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Discone/random wire etc

PostPosted: Fri Oct 04, 2019 5:14 am
by mike43
Some more daft questions as a learner. My receiver is a Tecsun S2000 which I use for SWL..I have a random wire slung around my small garden into a 9-1 unun into my homemade ATU. I also have my discone scanner antenna which is used for my BCT 15x. I went through the shortwave bands yesterday morning trying out reception on both antennas to the receiver. The discone performed better than the random wire, more able to pick up stations better. I have done this before. Even though the discone antenna has an impedance of 50 ohms I still put it through the ATU for the hell of it and the reception was even better. Is it that the ATU has a finer tuning capability or something else?. The ATU works very well all of the time. On another tack, the Tecsun has a 50 ohm SW input and a 500 ohm SW input with a ground input beside it. I have a ground outside the window down 6 feet into the soil/beach. In theory what would be the better input to use with the random wire, or try it out. Thanks. Mike.

Re: Discone/random wire etc

PostPosted: Fri Oct 04, 2019 7:02 am
by Chris P
Only a suggestion but could the feeder to the discone be acting as an antenna rather than the discone itself.

The 500 ohm input would be more suited to the random wire without the ATU . How is the atu configured ie is it a T match or a Pi matching arrangement and how is the ATU connected to the Rx

Re: Discone/random wire etc

PostPosted: Fri Oct 04, 2019 7:00 pm
by M3ZYH
I have an AOR 8600 hooked up to a Discone, and it works exceptionally well on HF. Pretty average on VHF/UHF!!. I'm not really questioning why, just enjoying the performance.

Re: Discone/random wire etc

PostPosted: Sat Oct 05, 2019 4:52 am
by mike43
Thanks very much for answers. The coax from the discone is RG213 down through the loft into my bedroom. Not sure I understand if the coax is part of the antenna or not. The ATU I built from plans on the internet and is a "T" match with a 1k linear pot as an attenuator. The ATU is connected to the receiver via a short length of RG8x with a PL259. As a learner it bewilders me how this piece of passive kit works. I got carried away at one point and made a few of them with different designs "P" match and others. The only problem I had was using plastic rotary switches and being not so savvy at the time melting the plastic on some terminals because I did not use some sort of heat sink. One of these days I will buy a couple of ceramic switches and do the job properly. Years ago when the grand kids were little I had a Radio Shack DX 394 with some old army signal wire strung around the garden. The grand kids accidentally spilt water on the receiver and I never bothered for years to get back into SWL. At the time of the DX 349 I had a book called Teach Yourself Radio by David Gibson which I still have. In this book were simple instructions as to build an ATU for a crystal set from a bit of broomstick and some magnet wire for the induction coil and a crocodile clip for tuning (matching?). I love this story because one night I received the South Island New Zealand weather forecast by moving up and down the coil on this simple little bit of kit. Somewhere in my ragged books is the exact date and time of this. Couldn't believe it at the time so called my wife to also listen to it. Going on here a bit, sorry. I will try the random wire into the 500 ohm input without ATU and see what happens. Thanks again for answers, very helpful. Mike....