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Author Topic: Frequency question  (Read 2497 times)
HIFIMAN
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« on: September 17, 2012, 06:06:41 PM »

I do SWL at this point while I am studying for my ticket. This is going to sound like a stupid question to many Im sure. I love to listen to LSB on 40 meters, 80 meters. Yesterday while listening many seemed to be frequencies talking such as 7.200.00 or 7.180.00 as an example. Well today most seem to be 10-15kc below.Like 7.199.85 or 7.179.85. Could it be that the receiver needs calibration? On certian days or times are the frequencies allowed to be used change. I just find it strange in the difference. Hope you can understand my question? Thanks
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HIFIMAN
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« Reply #1 on: September 17, 2012, 06:09:07 PM »

Meant to say many seemed to be "on" frequencies talking.
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AC5UP
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« Reply #2 on: September 17, 2012, 06:18:36 PM »

If your receiver has an adjustable knob for BFO frequency or 'pitch' a change in that setting can cause you to tune a bit lower or higher. The two work together. It's also possible to listen to LSB with the receiver in CW mode if the filters aren't too sharp. The offset will be different and the displayed frequency will reflect that.

BTW:  Don't become too anal about every signal lining up with 'dot zero zero zero'. Not everyone is exactly on the button and sometimes when you tune for a natural sounding voice you make an assumption about what that person sounds like. Tune for best voice quality and use the frequency display as a guide, not an absolute value.
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HIFIMAN
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« Reply #3 on: September 17, 2012, 06:24:43 PM »

Thanks. That is what I have been doing as far as tuning to where someones voice sounds the best to me. But to prove your point when I tuned to that Hams voice the guy he was talking to seemed off. I will take your advice and not be too picky about where I end up on the dial. Thanks for your input.
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WB6BYU
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« Reply #4 on: September 17, 2012, 06:27:29 PM »

What are you using for a receiver?

Many ham rigs have an "RIT" control that shifts the receive frequency relative to the transmit
frequency (which is displayed).  If so, there should be some way to turn it off.

With an older receiver, it might be that the frequency drifts over time.

With the exception of 60m and the repeaters at the top end of 10m, the HF bands are
not channelized, so nobody has to be on any exact frequency.  With the advent of
digital displays you often find people operating on integer numbers of kHz, but often
on a crowded band they will squeeze in wherever they can find a spot.  And some of
us still have older analog rigs there we're happy if the indicated frequency is within
5kHz across the band, so we don't worry on whether we're exactly on a "tidy" number.
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WB2WIK
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« Reply #5 on: September 17, 2012, 06:29:07 PM »

The difference you described isn't 10-15 kHz, it's 150 Hz.  That's not much.  A receiver can be off that far if it's warmer or colder than normal.

And hams can transmit anywhere their license allows, there's no golden rule about sticking with frequencies that end in "00."

When calling CQ, I never tune to an "even kHz" frequency.  I tune to a clear frequency, wherever that is.  It could be 7197.38.  Who cares?
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HIFIMAN
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« Reply #6 on: September 17, 2012, 06:57:46 PM »

Thanks guys. I did make sure it was cleared and RIT off. Im using a TS 950s with no mic hooked up and power and mic turned all the way down. Dont want to transmit by mistake. Plus Im just using an antenna made for SWL listening.  Thanks on everyones input. Learned something too. Thats always a plus. Cant wait to get my ticket. Shouldnt be long I hope.
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AC5UP
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« Reply #7 on: September 17, 2012, 07:11:14 PM »

BTW: If you want to check the accuracy of the frequency display, tune WWV on 2.5, 5, 10, 15 or 20 MHz. Pick one with a stable signal, line up the VFO display on 'dot zero zero' and listen in AM first. If they're in the sequence with a beat tone (dong, dong, dong) note the pitch in AM. Switch to LSB or USB. The pitch of the tone should be the same. It will sound slightly different due to the filter width being sharper in SSB, but otherwise the SSB beat tone pitch should be the same as AM     - IF -    the radio is aligned to perfection.

Don't sweat a minor discrepancy.... Some radios are built to near-perfect tolerance but neither you or I can afford one.    Wink
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NA0AA
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« Reply #8 on: September 21, 2012, 09:23:55 AM »

Amateurs share the upper part of 40 meters with broadcasters as well, so while we are permitted 7.000 to 7.300, we have bcasting on 7.2 to 7.3.  This tends a lot of the time to push the amateur activity down the band - other times there's no BC and that upper part is more active.

With the advent of digital readouts, we seem to be hearing a lot of stations closer to on frequency - and newer radios are darn good at that, but it's sure not a requirement - as as aside, amateurs are one of the few users of HF who are NOT channelized.  We get a lot more traffic into our limited bandwidth than any commercial users ever will.  Of course we tolerate a level of QRM/QRN that no commercial user would tolerate.

