Re: [softrock40] Softrock RXTX Ensemble with a Magnetic Loop Antenna
- The bandwidth is around 2.7 KHz for the loop made of 22mm copper tube.
73 ... Sid.
On 01/04/11 20:43, Richard wrote:
> On Fri, 2011-04-01 at 20:09 +0100, Sid Boyce wrote:
>> They work quite well. I even heard one guy say that when his beam
>> down he used one and was able to maintain his daily sked UK to ZL.
>> One other positive is that they don't need the height. Tony (G4OGP)
>> first sold magnetic loops in the UK said that he had used one on top
>> Blackpool tower and at ground level with no difference in performance.
>> Usually at the then Leicester show which was in a large steel hangar,
>> all the vendors could only show you their gear and say that antennas
>> couldn't work at that location, while Tony had one of his loops on
>> air, pulling in European stations at 59+ and making QSO's.
>> It was much much later before MFJ produced their magnetic loop.
>> They are a number of Windows and DOS calculator programs on the net,
>> mloop, mloop31, etc. so you can play with different parameters ahead
>> ordering any hardware. Also if anyone is interested in playing with
>> different sizes and shapes of magnetic loops, these programs give you
>> good idea. I start off with inputting different sizes of copper,
>> lengths and shapes and when I come up with something that I like, I
>> the materials and put it together.
>> I use a Gamma match for lowest SWR, usually close to 1:1 and fire it
>> Though copper is best, Tony's loops were made from aluminium tube,
>> customers were not only hams but Embassies and other government
>> agencies. I've seen some made of aluminium curtain track.
>> 73 ... Sid.
> You can also make them out of expensive heliax cable such as LDF4-50,
> once water gets in it its pretty usless and gets thrown away.
> But you only use the outside solid ( corrugated ), copper and its self
> supporting within reason, AND its an interference fit to 15 mm Cu
> tubing, 1/2" will be very close as well.
> I've a 6 mtr diameter loop in the garden I use on 160& 80 Mtrs.
> Two wood cross members and the whole thing is on a fibreglass pole.
> I'd be interested in how broadband your gamma match is Sid ?
> I use a loop and its gone a bit higher than normal.
Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks