Par EF-10/20/40 Antenna and a comparison

This afternoon I decided to take down my 10m halo for a while and replace it with a lower antenna: the LNR Precision (was Par) EF-10/20/40 end fed wire antenna, which I've owned for some years but not used recently. As it suggests, it covers 10, 20 and 40m with a very low SWR, although it is a reasonable match on several other HF bands too.

See http://www.hamradio.me/antennas/lnr-precision-ef-102040mkii-test-data.html for an analysis of this antenna.  The antenna works very well and on 40 and 20m WSPR I was getting plenty of spots with 500mW to 5W.

Photo on http://www.hamradio.me website of the Par antenna

On 40m I did a comparison between the horizontal EF antenna and the earth-electrode antenna. A series of transmissions was made with each antenna in turn, then I compared WSPR spot S/N received from a number of stations.

The conclusion is the earth-electrode antenna is around 9-16dB down on the EF antenna on 40m, so averaging about 2.5 S-points down. The test is not too accurate as conditions change, the earth-electrode and EF have some directivity and the reports sample size was small.

Grandchildren time and new projects

We've all 4 grandchildren coming to stay at different times over the next couple of weeks. As usual, this means that amateur radio activity will decrease somewhat as the upstairs shack gets used as a real bedroom again. It will still be possible to run WSPR on LF and MF and some of the HF bands from time-to-time, but not in the evenings.

Whilst this "interlude" is going on, it will be a good time to take stock and think of the next projects. The early part of 2013 has seen a burst of activity related to the earth-electrode antenna and the ferrite rod TX antenna, neither of which was planned. I also did some more work on a 136kHz transverter Several projects, including the 136kHz transverter, are still unfinished:

Tenbox 10m AM transceiver
Although most of this has been breadboarded and is working, it still has to be boxed and properly documented. I quite fancy a PCB for this simple design and that needs to be created.

471THz over-the-horizon tests
My PhlatLED very high power LEDs have yet to be switched on and I still have to build a more sensitive detector.

De-cluttering and Test equipment
With a move to a new QTH later this summer I really ought to think about de-cluttering and sell some lesser-used radio equipment. At the same time I could do with building some more pieces of simple test equipment such as a proper QRP power meter, a resistive SWR bridge, a better ATU, and a very basic spectrum analyser.

Other projects
There is a list as long as my arm of other projects I'd like to tackle, but it takes me all my time to do the ones I do! 

IC7100 Sneak Preview Video

There is a short YouTube video clip from ICOM America describing the IC7100 with a look at the various connections on the head and main unit. The thing that impressed me was just how small this transceiver is. It looked larger in the earlier pictures. The IC7100 is likely to be on sale in the UK in late spring at around £1700-1800 without the D-star option. Not cheap, but a lot of radio.

The specification of the IC7100 is available here.

Hard to believe this is without a conventional antenna

As 40m went rather quiet, I QSYed to 80m WSPR on the earth-electrode antenna this evening. The log below is from just one single 2 minute transmission with 2W.

12 spots in one 2min burst this evening with 20m spaced earth-electrode antenna

Earth-electrode antenna on 40m

This evening I have been trying my stealth antenna (20m separated earth-electrodes, wire in the grass!) on 40m again and getting plenty of WSPR spots. I did try to match it on 160m earlier but couldn't get it below about 3:1 using the Elecraft T1 auto-ATU. Spots from 6 countries in an hour (LA, DL, F, EI, GM, G) with strongest reports from Cornwall (-3dB S/N) which is in the line of the wires/loop.

WSPR spots received using 20m spaced earth-electrode antenna with NOTHING in the air.
 

Earlier today I had a visit from Ted G4NUA, so I showed him my 137kHz antenna, "Where is it?" he said. Exactly - the wire runs back to the house from the far earth rod IN the grass and it is all but invisible!

Earth-electrode antenna on 80m

This evening I have been using the 20m baseline earth-electrode antenna on 80m. From the shack (upstairs) there is a 20m coax down to the back of the garage where it picks up the earth electrode wires. On 160m the match is poor but on 80m a near perfect 1:1 match, so no radiation from the coax.

On receive there are plenty of signals visible and decoding on WSPR and on TX it seems to be getting out pretty well with 1W RF from the FT817.  I am not sure of the ERP on 80m, certainly higher than on 630m (472kHz), but it does appear to be quite effective.

Tomorrow evening I'll match the earth-electrode antenna with the Elecraft T1 auto-ATU and see how it performs on 160m. I'll put the ATU right at the earth-electrode end of the coax so that we'll see the radiation from the earth-electrodes and not the feeder.

10m WSPR

10m WSPR reports late this afternoon

This afternoon, whilst updating my website, I put on the 10m WSPR beacon. All was very quiet for the first hour or so and I was about to switch it off. Then I looked and saw a heap of stateside spots had appeared. This is the beauty of WSPR: you can get on with other things and use it to see when the band opens up. It will become especiallyuseful on 10m when the peak (such as it is) is over and we are looking at quiet conditions on 10m again. At least with WSPR there will be a much clearer picture of the openings that do occur.

137kHz E-field probe on my website

This afternoon I put a new page on my www.g3xbm.co.uk website describing the 137kHz E-field probe antenna used in my recent "drive around" tests in the local area out to 25km. You may recall I put my 6uW ERP QRSS3 beacon on and went out into the Cambridge countryside trying to see how strong it was in various locations.

The whole unit is fixed to a car mag-mount antenna and works very well indeed.

OFCOM licence exempt loopholes

Still trying to see if there are any loopholes that would allow me to legally carry out radiated tests between 40-80kHz as mentioned in earlier posts.

Currently I'm pondering an OFCOM document called IR 2030 - UK Interface Requirements 2030 Licence Exempt Short Range Devices .  This document seems to offer some hope by adopting the licence exemptions applicable to short range devices such as metal detectors and induction communications systems. For example, for metal detectors, it says,  

"That part of an induction system designed or adapted to produce:- (a) a controlled magnetic field; and (b) a predetermined recognisable signal when operating within that magnetic field" 

in the frequency range 9 - 148.5 kHz the emission level is [not greater than] 70 dBμA/m at 6 m. My maths is not good, but this is 3.15mA/m which sounds quite a lot. Some other specifications allow 72dBuA/m at 10m, which is considerably more. It seems I need to read a copy of document EN 300 330-2 which describes the rules and test methods. Although these rules are designed for systems that use induction field communications, the unknown is how much signal that meets these requirements might be radiated and detectable with sensitive kit in the far field?

Incidentally, it is surprising how many non-amateur frequencies can be used legally with (useful) QRPp power levels in the MF, HF, VHF range, no doubt with some type approval stipulation or at least CE declarations being required on the equipment. With WSPR or similar weak signal modulation systems, some most interesting experiments could be carried out in unusual parts of the LF, MF, HF and VHF spectrum, apparently without a licence being needed, as long as the emissions limits are met.

OFCOM ..."no you can't" again at LF

This afternoon I got another email from OFCOM. Although my requests have been passed upwards for other more empowered people to consider, it is effectively a refusal of permission to carry out experimental research for short periods even at 10uW EIRP on clear spot frequencies in the LF spectrum between 40 and 80kHz without getting a £50 Non Operational (T&D) Licence, which I am not prepared to do.