Monday, 28 January 2013

Mains Filter - Good Housekeeping ?

After reading an article in Radcoms 'In Practice' by GM3SEK sometime ago (May 2009) making reference to a filtered mains supply. This is based on a Belling Lee mains filter which filters line, neutral and earth. It is capable of passing 16 amps so well up to supplying the whole shack including computer.
Pictured is the unit mounted in a plastic box with plastic cable glands as strain relief. This unit then feed a strip of six sockets to supply the shack bench. obviously the lid must go on as there are exposed terminals with mains power.

The theory is that this unit should help prevent any RF currents going back into the house mains wiring possibly causing RFI issues. Another option is winding the mains cable on a stack of large ferrite cores.

GM3SEK's website

Wednesday, 16 January 2013

Attic Doublet on Topband

Bit of fun really. Just wondered if my Attic Doublet would put any kind of signal out on 160m Topband.
You couldn't make a qso but WSPR reporting shows:

WSPR on Topband

Terrible on receive though. May try some experiments with topband in the future.

Monday, 14 January 2013

MW0IAN Mobile Station

Just a quick look at my VHF / UHF mobile installation, consisting of a Yaesu FT7800 dual band with mobile whip.
The main problem in my opinion these days is installing a mobile rig in the car without it standing out like a sore thumb.Mag mount aerials are good because they can be easily removed but this can be inconvenient. The alternatives are hatch mounts or drill mounts.Hatch mounting was not possible for me, due to plastic spoiler-trim on the upper side of the hatchback.
This is my solution: remove the broadcast AM/FM factory fitted aerial and fit a PMR type mount in the same position . This saves drilling any new holes. Onto this mount is a Garex electronics dual band whip which is painted satin black to blend in (normally shiny stainless steel).No one has even noticed, including XYL !!

Garex whip on Pmr base

For the broadcast radio I installed a window mount active aerial onto the back window which is powered by the original DC feed to the factory broadcast band aerial.

Active window AM/FM antenna

To power the Radio in the car I fitted a direct (Fused) feed to the vehicle battery (supplied with radio). This meant drilling a hole into the bulkhead from inside the car ( carefully checking other side of hole) and feeding the wires through a sturdy grommet . These were then carefully routed around the car, under trim panels etc making sure nothing could rub causing damage to the cables. **12v dc car batteries carry high current and can melt cables easily if shorted out causing a potential fire risk ** see here for advice on mobile installations

Battery feed in engine bay
DC feed through under dashboard (passenger side)

The main body of the radio was mounted under the passenger seat with a remote external speaker.
The control head was mounted on the main console in front of the gear change and under the heater controls for the car.

Remote head in centre console

Just need to look for a hands free arrangement, now. I have a couple of ideas , more to follow..

Monday, 7 January 2013

Attic Doublet revisited

Just a quick post about my loaded doublet in the attic, fed into a remote smartuner.
This has proved quite useful and much better than expected. This I put down in part to some excellent choking on the coax feed-line from the smartuner back to the shack. This seems to keep the noise down a little and the use of electric fence insulators helps too rather than tacking directly to the timbers.
No this is not a DX aerial but a compromise solution where large plots are not available or stealth is desirable or enforced.
Downside is I would only run QRP 5watts due to proximity to household wiring and RF exposure.
This indoor aerial is only about 1-2s points down on my outdoor wire described earlier, though the latter is quieter.
The Smartuner could be omitted  and the aerial fed with coax for dualband 40/20m operation or fed into the shack via 300ohm feeder into a z-match or similar.
To recap: 40m/20m loaded doublet aprox 40ft long , inverted V and dog legged to fit in small attic.
Works 40m-10m with smartuner :-)

Details of choke Balun G3SEK in Practice Website

Smartuner fed with 300ohm below doublet

choke balun and DC control line.

40m loading coil dog leged

300ohm feedpoint

electric fence insulator


After quite a while I'm please to say I have finally got WSPR running on my Debian Linux PC..

This has taken quite an effort for me as I'm no computer tech by any means.
Now running nicely with my recently constructed  interface and £3 usb soundcard from ebay.
Also have FLDIGI running for PSK31 .techy
Should prove useful for aerial experiments etc.

WSPR K1JT         Fldigi W1HKJ