Balanced feeder

Hello all , I know this is not directly sota related but is radio related.

I been thinking to try a doublet at my home qth , but the possibilities to get the balanced feeder to my shack desk has me thinking how to do it .

The property is a UK bungalow and the shack in in a loft conversion , the desk is sat facing the rear window in the doormer and hence has roof tiles all around and 4 rows of tiles below the doormer then a flat roof which is the kitchen below . Where I normally run coax out of the sofit goes across the outside of a pipe with wiring for the garage, the pipe is a meter long before entering the garage itself. In a few week as the roof is being replaced with a metal roof so that side of the garden is a no go with balanced feeder . Other side of the garden is a gate which is owned by next door but no access from the rear of the house due to the flat roof .

So only options I got is to go under the tiles and through a stud wall by the desk itself while suspending feeder above the garaage and kitchen flat roof . Or to go through the window shut .

Anyone who used ballanced feeder can advise me what best route to go please ?

Thanks, 2e0fgx

Hi Mathew,
Not cheap, but if you are considering bringing in more feeders at that side of the loft in the future, perhaps something like this would be worth considering:

You’ll need to check if they work with dorma windows though.

73 Ed.

Hi Ed I was looking into this solution last week. As far as I can tell it only works with the sash type window opening. A pity it won’t work for me (nor I suspect Matthew), as it looked a quick and easy solution to the issue of bringing cables into the house.

Mine just runs through the window which shuts and holds it in place. An alternative is an external auto atu and a coax feed in.

Hi Ed , thanks i will have a look .

A dormer window in the UK is not the window type , it is where on a slope apex roof type you have a widow vertical and a flat roof build just below the ridge line . Window is a standard 3 payne type , 2 side openening left and right and a fixed middle .

Correct its more the older type sash windows . Mine are modern pvc and hinge left and right

Is that with window line or open wire feeders with spacers Richard ?


Hi Matthew.

I’ve had no problem bringing “computer ribbon feeder” (a la Norcal Doublet) in through the side of a uPVC window opening, just trap it in the gap and the rubber seals are flexible enough to accommodate it. Also has worked OK with RG174 coax. Just avoid the various bits of ironmongery and spacers associated with the hinges and locking system to avoid mangling the feeder!

I make sure my wires approach heading upwards and form a bit of a drip loop so that water won’t track along the cable and pass the seals

Should work with wire/spacer feeder too, so long as the wire isn’t too large or stiff, stranded would be best. Be aware that down the side of the window with the handle/locking mechanism on will be an exposed metal bar, so wires would need to be insulated or taken through the sides or top/bottom where the hinges are.

Would have thought window line would be too large diameter/too stiff to go through.

73 de Paul G4MD

Edit - note that uPVC window frames often have metal box section inserts within to reinforce them, I’ve never noticed any adverse effects due to these.

My main antenna is a doublet fed with 300 ohm ribbon. As it happens my shack has a ventilator and the ribbon passes nicely through one of the apartures. This worried me for some time as the grill is metal and might cause an imbalance, so I tried having a balun just outside the ventrilator and a short run of coax to the tuner. This worked but I could not discern any benefit so I went back to running the ribbon through to the tuner. In your case you might find the balun and coax solution will solve your problem as long as the coax is not long enough to cause losses from a mismatch. If the run of coax is long enough to cause concern then you might consider replacing the balun with an auto tuner.

Thanks all , that sounds the best solution to solder some ultra thin wire where travels through the window . I guess balanced feeder can run near metal or right next to it but kept short distances .

My pole is a metal pole but will have to slope away from the pole .

Hi Ed,

I prefer the external auto ATU and coax feed in that Richard mentioned.

We call it balanced feeder but in reality it is very difficult to create a balanced doublet with absolutely identical legs. Therefore there is always a degree of inbalance in the feeder and so if the feeder enters the shack you are bringing an amount of RF into the shack too.

In my case I am using a 18M Spiderpole and the ladderline is fixed to the mast. Each doublet wire also forms half of the feeder so there is no termination at the doublet centre to possibly fail. The spreaders are 110mm. At the base I have a homebrew high power 1:1 current balun and that goes to my auto ATU. Bringing coax into the shack is obviously a lot easier than balanced feeder.

73 Andrew G4AFI

Open wire line in my case.