[Antennas] Re: B&W window antenna

Wed, 3 Apr 2002 19:01:35 EST

Just some of my own input here.
I had the chance to help a local ham try to get his B&W window antenna to hum.
We tried everything and the best SWR on 20 meters was 4.1 to 1.
We then tried a tuner and could not get below 1.7.
We added grounds and 2 more radials.
We then tried the 40 meter and the instructions said to leave the wire for 
the tap OFF or hook it at the end of the coil.
Same problem.
SWR was better at 3.1 but at least we got it down flat with the tuner.
But a tuner should not be needed.
Now my home brew window antennas I had great difficulty finding the sweet 
spot on the coil for a low SWR but I did find it and the SWR was 1.3 and also 
was taken down lower by moving the radial..
We went back to the B&W and added 2 turns to the coil and we moved the tap 
just short of 1 full turn.
BINGO!! we had a 2.1 SWR.
Playing around we got as low as 1.4
I think I'll keep with my 9 foot job I built the first time.
Tomorrow B&W gets a call and I want to know why we had to add 2 turns or if 
it was a factory defect.
I have not seen the MFJ but it has a 4-1 balun built into it but I can't seem 
to get any info on it.
So if you feel the need for a short antenna and want to work DX build your 
own or just use a mobile stick..
The coil on my home brew has 50 turns and tapped appx 2.5 turns up from the 
bottom.
That gives me a flat SWR and I have a full 75 KC on 40 meters and the SWR 
climbs up to 1.3.
Close but no cigar.
Remember if you want to build one they work great but the taps are very fussy.
I used a needle to tap # 18 GA RS speaker wire.
I has a noise bridge in line and when that started to settle down I put the 
SRW meter in line.
A lot of fun and you can bag world wide DX with them as many have.
But B&W in the past had a coil for each band and I feel thats where they 
screwed up.
I guess as i'm not an EE.
I just assume.
As it stands right now i'd rather have a coil for each band.
Anyone have this problem with the B&W?
SAVE$$$$$$$$$$$$$$ and build.
Bob
AF2Qrp <tm>