Friday, 13 February 2015

RF in the shack!

my previous PC picked up a little interference when I was using CW on 10m with my G5RV 1/2 size.

just a slight ripple on the monitor.

well, new PC and new monitor and the whole thing freezes when I use 10m.  then takes 5 seconds or so to come back to life afterwards.

not good!!

so I asked those wise people over at Hamradiodeals what to do about it.

Naturally, as this was Hams there were a whole range of ideas!!

as always the old chestnut of "ditch the coax and go twin feeder came up, and while I accept that it may well work, I have three antennae, all connected by coax, and I have no experience of twin feeder other than as a part of a G5RV, so I'll respectfully pass on that.

other ideas were ferrite sleeves at the antenna end, a 1:1 balun and an ugly balun.

my ebay empire has been passable recently so I jumped on and ordered the bits to do all the above.

except the twin feeder thing!

first to arrive was the FT240-43  ferrite toroid (£7.99 inc post).  Google provided me with this diagram from VK6YSF

Figure 2  Wiring of the 1:1 Ruthroff voltage balun. 

OK, seems straight forward enough......

a rummage in my scraps box produces the wire, a plug and a socket......

as many turns as would fit on the ring.....

a few solder joints....

and a quick test before I bother to find a case.....

now, as some point I WILL case it up nicely.... but right now, the RF in the shack is gone, and on a pretty much dead 10m band I had a 10m QSO with UY5BO in Ukraine within seconds, and a couple of 20m contacts to make sure all was well there too.

so, problem solved for a total cost of £7.99, a few scraps and about 1/2 an hour's tinkering.

1 comment:

  1. A bal-un is used between a bal-anced and an un-balanced side.

    The photos show that on the receiver side you are connecting an asymmetric coax cable to the balun's unbalanced side as intended.

    On the balun's balanced side, it looks as if you're also attaching an unbalanced coax cable. However, it's not possible to see how long the unbalanced line is. The longer it is, the less the balun will work as expected.

    You might want to attach the balanced part, i.e. the symmetric feeder line, directly to the balanced port of the balun.