Think how protected the old HF long distance point to point telephone frequencies would need to be to provide an acceptable commerial phone line at several dollars per minute?



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W8JI
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« Reply #9 on: September 21, 2012, 06:23:03 PM »

I do SWL at this point while I am studying for my ticket. This is going to sound like a stupid question to many Im sure. I love to listen to LSB on 40 meters, 80 meters. Yesterday while listening many seemed to be frequencies talking such as 7.200.00 or 7.180.00 as an example. Well today most seem to be 10-15kc below.Like 7.199.85 or 7.179.85. Could it be that the receiver needs calibration? On certian days or times are the frequencies allowed to be used change. I just find it strange in the difference. Hope you can understand my question? Thanks

I think you might be confused by the answers.

Hams do NOT need to stay on any given frequency. They very well might be transmitting on 7.19985 MHz, or 7.19999, or anything else. There is some trend to stay on multiples of 500 Hz, but it is not always followed...nor is it any rule.

For example, I operate CW and SSB on 500 Hz multiples when I can. I might operate 1.82400 MHz CW, or 1.82450 MHz. But if something is bothering me on a multiple of 500 Hz, I don't hesitate to move 50 or 100 Hz lower or higher.

The same is true all across the bands.

We are not channelized, and so it doesn't matter if we operate on 7.211111111111, or 7.1999999999, or anything else we like.......although there is a trend to stay on an even 100 Hz multiple on CW or 500 Hz multiple on SSB.

Just tune it til it sounds right.

73 Tom
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N3QE
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« Reply #10 on: September 21, 2012, 07:37:59 PM »

We are not channelized, and so it doesn't matter if we operate on 7.211111111111, or 7.1999999999, or anything else we like.......although there is a trend to stay on an even 100 Hz multiple on CW or 500 Hz multiple on SSB.

I make a point of operating only irrational frequencies. The wonderful thing about irrational frequencies, is that there are way more of them than rational frequencies, so there's always plenty of space. See you guys on sqrt(49.3) MHz and, when 10M is open, 9*pi MHz!
« Last Edit: September 21, 2012, 07:40:16 PM by N3QE » Logged
K8AXW
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« Reply #11 on: September 21, 2012, 08:34:31 PM »

QE:  Thank you for my laugh of the day!!  Very good!

HIFIMAN:  As far as I know, hams and the military are the only ones who are allowed to use any frequency within a specific band. 
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K7MH
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Posts: 339




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« Reply #12 on: September 21, 2012, 11:13:51 PM »

There was also a time when we didn't have digital frequency displays. They came around in the late 70's or thereabouts. Or perhaps just were more widely being used about then or in the very early 80's. Just having a hash mark every 1KHz or every few KHz (sometimes only every 5KHz) made it a little tough to tell exactly where we were. When you get down to it, all you REALLY need to know is if you are in the band or not. I have seen a fair amount of homebrew gear through the years that just had a knob and that was it! Maybe a pencil mark where the band started and ended.
We are all quite SPOILED these days!!
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W8JI
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« Reply #13 on: September 23, 2012, 10:07:06 AM »

There was also a time when we didn't have digital frequency displays. They came around in the late 70's or thereabouts. Or perhaps just were more widely being used about then or in the very early 80's. Just having a hash mark every 1KHz or every few KHz (sometimes only every 5KHz) made it a little tough to tell exactly where we were. When you get down to it, all you REALLY need to know is if you are in the band or not. I have seen a fair amount of homebrew gear through the years that just had a knob and that was it! Maybe a pencil mark where the band started and ended.
We are all quite SPOILED these days!!

Even in the early 1980's, we were limted in frequency resolution. In the 1970's and earlier, the 100 kHz calibrator was a band edge location tool most people used. When the bands were divided at the 25 kHz point, the 25 kHz calibration marker became more important. But early on, up through the 1980's, WWV and the 100 kHz quartz crystal were our main tools.


The odd thing about this thread is how people assumed the contacts her quoted in his orignal question:

 
I do SWL at this point while I am studying for my ticket. This is going to sound like a stupid question to many Im sure. I love to listen to LSB on 40 meters, 80 meters. Yesterday while listening many seemed to be frequencies talking such as 7.200.00 or 7.180.00 as an example. Well today most seem to be 10-15kc below.Like 7.199.85 or 7.179.85. Could it be that the receiver needs calibration? On certian days or times are the frequencies allowed to be used change. I just find it strange in the difference. Hope you can understand my question? Thanks

...were immediately assumed to be a receiver calibration or operation issue.

He made a mistake by saying it was "10-15 kc", when it was really 150 Hz off from 10 kHz multiples, but there certainly isn't any standard mandating operation on tens of kilohertz. There is trend to stay on 500 Hz multiples on SSB or 100 Hz multiples on CW, but no rule, and I frequently find people on very odd numbers when bands are crowded.
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