Re: Topband: 1820 spur
ALL of the 10 KHz frequencies are bad somewhere in NA, and the same issues apply to the 9 KHz spaced MW stations in other parts of the world. Second harmonic, and regular ordered products abound. Example 980+840=1820 These products/harmonics are generated in lots and lots of things, from our own receiver front ends to the nearby rusty chain link fence, and our own guywires The stations need not be near by. Consider just how loud any 50KW Omni station is after just ONE hop. Easily many tens of millivolts will appear in every topband TRANSMIT vertical within 1000 miles - from each station. Just look at how hard the S meter pins at 60 dB over 50 microvolts when tuned to one of the powerhouse stations http://en.wikipedia.org/wiki/List_of_50_kW_AM_radio_stations_in_the_United_States This is JUST the 50KW stations, there are thousands more in the 1 to 10 KW class Run your own ordered mix calculator, and you will be surprised at the results. Its amazing we are not plagued much more than we are by products and harmonics. It takes a LOT of harmonic suppression to reduce 50KW to a power we can not hear with a beverage pointed at the station, FAR more than required by the rules. Bottom line, stay away from any exact KHz, especially any exact 10 KHz in North America. The worst possible freqs in NA are 1820, 1840, 1860, etc. as these can be both harmonic and product frequencies. Never use these (or any) exact frequencies. An offset if 150 Hz is often enough to make your signal easily readable where it would be obliterated by a weak carrier on the exact frequency Robin Critchell, WA6CDR - Original Message - From: Tim Duffy K3LR k...@k3lr.com To: 'Mike Waters' mikew...@gmail.com; 'topband' topband@contesting.com Sent: Friday, November 02, 2012 19:59 Subject: Re: Topband: 1820 spur Hello Mike: I believe that the 1820 spurs are created from multiple sources. That is why you can hear it at many QTHs around the world (although the spur content is technically different with respect to the origin). There are 57 different licensed AM broadcast stations in the USA and Canada that operate on 910 KHz. Most all of them are operating within licensed parameters with respect to second harmonic radiation limits. Topband stations are best to avoid operating directly on 1810, 1820, 1830, etc. for this reason. 73, Tim K3LR -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Mike Waters Sent: Friday, November 02, 2012 9:17 PM To: topband Subject: Re: Topband: 1820 spur It can be heard in Japan and Canada?! Where could it be coming from? 73, Mike www.w0btu.com ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: 1820 spur
And southwest Colorado 73 Art K6XT~~ Success is going from failure to failure without a loss of enthusiasm. ARRL, GMCC, CW OPS, NAQCC ARRL TA On 11/3/2012 6:54 AM, topband-requ...@contesting.com wrote: Message: 16 Date: Fri, 2 Nov 2012 21:16:39 -0500 From: Mike Watersmikew...@gmail.com To: topbandtopband@contesting.com Subject: Re: Topband: 1820 spur Message-ID: CA+FxYXjfecCoOpu5xr_eTMXgp9aKHBxN=VQV=vvq3bv2zne...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 It can be heard in Japan and Canada?! Where could it be coming from? 73, Mike www.w0btu.com ___ Topband reflector - topband@contesting.com
Re: Topband: 1820 spur
-Original Message- Subject: Re: Topband: 1820 spur It can be heard in Japan and Canada?! Where could it be coming from? 73, Mike www.w0btu. We can be sure it is not a harmonic of an IF. :-) 1820 is a particularly bad frequency because it involves 2nd harmonics of a popular channel (910) and also is a mixing product for many orders of multiple channels. I think most of it comes down to harmonics of 910. The actual law is the BC station has a certain maximum allowed spurious level, AND cannot cause harmful interference from any defect no matter what the level. My bet is a significant number of stations today don't even meet the allowed maximum harmonic level. This is because AM stations are going broke, and deregulation and budget cuts. The FCC dropped the 1st class FCC back in the 80's, so anyone can work on radio stations. I found a strong signal on 2.5 MHz from a station in north GA. A local CB shop worked on it, tuned the transmitter 4-400A PA to 2.5 MHz with the wrong dip, and adjusted the antenna tuning unit for a low SWR. It ran that way, with a kilowatt daytime on 2.5 MHz to a matched antenna, for months. I can hear radio Disney and some other thing every day below the AM band. It is a mixing of two stations. There are a multitude of things like this, plus illegal level switching supplies. One popular satellite TV company has gear that can be heard for miles on 160. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: 1820 spur
I understand that. I have heard weak spurs on multiples of 10 kHz that come and go on the low end of 160 ever since I put up Beverage antennas here. But the one on 1820 is the strongest I have ever heard, and it's there often. And several times in the last few weeks, weak DX stations have chosen 1820 to call CQ. :-) 73, Mike www.w0btu.com On Sat, Nov 3, 2012 at 1:15 AM, Robin wb6...@socal.rr.com wrote: ALL of the 10 KHz frequencies are bad somewhere in NA ... Bottom line, stay away from any exact KHz, especially any exact 10 KHz in North America. The worst possible freqs in NA are 1820, 1840, 1860, etc. as these can be both harmonic and product frequencies. Never use these (or any) exact frequencies. ___ Topband reflector - topband@contesting.com
Re: Topband: 1820 spur
Oops, I meant 910 kHz, not 920. On Fri, Nov 2, 2012 at 8:40 PM, Mike Waters mikew...@gmail.com wrote: Does anyone else have the constant carrier on 1820.0 at night? I've heard it for weeks, and it's interfered with several DX stations that I was trying to copy. And I see I'm not the only one. I just saw the following on http://www.dxscape.com/us160cw.html: UN5J 0114Z 1820.0 1820 bad fq, 1827 much better AA0RS I'm guessing it's a harmonic from a 920 kHz AM BC station. 73, Mike www.w0btu.com ___ Topband reflector - topband@contesting.com
Re: Topband: 1820 spur
Mike, We have the same situation as you. 1820 is noisy in JA too. 73's --- Harry JG7PSJ,JD1BMH,KW2X On Fri, 2 Nov 2012 20:40:55 -0500 Mike Waters mikew...@gmail.com wrote: Does anyone else have the constant carrier on 1820.0 at night? I've heard it for weeks, and it's interfered with several DX stations that I was trying to copy. And I see I'm not the only one. I just saw the following on http://www.dxscape.com/us160cw.html: UN5J 0114Z 1820.0 1820 bad fq, 1827 much better AA0RS I'm guessing it's a harmonic from a 920 kHz AM BC station. 73, Mike www.w0btu.com ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
