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Author Topic: 10 meter Q  (Read 1359 times)
K1BXI
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Posts: 812




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« Reply #15 on: July 15, 2009, 12:04:35 PM »

Jim....... yea, your right, my memory is suspect from those days. I went from AM to SSB kicking and screaming in the 60's, later than most!...... Tuning in a SSB signal on an old receiver without a product detector and riding the RF gain control probably had something to do with it.

I also seem to remember that the choice of upper and lower SSB may have had to do with the receiver mixers of those days and that once it was set up it was easier to keep the BFO on the same side of the 455 kHz IF when going from 75 to 20 meters. This required the shift in side band on transmit from 75 to 20. maybe this is the reason for the difference.

John
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K1BXI
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« Reply #16 on: July 15, 2009, 12:10:16 PM »

Or was it to keep the same tuning direction on the tuning knob CW for higher frequency and CCW for a lower frequency, or something like that.

John
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N2EY
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Posts: 3833




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« Reply #17 on: July 15, 2009, 12:53:07 PM »

To K1BXI:

It was a convention derived from the very early use of a 5.2 MHz SSB generator and a 9 MHz VFO.

Here's the math to prove that the old 9-MHz-SSB/5-MHz-VFO-inverts-the-sideband urban legend is a myth. The standard of LSB/USB in ham radio was set in 1949 at the latest, years before the Central Electronics exciters were made.

9 MHz filter and 5-5.5 MHz VFO

Start with a 9000 kHz USB signal (carrier at 9000, top end of audio at 9003)

Add a 5200 kHz VFO signal for 20 meters:

9000 carrier + 5200 VFO = 14200 carrier,
9003 top end + 5200 VFO = 14203 top end

Result is carrier at 14200, top end of audio at 14203 - still USB

Subtract a 5200 kHz VFO signal for 75 meters

9000 carrier - 5200 VFO = 3800 carrier,
9003 top end - 5200 VFO = 3803 top end

Result is carrier at 3800, top end of audio at 3803 - still USB!

The tuning direction reverses, but the sideband does not. The numbers tell the story.

However:

5.2 MHz filter and 8.7 - 9.2 MHz VFO:

Start with a 5200 kHz USB signal (carrier at 5200, top end of audio at 5203)

Add a 9000 kHz VFO signal for 20 meters:

9000 VFO + 5200 carrier = 14200 carrier,
9000 VFO + 5203 top end = 14203 top end of audio

Result is carrier at 14200, top end of audio at 14203 - still USB

Subtract the 5200 kHz USB signal from a 9000 kHz VFO signal for 75 meters:

9000 VFO - 5200 carrier = 3800 carrier,
9000 VFO - 5203 top end = 3797 top end of audio

Result is carrier at 3800, top end of audio at 3797 - now it's LSB! (because the sideband is now below the carrier)

I wish it *were* true about the 5 MHz VFO/9 MHz IF sideband inversion - it would make some projects simpler! But the numbers don't lie.

The only way you get sideband (not tuning direction!) inversion is if the LO is higher than both the input and output frequencies of a mixer.

That old urban legend has been repeated many times, and has even made its way into the pages of CQ magazine. But it is simply NOT TRUE, because it cannot be true; the basic principles of frequency conversion don't allow it.

73 de Jim, N2EY
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W7AIT
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Posts: 487




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« Reply #18 on: July 17, 2009, 12:41:49 AM »

Question for smart Elmers:

The precise quote from the FCC rules in regard to Technicians operating Phone in 28300 to 28500 segment:

97.307 (f) paragraph (10)

“(10) A station having the control operator holding a Novice Class operator license or a Technician Class operator license and who has received credit for proficiency in telegraphy in accordance with international requirements may only transmit a CW emission using international Morse Code or phone emissions J3E and R3E.”

Question:  What is R3E?

According to what I find R3E is modulation type R = Single Sideband Reduced Carrier, 3 = a single channel containing analog information, E = Telephony

What is Reduced Carrier?  

It is clear what J3E is – J= Single Sideband Suppressed Carrier, 3 = A single channel containing analog information, E = Telephony.

So according to the rules, techs can transmit CW, J3E and R3E.  

1.   What is R3E?  
2.   How is R3E different than J3E?  
3.   Why don’t we hear R3E transmissions?  
4.   What would R3E transmissions sound like?
5.      Does the rule dictate USB only?  Where does it say that?
6.      Does the rule allow both USB and LSB?  Where does it say that?
7.      Does the rule specifically exclude LSB?  If so where does it say that?
8.      Is it illegal for Techs to run LSB in the 28300 to 28500 segment?  If so where in the rules does it say that?
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N2EY
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Posts: 3833




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« Reply #19 on: July 17, 2009, 03:42:20 AM »

"1. What is R3E?"

