UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Closed Thread
 
Thread Tools
Old 14th Oct 2021, 2:13 pm   #1
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 6,394
Default Using theTECSUN AN-200 AM MW Tunable Medium Wave Gain Loop

I have a TECSUN AN-200 AM MW Tunable Medium Wave Gain Loop. I find it gives good results albeit a little sensitive to use, but not a problem. It removes a lot of the digital hash problems that are so common these days. Anyway, I generally use it in wired mode, connecting the dual wire output to the A and E terminals on a radio or AM tuner. I also have a long wire outdoor AM aerial up at chimney level that I installed a few years ago but unfortunately although it pulls in a strong AM signal, it suffers from the dreaded digital hash that it must be picking up on the indoors section. Now, it's just a simple thing to try out I know, and I will, but would loosely coupling the indoor end of the long wire aerial around the Tecsun's loop give better results? Kind of mixing the best of both aerials?
Attached Thumbnails
Click image for larger version

Name:	5ffbfefd364aacfdbbdd9446-1-large.jpeg
Views:	40
Size:	51.3 KB
ID:	243408  
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline  
Old 14th Oct 2021, 3:28 pm   #2
Andrew2
Octode
 
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 1,937
Default Re: Using theTECSUN AN-200 AM MW Tunable Medium Wave Gain Loop

Probably not, as the noise picked up by the wire aerial will just be passed on via the loop. There is one chance though. If you are prepared to do a lot of fiddling, you may be able to find a position of the loop in which the noise from the wire is in opposition to any noise picked up by the loop, thus reducing the noise even further.
It's a crude version of the 'QRM Eliminator' devices which take two inputs and subtract one from t'other.
__________________
Andy G1HBE.
Andrew2 is offline  
Old 14th Oct 2021, 5:07 pm   #3
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 6,394
Default Re: Using theTECSUN AN-200 AM MW Tunable Medium Wave Gain Loop

Quote:
Originally Posted by Andrew2 View Post
Probably not, as the noise picked up by the wire aerial will just be passed on via the loop. There is one chance though. If you are prepared to do a lot of fiddling, you may be able to find a position of the loop in which the noise from the wire is in opposition to any noise picked up by the loop, thus reducing the noise even further.
It's a crude version of the 'QRM Eliminator' devices which take two inputs and subtract one from t'other.
As it is now, I have to carefully adjust the orientation of the Tecsun so as to minimise the any interference. Would this null position be the same as the one you are referring to?
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline  
Old 14th Oct 2021, 11:32 pm   #4
Andrew2
Octode
 
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 1,937
Default Re: Using theTECSUN AN-200 AM MW Tunable Medium Wave Gain Loop

If the noise isn't nulling out sufficiently on the loop, a carefully introduced amount of noise from the wire may win you a useful reduction, but it will take some experimentation with the positioning of the wire. The distance of the wire from the loop will alter the amplitude of the noise injection, and the side of the loop the wire is on will reverse the phase.
Once you hear a reduction in the noise a slight rotation of the loop will 'fine tune' it. If the loop is tunable, this will also affect the phase.
My first experiments were along these lines, but I used a rather more 'built up' arrangement than you have at the moment. Good luck.
__________________
Andy G1HBE.
Andrew2 is offline  
Old 15th Oct 2021, 6:44 am   #5
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 6,394
Default Re: Using theTECSUN AN-200 AM MW Tunable Medium Wave Gain Loop

Hang on, how should I be loose coupling the long aerial wire to the Tecsun loop? I was thinking of a couple of loose winds around the top section?
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline  
Old 15th Oct 2021, 8:28 am   #6
Andrew2
Octode
 
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 1,937
Default Re: Using theTECSUN AN-200 AM MW Tunable Medium Wave Gain Loop

The wire can be just dangling near the loop which would cause capacitive coupling, or you could form a single-turn loop in the wire (size equal to or less than the Tecsun size) and take the free end to an earth connection. This is inductive coupling and the new loop can be flipped around on its axis to reverse the phase. It's all very iffy while it's in this state, but I got results from my system fairly quickly. A good starting point is to listen to the radio and adjust the noise coupling until you hear the noise just increasing. This means the noise from the Tecsun and the noise from the wire antenna are about the same. Then you only have the phase adjustment to do.
My first system used a ferrite rod antenna and a tuning cap mounted together on a baseboard and a wire antenna loosely coupled (via a small cap) into the 'top end' of the tuned circuit. Phase reversal was by turning the entire rod ass'y around 180 degrees and fine phase by small twiddlings to the tuning cap. I think I later graduated to a single turn coupling coil on the rod for the wire antenna, which enabled me to reverse the phase by slipping the winding off the rod and flipping it around.
Things became a lot easier when I stopped mucking around and made a boxed, active unit with amplitude controls and phase reversal switches!
I'm sorry if my description is a bit dense, but explaining something makes you realise just what a complex thing you've been doing without thinking about it!
__________________
Andy G1HBE.

Last edited by Andrew2; 15th Oct 2021 at 8:34 am.
Andrew2 is offline  
Old 18th Oct 2021, 12:05 am   #7
majoconz
Hexode
 
majoconz's Avatar
 
Join Date: Jan 2008
Location: Palmerston North, New Zealand
Posts: 481
Default Re: Using theTECSUN AN-200 AM MW Tunable Medium Wave Gain Loop

I made a 'qrm eliminator' a couple of years ago now. I surveyed the schematics of quite a few after Googling - some were very complicated but in the end I settled on two to try - the only real difference between the two was how the phasing transformer was wired - one gave a very sharp peak but didn't seem to work very well over a wide band of frequencies. Looking back to the original maker's diagram he had a switched coil pack, almost an antenna tuner! Fine if you have a single wire lead-in but no good for coax. My final arrangement gave an easily tuned peak and was wideband from the MW AM right up to about 18MHz. Unfortunately it made itself obsolete when I got an 8-channel multicoupler to feed 6 HF receivers all on different frequencies!
Attached Thumbnails
Click image for larger version

Name:	Final sml.jpg
Views:	44
Size:	73.7 KB
ID:	243647  
Attached Files
File Type: pdf QRM eliminator final.pdf (135.6 KB, 35 views)
__________________
Cheers - Martin ZL2MC
majoconz is offline  
Closed Thread

Thread Tools



All times are GMT. The time now is 3:34 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2022, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.