On Fri, 28 Jan 2005 09:59:35 +0000, [EMAIL PROTECTED] wrote: > > > Sorry this is "off topic" but there is so much experience here. I've been > licensed for only 2 years, my only rig is K1 so I've been QRP CW only (and > enjoyed it immensely). I've recently started using a PA to get up to 100W > on 3.5 to 21MHz, but RFI problems have started to appear. Here are the > symptoms: > > 50Hz hum on key down on hi fi > Similar problem on mains MW radio. > Freezing of PC modem on key down. > > These are all in different rooms of the house and all at least 15 feet away > from the rig. > > The rig is on the ground floor right next to the outside wall where the > coax feeder runs out at ground level. Feeder is about 70 feet long and all > at ground level until it rises to a multi dipole at 30 feet up, cut for > 80/40/20m. Feed point is at least 50 feet from house. The feeder shield is > connected directly to the PA ground point and therefore to the mains ground > wire. I have no Balun and no RF ground so I guess I've broken all the > rules. > > I suspect RF is on the mains 240V house wiring and can see it on my scope > (about 5mV P-P superimposed on the mains). I have a number of things to try > but not sure in what order of priority, maybe someone could help, I want to > tackle the source of the RFI first, rather than the affected domestic > equipment. > > Here's the list: > Make a coax choke balun in the feeder to reduce out of balance currents > (quick and cheap) > Fit a commercial balun (heavy and pricey) > Construct an RF ground in the garden and connect to feeder sheath at entry > into the house. (time consuming) > Fit a ferrite ring choke to the PA mains lead > Build an inductively coupled ATU to avoid connection of feeder sheath to > the mains ground. > Fit ferrite ring chokes to the affected equipment > Fit a proprietary RFI filter to the telephone line (to cure the modem > problem) > > Or maybe I should just go back to QRP hi. > > Any advice would be greatly appreciated as I don't want to run the risk of > causing RFI to the neighbours. > > > Why not take a look at our Web site? > http://www.simoncarves.com > > ************************************************************************* > The information in this email and any attachments may contain > privileged and/or confidential information intended solely for > the use of the individual or entity to whom it is addressed. > If the reader of this email is not the intended addressee, or the > employee or agent responsible to deliver it to the addressee, > you are hereby notified that any dissemination, distribution or > copying of this communication is strictly prohibited. > If you have received this communication in error, please notify > me by telephone or email and delete all copies immediately. > ************************************************************************* > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com
Things that I would try first:- a) Fit a balun (at the center of the dipole) or b) Make the antenna completely balanced by using open wire feeder, and a balanced ATU. You will notice a reduction in received noise as well as RFI reduction. Good luck 73 Stewart G3RXQ _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
