Miracle Antenna products

Although not the world's best performing antennas, the Miracle Whip and its associated variations have their uses when one is looking for a compact and easily tuned antenna for field use. On the higher HF bands the loss compared with a full 1/4 wave is less than might be expected if a decent counterpoise is used (1-2 S points down only).

Recently the Canadian owner, Robert, sadly died after a year or so of health problems. There were some doubts whether or not the company would continue, but it appears it will. Perrin VK3XPT made enquiries about the availability of one of their products, the Miracle Ducker and reported as follows to the Miracle Whip Yahoo Group:

UPDATE:

Here is the current status of Miracle Whip stock, globally. I hope this will help someone else here on the group!

- Miracle Antenna do not have any new stock of the Miracle Ducker range. They are waiting on some parts to arrive in the next couple of weeks, which enable them to complete a shipment of new Miracle Ducker TL that they will be sending to Hamcity. This looks to be the only shipment that will be made to any dealer for some time.

- WSPLC.com appear to have some stock, and I have placed an order with them. Fingers crossed that their website is up to date, and showing correct stock levels.

- I have contacted all (yes, all) other Miracle Antenna dealers, and even though some websites are showing stock, this is not actually the case!

So, if you want a Miracle Ducker TL any time soon, Hamcity and WSPLC.com look to be our only and best options. I hope this helps and I will keep the group updated on my progress.

73s
Perrin VK3XPT

Walking in Devon

No posts for a few days as I've been away staying with my 68 year old brother in South Devon. I managed a couple of nice walks along the cliffs and lanes in the cold bright winter sunshine. I believe in the Met Office definition of winter starting Dec 1st. The lanes were VERY muddy but Salcombe, my home town in my childhood was quiet and beautiful.

My 2 Devon walks plotted using the G730 GPS tracker

My Ventus G730 GPS tracker - available for around £34 from Martin Lynch - plotted the 2 walks.  One was around 14km and the other 16.5km.

This shot is of the coastal path near Thurlestone. There are a few nice seats on the walk and I have worked some good HF and VHF pedestrian portable DX from them, although I took no radio gear this time.

Long-term Solar Outlook - downwards!

Chris N7ZWY has put an interesting graph on his website showing his predictions for the future solar cycle progression. His graph shows the solar cycle progressions since the 17th century and Chris's predictions for the future. No-one can be certain of the accuracy of predictions, but as time goes by we are gathering more detailed understanding. I have little doubt Chris is broadly right.

Chris says:

"The average sunspot count for October was 61.4, higher than last month and no indication of the final decline which should bottom out around 2017 or 2018, which will then be followed by two more similarly low sunspot cycles and then a third with almost no activity during a phase reversal."

See http://www.home.earthlink.net/~christrask/Solar%20Activity%201600-2100.pdf

Now, looking at the plot it is highly likely that the sunspot peaks for the next 40-50 years will be weak ones, or even non-existent. The next few years are likely to see the end of the good times on the higher HF bands. Those of us who were around in the 1950s and 1960s didn't know just how lucky we were. Many newcomers to the hobby at that time worked all over the world with 5-10W of CW and AM with S9 signals.

Flying Pig 40m 5W transceiver

Thanks to Dave in Jakarta (don't know your call Dave) I've been pointed towards the Flying Pig 5W CW transceiver for 40m from Kits and Parts.

The receiver uses a clever direct conversion design using an NE602 with some AGC applied to it. Like the RockMite, it uses some front end crystal filtering to help overcome dynamic range/overload  issues, but with the limitation this is a single frequency radio, for example parked on 7.030MHz, the QRP frequency. Still, a full 5W on the QRP frequency will permit plenty of QSOs.

This is the photo on the http://www.kitsandparts.com/ website

The best news is the price - $40 only, which is good value for a kit. Available from Dec 10th 2012 according to the website.

Drawing schematic diagrams

Several people have asked me what I use to produce schematic diagrams for circuits I put on my website and here on the blog. Well I use a package called sPlan which is available from http://www.abacom-online.de/uk/html/splan.html.  This is the package that many SPRAT authors use. Mine is an early version but the latest version is available for 39.9 euros.

Abacom has a range of useful resources such as front panel labeling software and some very simple PCB layout software.  sPlan is remarkably easy to use and a circuit like the Tenbox can be drawn up in about an hour, simpler circuits even less time.

The Abacom website gives details of distributors in many countries.

Wikipedia

en.wikipedia.org/

Don't know about you, but I refer to Wikipedia just about every single day. It isn't perfect, but it certainly is one of the most useful free resources on the Internet. The quality and quantity of data available there is nothing short of remarkable. I've added a few entries myself over the years too. As a thank you I made a small donation via Paypal and encourage you to do the same if you can spare a little.

As they say in their thank you email, the resource is used by people from all over the world including in schools in developing countries. By ensuring Wikipedia remains free and neutral we are helping to keep the Internet free for future generations.

Magnetic loop HF TX antennas

Although I have successfully used a large 80m sq vertical wire loop (made with 32 x 0.2mm PVC covered wire) on both 137 and 500kHz, I have never tried a hi-Q small loop on HF transmit. There is a very useful calculator available at http://www.66pacific.com/calculators/small_tx_loop_calc.aspx which suggests a 3m circumference loop using a 5mm diameter conductor - for example small bore copper pipe or a thick coax cable - would have a loss of only 0.9dBd and a bandwidth of 352kHz at 28MHz.  This would comfortably cover both 28MHz CW, data, WSPR and beacons without retuning.

An advantage of magnetic loop antennas is reduced detuning from nearby objects so this antenna, if mounted in the loft space, might make a neat and efficient stealth antenna for 10m. I guess one could even arrange to switch the tuning capacitor remotely so that several sub-bands could be covered. When using QRP power levels, as I do, the high voltages and currents that are encountered in small loops are less problematic. For example, choice of variable or fixed tuning capacitors is less onerous than if using 100W.

http://www.kr1st.com/magloop.htm

KR1ST has some nice information on magnetic loop antennas on his website.  I hope he doesn't mind me linking to the image of his magnetic loop on his site. There is also some useful loop information on the Wikipedia site.

In all, I think I'm missing out (so far) on a whole range of antenna experiments!

SAQ (17.2kHz) transmission Dec 24th

The following is from the SAQ (Sweden) website:

We plan for a traditional transmission on Christmas Eve Monday 24 December. We plan to start the transmitter at 07:30 UTC and will be on air a few minutes later. A message will be sent at 08:00 UTC. The frequency is 17.2 kHz CW.

 QSL-reports are kindly received:

 QSL reports can be given via:

- E-mail to: info@alexander.n.se
- or fax to: +46-340-674195
- or via SM bureau
- or direct by mail to: Alexander - Grimeton Veteranradios Vaenner, Radiostationen, Grimeton 72, S-432 98 Grimeton, SWEDEN

Note: SAQ is a member of the Swedish Amateur Association (SSA) and "QSL via bureau" is OK.

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.