measuring it on a signal generator.

So, I set up my FT817 on 10m AM TX on the lowest power setting, which is around 150mW carrier, and fed this into a makeshift vertical tuned with the T1 ATU. Using my PC, I made a short message "G3XBM testing on 10m AM" that I played in auto-repeat.

I then went for a drive locally with the little super-regen RX in the car being fed from a vertical mag-mount antenna on the car roof. The only antenna I had was an ATX15 base loaded whip for 15m, so I pushed a few sections in to make it resonate on 29MHz.

Results were encouraging. Out in the car my 150mW AM TX beacon message could be copied out to about 2 miles away, although this was limited by QRM from W2VW (!) and VE3OWV (!) who were coming through with 59 signals on the RX on 29MHz AM. When they dropped carriers copy was fine. It's fascinating to think my 150mW AM signal was having QRM from 5000km away!

A super-regen is not really suitable for use when 10m is wide open, like it was this afternoon. Nonetheless I was able to copy stateside stations on 10m AM on a short base loaded mag-mount pretty well. For its intended purpose as a local across town natter box, I think the Tenbox is going to be fun. With 6dB more power out (my aim for it) it should be certainly possible to work G6ALB 3km away in the next village.

The next stage is now to build the TX part and test this.

After the noise: 160m CW QSO

Following my small successes last night battling my local man-made noise sources, this evening I managed nearly a full QSO with GW0IRW on 160m CW when running 5W to my vertical coax to the 10m halo. The noise level is now low enough to sensibly copy stations on 160m, which I've not been able to do for months at night.

I am now monitoring 474.2kHz WSPR hoping to improve on my reports now the local noise floor is much lower. SM6BHZ is already coming in at a respectable -14dB S/N. He is usually pretty strong so it will be interesting to see how many others come through this evening.

Winning the noise battle a step at a time

This evening I've been trying to track down various noise sources that have been making reception on MF and the lower HF bands all but impossible in recent weeks. I'm pleased to report a couple of successes.

My first "trap" was the 12V Netgear AD6612 AC-DC adaptor that feeds my Virgin Media internet superhub. This little terror was producing an S6-8 noise floor on many of the lower ham bands. I tried ferrite chokes in the leads but to no avail. Fortunately I had an old Linksys 12V supply with the same sort of rating and 12V plug. Swapping the PSUs over and, guess what, the lower HF bands were much quieter once again.

At 470-500kHz though I still had an S8 noise floor, so there was another candidate noise generator around. Switching everything off in the house the noise floor dropped, so it was in the house. In the end I tracked this down to a Salus mains powered controller that receives wireless signals from the central heating roomstat. Turning this off and, guess what, 470-500kHz goes much quieter too! This unit is quite close to my antenna wire and must have a noisy SMPSU inside. Luckily we tend not to have the central heating on in the evening so all I have to do is turn off the Salus wall unit controlling the central heating boiler and I can, I think, go back to better reception on the MF bands in the evenings.

In 30 minutes I've reduced the noise floor in my home considerably from LF to at least 10MHz. This goes to prove that with a little bit of detective work we can do a lot to overcome many of the noise issues plaguing us these days. Both the Virgin Media superhub and the Salus unit are new (less than 6 months old) so this also explains why the noise issue was not such a problem last autumn and winter.

If you have a noise problem then I recommend you do some detective work and very good luck.

Coils for projects

Many of the old TOKO range of coils are hard to find these days but an alternative source for many of these is now available from Spectrum Communications in the UK. See http://www.spectrumcomms.co.uk/Components.htm for more details. If you are a member of the GQRP Club, many of these are available through its excellent club sales. An example, the 45uH coil specified in my 472kHz transverter is available from the above suppliers.

Spectrum also sell a useful range of crystals as well as some of the harder to find, once common, MOSFETs.

SHAMateur radio

Today the December 2012 RadCom dropped on my doormat.  P16-17 contains a review of the Acom 1500 1500W linear amplifier for HF and 6m. Now, I am sure this is a very well engineered piece of kit, but at £2750 including VAT surely this is not for real amateur radio?

Anyone buying this has probably spent a few thousand on a big Yaecom black box multi-mode HF rig, another £400-500 on a beefy rotator, another few hundred on a mast and another few hundred on an HF beam to put on the top. Total bill for all this approaching £5000 if not more! They may be able to work some DX slightly more easily than me with a 5W or less radio and a small wire antenna strung up in the tree, but I bet they have less fun.

I have no objection per se to people spending the money they earn as they choose, but what I object to is this sort of expensive kit being projected as a necessity to enjoy our hobby.

To my mind this is SHAMateur radio, not amateur radio. It is a cheque book hobby far far removed from the hobby I wish to be associated with.

I wish our national magazine would publish more articles about REAL amateur radio, the sort that young kids and people on tight budgets can afford and enjoy. If the RSGB is short of material then it should ask the GQRP club for some ideas and circuits! Amateur radio is a very varied hobby and I do not want to be a killjoy, but anyone picking up RadCom would believe you need a very deep wallet to be able to enter the hobby. This simply is NOT the case. OK there is some good beginners content (for example the excellent series by Eamon Skilton) but not nearly enough.

