[RFI] DFing progress
Wed, 18 Dec 2002 10:36:37 -0500
What I suggest for an attenuator is a simple 10-dB design for a pi-net attenuator. The input Rs go to ground, with a resistor in between them. For 10 dB, the input and output resistors should be 100 ohms and the series resistance should be 72 ohms.
Now, replace the 72-ohm resistor with a 500-ohm trimpot. You can now set the attenuation to range from a couple of dB to tens of dB. The pad is not a perfect match any more, but on receive, for this purpose, that is just fine.
Ed Hare, W1RFI
225 Main St
Newington, CT 06111
> -----Original Message-----
> From: Pete Smith [mailto:email@example.com]
> Sent: Tuesday, December 17, 2002 7:55 PM
> To: firstname.lastname@example.org
> Subject: [RFI] DFing progress
> I wented to let everyone know that I've succeeded in mating the Moxon
> rectangle antenna from the March 2001 RFI receiver project to my Icom
> IC-Q7A handitalky. I cobbled up the antenna out of aluminum
> rod, mounted
> it to a board with screw eyes, and threaded the ends of the
> rod for nuts to
> attach the feedline. The resulting antenna resonated at 137
> MHz first try,
> and has a broad front lobe, fair attentuation off the sides,
> and a very
> narrow cardioid-style notch off the back, all just as advertised.
> The only small downside is that the thing is almost too
> sensitive. Anyone
> got any suggestions for a simple non-calibrated attenuator
> that I could put
> between the antenna and the radio to make it work a bit
> better close in to
> the noise source?
> 73, Pete N4ZR
> Happy Holidays
> RFI mailing list