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Latest Topics

Topic Created Posts Views Last Activity
questions about AM broadcast band images Aug 24th, 13:20 2 65 1 week, 4 days ago
Use of old laptop power packs ? Dec 28th 2014, 15:30 1 437 on 28/12/14
Strange RFI on 10 meters and 6 meters Jun 19th 2014, 17:12 2 653 on 19/6/14
Two important functions missing in new radios ? Feb 4th 2013, 15:16 5 1,290 on 28/2/13

Latest Posts

Topic Author Posted On
questions about AM broadcast band images AB3FN 1 week, 4 days ago
I want to explore the spectrum below the AM broadcast band. The second IF in my late-model triple-conversion radio is 455 kHz, and I'm getting swamped with broadcast band images. E.g., an AM station broadcasting on x kHz has a powerful image at x-910 kHz. My radio is a modern one, but I live near a large metropolitan area with a lot of AM broadcasters.

Is this a common problem with modern radios? Any comments about specific brands / models? I've had marginal results with a home-brew filter - any suggestions about filters? Of course, I'm only interested in receiving, not transmitting.

Thanks in advance for your comments and suggestions.
Use of old laptop power packs ? AB3FN on 28/12/14
Laptop power packs typically put out 16-18 VDC at a few amps. Is there any obvious problem with using several and putting the outputs in series to get higher voltages ? Is there adequate isolation between the 110 VAC input and the output ? Problems with regulation ? Has anybody done this ? Of course, depending on the specific power packs and the desired output, there might be a need to insert a series resistor or something else to reduce the voltage. Thanks in advance for your reply, insight, and suggestions.
Multimeter Calibration in Atlanta KK4ZWM on 17/11/14
Note that the left-most digit in the display can only be "1". Referring to the operation manual, you will see that the maximum display for the 20 volt range is 19.99. The lab is probably referring to the 20 volt range. This approach was very common with older gear.
Strange RFI on 10 meters and 6 meters AB3FN on 19/6/14
I've recently started hearing noise at approximately 57.3 KHz intervals. The noise is strongest on 6 meters, slightly weaker on 10 meters, and continues to weaken all the way down to 40 meters. This seems "backwards" to other RFI situations. I plan to swap power supplies, use ferrite cores on various lines, etc., but would welcome any thoughts. Thanks.
Two important functions missing in new radios ? AB3FN on 4/2/13
Maybe I'm missing the boat here, but I'd like to understand why our radios don't use signals from GPS or WWV. Lots of low cost consumer electronics does.

Instead of a TCXO, for example, a radio's frequency reference could be derived from GPS or WWV. If those signals were unavailable, then the radio would use its internal reference.

Similarly, why don't our radios include a clock, which would also derive the time from GPS or WWV ? And again, if those signals were not available, then the clock would revert to its own internal crystal.

Seems to me that both features would be easy and cheap to incorporate. Are there technical issues that I'm just not seeing ?

Thanks in advance for your thoughts and for educating me.

73 - Allan, AB3FN

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