One thing that IS good in this month's RadCom is the review of QRP Basics by G3RJV on p39. The first edition of this was a very good book that showed what amateur radio is really all about. I expect the new second edition will be even better. I commend it to you!

Are you a radio amateur or a radio shamateur?

Dell Inspiron 1545 power socket repair

My wife's laptop is a 3 year old Dell Inspiron 1545. Although otherwise a nice PC, this has a stupid design weakness: the power connector socket. This is on the side of the PC (back left) and it is almost impossible to use the machine and not snag the cord and socket regularly.

Consequently, over time, the SMA connector inside the PC has gone intermittent. The PC is covered by a 4 year hardware warranty and I hope that Dell will just fix this and not argue "wear and tear". I have had other PCs where the power socket is strain relieved within the housing and not had a problem.

One has just to look at the number of videos telling you how to fix this very issue to see it is a very common one. I like this video showing the repair in 3 minutes, although in reality it would take about 1 hour. In the limit I could do it myself, but let's see if Dell are in a good mood and are helpful first!

I do get really annoyed when a consumer product goes to market with such an elementary design weakness: this is the sort of rubbish that should have been spotted early in the design phase by design reviews looking for possible failure mechanisms. Dell should know better.

Tenbox progress (10m QRP AM transceiver)

Tenbox breadboard RX -115dBm MDS

Today I breadboarded a simple, but sensitive receiver for 10m AM in the Fredbox tradition. The standard Fredbox and Sixbox circuit was simply scaled down to 29MHz with great results using the breadboard with the Marconi 2022 generator. MDS for a well modulated AM signal is better than -115dBm (around about 0.5uV) which is actually better than I was achieving on 6m and 2m. Not bad for just 2 MPF102 FETs and 1 2N3904. For the tuned circuits (RF amp output and detector) I used a couple of T37-6 (yellow) toroids tuned with 15pF trimmers. There is a 10pF coupling capactor between them.  Of course this is a super-regen with a grounded gate RF amp to isolate the detector from the antenna.

The intended use of the Tenbox is local "across town" nattering when the band is quiet. The selectivity would NOT be suitable for DX use, although I'm sure it would pick up stateside 10m AM stations OK.  I am always amazed by how well a simple super-regen RX works: they just fly for me and are always incredibly sensitive and non-critical. People who have not played with these do not know what they are missing. I highly recommend the RX in the Fredbox

Next stage is to breadboard up a simple AM modulator and TX strip. Again, I shall copy the basic Sixbox design but this time add a linear amp (a few 2N3904s in parallel as in the WISPY beacon) to get the carrier power to a useful level.

In summary, an interesting and productive hour or so after tea.

Weak signalling comparisons

Over the last few days I've been trying out my Lesser Chirpy 10m 80mW CW rig putting out CQ calls on 28.060 periodically and listening for replies and RBN reports. In three days I've only managed 2 RBN reports at around 3000km with it. So, this morning I fired up the hombrew WISPY WSPR beacon on 10m to see what happened. This runs about 6dB more power at around 200-250mW pep effective on the WSPR band. On the first transmission I got 3 reports immediately at 2200-3500km. With WSPR it is SO much easier.

Conclusions? Well if you just want to know what propagation is like then a small homebrew WSPR beacon is all you need. If you want the fun of the chase and the chance of a few QRP CW contacts with a human then the Lesser Chirpy rig is up for the challenge.

Life is too short to sit there endlessly calling CQ with the key though. So, I think Lesser Chirpy will be brought out when  conditions and activity are good. Otherwise WISPY will whisper away quietly in the shack whilst I get on with designing interesting new little projects, HI.

UPDATE: After a few hours of 10m WSPR at 200mW I had a page of reports out to around 6500km. Back on 10m CW I tried a brief call with the FT817 at 5W and got a couple of USA spots on the RBN. A further 30 minutes of calling CQ with the 80mW transceiver and no reports or QSOs. Think I'll have to come back to 10m QRPp another day!

AM broadcasts on Medium Wave

The BBC recently switched off some of its MW local radio AM outlets for some weeks to see if anyone was listening. Results suggest few people listen to their radios in the UK on Medium Wave any more. I know I am one of them, preferring to use Band 2 FM. We also have a DAB radio but it is pretty useless in the kitchen where FM is perfect. I think it is a signal strength issue.

So, will the BBC switch off all its MW output? Will anyone care? It may soon be that AM will be a dying mode unless we radio amateurs use it and show its strengths.

See www.theregister.co.uk/2012/11/08/dab_am_bbc/.

Microsoft Essentials virus protection

On our regular local Monday night 2m net on 144.575MHz (in the all mode section) - anyone is welcome to join us in the East Cambridgeshire area - the subject of PC virus protection came up tonight. Some months back someone told me about Microsoft Essentials which is a free virus protection package. I still use McAfee here and have another year to run on it, but wonder what people think about the free Microsoft package? Does it work well?