Single sideband voice with reduced carrier
 
"2. How is R3E different than J3E?"

The carrier in J3E is so low (typically 40+ dB suppressed) that it serves no purpose. The carrier in R3E isn't suppressed as much, and can be used for things like automatically fine-tuning the receiver.
 
"3. Why don’t we hear R3E transmissions?"

Because they offer little advantage to amateurs compared to J3E.
 
"4. What would R3E transmissions sound like?"

You might hear the carrier whistling when you tune through a strong R3E signal.
 
"5. Does the rule dictate USB only?"

No. The only place in US amateur rules (Part 97) where the sideband is required to be one or the other by regulation is on the 5 channels of 60 meters. The use of USB on 10 meters is simply a gentleman's agreement among hams.

However, note that regulations require that the entire signal be inside the subband, and that amateur rigs almost universally indicate the suppressed-carrier frequency on the dial.

So if an accurately-calibrated rig is set to 28,301.00 kHz USB, it will be legal in the US, but if the same accurately-calibrated rig is set to 28,302.00 kHz LSB, it won't be.

"6. Does the rule allow both USB and LSB?"

Yes.

"7. Does the rule specifically exclude LSB?"

No.
 
"8. Is it illegal for Techs to run LSB in the 28300 to 28500 segment?"

No. But see the caution above about having the whole signal inside the subband.

And while it may be *legal* to do something, it may not be smart to do it. LSB will not make your signal any louder or clearer on 10 meters.  
 
73 de Jim, N2EY
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WA3SKN
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Posts: 5420




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« Reply #20 on: July 17, 2009, 04:23:28 AM »

With "single sideband suppressed carrier" the carrier amplitude was lowered by a minimum of 20 dB.
With "single sideband reduced carrier" the carrier amplitude was only lowered by 6 dB.
All amateur radios (since the early 70s, anyway)  produce a single sideband suppressed carrier typically with about 40 dB suppression... well beyond the minimum for definition.
73s.

-Mike.
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WB5JEO
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Posts: 805




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« Reply #21 on: July 17, 2009, 07:03:01 AM »

A bit more on the antenna. If you modify an 11 meter ground plane antenna, lengthen both the radiator and the ground planes, typically four. If you measure the existing 11 meter, you'll likely find that the radials are a bit longer than the vertical. An elevated quarter-wave vertical needs few radials, but they must be tuned, which turns out to me slightly longer than 1/4L. Proximity to nearby metal can detune them.

You can ground mount a quarter-wave vertical to good effect, but the return path is then through the earth, which is nearly everywhere a poor conductor. That's why ground-mounted verticals require a fair number of wires laid out on the ground or just under the ground. They need not be tuned and can be any length, as practical, preferably at least as long as the antenna is tall. 32 wires or more. The more you put out, the less ground loss. Failures of ground-mounted 1/4L verticals is nearly always due to failure to provide a good ground screen. They will indeed work very well on the ground. Any old wire will do. Don't try to mix these concepts. Tuned ground plane elements mounted close to the ground are detuned by the nearby earth and just become a very poor ground screen. And elevating a 1/4L vertical without ground plane above a ground screen will cause the ground lead running to the ground to mess you up.

Whether you elevate the vertical or not is largely a matter of how in the clear it is. I run my verticals on the ground, but I have lots of clear space. You don't need to spend a lot of money getting a ground plane WAY off the ground. You just need it high enough that the radials don't interact with the earth. Remember, at 10-meters, 15 feet up is a half wavelength and is more than enough.

Ten meters is a nice place to play with antennas, because you can get an effective height above ground without expensive supports and because the physical size keeps down the cost of materials. A 10-meter two or three element Yagi is a very doable project, with locally available materials, and is a great learning experience, as well as a very effective antenna. Lot's of plans available on the Internet.
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AD7WN
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Posts: 113




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« Reply #22 on: July 17, 2009, 07:20:24 PM »

USB is propogated the same way as LSB.  The convention resulted from the way frequencies were mixed in the early years of ham ssb.

As to 10 meter antennas, quite a few years ago I was able to buy a cheap 3 element beam made for 11 meter CB use.  After trimming the elements for 10 meter use, I had a cheap bean that performed well on 10 meters.  Maybe these cheap beams are still being made, dunno.

73 de John/AD7WN
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